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scripts/smb2-main: Reset script-level state upon smb2_discarded_messages_state()

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This is similar to what the external corelight/zeek-smb-clear-state script
does, but leverages the smb2_discarded_messages_state() event instead of
regularly checking on the state of SMB connections.

The pcap was created using the dperson/samba container image and mounting
a share with Linux's CIFS filesystem, then copying the content of a
directory with 100 files. The test uses a BPF filter to imitate mostly
"half-duplex" traffic.
This commit is contained in:
Arne Welzel 2023-04-25 17:19:14 +02:00
parent 5caab1a667
commit 3ac877e20d
8 changed files with 89 additions and 0 deletions
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7
scripts/base/protocols/smb/main.zeek
View file

@ -44,6 +44,13 @@ export {
PRINT_CLOSE,
};
## Whether to reset a connection's SMB script state whenever a
## :zeek:see:`smb2_discarded_messages_state` event is raised.
##
## This setting protects from unbounded script state growth in
## environments with high capture loss or traffic anomalies.
option enable_clear_script_state = T;
## This record is for the smb_files.log
type FileInfo: record {
## Time when the file was first discovered.

24
scripts/base/protocols/smb/smb2-main.zeek
View file

@ -1,3 +1,5 @@
@load base/frameworks/notice/weird
@load ./main
module SMB2;
@ -344,3 +346,25 @@ event smb2_close_request(c: connection, hdr: SMB2::Header, file_id: SMB2::GUID)
#Reporter::warning("attempting to close an unknown file!");
}
}
event smb2_discarded_messages_state(c: connection, state: string)
{
if ( ! c?$smb_state )
return;
local addl = fmt("state=%s fid_map=%s tid_map=%s pending_cmds=%s pipe_map=%s",
state, |c$smb_state$fid_map|, |c$smb_state$tid_map|,
|c$smb_state$pending_cmds|, |c$smb_state$pipe_map|);
Reporter::conn_weird("SMB_discarded_messages_state", c, addl, "SMB2");
if ( ! SMB::enable_clear_script_state )
return;
# Wipe out script-level state for this connection.
c$smb_state$fid_map = table();
c$smb_state$pending_cmds = table();
# Not expected to grow overly large and the original
# zeek-smb-clear-state package didn't reset these either.
# c$smb_state$tid_map = table();
# c$smb_state$pipe_map = table();
}