nginx: fix CVE-2021-3618

Backport with no change a patch from version 1.21.0.  This patch
was not cherry-picked by nginx to version 1.20.1.

Information about this CVE comes from
https://ubuntu.com/security/CVE-2021-3618.

Signed-off-by: Joe Slater <joe.slater@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

2 files changed, 109 insertions, 0 deletions

diff --git a/meta-webserver/recipes-httpd/nginx/files/CVE-2021-3618.patch b/meta-webserver/recipes-httpd/nginx/files/CVE-2021-3618.patch
new file mode 100644
index 0000000000..be42a1ed5e
--- /dev/null
+++ b/meta-webserver/recipes-httpd/nginx/files/CVE-2021-3618.patch
@@ -0,0 +1,107 @@
+From 6dafcdebde58577f4fcb190be46a0eb910cf1b96 Mon Sep 17 00:00:00 2001
+From: Maxim Dounin <mdounin@mdounin.ru>
+Date: Wed, 19 May 2021 03:13:31 +0300
+Subject: [PATCH 1/1] Mail: max_errors directive.
+
+Similarly to smtpd_hard_error_limit in Postfix and smtp_max_unknown_commands
+in Exim, specifies the number of errors after which the connection is closed.
+--- end of original header ---
+
+CVE: CVE-2021-3618
+
+Upstream-Status: Backport
+                 https://github.com/nginx/nginx.git
+                 commit 173f16f736c10eae46cd15dd861b04b82d91a37a
+
+Signed-off-by: Joe Slater <joe.slater@windriver.com>
+---
+ src/mail/ngx_mail.h             |  3 +++
+ src/mail/ngx_mail_core_module.c | 10 ++++++++++
+ src/mail/ngx_mail_handler.c     | 15 ++++++++++++++-
+ 3 files changed, 27 insertions(+), 1 deletion(-)
+
+diff --git a/src/mail/ngx_mail.h b/src/mail/ngx_mail.h
+index b865a3b9..76cae37a 100644
+--- a/src/mail/ngx_mail.h
++++ b/src/mail/ngx_mail.h
+@@ -115,6 +115,8 @@ typedef struct {
+     ngx_msec_t              timeout;
+     ngx_msec_t              resolver_timeout;
+ 
++    ngx_uint_t              max_errors;
++
+     ngx_str_t               server_name;
+ 
+     u_char                 *file_name;
+@@ -231,6 +233,7 @@ typedef struct {
+     ngx_uint_t              command;
+     ngx_array_t             args;
+ 
++    ngx_uint_t              errors;
+     ngx_uint_t              login_attempt;
+ 
+     /* used to parse POP3/IMAP/SMTP command */
+diff --git a/src/mail/ngx_mail_core_module.c b/src/mail/ngx_mail_core_module.c
+index 40831242..115671ca 100644
+--- a/src/mail/ngx_mail_core_module.c
++++ b/src/mail/ngx_mail_core_module.c
+@@ -85,6 +85,13 @@ static ngx_command_t  ngx_mail_core_commands[] = {
+       offsetof(ngx_mail_core_srv_conf_t, resolver_timeout),
+       NULL },
+ 
++    { ngx_string("max_errors"),
++      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
++      ngx_conf_set_num_slot,
++      NGX_MAIL_SRV_CONF_OFFSET,
++      offsetof(ngx_mail_core_srv_conf_t, max_errors),
++      NULL },
++
+       ngx_null_command
+ };
+ 
+@@ -163,6 +170,8 @@ ngx_mail_core_create_srv_conf(ngx_conf_t *cf)
+     cscf->timeout = NGX_CONF_UNSET_MSEC;
+     cscf->resolver_timeout = NGX_CONF_UNSET_MSEC;
+ 
++    cscf->max_errors = NGX_CONF_UNSET_UINT;
++
+     cscf->resolver = NGX_CONF_UNSET_PTR;
+ 
+     cscf->file_name = cf->conf_file->file.name.data;
+@@ -182,6 +191,7 @@ ngx_mail_core_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
+     ngx_conf_merge_msec_value(conf->resolver_timeout, prev->resolver_timeout,
+                               30000);
+ 
++    ngx_conf_merge_uint_value(conf->max_errors, prev->max_errors, 5);
+ 
+     ngx_conf_merge_str_value(conf->server_name, prev->server_name, "");
+ 
+diff --git a/src/mail/ngx_mail_handler.c b/src/mail/ngx_mail_handler.c
+index 0aaa0e78..71b81512 100644
+--- a/src/mail/ngx_mail_handler.c
++++ b/src/mail/ngx_mail_handler.c
+@@ -871,7 +871,20 @@ ngx_mail_read_command(ngx_mail_session_t *s, ngx_connection_t *c)
+         return NGX_MAIL_PARSE_INVALID_COMMAND;
+     }
+ 
+-    if (rc == NGX_IMAP_NEXT || rc == NGX_MAIL_PARSE_INVALID_COMMAND) {
++    if (rc == NGX_MAIL_PARSE_INVALID_COMMAND) {
++
++        s->errors++;
++
++        if (s->errors >= cscf->max_errors) {
++            ngx_log_error(NGX_LOG_INFO, c->log, 0,
++                          "client sent too many invalid commands");
++            s->quit = 1;
++        }
++
++        return rc;
++    }
++
++    if (rc == NGX_IMAP_NEXT) {
+         return rc;
+     }
+ 
+-- 
+2.25.1
+
diff --git a/meta-webserver/recipes-httpd/nginx/nginx_1.20.1.bb b/meta-webserver/recipes-httpd/nginx/nginx_1.20.1.bb
index 7f159a2a30..d686c627f2 100644
--- a/meta-webserver/recipes-httpd/nginx/nginx_1.20.1.bb
+++ b/meta-webserver/recipes-httpd/nginx/nginx_1.20.1.bb
@@ -1,5 +1,7 @@
 require nginx.inc
 
+SRC_URI += "file://CVE-2021-3618.patch"
+
 LIC_FILES_CHKSUM = "file://LICENSE;md5=206629dc7c7b3e87acb31162363ae505"
 
 SRC_URI[md5sum] = "8ca6edd5076bdfad30a69c9c9b41cc68"