Hi everyone, I’ve been trying to understand how MiTM setups like a transparent proxy work.
Obviously, the use-case here is in a personal scope: I’d like to inspect the traffic of some of my machines. I am aware that Squid can be a transparent proxy, and some might use the Burp Suite to analyse network traffic.
Could someone explain the basic networking and the concept of certificates in this scenario? I feel like I don’t understand how certificates are used well enough.
For example: I realise that if someone inserts a root certificate in the certificate store of an OS, the machine trusts said CA, thus allowing encrypted traffic from the machine to be decrypted. However, say the machine was trying to access Amazon; won’t Amazon have its own certificate? I don’t know how I’m confused about such a simple matter. Would really appreciate your help!
There are some cases where this would not work by the way. It’s called certificate pinning and it’s basically when an application comes with the trusted certificate for a host built-in. Even if you were to override it with a root certificate in the certificate store, the app simply wouldn’t use it.
No, not at all. The request never hits the cache. The certificate is stored within the app and all internet communication is specifically pinned to said certificate. It doesn’t even ask your certificate store.
Yeah, unfortunately it’s a huge barrier if you’re wanting to see why your devices are phoning home and the data being sent. It makes it extremely difficult if not impossible for most people to bypass.
Specifically for attempting to bypass certificate pinning you’re solidly in the realm of reverse engineering. I haven’t attempting it myself but I have read the efforts of others over the years and the process was quite evolved and ever changing. If you are interested in going down this rabbit hole you may use these links as starting points but be prepared to adapt them.
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There are some cases where this would not work by the way. It’s called certificate pinning and it’s basically when an application comes with the trusted certificate for a host built-in. Even if you were to override it with a root certificate in the certificate store, the app simply wouldn’t use it.
Shouldn’t flushing the cache mitigate this problem?
No, not at all. The request never hits the cache. The certificate is stored within the app and all internet communication is specifically pinned to said certificate. It doesn’t even ask your certificate store.
I see. Thanks, I’ll have to rethink the idea in that case.
Yeah, unfortunately it’s a huge barrier if you’re wanting to see why your devices are phoning home and the data being sent. It makes it extremely difficult if not impossible for most people to bypass.
I understand. What other methods would you suggest to be able to snoop on/decrypt the traffic from my device?
Specifically for attempting to bypass certificate pinning you’re solidly in the realm of reverse engineering. I haven’t attempting it myself but I have read the efforts of others over the years and the process was quite evolved and ever changing. If you are interested in going down this rabbit hole you may use these links as starting points but be prepared to adapt them.
https://felipe-herranz.medium.com/uncertify-a-tool-for-recompiling-android-apps-bypassing-different-certificate-pinning-techniques-de3d30ded2c6
https://gist.github.com/approovm/e550374428065ff1ecafca6a0488d384
https://frida.re/
https://codeshare.frida.re/browse
Best of luck.
Thanks, I had heard of frida before, but never tried it. I’ll save this comment, many thanks for the pointers!