Tag: TLS

badssl.com

Today I discovered badssl.com, a very useful website to test various exceptional TLS/SSL cases. E.g., I tested what will happen if client supports TLS 1.3 only while server supports TLS 1.2 only:

# openssl s_client -connect tls-v1-2.badssl.com:1012 -tls1_3
CONNECTED(00000005)
01000000:error:0A000410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure:ssl/record/rec_layer_s3.c:1584:SSL alert number 40
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 7 bytes and written 253 bytes
Verification: OK
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
---

Use OpenSSL to simulate TLS 1.3 “Session Resumption”

Thanks the great help from OpenSSL community, I finally can simulate an TLS 1.3 “Session Resumption”. The Operation System I used is OmniOS, and OpenSSL version is 1.1.1k, but I think the methods here can also be applied to other platforms:

(1) Open one terminal to launch tcpdump to capture TLS packets:

$ pfexec /opt/ooce/sbin/tcpdump -w tls.pcap port 443

(2) Open another terminal to initiate the first TLS 1.3 session:

$ openssl s_client -connect cloudflare.com:443 -tls1_3 -sess_out sess.pem -keylogfile keys1.txt
......

Once the connection is established, input “GET /” to trigger TLS 1.3 Server to send “New Session Ticket” message, and this will be saved in sess.pem file.

(3) Initiate another TLS 1.3 session to reuse the saved “Session Ticket“:

$ echo | openssl s_client -connect cloudflare.com:443 -tls1_3 -sess_in sess.pem -keylogfile keys2.txt

(4) Stop the tcpdump process.

(5) Combine two keys file into one:

$ cat keys1.txt keys2.txt > keys.txt

Then the keys.txt can be used to decrypt the two TLS 1.3 sessions (refer Use Wireshark to decrypt TLS flows).

Use Wireshark to decrypt TLS flows

TLS debugging is an awesome introduction of using Wireshark to debug TLS issues (The presentation material can be found here). I just summarise how to decrypt TLS flows here:

(1) Set the filter and capture only TLS flows:

(2) Open chromium and save session secrets in command line:

SSLKEYLOGFILE="$PWD/keys.txt" /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --user-data-dir=/tmp/cr

(3)After saving pcap file, Load key and decrypt TLS flows: