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422e4892cc
When Suricata picks up a flow it assumes the first packet is toserver. In a perfect world without packet loss and where all sessions neatly start after Suricata itself started, this would be true. However, in reality we have to account for packet loss and Suricata starting to get packets for flows already active be for Suricata is (re)started. The protocol records on the wire would often be able to tell us more though. For example in SMB1 and SMB2 records there is a flag that indicates whether the record is a request or a response. This patch is enabling the procotol detection engine to utilize this information to 'reverse' the flow. There are three ways in which this is supported in this patch: 1. patterns for detection are registered per direction. If the proto was not recognized in the traffic direction, and midstream is enabled, the pattern set for the opposing direction is also evaluated. If that matches, the flow is considered to be in the wrong direction and is reversed. 2. probing parsers now have a way to feed back their understanding of the flow direction. They are now passed the direction as Suricata sees the traffic when calling the probing parsers. The parser can then see if its own observation matches that, and pass back it's own view to the caller. 3. a new pattern + probing parser set up: probing parsers can now be registered with a pattern, so that when the pattern matches the probing parser is called as well. The probing parser can then provide the protocol detection engine with the direction of the traffic. The process of reversing takes a multi step approach as well: a. reverse the current packets direction b. reverse most of the flows direction sensitive flags c. tag the flow as 'reversed'. This is because the 5 tuple is *not* reversed, since it is immutable after the flows creation. Most of the currently registered parsers benefit already: - HTTP/SMTP/FTP/TLS patterns are registered per direction already so they will benefit from the pattern midstream logic in (1) above. - the Rust based SMB parser uses a mix of pattern + probing parser as described in (3) above. - the NFS detection is purely done by probing parser and is updated to consider the direction in that parser. Other protocols, such as DNS, are still to do. Ticket: #2572 |
6 years ago | |
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| src | 6 years ago | |
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| Cargo.toml.in | 6 years ago | |
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