From 2105dae0f9d7a964375ce681e53cb165375f84c1 Mon Sep 17 00:00:00 2001 From: Glenn Strauss Date: Sun, 1 Jul 2018 12:38:28 -0400 Subject: [PATCH] [mod_alias] security: potential path traversal with specific configs Security: potential path traversal of a single directory above the alias target with a specific mod_alias config where the alias which is matched does not end in '/', but alias target filesystem path does end in '/'. e.g. server.docroot = "/srv/www/host/HOSTNAME/docroot" alias.url = ( "/img" => "/srv/www/hosts/HOSTNAME/images/" ) If a malicious URL "/img../" were passed, the request would be for directory "/srv/www/hosts/HOSTNAME/images/../" which would resolve to "/srv/www/hosts/HOSTNAME/". If mod_dirlisting were enabled, which is not the default, this would result in listing the contents of the directory above the alias. An attacker might also try to directly access files anywhere under that path, which is one level above the intended aliased path. credit: Orange Tsai(@orange_8361) from DEVCORE --- src/mod_alias.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/src/mod_alias.c b/src/mod_alias.c index 18569943..eec14f24 100644 --- a/src/mod_alias.c +++ b/src/mod_alias.c @@ -181,6 +181,21 @@ PHYSICALPATH_FUNC(mod_alias_physical_handler) { strncmp(uri_ptr, ds->key->ptr, alias_len))) { /* matched */ + /* check for path traversal in url-path following alias if key + * does not end in slash, but replacement value ends in slash */ + if (uri_ptr[alias_len] == '.') { + char *s = uri_ptr + alias_len + 1; + if (*s == '.') ++s; + if (*s == '/' || *s == '\0') { + size_t vlen = buffer_string_length(ds->value); + if (0 != alias_len && ds->key->ptr[alias_len-1] != '/' + && 0 != vlen && ds->value->ptr[vlen-1] == '/') { + con->http_status = 403; + return HANDLER_FINISHED; + } + } + } + buffer_copy_buffer(con->physical.basedir, ds->value); buffer_copy_buffer(srv->tmp_buf, ds->value); buffer_append_string(srv->tmp_buf, uri_ptr + alias_len);