PolarProxy is a transparent SSL/TLS proxy created for incident responders and malware researchers. PolarProxy is primarily designed to intercept and decrypt TLS encrypted traffic from malware. PolarProxy decrypts and re-encrypts TLS traffic, while also saving the decrypted traffic in a PCAP file that can be loaded into Wireshark or an intrusion detection system (IDS).
Here is an example PCAP file generated by PolarProxy:
PolarProxy is released under a
CC BY-ND 4.0 license,
which means you are free to use the software for any purpose, even commercially.
There is one limitation though, the tool only allows up to 10 GB of data
If you need to proxy more than 10 GB of data
|License:||None||Level 1||Level 2||Level 3|
|Bytes per day:||10 GB||100 GB||300 GB||1 TB|
|Sessions per day:||
||1 000 000|
|Price:||Free||Contact Netresec||Contact Netresec||Contact Netresec|
You can also contact Netresec if you'd like a quote for a volume license that exceeds the limits specified in Level 3.
Free Licenses for Pro-Bono Work
We can provide vetted security researchers and malware analysts, who do pro bono work, with free L1-L3 licenses. If you are a security researcher or organization performing research or analysis of malware for the public good, then please contact us to go through our vetting procedure and get your own free license. We particularly favor projects that run malware in sandboxes and share PCAP files from the malware executions for free, either openly or within vetted security communities.
PolarProxy supports many different modes of operation, such as:
PolarProxy can be run in a container using OS-level virtualization. Our blog post "PolarProxy in Docker" describes how to deploy PolarProxy in Docker. If you prefer Podman, then check out the "PolarProxy in Podman" blog post instead.
See our blog post "Raspberry Pi WiFi Access Point with TLS Inspection" for instructions on how to install PolarProxy on a Linux ARM computer, such as a Raspberry Pi. We also have a blog post that covers how to install PolarProxy in Security Onion. For instructions on how to install PolarProxy on a generic 64-bit Linux machine, simply continue reading below.
PolarProxy can be run as a systemd service, but you can also run it as a regular command line application if you just wanna proxy a few sessions or take PolarProxy for a test ride. Follow these instructions in order download and start PolarProxy on TCP 443 on a Linux machine:
To run some traffic through PolarProxy, simply edit the hosts file of any client PC on your network so that some domain name(s) point to your proxy.
You will also need to install the generated
In order to use the firewall rules below, while running PolarProxy on the command line, you will need to bind the proxy to TCP port 10443 instead of 443:
Another cool option is to write the PCAP data to standard output using the "
If the default gateway (GW) out from the intercepted network is a Linux router or firewall that you manage, then we recommend installing PolarProxy directly on the gateway. If not, then you will need to install PolarProxy on a separate machine.
Note: eth1 is the "inside" interface on the GW pointing towards the clients.
Note 1: The following firewall rules should be added to the router/firewall acting as the default gateway (GW), not to the PolarProxy machine.
eth1 is the "inside" interface on the GW pointing towards the clients.
PolarProxy server has ip address 10.11.12.13.
The "-m state" rules requires that you have a related or established rule configured. If you don't have that you can add it with:
If your gateway is using the conntrack module instead of state module then you can just change "-m state --state" to "-m conntrack --ctstate".
This configuration will only proxy the traffic for the local user with uid 1000. Make sure PolarProxy runs under a different uid, it will otherwise end up connecting to itself in an endless loop. One way to get around this issue is to start PolarProxy with "sudo" to ensure it us runs as uid 0 (root). Another option is to create a special user just for running PolarProxy, as explained in "Installing PolarProxy as a systemd service in Linux" above.
Test the firewall rule(s) with curl:
Now is a good time to save your iptables rules!
The root CA certificate used by PolarProxy must be trusted by all clients that will have their TLS traffic routed through the proxy. Your PolarProxy root CA must be trusted by both the operating system and any browsers or applications that have their own list of trusted root certificates in order to get a seamless integration of the proxy.
There are two ways you can export your PolarProxy’s root CA as a DER encoded X.509 certificate.
How and where to install the public root CA certificate varies between operating systems and applications. A few common examples are listed here below.
Install the certificate in GUI:
Install the certificate without GUI:
Verify that it was successfully installed:
A root CA certificate can be pushed to all clients in an Active Directory domain with a Group Policy Object (GPO).
We also recommend disabling certificate revocation checks through OCSP through a group policy.
Replace "10.11.12.13" below with the IP of PolarProxy.
Replace "10.11.12.13" below with the IP of PolarProxy.
Ronnie Flathers has posted a great writeup titled "Proxying and Intercepting CLI Tools" where he covers how to install Burp certificates into keystores for Java, Python, Node JS and Golang. You can install PolarProxy's root CA certificate using the same methods as Ronnie describes in his blog post.
Q: Can PolarProxy be configured to listen to a high port (≥1024), so that I won’t need root permissions to run the proxy?
Yes, Polar Proxy can be configured to listen to a high port but still use a well-known low port for the outgoing TCP session. The following “-p” argument will have PolarProxy listen on TCP 10443, save the decrypted traffic as TCP 80 in the generated PCAP files and use TCP 443 for the outgoing connections to the real web servers:
Q: Does PolarProxy use a static built-in private certificate for the SSL interception?
No, PolarProxy dynamically creates a new and unique private certificate when it is first run on a machine. The purpose for doing so is to protect against man-in-the-middle attacks performed by others with access to the private certificate from some other PolarProxy instance.
Q: Can we have PolarProxy use our own private CA certificate instead of the dynamically generated one?
Yes. If you have a PKCS12 file with your private CA certificate, then simply use the “-c” command line switch to load the certificate (use “--help” for more details).
Q: Why do I get an error when I try to import PolarProxy's CA certificate (polarproxy.cer) as a PEM file?
The public CA certificate exported by PolarProxy (with -x or --certhttp) is using the DER encoding. You can convert it to a PEM file with openssl:
Q: Can I supply a list of whitelisted domains for which the TLS decryption should be bypassed?
Yes, use the “--bypass <file>” command line argument to point PolarProxy to a file containing one or multiple regular expressions (one per line). The TLS decryption will be bypassed for domains that are matched by any of the regular expressions in the supplied whitelist file. If you're intercepting Chrome devices, then use this bypass/allow list in order to avoid errors.
Q: I'm getting a Security Alert window saying
"Revocation information for the security certificate for this site is not available. Do you want to proceed?".
How do I disable OCSP certificate revocation checks in Windows?
Run "inetcpl.cpl" or open Control Panel > Internet Options, press the "Advanced" tab, scroll down to "Security" and uncheck the "Check for server certificate revocation" box. You should not see these alerts any more after rebooting.
Q: Which protocols (and ports) can be decrypted by PolarProxy?
PolarProxy only decrypts TLS and SSL traffic. However, many application layer protocols use TLS for encryption, such as HTTPS (TCP 443), DNS-over-TLS (853), FTPS (990), SMTPS (465), IMAPS (993), POP3S (995) and SIP-TLS (5061). These TLS wrapped protocols can be decrypted using PolarProxy, so that you can analyze them in their clear text format.
Q: Can PolarProxy alert on malicious activity?
No, PolarProxy only decrypts the SSL/TLS encrypted traffic and saves it in a capture file (a.k.a. PCAP file). Read the PCAP file with an IDS of your choice, like Snort, Suricata or Zeek in order to generate alerts for malicious traffic.
Q: How is PolarProxy different from mitmproxy / Burp Suite / Fiddler / Charles Proxy / Bettercap?
Unlike many other proxies, PolarProxy is not designed to interfere with the data inside the encrypted stream. PolarProxy only decrypts the TLS stream for inspection and then re-encrypts the exact same stream again. Another unique feature of PolarProxy is that it writes the decrypted data to a PCAP file containing the decrypted data, this PCAP file can be loaded into Wireshark, NetworkMiner or an IDS tool for inspection.
Q: What about TLS wrapped protocols other than HTTPS?
You can run any TLS wrapped protocol through PolarProxy to see the decrypted contents. It doesn’t matter if it is a proprietary protocol running inside the TLS session or if it is a well-known TLS wrapped protocol like HTTP/2, SMTPS, IMAPS or POP3S. They are all decrypted by PolarProxy, as long as you have configured it to listen on the desired port using the “
Q: How about badssl.com?
PolarProxy is designed to forward all properties of the external TLS session to the internal one as far as possible. This means that visiting, for example https://expired.badssl.com, will yield an expired certificate also on the inside. The same thing goes for most other badssl tests, like self signed certs, certs with wrong hostname etc.
Q: Is PolarProxy free? Can I use this software commercially?
Yes, and yes. PolarProxy is released under a Creative Commons Attribution-NoDerivatives 4.0 International License, which means that you can copy and redistribute PolarProxy in any medium or format for any purpose, even commercially.
Q: Can PolarProxy decrypt HTTPS traffic from a network tap or pcap file if I have a key log file or private RSA key?
No. PolarProxy will need to communicate with both the client and server in order to decrypt the traffic. Please use Wireshark in order to do passive decryption with SSLKEYLOGFILE.
Q: I'm running PolarProxy as a service and have successfully used it to proxy an HTTPS session.
Why don't I get any packets in the PCAP file?
PolarProxy will start writing to a new capture file every 60 minutes. However, the captured packets are not written to disk instantly because PolarProxy uses buffered file writing in order to improve performance. You can restart the proxy service if you wish to flush the buffered packets to disk and have PolarProxy rotate to a new capture file with: