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# HG changeset patch
# User Ruslan Ermilov <ru@nginx.com>
# Date 1541510989 -10800
# Node ID 9200b41db765fbd6709765ba2d218e78ad8e9860
# Parent 1c6b6163c03945bcc65c252cc42b0af18744c085
HTTP/2: limit the number of idle state switches.
An attack that continuously switches HTTP/2 connection between
idle and active states can result in excessive CPU usage.
This is because when a connection switches to the idle state,
all of its memory pool caches are freed.
This change limits the maximum allowed number of idle state
switches to 10 * http2_max_requests (i.e., 10000 by default).
This limits possible CPU usage in one connection, and also
imposes a limit on the maximum lifetime of a connection.
Initially reported by Gal Goldshtein from F5 Networks.
Patch-Source: http://hg.nginx.org/nginx/rev/9200b41db765
diff -r 1c6b6163c039 -r 9200b41db765 src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c Tue Nov 06 16:29:35 2018 +0300
+++ b/src/http/v2/ngx_http_v2.c Tue Nov 06 16:29:49 2018 +0300
@@ -4481,12 +4481,19 @@
#endif
+ h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
+ ngx_http_v2_module);
+
+ if (h2c->idle++ > 10 * h2scf->max_requests) {
+ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
+ "http2 flood detected");
+ ngx_http_v2_finalize_connection(h2c, NGX_HTTP_V2_NO_ERROR);
+ return;
+ }
+
c->destroyed = 0;
ngx_reusable_connection(c, 0);
- h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
- ngx_http_v2_module);
-
h2c->pool = ngx_create_pool(h2scf->pool_size, h2c->connection->log);
if (h2c->pool == NULL) {
ngx_http_v2_finalize_connection(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
diff -r 1c6b6163c039 -r 9200b41db765 src/http/v2/ngx_http_v2.h
--- a/src/http/v2/ngx_http_v2.h Tue Nov 06 16:29:35 2018 +0300
+++ b/src/http/v2/ngx_http_v2.h Tue Nov 06 16:29:49 2018 +0300
@@ -121,6 +121,7 @@
ngx_uint_t processing;
ngx_uint_t frames;
+ ngx_uint_t idle;
ngx_uint_t pushing;
ngx_uint_t concurrent_pushes;
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