Print human-readable format for TLS handshake (ClientHello and ServerHello)

[pkropachev]

Hello Team!

Could you please advice if there is some way to print TLS handshake in human-readable format using CURLOPT_DEBUGFUNCTION?

== Info: TLSv1.2 (OUT), TLS handshake, Client hello (1):
0x7f7e979f45c0
=> Send SSL data, 0000000512 bytes (0x00000200)
0000: ......y....s.).2..[.[.$.0........F3..B ...M@..]{..].T...D..F.*..
0040: 5....y..$.......+./.,.0................./.5...............httpbi
0080: n.testdomain.com..................................h2.http/1.1...
00c0: ......................3.&.$... ..O..........$.t...K.[..TU.....O.
0100: -.....+.........................................................
0140: ................................................................
0180: ................................................................
01c0: ................................................................
0x7f7e979f45c0
<= Recv SSL data, 0000000005 bytes (0x00000005)
0000: ....z
== Info: TLSv1.2 (IN), TLS handshake, Server hello (2):
0x7f7e979f45c0
<= Recv SSL data, 0000000122 bytes (0x0000007a)
0000: ...v..Yj..'...wV.=.{K..2...w.....I.4J. ...M@..]{..].T...D..F.*..
0040: 5....y.......+.....3.$... .a....J,.t...7uyO.L..#.\. ..0^=
0x7f7e979f45c0

Thanks!

[dfandrich]

curl doesn't know anything about TLS on the wire; all that is taken care of by the TLS libraries it uses. You can look at decoded TLS frames using a packet sniffer like Wireshark.

[bagder]

SSLKEYLOGFILE might be the friend you're looking for if you go the wireshark route: https://everything.curl.dev/usingcurl/tls/sslkeylogfile.html

[pkropachev]

Ok, thanks!
We'd like to use it in tests for TLS versions and Cipher Suites. So, unfortunately Wireshark cannot be applied here.