Project

General

Profile

Actions

Feature #3260

open

SMTP Base64 Decoding of Message Body

Added by Brandon Murphy over 4 years ago. Updated about 4 years ago.

Status:
New
Priority:
Normal
Assignee:
Target version:
Effort:
Difficulty:
Label:
Protocol

Description

In attempting to write signatures for the Base64 decoded message body (not an attachment) I find that signatures do not fire as expected.

FWIW, I've observed the same issue for quoted-printable encoding of the message body as well. But intend on opening another issue for that.

I have attached a zip that contains pcap, IDS output, rules, etc.

The pcap has two different tcp sessions, one which includes only a base64 message body (tcp.port 4204), and another that includes the same base64 as an attachment (tcp.port 44228). This was done to validate that base64 decoding of SMTP attachments worked and could be triggered via the file_data keyword as per https://redmine.openinfosecfoundation.org/issues/3190.

The pcap is capturing while using python scripts to read an EML and send it to a python "SMTP Sink". I then used tcprewrite to rewrite the src/dst ips from 127.0.0.1 to something more representative of the traffic I'm attempting to signature.

Please let me know if anything else is required.


Files

base64_message_body_trbl.zip (32.6 KB) base64_message_body_trbl.zip Brandon Murphy, 10/17/2019 06:42 PM

Related issues 3 (3 open0 closed)

Related to Suricata - Feature #3261: SMTP quoted-printable Decoding of Message BodyNewOISF DevActions
Related to Suricata - Task #4097: Suricon 2020 brainstormAssignedVictor JulienActions
Related to Suricata - Task #6443: Suricon 2023 brainstormAssignedVictor JulienActions
Actions

Also available in: Atom PDF