![]() ![]() Here, the client tells the server the algorithms it supports for each function (encryption, MAC, key exchange, host authentication, compression), in order of preference. The client and the server begin by sending to each other the protocol and software versions they are using. I don't know the exact details and (un)fortunately all this is encrypted. Ok, I suppose there's a lot going on after this (server public key verification, user authentication, establishment of data channels for shell/sftp/scp/tunnels, etc). It is small and contains no significative data. This looks like a simple acknowlegding message to me. Following wikipedia notation this would be step 2 (Alice sends g a).Īfter receiving this packet both peers know the secret key (g ab) and establish a pseudo-secure channel with it (secure against casual eavesdropping, but not against man-in-the-middle-attacks). SSHv2 Server: Diffie-Hellman Key Exchange Replyįirst actual exchange of DH. (See RFC4419 section 3 for more details). Negotiation of the DH parameters about mathematical group. SSHv2 Client: Diffie-Hellman Key Exchange Init Several parameters negotiation, like compression and some crypto algorithms. ![]() Bob picks a random natural number b and sends g b to Alice.Īs a result they have generated a safe random secret g ab.Alice picks a random natural number a and sends g a to Bob.Let g be a known public number from a finite cyclic group.This is an interesting concept to me.įrom the wikipedia article here is a simplified structure of the exchange: It generates random number that cannot be determined by neither of the peers alone, but the two together. This is done after DH exchange, so it is encrypted and cannot be analyzed with wireshark at this time. This kind of attacks are prevented through verification of host key. Diffie-Hellman Does NOT protect against man-in-the middle attacks.Someone sniffing on the channel cannot decrypt it. It allow to establish a channel between 2 endpoints with these features: I guess another way is to extract the private key from pkcs12 file and then add it as RSA key in wireshark.First of all you should understand the concept of a Diffie-Hellman exchange. wish everyone can solve the challenge they encounter while learning. I am so happy I figured this out so that I learn about how http2 encoding the body message and Wireshark usage, and verify json is still being sent in ASCII rather than binary. Then we can view decrypted data directly in wireshark: If you use a browser, you just need to export the env var in the terminal or shell:Įxport SSLKEYLOGFILE= SSLKEYLOGFILE= curl -http2 -v -k -X POST -H "Content-Type: application/json" -d '' We just need to put SSLKEYLOGFILE= at the very beginning of the curl command I am gonna run: The second step is to just enable logging for your client which can be curl utility or browser. Here tlskey.log is just an empty file created by myself Therefore we need to log this key which is allowed for debugging purposes: Steps: I think I figure out the answer on my own:įirst, as point out, the key is generated by the client and then is safely encrypted using public key and sent to the server. So I follow the example with ssl on the website but the key is not showing up lol However when capturing the packet using wireshark, it is encrypted but I really don't know how to use the cert to decrypt it. Keytool -genkey -alias undertow -storetype PKCS12 -keyalg RSA -keysize 2048 -keystore keystore.p12 -dname "CN=localhost, OU=localhost, O=localhost, L=Zhengzhou, ST=Henan, C=CN" I am doing this is because I have used keytool to generate the key/cert and run a small http2 server with this cert/key: Is there another way to view the comments? Can anyone try the linked file:įile: http2-16-ssl.pcapng (HTTP2 with ALPN h2-16 extension) (5.1 KB, from, SSL keys in capture file comments) On the wireshark website, it says the SSL keys are in the comment but I just didn't see it. To follow decryption example from wireshark:I download the capture file but didn't see the key in the comments of that capture file: ![]()
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