Snort mailing list archives

Re: smtp: ignore flow after STARTTLS if ignore_tls_data is set


From: Florian Westphal <florian.westphal () sophos com>
Date: Mon, 26 Aug 2013 17:40:00 +0200

Bhagya Bantwal <bbantwal () sourcefire com> wrote:
Florian,

Thank you for your email. Snort actually does whitelist the SMTP traffic.
Code that does that is in SnortSMTP (dir == SMTP_PKT_FROM_CLIENT)
line:2370. Snort only parses the Client and server certificates (Not the
complete handshake)

       if ((smtp_ssn->state == STATE_TLS_DATA)
                || (smtp_ssn->state == STATE_TLS_SERVER_PEND))
        {
            /* if we're ignoring tls data, set a zero length alt buffer */
            if (smtp_eval_config->ignore_tls_data)
            {
                _dpd.SetAltDecode(0);
                _dpd.streamAPI->stop_inspection( p->stream_session_ptr, p,
SSN_DIR_BOTH, -1, 0 );
                return;
            }
        }

Hm.  Does not work for me with 2.9.5.3.

http://strlen.de/fw/starttls-pcap.cap

$ src/snort -r ~/starttls-test.cap  -c snort.conf -k none -K none -P 0xffff
[..]
Verdicts:
      Allow:           26 (100.000%)
      Block:            0 (  0.000%)
    Replace:            0 (  0.000%)
  Whitelist:            0 (  0.000%)
  Blacklist:            0 (  0.000%)
     Ignore:            0 (  0.000%)

With patch, i get "Whitelist: 16"

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