[nginx] Mail: fixed handling of invalid SMTP commands split between reads.

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/6a81d96d3733
branches:  
changeset: 7836:6a81d96d3733
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Wed May 19 03:13:15 2021 +0300
description:
Mail: fixed handling of invalid SMTP commands split between reads.

Previously, if an invalid SMTP command was split between reads, nginx failed
to wait for LF before returning an error, and interpreted the rest of the
command received later as a separate command.

The sw_invalid state in ngx_mail_smtp_parse_command(), introduced in
04e43d03e153, did not work, since ngx_mail_smtp_auth_state() clears
s->state when returning an error due to NGX_MAIL_PARSE_INVALID_COMMAND.
And not clearing s->state will introduce another problem: the rest
of the command would trigger duplicate error when rest of the command is
received.

Fix is to return NGX_AGAIN from ngx_mail_smtp_parse_command() until full
command is received.

diffstat:

 src/mail/ngx_mail_parse.c |  6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diffs (21 lines):

diff -r c72d8839f427 -r 6a81d96d3733 src/mail/ngx_mail_parse.c
--- a/src/mail/ngx_mail_parse.c	Wed May 19 03:13:12 2021 +0300
+++ b/src/mail/ngx_mail_parse.c	Wed May 19 03:13:15 2021 +0300
@@ -846,14 +846,14 @@ invalid:
     for (p = s->buffer->pos; p < s->buffer->last; p++) {
         if (*p == LF) {
             s->state = sw_start;
-            p++;
-            break;
+            s->buffer->pos = p + 1;
+            return NGX_MAIL_PARSE_INVALID_COMMAND;
         }
     }
 
     s->buffer->pos = p;
 
-    return NGX_MAIL_PARSE_INVALID_COMMAND;
+    return NGX_AGAIN;
 }