challenger

commit 3b2ba8d5037b6c75065deb8cccaa0a9165731319
parent 6e4f2b8aab871ccb5ceb21228f959164d38fa4eb
Author: Christian Grothoff <grothoff@gnunet.org>
Date:   Sat, 18 Jul 2026 00:59:36 +0200

use TALER_strcmp_ct()

Diffstat:
M
src/challenger/challenger-httpd_token.c
 | 
41
+++++++++--------------------------------

1 file changed, 9 insertions(+), 32 deletions(-)
diff --git a/src/challenger/challenger-httpd_token.c b/src/challenger/challenger-httpd_token.c
@@ -33,32 +33,6 @@
 
 #define MAX_RETRIES 3
 
-/**
- * Compare two NUL-terminated strings @a a and @a b in constant time
- * with respect to their contents.  Used for comparing secret/MAC
- * material (authorization codes, PKCE challenges) to avoid leaking
- * information via a timing oracle, as plain strcmp() short-circuits
- * at the first differing byte.  Note that the string lengths may
- * still leak, which is acceptable here as the token length is not
- * a secret at all.
- *
- * @param a first string
- * @param b second string
- * @return 0 if the strings are equal, non-zero otherwise
- */
-static int
-ct_strcmp (const char *a,
-           const char *b)
-{
-  size_t alen = strlen (a);
-
-  if (strlen (b) != alen)
-    return 1;
-  return GNUNET_memcmp_ct_ (a,
-                            b,
-                            alen);
-}
-
 
 /**
  * Context for a /token operation.
@@ -639,8 +613,9 @@ CH_handler_token (struct CH_HandlerContext *hc,
               "Failed to encode hash to Base64 URL");
           }
 
-          if (0 != ct_strcmp (encoded_hash,
-                              code_challenge))
+          if (0 !=
+              TALER_strcmp_ct (encoded_hash,
+                               code_challenge))
           {
             GNUNET_break_op (0);
             json_decref (address);
@@ -661,8 +636,9 @@ CH_handler_token (struct CH_HandlerContext *hc,
         }
         break;
       case CHALLENGER_CM_PLAIN:
-        if (0 != ct_strcmp (bc->code_verifier,
-                            code_challenge))
+        if (0 !=
+            TALER_strcmp_ct (bc->code_verifier,
+                             code_challenge))
         {
           GNUNET_break_op (0);
           json_decref (address);
@@ -723,8 +699,9 @@ CH_handler_token (struct CH_HandlerContext *hc,
     GNUNET_free (client_redirect_uri);
     GNUNET_free (client_state);
     GNUNET_free (code_challenge);
-    if (0 != ct_strcmp (code,
-                        bc->code))
+    if (0 !=
+        TALER_strcmp_ct (code,
+                         bc->code))
     {
       GNUNET_break_op (0);
       GNUNET_free (code);