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HTTP/2: limit the number of idle state switches.

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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.
This commit is contained in:
Ruslan Ermilov 2018-11-06 16:29:49 +03:00
parent 8ec4146e1a
commit 60b93594cc
2 changed files with 11 additions and 3 deletions
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13
src/http/v2/ngx_http_v2.c
View File

@ -4511,12 +4511,19 @@ ngx_http_v2_idle_handler(ngx_event_t *rev)
#endif
c->destroyed = 0;
ngx_reusable_connection(c, 0);
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);
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);

1
src/http/v2/ngx_http_v2.h
View File

@ -121,6 +121,7 @@ struct ngx_http_v2_connection_s {
ngx_uint_t processing;
ngx_uint_t frames;
ngx_uint_t idle;
ngx_uint_t pushing;
ngx_uint_t concurrent_pushes;