zeek/scripts/base/protocols/ftp/files.zeek
Arne Welzel 31b548babc ftp: Reset fuid after logging
A user reported being confused about the fuid association of subsequent
FTP commands when a data transfer has completed. It seems reasonable to
unset fuid upon logging a FTP command which had a fuid.

The current behavior results in the PORT or PASV commands after a RETR or STOR
to have the fuid of the prior file transfer. Similarly, any CWD or DEL commands
following a file transfer will unnecessarily be logged with the fuid of the
prior file transfer.

This tickles the baselines for the private testing PCAP a lot, primarily
because there data connections in that pcap are never established properly.
E.g, the fuids FzDzid1Dxm9srVKHXf and FEfYX73q5C6GEQZXX9 have been re-used
for multiple commands.

This may look like we're losing information, but the fuids vanishing
in the normal btests belong to a LIST command that isn't logged by
default into ftp.log. If it was, the fuid would be attached to it.
2024-02-21 12:41:32 +01:00

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@load ./info
@load ./main
@load ./utils
@load base/utils/conn-ids
@load base/frameworks/files
module FTP;
export {
## Default file handle provider for FTP.
global get_file_handle: function(c: connection, is_orig: bool): string;
## Describe the file being transferred.
global describe_file: function(f: fa_file): string;
redef record fa_file += {
ftp: FTP::Info &optional;
};
}
function get_file_handle(c: connection, is_orig: bool): string
{
if ( [c$id$resp_h, c$id$resp_p] !in ftp_data_expected )
return "";
return cat(Analyzer::ANALYZER_FTP_DATA, c$start_time, c$id, is_orig);
}
function describe_file(f: fa_file): string
{
# This shouldn't be needed, but just in case...
if ( f$source != "FTP" )
return "";
for ( _, c in f$conns )
{
if ( c?$ftp )
return FTP::describe(c$ftp);
}
return "";
}
event zeek_init() &priority=5
{
Files::register_protocol(Analyzer::ANALYZER_FTP_DATA,
[$get_file_handle = FTP::get_file_handle,
$describe = FTP::describe_file]);
}
event file_over_new_connection(f: fa_file, c: connection, is_orig: bool) &priority=5
{
if ( [c$id$resp_h, c$id$resp_p] !in ftp_data_expected )
return;
local ftp = ftp_data_expected[c$id$resp_h, c$id$resp_p];
ftp$fuid = f$id;
f$ftp = ftp;
}
event file_sniff(f: fa_file, meta: fa_metadata) &priority=5
{
if ( ! f?$ftp )
return;
if ( ! meta?$mime_type )
return;
f$ftp$mime_type = meta$mime_type;
}