[nly]

Inaccurate. Most browsers will now be using ephemeral key exchange. You pretty much have to configure one of the end points to dump session keys to a log file, then load that in to wireshark alongside the packet dump.

[amelius]

It would be nice if there was some automated way to do this.

[mhils]

You can use mitmproxy [1] to dump the TLS Master Secrets for all connnections it intercepts [2]. The dumpfile goes straight into WireShark.

Obligatory disclaimer: I'm one of the mitmproxy authors - happy to answer any questions.

[1] https://mitmproxy.org/

[2] http://docs.mitmproxy.org/en/stable/dev/sslkeylogfile.html