If an SMB record is seen in the wrong direction, set an event on the PDU
frame and don't process the record in the state.
No error is returned, so the next record will be processed.
The bits were being parsed in the order they're displayed in Wireshark,
rather than the order they were being seen on the wire, resulting in
direction and async being 0 more often than they should be.
Instead of bits, take the 4 bytes as an le_u32 and just use bit masks to
extract what we need into a struct, I think its easier to reason about
this way when comparing to the Microsoft documentation.
SMB1 record parsing code simplification.
Frames:
nbss.pdu
nbss.hdr
nbss.data
smb1.pdu
smb1.hdr
smb1.data
smb2.pdu
smb2.hdr
smb2.data
smb3.pdu
smb3.hdr
smb3.data
The smb* frames are created for valid SMB records.
Unfortunately, the transition to nom 5 (and functions instead of macros)
has side-effects, one of them being requiring lots of types annotations
when using a parsing, for ex in a match instruction.
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
parse_smb2_response_read()/parse_smb2_response_write() can be called on
incomplete data, so they didn't use the read/write length field to grab
the data field. Instead it just used rest(). However in some cases
SMB2 records have trailing data, which would be included in the
READ/WRITE data.
This patch addresses this by using the length field if enough data is
available.
Implement SMB app-layer parser for SMB1/2/3. Features:
- file extraction
- eve logging
- existing dce keyword support
- smb_share/smb_named_pipe keyword support (stickybuffers)
- auth meta data extraction (ntlmssp, kerberos5)
Philippe Antoine
Jason Ish
Victor Julien
Pierre Chifflier
Philippe Antoine
Victor Julien