[nginx] Mail: handling of LOGIN IMAP command untagged response.

[noreply at nginx.com]

details:   https://github.com/nginx/nginx/commit/ce88b171236de50843dba2c427a8b3e42778f2ca
branches:  master
commit:    ce88b171236de50843dba2c427a8b3e42778f2ca
user:      Sergey Kandaurov <pluknet at nginx.com>
date:      Thu, 24 Oct 2024 00:52:21 +0400
description:
Mail: handling of LOGIN IMAP command untagged response.

In particular, an untagged CAPABILITY response as described in the
interim RFC 3501 internet drafts was seen in various IMAP servers.
Previously resulted in a broken connection, now an untagged response
is proxied to client.

---
 src/mail/ngx_mail_proxy_module.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/mail/ngx_mail_proxy_module.c b/src/mail/ngx_mail_proxy_module.c
index efed9ab3e..1c6d0372e 100644
--- a/src/mail/ngx_mail_proxy_module.c
+++ b/src/mail/ngx_mail_proxy_module.c
@@ -1019,12 +1019,36 @@ ngx_mail_proxy_read_response(ngx_mail_session_t *s, ngx_uint_t state)
             break;
 
         case ngx_imap_passwd:
+
+            /*
+             * untagged CAPABILITY response (draft-crispin-imapv-16),
+             * known to be sent by SmarterMail and Gmail
+             */
+
+            if (p[0] == '*' && p[1] == ' ') {
+                p += 2;
+
+                while (p < b->last - 1) {
+                    if (p[0] == CR && p[1] == LF) {
+                        p += 2;
+                        break;
+                    }
+
+                    p++;
+                }
+
+                if (b->last - p < 4) {
+                    return NGX_AGAIN;
+                }
+            }
+
             if (ngx_strncmp(p, s->tag.data, s->tag.len) == 0) {
                 p += s->tag.len;
                 if (p[0] == 'O' && p[1] == 'K') {
                     return NGX_OK;
                 }
             }
+
             break;
         }