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Bug #4311

closed

Transformation keyword can’t trigger an alert

Added by Jeff Lucovsky over 1 year ago. Updated over 1 year ago.

Status:
Closed
Priority:
Normal
Assignee:
Target version:
Affected Versions:
Effort:
Difficulty:
Label:

Description

I test the transformation keyword url_decode by writing 2 rules. And I get an alert by only using rule2.
However, if I using rule1 and rule2 together, then no alert occurs.

rule1:
alert http any any -> $HOME_NET any (msg:"detecting (/etc/passwd)"; flow:to_server,established; http.request_body; content:"\\\etc\\\passwd")

rule2:
alert http any any -> $HOME_NET any (msg:"detecting (/etc/passwd)"; flow:to_server,established; http.request_body; url_decode; content:"\\\etc\\\passwd")

I debug the detection part of the code and figuring out the workflow of transformation. If a rule file containing rule1 detecting a sticky buffer and rule2 detecting the sticky buffer after transformation, Suricata starts from inepecting the original sticky buffer. After this process, the sticky buffer would be flagged as "already inspected". So transformation can't be performed on this sticky buffer since it's already taken and inspected. Therefore, rule2 can't trigger any alert.

I wonder, if it's a BUG of transformation. I can't find any other useful information through the [documentation](https://suricata.readthedocs.io/en/suricata-6.0.0/rules/transforms.h).


Files

http-forum.pcap (2.03 KB) http-forum.pcap Jeff Lucovsky, 12/12/2020 01:30 PM

Related issues 1 (0 open1 closed)

Copied from Bug #4199: Transformation keyword can’t trigger an alert ClosedVictor JulienActions
Actions #1

Updated by Jeff Lucovsky over 1 year ago

  • Copied from Bug #4199: Transformation keyword can’t trigger an alert added
Actions #2

Updated by Victor Julien over 1 year ago

  • Status changed from Assigned to In Progress
  • Assignee changed from Shivani Bhardwaj to Victor Julien
  • Affected Versions 6.0.1 added
Actions #3

Updated by Victor Julien over 1 year ago

  • Status changed from In Progress to Closed
  • Priority changed from High to Normal
Actions

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