The added disable-certificate-events-known-certs.zeek disables repeated
X509 events in SSL connections, given that the connection terminates at
the same server and used the samt SNI as a previously seen connection
with the same certificate.
For people that see significant amounts of TLS 1.2 traffic, this could
reduce the amount of raised events significantly - especially when a
lot of connections are repeat connections to the same servers.
The practical impact of not raising these events is actually very little
- unless a script directly interacts with the x509 events, everything
works as before - the x509 variables in the connection records are still
being set (from the cache).
This policy script significantly extends the details that are logged
about SSL/TLS handshakes.
I am a bit tempted to just make this part of the default log - but it
does add a bunch logging overhead for each connection.
Extract-certs-pem writes pem files to a dedicated file; since it does
not really work in cluster-environments it was never super helpful.
This commit deprecates this file and, instead, adds
log-certs-base64.zeek, which adds the base64-encoded certificate (which
is basically equivalent with a PEM) to the log-file. Since, nowadays,
the log-files are deduplicates this should not add a huge overhead.
Several limitations still apply:
- TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 is the only supported cipher suite
- Some tests are broken due to a failing assertion regarding bytestring
- No newly written tests for decryption (the patch was tested extensively for our paper)
- Several small open technical questions marked with FIXME
- Architecture in the ssl module might not be optimal
These are no longer loaded by default due to the performance impact they
cause simply by being loaded (they have event handlers for commonly
generated events) and they aren't generally useful enough to justify it.
This commit removed functions/events that have been deprecated in Bro
2.6. It also removes the detection code that checks if the old
communication framework is used (since all the functions that are
checked were removed).
Addresses parts of GH-243
