nginx: fix CVE-2023-44487

The HTTP/2 protocol allows a denial of service (server resource consumption)
because request cancellation can reset many streams quickly, as exploited in
the wild in August through October 2023.

References:
https://nvd.nist.gov/vuln/detail/CVE-2023-44487

Signed-off-by: Meenali Gupta <meenali.gupta@windriver.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

2 files changed, 80 insertions, 0 deletions

diff --git a/meta-webserver/recipes-httpd/nginx/files/CVE-2023-44487.patch b/meta-webserver/recipes-httpd/nginx/files/CVE-2023-44487.patch
new file mode 100644
index 0000000000..7df62fd61a
--- /dev/null
+++ b/meta-webserver/recipes-httpd/nginx/files/CVE-2023-44487.patch
@@ -0,0 +1,79 @@
+From 95d09cafae12d4b314df32027b97e828ecf798de Mon Sep 17 00:00:00 2001
+From: Maxim Dounin <mdounin@mdounin.ru>
+Date: Tue, 10 Oct 2023 15:13:39 +0300
+Subject: [PATCH] HTTP/2: per-iteration stream handling limit. To ensure that
+attempts to flood servers with many streams are detected early, a limit of no
+more than 2 * max_concurrent_streams new streams per one event loop iteration
+was introduced.  This limit is applied even if max_concurrent_streams is not
+yet reached - for example, if corresponding streams are handled synchronously
+or reset.
+
+Further, refused streams are now limited to maximum of max_concurrent_streams
+and 100, similarly to priority_limit initial value, providing some tolerance
+to clients trying to open several streams at the connection start, yet
+low tolerance to flooding attempts.
+
+Upstream-Status: Backport [https://github.com/nginx/nginx/commit/6ceef192e7af1c507826ac38a2d43f08bf265fb9]
+CVE: CVE-2023-44487
+
+Signed-off-by: Meenali Gupta <meenali.gupta@windriver.com>
+---
+ src/http/v2/ngx_http_v2.c | 15 +++++++++++++++
+ src/http/v2/ngx_http_v2.h |  2 ++
+ 2 files changed, 17 insertions(+)
+
+diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
+index ea3f27c..1116e56 100644
+--- a/src/http/v2/ngx_http_v2.c
++++ b/src/http/v2/ngx_http_v2.c
+@@ -361,6 +361,7 @@ ngx_http_v2_read_handler(ngx_event_t *rev)
+     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http2 read handler");
+
+     h2c->blocked = 1;
++    h2c->new_streams = 0;
+
+     if (c->close) {
+         c->close = 0;
+@@ -1321,6 +1322,14 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
+         goto rst_stream;
+     }
+
++    if (h2c->new_streams++ >= 2 * h2scf->concurrent_streams) {
++        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
++                      "client sent too many streams at once");
++
++        status = NGX_HTTP_V2_REFUSED_STREAM;
++        goto rst_stream;
++    }
++
+     if (!h2c->settings_ack
+         && !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG)
+         && h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW)
+@@ -1386,6 +1395,12 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
+
+ rst_stream:
+
++    if (h2c->refused_streams++ > ngx_max(h2scf->concurrent_streams, 100)) {
++        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
++                      "client sent too many refused streams");
++        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_NO_ERROR);
++    }
++
+     if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) {
+         return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
+     }
+diff --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
+index 4e25293..b9daf92 100644
+--- a/src/http/v2/ngx_http_v2.h
++++ b/src/http/v2/ngx_http_v2.h
+@@ -124,6 +124,8 @@ struct ngx_http_v2_connection_s {
+     ngx_uint_t                       processing;
+     ngx_uint_t                       frames;
+     ngx_uint_t                       idle;
++    ngx_uint_t                       new_streams;
++    ngx_uint_t                       refused_streams;
+     ngx_uint_t                       priority_limit;
+
+     ngx_uint_t                       pushing;
+--
+2.40.0
diff --git a/meta-webserver/recipes-httpd/nginx/nginx.inc b/meta-webserver/recipes-httpd/nginx/nginx.inc
index 9f93c7051d..9cbe35a13a 100644
--- a/meta-webserver/recipes-httpd/nginx/nginx.inc
+++ b/meta-webserver/recipes-httpd/nginx/nginx.inc
@@ -23,6 +23,7 @@ SRC_URI = " \
     file://nginx.service \
     file://nginx-fix-pidfile.patch \
     file://0001-configure-libxslt-conf.patch \
+    file://CVE-2023-44487.patch \
 "
 
 inherit siteinfo update-rc.d useradd systemd