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Could someone explain the networking behind transparent proxies and MiTM snooping using certificates to me? (lemmy.world)

submitted 1 year ago by MigratingtoLemmy@lemmy.world to c/selfhosted@lemmy.world

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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!

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[–] MigratingtoLemmy@lemmy.world 1 points 1 year ago (24 children)

the proxy sends a cert to the client saying ‘I’m Amazon’, and the client believes it

Thanks, could you explain this a bit more? I didn't understand what you mean by "sends a cert saying 'I'm Amazon'"

[–] SheeEttin@lemmy.world 3 points 1 year ago (9 children)

That's literally it. It sends a cert for amazon.com, that your client trusts, because the CA cert used to sign it is in your trusted store.

[–] MigratingtoLemmy@lemmy.world 1 points 1 year ago (8 children)

I see, thanks for the explanation. Amazon sends the certificate to the proxy, and the proxy sends its own certificate, masquerading as amazon, to the user.

Thanks

[–] losttourist@kbin.social 2 points 1 year ago (1 children)

Yes, I think that 'masquerading' is the key bit to grasp. The MITM Proxy isn't just intercepting the traffic, it alters the traffic as it passes through.

[–] MigratingtoLemmy@lemmy.world 1 points 1 year ago

Thanks, got it!

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