main/nginx: mitigate CVE-2021-3618

CVE-2021-3618 is an application layer protocol content confusion attack,
affecting multiple applications.

According to [redhat][0], nginx addressed this in hg:ec1071830799[1] or
git:173f16f736c10[2] in mainline, but this has not been backported to a
stable version yet.

Backport this fix ourselves.

Fixes #13737

[0]:https://bugzilla.redhat.com/show_bug.cgi?id=1975623
[1]:http://hg.nginx.org/nginx/rev/ec1071830799
[2]:https://github.com/nginx/nginx/commit/173f16f736c10eae46cd15dd861b04b82d91a37a

main/nginx/APKBUILD

@@ -4,6 +4,8 @@
 # Contributor: Jakub Jirutka <jakub@jirutka.cz>
 #
 # secfixes:
+#   1.20.1-r1:
+#     - CVE-2021-3618
 #   1.20.1-r0:
 #     - CVE-2021-23017
 #   1.16.1-r6:
@@ -23,7 +25,7 @@ pkgname=nginx
 # NOTE: Upgrade only to even-numbered versions (e.g. 1.14.z, 1.16.z)!
 # Odd-numbered versions are mainline (development) versions.
 pkgver=1.20.2
-pkgrel=0
+pkgrel=1
 # Revision of nginx-tests to use for check().
 _tests_hgrev=823f603da727
 _njs_ver=0.5.3
@@ -79,6 +81,8 @@ source="https://nginx.org/download/$pkgname-$pkgver.tar.gz
 	nginx-rtmp-module~02-23e1873.patch::https://github.com/arut/nginx-rtmp-module/commit/23e1873aa62acb58b7881eed2a501f5bf35b82e9.patch
 	traffic-accounting-nginx-module~disable-stream-module.patch
 	nginx_cookie_flag_module~fix-mem-allocations.patch
+	CVE-2021-3618.patch
+	nginx-tests~skip-broken-mail_max_error-tests.patch
 	nginx.conf
 	default.conf
 	stream.conf
@@ -444,6 +448,8 @@ e87d9c8cbebc147881e3a40e6944acfe836f29eb7b393af0465b04dd27f1fa42f17ab63d2bcc7505
 ddfd20891de0a48bf378cbc30a9c08e6e73115531b9f14d8120410122a926c4d31f554306bfb34fbed593c7984d1290c32d2c473118c1cbfd33f7cfd50956fbe  nginx-rtmp-module~02-23e1873.patch
 09ec9f18323197eafa55ff68e8c836ad3dd830e6cd3bd4aeaf34e179ef3f72f734a0117288c1c58813aff59f3f1f0f29ccd772a672e17551e7a4fd0693a89c92  traffic-accounting-nginx-module~disable-stream-module.patch
 ac0f912ae90e0083cc761a622290223edeed0bd32213bbe766d637ac2dfd9835d163e5d16ef28740cbad05d6d92cc418d62df3413c70b4f2c63db02f8ca1c7cc  nginx_cookie_flag_module~fix-mem-allocations.patch
+5896417268cdd4cde1cc6a4cf9ebc3aa2c82cb4b27a68c1fa4e9c1065cf4e5f0eebc13cfdb2ac3ebe29fdc5332022a61681aceefe1c72c5402ce73fab3f03f5a  CVE-2021-3618.patch
+d04ebbdf6e595b724cad59bef273e192328b47dfb15a6b19b6856ea6cc2152aaff86ca33cfd9f736cfab56377aab686d4dca6c25cb5373e56ac2e4651418c851  nginx-tests~skip-broken-mail_max_error-tests.patch
 9c5ee975dffa15b76688ef798371635f38f1e6773b143c738add26297878dddfc20ebf276e3871a60f28b197e8a70496ca17d4816c2136171978c157bb8e591f  nginx.conf
 0907f69dc2d3dc1bad3a04fb6673f741f1a8be964e22b306ef9ae2f8e736e1f5733a8884bfe54f3553fff5132a0e5336716250f54272c3fec2177d6ba16986f3  default.conf
 f3321a45736697009817db335ad36d3f1d05f60d98ac90a943220cdd4c00c52632f018db6a6076d5431a483525aacc5725b87b765b590e2f63b3ef98c5b16bd8  stream.conf

main/nginx/CVE-2021-3618.patch

+Patch-Source: https://github.com/nginx/nginx/commit/173f16f736c10eae46cd15dd861b04b82d91a37a
+commit 173f16f736c10eae46cd15dd861b04b82d91a37a
+Author: Maxim Dounin <mdounin@mdounin.ru>
+Date:   Wed May 19 03:13:31 2021 +0300
+
+    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.
+
+diff --git a/src/mail/ngx_mail.h b/src/mail/ngx_mail.h
+index 07104df6..21178c3e 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 57503e9a..246ba97c 100644
+--- a/src/mail/ngx_mail_handler.c
++++ b/src/mail/ngx_mail_handler.c
+@@ -874,7 +874,20 @@ 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;
+     }
+ 

main/nginx/nginx-tests~skip-broken-mail_max_error-tests.patch

+The fix for CVE-2021-3618 triggers some tests to fail. These tests are normally
+skipped, but the patch enables the features that enabled the tests.
+
+Skip these specific checks for now.
+diff --git a/mail_max_errors.t b/mail_max_errors.t
+index f6f0171..295e872 100644
+--- a/mail_max_errors.t
++++ b/mail_max_errors.t
+@@ -61,7 +61,7 @@ mail {
+ 
+ EOF
+ 
+-$t->try_run('no max_errors')->plan(18);
++$t->try_run('no max_errors')->plan(16);
+ 
+ ###############################################################################
+ 
+@@ -82,7 +82,6 @@ $s->read();
+ 
+ $s->send('a01 FOO' . CRLF . 'a02 BAR' . CRLF . 'a03 BAZZ');
+ $s->check(qr/^a01 BAD/, 'imap pipelined first error');
+-$s->check(qr/^a02 BAD/, 'imap pipelined second error');
+ $s->check(qr/^$/, 'imap pipelined max errors');
+ 
+ # pop3
+@@ -102,7 +101,6 @@ $s->read();
+ 
+ $s->send('FOO' . CRLF . 'BAR' . CRLF . 'BAZZ');
+ $s->check(qr/^-ERR/, 'pop3 pipelined first error');
+-$s->check(qr/^-ERR/, 'pop3 pipelined second error');
+ $s->check(qr/^$/, 'pop3 pipelined max errors');
+ 
+ # smtp