httpd(8): fix location access test with empty server root

[Matthias Pressfreund]

Given the following httpd(8) configuration:

server "example.com" {
        ...
        location found "/htdocs*" {
                root ""
                directory auto index
        }
        ...
}

Instead of showing the directory index, accessing http://example.com/htdocs
fails with status code 500.  The diff below fixes this error along
with some cleanup.


Index: usr.sbin/httpd/server_http.c
===================================================================
RCS file: /cvs/src/usr.sbin/httpd/server_http.c,v
retrieving revision 1.142
diff -u -p -u -p -r1.142 server_http.c
--- usr.sbin/httpd/server_http.c        29 Oct 2020 12:30:52 -0000      1.142
+++ usr.sbin/httpd/server_http.c        6 Nov 2020 16:07:00 -0000
@@ -1320,11 +1320,8 @@ server_response(struct httpd *httpd, str
                goto fail;
 
        /* Now search for the location */
-       if ((srv_conf = server_getlocation(clt,
-           desc->http_path)) == NULL) {
-               server_abort_http(clt, 500, desc->http_path);
-               return (-1);
-       }
+       if ((srv_conf = server_getlocation(clt, desc->http_path)) == NULL)
+               goto rooterr;
 
        /* Optional rewrite */
        if (srv_conf->flags & SRVFLAG_PATH_REWRITE) {
@@ -1361,10 +1358,8 @@ server_response(struct httpd *httpd, str
 
                /* Now search for the updated location */
                if ((srv_conf = server_getlocation(clt,
-                   desc->http_path_alias)) == NULL) {
-                       server_abort_http(clt, 500, desc->http_path_alias);
-                       return (-1);
-               }
+                   desc->http_path_alias)) == NULL)
+                       goto rooterr;
        }
 
        if (clt->clt_toread > 0 && (size_t)clt->clt_toread >
@@ -1386,6 +1381,11 @@ server_response(struct httpd *httpd, str
  fail:
        server_abort_http(clt, 400, "bad request");
        return (-1);
+
+ rooterr: /* server root inaccessible */
+       srv_conf = clt->clt_srv_conf;
+       server_abort_http(clt, 500, srv_conf->root);
+       return (-1);
 }
 
 const char *
@@ -1456,7 +1456,9 @@ server_locationaccesstest(struct server_
            srv_conf->flags) == 0)
                return (0);
 
-       if ((rootfd = open(srv_conf->root, O_RDONLY)) == -1)
+       /* If the server root is not accessible, we have a problem */
+       if ((rootfd = open(*srv_conf->root != '\0' ? srv_conf->root : "/",
+           O_RDONLY)) == -1)
                return (-1);
 
        path = server_root_strip(path, srv_conf->strip) + 1;