Victor Julien
6792375d62
A flow that hit an unrecoverable ssh parse error (invalid banner or invalid record) was never visible in the eve ssh output: the log condition only admitted a successful handshake (both directions at kex or session), and the tx logger is one-shot, so the successful-handshake log fired before a later failure could be reported and the failure was then silent - the reason was only visible through the app-layer events. The log condition is now failure-only: the failure latches, so the object is emitted exactly once - at the failure, carrying the error field (invalid_banner / invalid_record) and the state field (the state the failure occurred in - banner, kex, or session if a later record fails after NewKeys) - and successful flows are logged at the flow-end flush, where the engine logs unconditionally. Logging on the success condition mid-flow would consume the one-shot tx log and drop a later failure, so it is not done. The state field is emitted only alongside the error. The object may be error + state only, when no banner was parsed. A unit test pins the condition for a failed, a banner-only and a both-at-kex flow (the failure admits the log on the failing delivery); the user guide and eve reference doc commits that follow carry the field docs. That flow-end flush is skipped for flows that end without a further app-layer update, though: in IPS/firewall mode a drop disables the app layer (StreamTcpCheckFlowDrops -> StreamTcpDisableAppLayer), after which no app-layer update reaches the tx loggers, and a bypassed flow gets no flow-end packet either. A successful ssh record - e.g. one that only saw the banners - was therefore never emitted for those flows. The hook is the app-layer end: on the transition to app-layer EOF, StreamTcpDisableAppLayer raises FLOW_APP_LAYER_FLUSH_PENDING, and FlowUpdateState raises it on the transition to a bypassed state; OutputTxLog runs the tx loggers once for the next packet, also when that packet itself has no app-layer update and is not marked established (the disabling packet returns from the stream engine before that), and flow-worker clears the flag when it frees the app layer of a bypassed flow. The flush is deliberately not a flow-end flush: when the flush is the only reason to run the loggers, eof is not forced, so each logger's condition decides and no other parser starts logging records it suppressed; a disabling packet that does carry an app-layer update keeps the existing EOF behaviour. SSHTxLogCondition admits an IPS drop or a bypass, so the pending record is emitted there; an IDS drop does not end the app layer, so the condition stays failure-only - a later failure still wins, and the success record is emitted by the flow-end flush, which the flow timeout path now also runs for IDS-dropped flows. The unrelated schema-sort ordering of the new state keys is fixed up as well. Ticket: #9046.
Suricata
Introduction
Suricata is a network IDS, IPS and NSM engine developed by the OISF and the Suricata community.
Resources
Contributing
We're happily taking patches and other contributions. Please see our Contribution Process for how to get started.
Suricata is a complex piece of software dealing with mostly untrusted input. Mishandling this input will have serious consequences:
- in IPS mode a crash may knock a network offline
- in passive mode a compromise of the IDS may lead to loss of critical and confidential data
- missed detection may lead to undetected compromise of the network
In other words, we think the stakes are pretty high, especially since in many common cases the IDS/IPS will be directly reachable by an attacker.
For this reason, we have developed a QA process that is quite extensive. A consequence is that contributing to Suricata can be a somewhat lengthy process.
On a high level, the steps are:
- GitHub-CI based checks. This runs automatically when a pull request is made.
- Review by devs from the team and community
- QA runs from private QA setups. These are private due to the nature of the test traffic.
Overview of Suricata's QA steps
OISF team members are able to submit builds to our private QA setup. It will run a series of build tests and a regression suite to confirm no existing features break.
The final QA runs takes a few hours minimally, and generally runs overnight. It currently runs:
- extensive build tests on different OS', compilers, optimization levels, configure features
- static code analysis using cppcheck, scan-build
- runtime code analysis using valgrind, AddressSanitizer, LeakSanitizer
- regression tests for past bugs
- output validation of logging
- unix socket testing
- pcap based fuzz testing using ASAN and LSAN
- traffic replay based IDS and IPS tests
Next to these tests, based on the type of code change further tests can be run manually:
- traffic replay testing (multi-gigabit)
- large pcap collection processing (multi-terabytes)
- fuzz testing (might take multiple days or even weeks)
- pcap based performance testing
- live performance testing
- various other manual tests based on evaluation of the proposed changes
It's important to realize that almost all of the tests above are used as acceptance tests. If something fails, it's up to you to address this in your code.
One step of the QA is currently run post-merge. We submit builds to the Coverity Scan program. Due to limitations of this (free) service, we can submit once a day max. Of course it can happen that after the merge the community will find issues. For both cases we request you to help address the issues as they may come up.
FAQ
Q: Will you accept my PR?
A: That depends on a number of things, including the code quality. With new features it also depends on whether the team and/or the community think the feature is useful, how much it affects other code and features, the risk of performance regressions, etc.
Q: When will my PR be merged?
A: It depends, if it's a major feature or considered a high risk change, it will probably go into the next major version.
Q: Why was my PR closed?
A: As documented in the Suricata GitHub workflow, we expect a new pull request for every change.
Normally, the team (or community) will give feedback on a pull request after which it is expected to be replaced by an improved PR. So look at the comments. If you disagree with the comments we can still discuss them in the closed PR.
If the PR was closed without comments it's likely due to QA failure. If the GitHub-CI checks failed, the PR should be fixed right away. No need for a discussion about it, unless you believe the QA failure is incorrect.
Q: The compiler/code analyser/tool is wrong, what now?
A: To assist in the automation of the QA, we're not accepting warnings or errors to stay. In some cases this could mean that we add a suppression if the tool supports that (e.g. valgrind, DrMemory). Some warnings can be disabled. In some exceptional cases the only 'solution' is to refactor the code to work around a static code checker limitation false positive. While frustrating, we prefer this over leaving warnings in the output. Warnings tend to get ignored and then increase risk of hiding other warnings.
Q: I think your QA test is wrong
A: If you really think it is, we can discuss how to improve it. But don't come to this conclusion too quickly, more often it's the code that turns out to be wrong.
Q: Do you require signing of a contributor license agreement?
A: Yes, we do this to keep the ownership of Suricata in one hand: the Open Information Security Foundation. See http://suricata.io/about/open-source/ and http://suricata.io/about/contribution-agreement/