HTTP/2: reject self-dependent streams.

Per RFC7540, a stream cannot depend on itself.

Previously, this requirement was enforced on PRIORITY frames, but not on
HEADERS frames and due to the implementation details nginx worker would
crash (stack overflow) while opening self-dependent stream.

Found with afl-fuzz.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
index 91f7bc9e1..6cca2b9a3 100644
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -1133,6 +1133,22 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
 
     h2c->last_sid = h2c->state.sid;
 
+    if (depend == h2c->state.sid) {
+        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
+                      "client sent HEADERS frame for stream %ui "
+                      "with incorrect dependency", h2c->state.sid);
+
+        if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid,
+                                        NGX_HTTP_V2_PROTOCOL_ERROR)
+            != NGX_OK)
+        {
+            return ngx_http_v2_connection_error(h2c,
+                                                NGX_HTTP_V2_INTERNAL_ERROR);
+        }
+
+        return ngx_http_v2_state_skip_headers(h2c, pos, end);
+    }
+
     h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
                                          ngx_http_v2_module);