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nginx: fix CVE-2023-44487

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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.

Signed-off-by: Meenali Gupta <meenali.gupta@windriver.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
This commit is contained in:
Meenali Gupta 2023-12-21 03:45:50 +00:00 committed by Armin Kuster
parent b0d67900ae
commit 8e1f0fa6bf
2 changed files with 81 additions and 0 deletions
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80
meta-webserver/recipes-httpd/nginx/files/CVE-2023-44487.patch Normal file
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@ -0,0 +1,80 @@
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] nginx: 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

1
meta-webserver/recipes-httpd/nginx/nginx.inc
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@ -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