This commit revamps the handling of analyzer violations that happen
before an analyzer confirms the protocol.
The current state is that an analyzer is disabled after 5 violations, if
it has not been confirmed. If it has been confirmed, it is disabled
after a single violation.
The reason for this is a historic mistake. In Zeek up to versions 1.5,
analyzers were unconditianally removed when they raised the first
protocol violation.
When this script was ported to the new layout for Zeek 2.0 in
b4b990cfb5, a logic error was introduced
that caused analyzers to no longer be disabled if they were not
confirmed.
This was the state for ~8 years, till the DPD::max_violations options
was added, which instates the current approach of disabling unconfirmed
analyzers after 5 violations. Sadly, there is not much discussion about
this change - from my hazy memory, I think this was discovered during
performance tests and the new behavior was added without checking into
the history of previous changes.
This commit reinstates the originally intended behavior of DPD. When an
analyzer that has not been confirmed raises a protocol violation, it is
immediately removed from the connection. This also makes a lot of sense
- this allows the analyzer to be in a "tasting" phase at the beginning
of the connection, and to error out quickly once it realizes that it was
attached to a connection not containing the desired protocol.
This change also removes the DPD::max_violations option, as it no longer
serves any purpose after this change. (In practice, the option remains
with an &deprecated warning, but it is no longer used for anything).
There are relatively minimal test-baseline changes due to this; they are
mostly triggered by the removal of the data structure and by less
analyzer errors being thrown, as unconfirmed analyzers are disabled
after the first error.
Processing out-of-order commands or finishing commands based on invalid
server responses resulted in inconsistent analyzer state, potentially
triggering null pointer references for crafted traffic.
This commit reworks cf9fe91705 such that
too many pending commands are simply discarded, rather than any attempt
being made to process them. Further, invalid server responses do not
result in command completion anymore.
Test PCAP was crafted based on traffic produced by the OSS-Fuzz reproducer.
Closes#215
The cmds list may grow unbounded due to the POP3 analyzer being in
multiLine mode after seeing `AUTH` in a Redis connection, but never
a `.` terminator. This can easily be provoked by the Redis ping
command.
This adds two heuristics: 1) Forcefully process the oldest commands in
the cmds list and cap it at max_pending_commands. 2) Start raising
analyzer violations if the client has been using more than
max_unknown_client_commands commands (default 10).
Closes#3936
