1From 6ceef192e7af1c507826ac38a2d43f08bf265fb9 Mon Sep 17 00:00:00 2001
2From: Maxim Dounin <mdounin@mdounin.ru>
3Date: Wed, 10 Jan 2024 18:52:11 +0000
4Subject: [PATCH] HTTP/2: per-iteration stream handling limit.
5
6To ensure that attempts to flood servers with many streams are detected
7early, a limit of no more than 2 * max_concurrent_streams new streams per one
8event loop iteration was introduced.  This limit is applied even if
9max_concurrent_streams is not yet reached - for example, if corresponding
10streams are handled synchronously or reset.
11
12Further, refused streams are now limited to maximum of max_concurrent_streams
13and 100, similarly to priority_limit initial value, providing some tolerance
14to clients trying to open several streams at the connection start, yet
15low tolerance to flooding attempts.
16
17Upstream-Status: Backport [https://github.com/nginx/nginx/commit/6ceef192e7af1c507826ac38a2d43f08bf265fb9]
18CVE: CVE-2023-44487
19
20Signed-off-by: alperak <alperyasinak1@gmail.com>
21---
22 src/http/v2/ngx_http_v2.c | 15 +++++++++++++++
23 src/http/v2/ngx_http_v2.h |  2 ++
24 2 files changed, 17 insertions(+)
25
26diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
27index ea3f27c..1116e56 100644
28--- a/src/http/v2/ngx_http_v2.c
29+++ b/src/http/v2/ngx_http_v2.c
30@@ -361,6 +361,7 @@ ngx_http_v2_read_handler(ngx_event_t *rev)
31     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http2 read handler");
32
33     h2c->blocked = 1;
34+    h2c->new_streams = 0;
35
36     if (c->close) {
37         c->close = 0;
38@@ -1321,6 +1322,14 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
39         goto rst_stream;
40     }
41
42+    if (h2c->new_streams++ >= 2 * h2scf->concurrent_streams) {
43+        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
44+                      "client sent too many streams at once");
45+
46+        status = NGX_HTTP_V2_REFUSED_STREAM;
47+        goto rst_stream;
48+    }
49+
50     if (!h2c->settings_ack
51         && !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG)
52         && h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW)
53@@ -1386,6 +1395,12 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
54
55 rst_stream:
56
57+    if (h2c->refused_streams++ > ngx_max(h2scf->concurrent_streams, 100)) {
58+        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
59+                      "client sent too many refused streams");
60+        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_NO_ERROR);
61+    }
62+
63     if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) {
64         return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
65     }
66diff --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
67index 4e25293..b9daf92 100644
68--- a/src/http/v2/ngx_http_v2.h
69+++ b/src/http/v2/ngx_http_v2.h
70@@ -124,6 +124,8 @@ struct ngx_http_v2_connection_s {
71     ngx_uint_t                       processing;
72     ngx_uint_t                       frames;
73     ngx_uint_t                       idle;
74+    ngx_uint_t                       new_streams;
75+    ngx_uint_t                       refused_streams;
76     ngx_uint_t                       priority_limit;
77
78     ngx_uint_t                       pushing;
79