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Resolves: RHEL-12518 - nginx: HTTP/2: Multiple HTTP/2 enabled web servers are

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vulnerable to a DDoS attack (Rapid Reset Attack) (CVE-2023-44487)
This commit is contained in:
Luboš Uhliarik 2023-10-16 19:42:42 +02:00
parent fef0a05b6b
commit ba15c0f4a4
2 changed files with 82 additions and 1 deletions
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74
0008-CVE-2023-44487-HTTP-2-per-iteration-stream-handling.patch Normal file
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@ -0,0 +1,74 @@
From b6aa9504cdfb6391d895dcbddc87b9260ea6968c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lubo=C5=A1=20Uhliarik?= <luhliari@redhat.com>
Date: Wed, 11 Oct 2023 09:59:23 +0200
Subject: [PATCH] CVE-2023-44487 - 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.
---
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 3611a2e..291677a 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;
@@ -1320,6 +1321,14 @@ 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)
@@ -1385,6 +1394,12 @@ 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 3492297..6a7aaa6 100644
--- a/src/http/v2/ngx_http_v2.h
+++ b/src/http/v2/ngx_http_v2.h
@@ -125,6 +125,8 @@ 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;

9
nginx.spec
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@ -41,7 +41,7 @@
Name: nginx
Epoch: 1
Version: 1.20.1
Release: 14%{?dist}
Release: 15%{?dist}
Summary: A high performance web server and reverse proxy server
# BSD License (two clause)
@ -91,6 +91,9 @@ Patch5: 0006-Fix-ALPACA-security-issue.patch
# downstream patch for RHEL - https://bugzilla.redhat.com/show_bug.cgi?id=2028781
Patch6: 0007-Enable-TLSv1.3-by-default.patch
# security patch - https://issues.redhat.com/browse/RHEL-12518
Patch7: 0008-CVE-2023-44487-HTTP-2-per-iteration-stream-handling.patch
BuildRequires: make
BuildRequires: gcc
BuildRequires: gnupg2
@ -602,6 +605,10 @@ fi
%changelog
* Mon Oct 16 2023 Luboš Uhliarik <luhliari@redhat.com> - 1:1.20.1-15
- Resolves: RHEL-12518 - nginx: HTTP/2: Multiple HTTP/2 enabled web servers are
vulnerable to a DDoS attack (Rapid Reset Attack) (CVE-2023-44487)
* Thu Nov 24 2022 Luboš Uhliarik <luhliari@redhat.com> - 1:1.20.1-14
- Resolves: #2086527 - Fix logrotate config and nginx log dir permissions