Merge r1885659 from trunk:

mod_auth_digest: Fast validation of the nonce's base64 to fail early if
                 the format can't match anyway.

Submitted by: ylavic
Reviewed by: ylavic, covener, jailletc36


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1885666 13f79535-47bb-0310-9956-ffa450edef68

CHANGES

@@ -1,6 +1,9 @@
                                                          -*- coding: utf-8 -*-
 Changes with Apache 2.4.47
 
+  *) mod_auth_digest: Fast validation of the nonce's base64 to fail early if
+     the format can't match anyway.  [Yann Ylavic]
+
   *) mod_proxy_fcgi: Honor "SetEnv proxy-sendcl" to forward a chunked
      Transfer-Encoding from the client, spooling the request body when needed
      to provide a Content-Length to the backend.  PR 57087.  [Yann Ylavic]

modules/aaa/mod_auth_digest.c

@@ -1426,9 +1426,14 @@ static int check_nonce(request_rec *r, digest_header_rec *resp,
     time_rec nonce_time;
     char tmp, hash[NONCE_HASH_LEN+1];
 
-    if (strlen(resp->nonce) != NONCE_LEN) {
+    /* Since the time part of the nonce is a base64 encoding of an
+     * apr_time_t (8 bytes), it should end with a '=', fail early otherwise.
+     */
+    if (strlen(resp->nonce) != NONCE_LEN
+            || resp->nonce[NONCE_TIME_LEN - 1] != '=') {
         ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01775)
-                      "invalid nonce %s received - length is not %d",
+                      "invalid nonce '%s' received - length is not %d "
+                      "or time encoding is incorrect",
                       resp->nonce, NONCE_LEN);
         note_digest_auth_failure(r, conf, resp, 1);
         return HTTP_UNAUTHORIZED;