exchange

commit 2fb11e8cd2b200c252ecfbf00dc5b1d2ff1fc485
parent 5d579f975b92a0f9a49f71d0740c6e95b49fa32b
Author: Christian Grothoff <christian@grothoff.org>
Date:   Sun, 11 Oct 2026 14:11:27 +0200

improve CS handling

Diffstat:
M
src/exchange/taler-exchange-httpd_post-reveal-withdraw.c
 | 
44
+++++++++++++++++++++++++++++++++-----------

1 file changed, 33 insertions(+), 11 deletions(-)
diff --git a/src/exchange/taler-exchange-httpd_post-reveal-withdraw.c b/src/exchange/taler-exchange-httpd_post-reveal-withdraw.c
@@ -401,22 +401,44 @@ verify_commitment_and_max_age (
     }
   }
 
+  /**
+   * Sanity check:
+   * The number of CS denominations must match the R-values that were
+   * persisted with the original /withdraw request.
+   */
+  if ( (cs_count != wd->num_cs_r_values) ||
+       ( (0 < cs_count) &&
+         (wd->no_blinding_seed ||
+          (NULL == wd->cs_r_values) ) ) )
+  {
+    GNUNET_break (0);
+    *result = TALER_MHD_reply_with_error (
+      con,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+      NULL);
+    return GNUNET_SYSERR;
+  }
+
   hash_context = GNUNET_CRYPTO_hash_context_start ();
 
   {
-    uint32_t cs_indices[cs_count];
-    union GNUNET_CRYPTO_BlindSessionNonce nonces[cs_count];
+    uint32_t cs_indices[GNUNET_NZL (cs_count)];
+    union GNUNET_CRYPTO_BlindSessionNonce nonces[GNUNET_NZL (cs_count)];
     size_t cs_idx = 0; /* [0...cs_count) */
 
-    for (size_t i = 0; i < wd->num_coins; i++)
-      if (is_cs[i])
-        cs_indices[cs_idx++] = i;
-
-    TALER_cs_derive_only_cs_blind_nonces_from_seed (&wd->blinding_seed,
-                                                    false, /* not for melt */
-                                                    cs_count,
-                                                    cs_indices,
-                                                    nonces);
+    if (0 < cs_count)
+    {
+      for (size_t i = 0; i < wd->num_coins; i++)
+        if (is_cs[i])
+          cs_indices[cs_idx++] = i;
+
+      TALER_cs_derive_only_cs_blind_nonces_from_seed (&wd->blinding_seed,
+                                                      false, /* not for melt */
+                                                      cs_count,
+                                                      cs_indices,
+                                                      nonces);
+    }
 
     for (uint8_t gamma = 0; gamma<TALER_CNC_KAPPA; gamma++)
     {