The filestore keyword until now flagged a file, tx or ssn for storage as soon
as the keyword was inspected. This happens before flowbits and some other
keywords, so files were stored that weren't supposed to.
This patch makes the filestore keyword fill an array in the detect engine
thread ctx. Then if the full signature matches, a post-match filestore
function makes the store final.
Filestore keyword by default (... filestore; ... ) marks only the file in the
same direction as the rule match for storing. This makes sense when inspecting
individual files (filemagic, filename, etc) but not so much when looking at
suspicious file requests, where the actual file is in the response.
The filestore keyword now takes 2 optional options:
filestore:<direction>,<scope>;
By default the direction is "same as rule match", and scope is "currently
inspected file".
For direction the following values are possible: "request" and "to_server",
"response" and "to_client", "both".
For scope the following values are possible: "tx" for all files in the current
HTTP/1.1 transation, "ssn" and "flow" for all files in the session/flow.
For the above case, where a suspious request should lead to a response file
download, this would work:
alert http ... content:"/suspicious/"; http_uri; filestore:response; ...
Victor Julien