NETRESEC Network Security Blog - Tag : curl


PolarProxy in Podman

PolarProxy + Podman Logo

Podman is a daemonless Linux container engine, which can be used as a more secure alternative to Docker. This blog post demonstrates how to run PolarProxy in a rootless container using Podman. If you still prefer to run PolarProxy in Docker, then please read our blog post "PolarProxy in Docker" instead.

Install Podman and fuse-overlayfs

Install Podman according to the official Podman installation instructions. Then install fuse-overlayfs, which is an overlay file system for rootless containers. Fuse-overlayfs can be installed in Debian/Ubuntu with "sudo apt install fuse-overlayfs" and in CentOS with "sudo yum install fuse-overlayfs".

Create a Podman Image for PolarProxy

Create a Dockerfile with the following contents:

FROM mcr.microsoft.com/dotnet/core/runtime:2.2
EXPOSE 10443
EXPOSE 10080
EXPOSE 57012
RUN groupadd -g 31337 polarproxy && useradd -m -u 31337 -g polarproxy polarproxy && mkdir -p /var/log/PolarProxy /opt/polarproxy && chown polarproxy:polarproxy /var/log/PolarProxy && curl -s https://www.netresec.com/?download=PolarProxy | tar -xzf - -C /opt/polarproxy
USER polarproxy
WORKDIR /opt/polarproxy/
ENTRYPOINT ["dotnet", "PolarProxy.dll"]
CMD ["-v", "-p", "10443,80,443", "-o", "/var/log/PolarProxy/", "--certhttp", "10080", "--pcapoverip", "57012"]

Save the Docker file as "Dockerfile" (no extension) in an empty directory and start a shell in that directory. Build a PolarProxy Podman image with:

podman build -f Dockerfile -t polarproxy

Test the PolarProxy Podman Image

Take the polarproxy Podman image for a test run. Start it with:

podman run -it --rm --name polarproxy -p 10443 localhost/polarproxy

Establish an HTTPS connection through PolarProxy by running this curl command from another shell on the same machine:

curl --insecure --connect-to www.netresec.com:443:127.0.0.1:10443 https://www.netresec.com/

If everything works alright, then curl should output HTML and the interactive Podman session running the polarproxy image should print something like:

<6>[10443] 127.0.0.1 -> N/A Connection from: 127.0.0.1:44122
<6>[10443] 127.0.0.1 -> www.netresec.com Connection request for: www.netresec.com from 127.0.0.1:44122
<6>[10443] 127.0.0.1 -> www.netresec.com Action: DECRYPT

Create a Podman Container for PolarProxy

Create directories "pcap" and "polarproxy", where PolarProxy should store the decrypted network traffic and its root CA certificate.

mkdir pcap polarproxy
podman unshare chown 31337:31337 pcap polarproxy

Create a container called "polarproxy", which has the "pcap" and "polarproxy" directories mounted as volumes. The service on TCP 10080 will serve the proxy's public root cert over HTTP. The localhost:57012 service is a Pcap-over-IP server, from which the decrypted network traffic can be streamed in real-time.

podman create --name polarproxy -v $(pwd)/pcap:/var/log/PolarProxy -v $(pwd)/polarproxy:/home/polarproxy -p 10443 -p 10080 -p 127.0.0.1:57012:57012 localhost/polarproxy

Create and enable a systemd user service that will run the container.

mkdir -p ~/.config/systemd/user/
podman generate systemd -n polarproxy > ~/.config/systemd/user/container-polarproxy.service
systemctl --user enable container-polarproxy.service

Start the systemd user service to activate the PolarProxy container.

systemctl --user start container-polarproxy.service

Verify that the service is running and that you can view the logs from PolarProxy.

systemctl --user status container-polarproxy.service
podman logs polarproxy

Expose PolarProxy to the Network

Create a firewall rule to redirect incoming TCP 443 packets to the PolarProxy service listening on port 10443.
sudo iptables -t nat -A PREROUTING -d 10.11.12.13 -p tcp --dport 443 -j REDIRECT --to 10443
Note: Replace "10.11.12.13" with the IP of the PolarProxy machine

Try making an HTTPS connection via PolarProxy from another PC on the network.

C:\> curl --insecure --resolve www.netresec.com:443:10.11.12.13 https://www.netresec.com/
Note: Replace "10.11.12.13" with the IP of the PolarProxy machine

Don't forget to save the firewall redirect rule if it is working as desired!

Redirect HTTPS and Trust the Root CA

You can now redirect outgoing TCP 443 traffic from your network to your Podman/PolarProxy host. Review the "Routing HTTPS Traffic to the Proxy" section on the PolarProxy page for recommendations on how to redirect outgoing traffic to PolarProxy.

Finally, configure the operating system, browsers and other applications that will get their TLS traffic proxied by PolarProxy to trust the root CA of the PolarProxy service running in your Podman container. Follow the steps in the "Trusting the PolarProxy root CA" section of the PolarProxy documentation in order to install the root cert.

Accessing Decrypted TLS Traffic

You should be able to access PCAP files with the decrypted HTTPS traffic in the "pcap" directory.

It is also possible view the decrypted traffic in real-time by using netcat and tcpdump as a Pcap-over-IP client like this:

nc localhost 57012 | tcpdump -nr - -X

It probably makes more sense to forward the decrypted traffic to an IDS or other type of network security monitoring tool though. See our blog post "Sniffing Decrypted TLS Traffic with Security Onion" for instructions on how to use netcat and tcpreplay to send the decrypted traffic to a monitor interface.

PolarProxy in Podman on ARM Linux

PolarProxy can also run on ARM Linux installations, such as a Raspberry Pi. However, the Dockerfile must be modified slightly in order to do so.

ARM 32-bit / AArch32 / ARMv7 If you're running an "arm32" Linux OS, then change the download link in the "RUN" instruction to the following URL:
https://www.netresec.com/?download=PolarProxy_linux-arm

ARM 64-bit / AArch64 / ARMv8 If you're running an "arm64" Linux OS, then change the download link in the "RUN" instruction to the following URL:
https://www.netresec.com/?download=PolarProxy_linux-arm64

Don't know if you're running a 32-bit or 64-bit OS? Run "uname -m" and check if the output says "armv7*" (arm32) or "armv8*" (arm64).

See our blog post "Raspberry PI WiFi Access Point with TLS Inspection" for more details about deploying PolarProxy on a Raspberry Pi.

ʕ•ᴥ•ʔ + 🦭 = 💜

Posted by Erik Hjelmvik on Tuesday, 27 October 2020 18:33:00 (UTC/GMT)

Tags: #PolarProxy #Docker #TLS #HTTPS #Proxy #curl #PCAP #Dockerfile #DNAT #container #arm32 #arm64 #AArch64 #PCAP-over-IP #pcapoverip

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PolarProxy in Docker

PolarProxy + Docker

Our transparent TLS proxy PolarProxy is gaining lots of popularity due to how effective it is at generating decrypted PCAP files in combination with how easy it is to deploy. In this blog post we will show how to run PolarProxy in Docker.

Installation Instructions

Create a Dockerfile with the following contents:

FROM mcr.microsoft.com/dotnet/core/runtime:2.2
EXPOSE 10443
EXPOSE 10080
EXPOSE 57012
RUN groupadd -g 31337 polarproxy && useradd -m -u 31337 -g polarproxy polarproxy && mkdir -p /var/log/PolarProxy /opt/polarproxy && chown polarproxy:polarproxy /var/log/PolarProxy && curl -s https://www.netresec.com/?download=PolarProxy | tar -xzf - -C /opt/polarproxy
VOLUME ["/var/log/PolarProxy/", "/home/polarproxy/"]
USER polarproxy
WORKDIR /opt/polarproxy/
ENTRYPOINT ["dotnet", "PolarProxy.dll"]
CMD ["-v", "-p", "10443,80,443", "-o", "/var/log/PolarProxy/", "--certhttp", "10080", "--pcapoverip", "0.0.0.0:57012"]

Save the Docker file as "Dockerfile" (no extension) in an empty directory and start a shell in that directory with root privileges. Build the PolarProxy Docker image with:

docker build -t polarproxy-image .

Next, create a Docker container named "polarproxy":

docker create -p 443:10443 -p 10443:10443 -p 10080:10080 --name polarproxy polarproxy-image
The "-p" switches in this command define three DNAT rules that will get activated when the polarproxy container is started. The first DNAT rule forwards incoming TCP port 443 traffic to the polarproxy Docker container's transparent TLS proxy service on TCP port 10443. The second one does the same thing, but for incoming traffic to TCP 10443. The last one forwards TCP port 10080 traffic to a web server that delivers the public X.509 certificate of the proxy.

It is now time to start the polarproxy container:

docker start polarproxy

Verify that PolarProxy is running:

docker ps
docker logs polarproxy

Try fetching PolarProxy's public root CA certificate with curl and then connect to a website over HTTPS through the proxy:

curl -sL http://localhost:10080 | openssl x509 -inform DER -issuer -noout -dates
curl --insecure --connect-to www.netresec.com:443:127.0.0.1:10443 https://www.netresec.com/
curl --insecure --resolve www.netresec.com:443:127.0.0.1 https://www.netresec.com/

Redirect HTTPS and Trust the Root CA

You can now redirect outgoing TCP 443 traffic from your network to your Docker host. Review the "Routing HTTPS Traffic to the Proxy" section on the PolarProxy page for recommendations on how to redirect outgoing traffic to PolarProxy.

Finally, configure the operating system, browsers and other applications that will get their TLS traffic proxied by PolarProxy to trust the root CA of the PolarProxy service running in your Docker container. Follow the steps in the "Trusting the PolarProxy root CA" section of the PolarProxy documentation in order to install the root cert.

Docker Volumes

The Docker file we used in this blog post defines two volumes. The first volume is mounted on "/var/log/PolarProxy" in the container, which is where the decrypted network traffic will be stored as hourly rotated PCAP files. The second volume is the polarproxy home directory, under which PolarProxy will store its private root CA certificate.

The volumes are typically located under "/var/lib/docker/volumes" on the Docker host's file system. You can find the exact path by running:

docker volume ls
docker volume inspect <VOLUME_NAME>

Or use find to list *.pcap files in the Docker volumes directory:

find /var/lib/docker/volumes/ -name *.pcap
/var/lib/docker/volumes/7ebb3f56fd4ceab96[...]/_data/​proxy-201006-095937.pcap/var/lib/docker/volumes/7ebb3f56fd4ceab96[...]/_data/​proxy-201006-105937.pcap/var/lib/docker/volumes/7ebb3f56fd4ceab96[...]/_data/​proxy-201006-115937.pcap

The full path of your private PolarProxy Root CA certificate, which is located under "/home/polarproxy/" in the Docker container, can also be located using find:

find /var/lib/docker/volumes/ -name *.p12
/var/lib/docker/volumes/dcabbbac10e1b1461[...]/_data/​.local/share/PolarProxy/​e249f9c497d7b5c41339f153a31eda1c.p12

We recommend reusing the "/home/polarproxy/" volume, when deploying new PolarProxy instances or upgrading to a new version of PolarProxy, in order to avoid having to re-configure clients to trust a new root CA every time a new PolarProxy container is created.

PolarProxy in Docker on ARM Linux

PolarProxy can also run on ARM Linux installations, such as a Raspberry Pi. However, the Dockerfile must be modified slightly in order to do so.

ARM 32-bit / AArch32 / ARMv7 If you're running an "arm32" Linux OS, then change the download link in the "RUN" instruction to the following URL:
https://www.netresec.com/?download=PolarProxy_linux-arm

ARM 64-bit / AArch64 / ARMv8 If you're running an "arm64" Linux OS, then change the download link in the "RUN" instruction to the following URL:
https://www.netresec.com/?download=PolarProxy_linux-arm64

Don't know if you're running a 32-bit or 64-bit OS? Run "uname -m" and check if the output says "armv7*" (arm32) or "armv8*" (arm64).

See our blog post "Raspberry PI WiFi Access Point with TLS Inspection" for more details about deploying PolarProxy on a Raspberry Pi (without Docker).

Credits

We'd like to thank Jonas Lejon for contacting us back in February about the work he had done to get PolarProxy running in Docker. We used Jonas' work as a starting point when building the installation instructions in this how-to guide.

We also want to thank Erik Ahlström for providing valuable feedback on the instructions in this guide.

ʕ•ᴥ•ʔ + 🐳 = 💜

Posted by Erik Hjelmvik on Wednesday, 07 October 2020 08:09:00 (UTC/GMT)

Tags: #PolarProxy #Docker #TLS #HTTPS #Proxy #TLSI #Dockerfile #curl #x509 #X.509 #PCAP #DNAT #container #DNAT #arm32 #arm64 #AArch64 #PCAP-over-IP #pcapoverip

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Sniffing Decrypted TLS Traffic with Security Onion

Wouldn't it be awesome to have a NIDS like Snort, Suricata or Zeek inspect HTTP requests leaving your network inside TLS encrypted HTTPS traffic? Yeah, we think so too! We have therefore created this guide on how to configure Security Onion to sniff decrypted TLS traffic with help of PolarProxy.

Network drawing with Clients, SecurityOnion and the Internet

PolarProxy is a forward TLS proxy that decrypts incoming TLS traffic from clients, re-encrypts it and forwards it to the server. One of the key features in PolarProxy is the ability to export the proxied traffic in decrypted form using the PCAP format (a.k.a. libpcap/tcpdump format). This makes it possible to read the decrypted traffic with external tools, without having to perform the decryption again. It also enables packet analysis using tools that don't have built-in TLS decryption support.

This guide outlines how to configure PolarProxy to intercept HTTPS traffic and send the decrypted HTTP traffic to an internal network interface, where it can be sniffed by an IDS.

STEP 1 ☆ Install Ubuntu

Download and install the latest SecurityOnion ISO image, but don't run the "Setup" just yet.

STEP 2 ☆ Add a Dummy Network Interface

Add a dummy network interface called "decrypted", to which decrypted packets will be sent.

ip link add decrypted type dummy
ip link set decrypted arp off up
Add the commands above to /etc/rc.local before "exit 0" to have the network interface automatically configured after reboots.

dummy interface in rc.local

STEP 3 ☆ Install Updates

Install updates in Security Onion by running "sudo soup".

STEP 4 ☆ Run the Security Onion Setup

Run the Security Onion setup utility by double-clicking the "Setup" desktop shortcut or executing "sudo sosetup" from a terminal. Follow the setup steps in the Production Deployment documentation and select "decrypted" as your sniffing interface.

Sniffing Interface Selection Window

Reboot and run Setup again to continue with the second phase of Security Onion's setup. Again, select "decrypted" as the interface to be monitored.

STEP 5 ☆ Install PolarProxy Service

Download and install PolarProxy:

sudo adduser --system --shell /bin/bash proxyuser
sudo mkdir /var/log/PolarProxy
sudo chown proxyuser:root /var/log/PolarProxy/
sudo chmod 0775 /var/log/PolarProxy/

sudo su - proxyuser
mkdir ~/PolarProxy
cd ~/PolarProxy/
curl https://www.netresec.com/?download=PolarProxy | tar -xzf -
exit

sudo cp /home/proxyuser/PolarProxy/PolarProxy.service /etc/systemd/system/PolarProxy.service

Edit /etc/systemd/system/PolarProxy.service and add "--pcapoverip 57012" at the end of the ExecStart command.

--pcapoverip 57012 in PolarProxy.service

Start the PolarProxy systemd service:

sudo systemctl enable PolarProxy.service
sudo systemctl start PolarProxy.service

STEP 6 ☆ Install Tcpreplay Service

The decrypted traffic can now be accessed via PolarProxy's PCAP-over-IP service on TCP 57012. We can leverage tcpreplay and netcat to replay these packets to our dummy network interface in order to have them picked up by Security Onion.

nc localhost 57012 | tcpreplay -i decrypted -t -
However, it's better to create a systemd service that does this automatically on bootup. We therefore create a file called /etc/systemd/system/tcpreplay.service with the following contents:
[Unit]
Description=Tcpreplay of decrypted traffic from PolarProxy
After=PolarProxy.service

[Service]
Type=simple
ExecStart=/bin/sh -c 'nc localhost 57012 | tcpreplay -i decrypted -t -'
Restart=on-failure
RestartSec=3

[Install]
WantedBy=multi-user.target

Start the tcpreplay systemd service:

sudo systemctl enable tcpreplay.service
sudo systemctl start tcpreplay.service

STEP 7 ☆ Add firewall rules

Security Onion only accepts incoming connections on TCP 22 by default, we also need to allow connections to TCP port 10443 (proxy port), and 10080 (root CA certificate download web server). Add allow rules for these services to the Security Onion machine's firewall:

sudo ufw allow in 10443/tcp
sudo ufw allow in 10080/tcp

Verify that the proxy is working by running this curl command on a PC connected to the same network as the Security Onion machine:

curl --insecure --connect-to www.netresec.com:443:[SecurityOnionIP]:10443 https://www.netresec.com/
Note: You can even perform this test from a Win10 PC, since curl is included with Windows 10 version 1803 and later.

Add the following lines at the top of /etc/ufw/before.rules (before the *filter section) to redirect incoming packets on TCP 443 to PolarProxy on port 10443.

*nat
:PREROUTING ACCEPT [0:0]
-A PREROUTING -i enp0s3 -p tcp --dport 443 -j REDIRECT --to 10443
COMMIT

Note: Replace "enp0s3" with the Security Onion interface to which clients will connect.

After saving before.rules, reload ufw to activate the port redirection:

sudo ufw reload

Verify that you can reach the proxy on TCP 443 with this command:

curl --insecure --resolve www.netresec.com:443:[SecurityOnionIP] https://www.netresec.com/

STEP 8 ☆ Redirect HTTPS traffic to PolarProxy

It's now time to configure a client to run its HTTPS traffic through PolarProxy. Download and install the PolarProxy X.509 root CA certificate from PolarProxy's web service on TCP port 10080:

http://[SecurityOnionIP]:10080/polarproxy.cer

Install the certificate in the operating system and browser, as instructed in the PolarProxy documentation.

You also need to forward packets from the client machine to the Security Onion machine running PolarProxy. This can be done either by configuring a local NAT rule on each monitored client (STEP 8.a) or by configuring the default gateway's firewall to forward HTTPS traffic from all clients to the proxy (STEP 8.b).

STEP 8.a ☆ Local NAT

Use this firewall rule on a Linux client to configure it to forward outgoing HTTPS traffic to the Security Onion machine:

sudo iptables -t nat -A OUTPUT -p tcp --dport 443 -j DNAT --to [SecurityOnionIP]

STEP 8.b ☆ Global NAT Network drawing Firewall, PolarProxy, Clients

If the client isn't running Linux, or if you wanna forward HTTPS traffic from a whole network to the proxy, then apply the following iptables rules to the firewall in front of the client network. See "Routing Option #2" in the PolarProxy documentation for more details.

  1. Add a forward rule on the gateway to allow forwarding traffic to our PolarProxy server:
    sudo iptables -A FORWARD -i eth1 -d [SecurityOnionIP] -p tcp --dport 10443 -m state --state NEW -j ACCEPT
  2. Add a DNAT rule to forward 443 traffic to PolarProxy on port 10443:
    sudo iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 443 -j DNAT --to [SecurityOnionIP]:10443
  3. If the reverse traffic from PolarProxy to the client doesn't pass the firewall (i.e. they are on the same LAN), then we must add this hide-nat rule to fool PolarProxy that we are coming from the firewall:
    sudo iptables -t nat -A POSTROUTING -o eth1 -d [SecurityOnionIP] -p tcp --dport 10443 -j MASQUERADE
For other network configurations, please see the various routing setups in the PolarProxy documentation.

STEP 9 ☆ Inspect traffic in SecurityOnion

Wait for the Elastic stack to initialize, so that the intercepted network traffic becomes available through the Kibana GUI. You can check the status of the elastic initialization with "sudo so-elastic-status".

You should now be able to inspect decrypted traffic in Security Onion using Kibana, Squert, Sguil etc., just as if it was unencrypted HTTP.

Bro HTTP traffic in Kibana Image: Kibana showing HTTP traffic info from decrypted HTTPS sessions

MIME types in Kibana Image: MIME types in Kibana

NIDS alerts in Kibana Image: NIDS alerts from payload in decrypted traffic shown in Kibana

Snort alerts in Squert Image: Snort alerts from decrypted traffic shown in Squert

Security Considerations and Hardening

Security Onion nodes are normally configured to only allow access by SOC/CERT/CSIRT analysts, but the setup described in this blog post requires that "normal" users on the client network can access the PolarProxy service running on the Security Onion node. We therefore recommend installing PolarProxy on a dedicated Security Onion Forward Node, which is configured to only monitor traffic from the proxy.

We also recommend segmenting the client network from the analyst network, for example by using separate network interfaces on the Security Onion machine or putting it in a DMZ. Only the PolarProxy service (TCP 10080 and 10443) should be accessable from the client network.

PolarProxy could be used to pivot from the client network into the analyst network or to access the Apache webserver running on the Security Onion node. For example, the following curl command can be used to access the local Apache server running on the Security Onion machine via PolarProxy:

curl --insecure --connect-to localhost:443:[SecurityOnionIP]:10443 https://localhost/
We therefore recommend adding firewall rules that prevent PolarProxy from accessing the analyst network as well as the local Apache server.

Hardening Steps:

  • Configure the Security Onion node as a Forward Node
  • Segment client network from analyst network
  • Add firewall rules to prevent PolarProxy from accessing services on the local machine and analyst network

For additional info on hardening, please see the recommendations provided by Wes Lambert on the Security-Onion mailing list.

Posted by Erik Hjelmvik on Monday, 20 January 2020 09:40:00 (UTC/GMT)

Tags: #SecurityOnion #Security Onion #PCAP #Bro #PolarProxy #Snort #Suricata #TLS #SSL #HTTPS #tcpreplay #PCAP-over-IP #IDS #NIDS #netcat #curl

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Detecting the Pony Trojan with RegEx using CapLoader

This short video demonstrates how you can search through PCAP files with regular expressions (regex) using CapLoader and how this can be leveraged in order to improve IDS signatures.

The EmergingThreats snort/suricata rule mentioned in the video is SID 2014411 “ET TROJAN Fareit/Pony Downloader Checkin 2”.

The header accept-encoding header with quality factor 0 used by the Pony malware is:
Accept-Encoding: identity, *;q=0

And here is the regular expression used to search for that exact header: \r\nAccept-Encoding: identity, \*;q=0\r\n

After recording the video I noticed that the leaked source code for Pony 2.0 actually contains this accept-encoding header as a hard-coded string. Have a look in the redirect.php file, where they set curl’s CURLOPT_HTTPHEADER to this specific string.

Pony using curl to set: Accept-Encoding: identity, *;q=0

Wanna learn more about the intended use of quality factors in HTTP accept headers? Then have a look at section 14.1 of RFC 2616section 5.3.4 of RFC 7231, which defines how to use qvalues (i.e. quality factors) in the Accept-Encoding header.

Finally, I'd like to thank Brad Duncan for running the malware-traffic-analysis.net website, your PCAP files often come in handy!

Update 2018-07-05

I submitted a snort/suricata signature to the Emerging-Sigs mailinglist after publishing this blog post, which resulted in the Emerging Threats signature 2014411 being updated on that same day to include:

content:"|0d 0a|Accept-Encoding|3a 20|identity,|20 2a 3b|q=0|0d 0a|"; http_header;

Thank you @EmergingThreats for the fast turnaround!

Posted by Erik Hjelmvik on Wednesday, 04 July 2018 07:39:00 (UTC/GMT)

Tags: #video #regex #malware #IDS #curl #videotutorial

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Recommended Books

» The Practice of Network Security Monitoring, Richard Bejtlich (2013)

» Applied Network Security Monitoring, Chris Sanders and Jason Smith (2013)

» Network Forensics, Sherri Davidoff and Jonathan Ham (2012)

» The Tao of Network Security Monitoring, Richard Bejtlich (2004)

» Practical Packet Analysis, Chris Sanders (2017)

» Windows Forensic Analysis, Harlan Carvey (2009)

» TCP/IP Illustrated, Volume 1, Kevin Fall and Richard Stevens (2011)

» Industrial Network Security, Eric D. Knapp and Joel Langill (2014)