[nginx] Mail: stricter checking of IMAP tags.

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/4b15f1b92100
branches:  
changeset: 7842:4b15f1b92100
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Wed May 19 03:13:26 2021 +0300
description:
Mail: stricter checking of IMAP tags.

Only "A-Za-z0-9-._" characters now allowed (which is stricter than what
RFC 3501 requires, but expected to be enough for all known clients),
and tags shouldn't be longer than 32 characters.

diffstat:

 src/mail/ngx_mail_parse.c |  11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diffs (21 lines):

diff -r ccdf83bee8c1 -r 4b15f1b92100 src/mail/ngx_mail_parse.c
--- a/src/mail/ngx_mail_parse.c	Wed May 19 03:13:23 2021 +0300
+++ b/src/mail/ngx_mail_parse.c	Wed May 19 03:13:26 2021 +0300
@@ -265,6 +265,17 @@ ngx_mail_imap_parse_command(ngx_mail_ses
             case LF:
                 s->state = sw_start;
                 return NGX_MAIL_PARSE_INVALID_COMMAND;
+            default:
+                if ((ch < 'A' || ch > 'Z') && (ch < 'a' || ch > 'z')
+                    && (ch < '0' || ch > '9') && ch != '-' && ch != '.'
+                    && ch != '_')
+                {
+                    goto invalid;
+                }
+                if (p - s->buffer->start > 31) {
+                    goto invalid;
+                }
+                break;
             }
             break;