This changeset makes changes to the TX logging path. Since the txn
is passed to the TX logger, the TX can be used directly instead of
through the TX id.
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
Cipher suites length should always be divisible by two. If it is a
odd number, which should not happen with normal traffic, it ends up
reading one byte too much.
Pass extension length to functions decoding extensions, instead of
passing the length left in the record. This enables us to also
decode empty extensions.
Much of encrypted traffic is uninteresting to Suricata. Once encrypted
communication starts, inspecting the packet payloads is generally
not interesting anymore. The default behavior is to disable the parts
of the detection engine and stream reassembly that relate to raw content
inspection.
The tls app-layer parser also had a crude option to affect this behavior:
set 'no-reassemble' to true went much further than the default behavior.
It disabled the TCP reassembly on the flow completely, disabled all
inspection on the flow and enabled bypass if available.
This patch adds a new option: full inspection. This continues to treat
a TLS session as any other, so without any limits to inspection.
The new option is implemented in a new config option 'encrypt-handling',
that replaces 'no-reassemble'. The new option has 3 values:
'default', 'full' and 'bypass'. Default is the current default behavior,
'bypass' is the current 'no-reassemble = true' behavior and 'full'
is the new full inspection mode.
Also remove the now useless 'state' argument from the SetTxDetectState
calls. For those app-layer parsers that use a state == tx approach,
the state pointer is passed as tx.
Update app-layer parsers to remove the unused call and update the
modified call.
Avoid looping in transaction output.
Update app-layer API to store the bits in one step
and retrieve the bits in a single step as well.
Update users of the API.
Victor Julien
Nick Price
Philippe Antoine
Jeff Lucovsky
Mats Klepsland
Jason Ish