From: Shivani Bhardwaj <shivani@oisf.net>
Date: Tue, 25 Apr 2023 07:12:16 +0000 (+0530)
Subject: smtp: return on line completion
X-Git-Tag: suricata-6.0.12~15
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e95e9281caec46afeb0dadf95969c353ce8850a2;p=thirdparty%2Fsuricata.git

smtp: return on line completion

Problem:
If we receive a long line w/o LF, we cap it to 4k bytes and wait until a
line with LF comes in order to consider the previous line complete. Any
data post the 4k bytes is discarded. Currently, if a line with LF comes
in after a long line, we reset all the parameters used for processing it
like the line.len and line.delim_len but we still make the call to
SMTPProcessRequest fn without even the need to process anything. Since
such a line (with len and delim_len set to 0) should not reach mime
decoder, a debug assertion triggers there in this case.

Fix:
Make sure to return early as the line has to be skipped and not
processed at all.

Bug 6019

(cherry picked from commit c0067a5fffeb8b014b6756a572afe437d2bb561d)
---

diff --git a/src/app-layer-smtp.c b/src/app-layer-smtp.c
index f3bcd623ee..46637fd6ae 100644
--- a/src/app-layer-smtp.c
+++ b/src/app-layer-smtp.c
@@ -1051,6 +1051,13 @@ static int SMTPProcessRequest(SMTPState *state, Flow *f,
     SCEnter();
     SMTPTransaction *tx = state->curr_tx;
 
+    /* If current input is to be discarded because it completes a long line,
+     * line's length and delimeter len are reset to 0. Skip processing this line.
+     * This line is only to get us out of the state where we should discard any
+     * data till LF. */
+    if (state->current_line_len == 0 && state->current_line_delimiter_len == 0) {
+        return 0;
+    }
     if (state->curr_tx == NULL || (state->curr_tx->done && !NoNewTx(state))) {
         tx = SMTPTransactionCreate();
         if (tx == NULL)