Fixed segfault with incorrect location nesting.

A configuration with a named location inside a zero-length prefix
or regex location used to trigger a segmentation fault, as
ngx_http_core_location() failed to properly detect if a nested location
was created.  Example configuration to reproduce the problem:

    location "" {
        location @foo {}
    }

Fix is to not rely on a parent location name length, but rather check
command type we are currently parsing.

Identical fix is also applied to ngx_http_rewrite_if(), which used to
incorrectly assume the "if" directive is on server{} level in such
locations.

Reported by Markus Linnala.
Found with afl-fuzz.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/http/modules/ngx_http_rewrite_module.c b/src/http/modules/ngx_http_rewrite_module.c
index f24119645..754512fb1 100644
--- a/src/http/modules/ngx_http_rewrite_module.c
+++ b/src/http/modules/ngx_http_rewrite_module.c
@@ -612,7 +612,7 @@ ngx_http_rewrite_if(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
     save = *cf;
     cf->ctx = ctx;
 
-    if (pclcf->name.len == 0) {
+    if (cf->cmd_type == NGX_HTTP_SRV_CONF) {
         if_code->loc_conf = NULL;
         cf->cmd_type = NGX_HTTP_SIF_CONF;