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77 lines
3.0 KiB
77 lines
3.0 KiB
5 months ago
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From b6aa9504cdfb6391d895dcbddc87b9260ea6968c Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Lubo=C5=A1=20Uhliarik?= <luhliari@redhat.com>
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Date: Wed, 11 Oct 2023 09:59:23 +0200
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Subject: [PATCH] CVE-2023-44487 - HTTP/2: per-iteration stream handling limit.
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To ensure that attempts to flood servers with many streams are detected
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early, a limit of no more than 2 * max_concurrent_streams new streams per one
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event loop iteration was introduced. This limit is applied even if
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max_concurrent_streams is not yet reached - for example, if corresponding
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streams are handled synchronously or reset.
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Further, refused streams are now limited to maximum of max_concurrent_streams
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and 100, similarly to priority_limit initial value, providing some tolerance
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to clients trying to open several streams at the connection start, yet
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low tolerance to flooding attempts.
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---
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src/http/v2/ngx_http_v2.c | 15 +++++++++++++++
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src/http/v2/ngx_http_v2.h | 2 ++
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2 files changed, 17 insertions(+)
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diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
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index 3611a2e..291677a 100644
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--- a/src/http/v2/ngx_http_v2.c
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+++ b/src/http/v2/ngx_http_v2.c
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@@ -361,6 +361,7 @@ ngx_http_v2_read_handler(ngx_event_t *rev)
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ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http2 read handler");
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h2c->blocked = 1;
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+ h2c->new_streams = 0;
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if (c->close) {
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c->close = 0;
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@@ -1320,6 +1321,14 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
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goto rst_stream;
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}
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+ if (h2c->new_streams++ >= 2 * h2scf->concurrent_streams) {
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+ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
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+ "client sent too many streams at once");
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+
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+ status = NGX_HTTP_V2_REFUSED_STREAM;
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+ goto rst_stream;
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+ }
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+
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if (!h2c->settings_ack
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&& !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG)
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&& h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW)
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@@ -1385,6 +1394,12 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
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rst_stream:
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+ if (h2c->refused_streams++ > ngx_max(h2scf->concurrent_streams, 100)) {
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+ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
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+ "client sent too many refused streams");
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+ return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_NO_ERROR);
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+ }
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+
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if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) {
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return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
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}
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diff --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
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index 3492297..6a7aaa6 100644
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--- a/src/http/v2/ngx_http_v2.h
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+++ b/src/http/v2/ngx_http_v2.h
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@@ -125,6 +125,8 @@ struct ngx_http_v2_connection_s {
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ngx_uint_t processing;
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ngx_uint_t frames;
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ngx_uint_t idle;
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+ ngx_uint_t new_streams;
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+ ngx_uint_t refused_streams;
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ngx_uint_t priority_limit;
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ngx_uint_t pushing;
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--
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2.31.1
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