merchant

commit c926288c9c36394efda1007c7d130cad86832c13
parent ac8357c5a6a45c114214395a1684dd306ade1c10
Author: Florian Dold <florian@dold.me>
Date:   Thu, 16 Oct 2025 18:33:34 +0200

fix idempotent pay requests with tokens

Diffstat:
M
src/backend/taler-merchant-httpd_post-orders-ID-pay.c
 | 
80
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------------

1 file changed, 62 insertions(+), 18 deletions(-)
diff --git a/src/backend/taler-merchant-httpd_post-orders-ID-pay.c b/src/backend/taler-merchant-httpd_post-orders-ID-pay.c
@@ -464,6 +464,13 @@ struct PayContext
   unsigned int output_index_gen;
 
   /**
+   * Counter used to generate the output index in append_output_token_sig().
+   *
+   * Counts the generated tokens _within_ the current output_index_gen.
+   */
+  unsigned int output_token_cnt;
+
+  /**
    * HTTP status code to use for the reply, i.e 200 for "OK".
    * Special value UINT_MAX is used to indicate hard errors
    * (no reply, return #MHD_NO).
@@ -3484,6 +3491,37 @@ handle_output_donation_receipt (
 
 
 /**
+ * Count tokens produced by an output.
+ *
+ * @param pc pay context
+ * @param output output to consider
+ * @returns number of output tokens
+ */
+static unsigned int
+count_output_tokens (const struct PayContext *pc,
+                     const struct TALER_MERCHANT_ContractOutput *output)
+{
+  switch (output->type)
+  {
+    case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_INVALID:
+      GNUNET_assert (0);
+      break;
+    case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_TOKEN:
+      return output->details.token.count;
+    case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_DONATION_RECEIPT:
+#ifdef HAVE_DONAU_DONAU_SERVICE_H
+      return pc->parse_wallet_data.num_bkps;
+#else
+      return 0;
+#endif
+      break;
+  }
+  /* Not reached. */
+  GNUNET_assert (0);
+}
+
+
+/**
  * Validate tokens and token envelopes. First, we check if all tokens listed
  * in the 'inputs' array of the selected choice are present in the 'tokens'
  * array of the request. Then, we validate the signatures of each provided
@@ -3648,23 +3686,8 @@ phase_validate_tokens (struct PayContext *pc)
         const struct TALER_MERCHANT_ContractOutput *output
           = &selected->outputs[i];
 
-        cnt = 0;
-        switch (output->type)
-        {
-        case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_INVALID:
-          GNUNET_assert (0);
-          break;
-        case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_TOKEN:
-          cnt = output->details.token.count;
-          output_off += cnt;
-          break;
-        case TALER_MERCHANT_CONTRACT_OUTPUT_TYPE_DONATION_RECEIPT:
-#ifdef HAVE_DONAU_DONAU_SERVICE_H
-          cnt = pc->parse_wallet_data.num_bkps;
-          output_off += pc->parse_wallet_data.num_bkps;
-#endif
-          break;
-        }
+        output_off += count_output_tokens (pc,
+                                           output);
         for (unsigned int j = 0; j<cnt; j++)
           pc->output_tokens[output_off + j].output_index = i;
       }
@@ -3850,13 +3873,34 @@ append_output_token_sig (void *cls,
 {
   struct PayContext *pc = cls;
   struct SignedOutputToken out;
+  struct TALER_MERCHANT_ContractChoice *choice;
+  const struct TALER_MERCHANT_ContractOutput *output;
+  unsigned int cnt;
+
+  GNUNET_assert (TALER_MERCHANT_CONTRACT_VERSION_1 ==
+                 pc->check_contract.contract_terms->version);
 
-  out.output_index = pc->output_index_gen++;
+  choice = &pc->check_contract.contract_terms->details.v1
+    .choices[pc->parse_wallet_data.choice_index];
+  output = &choice->outputs[pc->output_index_gen];
+  cnt = count_output_tokens (pc,
+                             output);
+
+  out.output_index = pc->output_index_gen;
   out.h_issue.hash = *h_issue;
   out.sig.signature = sig;
   GNUNET_array_append (pc->output_tokens,
                        pc->output_tokens_len,
                        out);
+
+
+  /* Go to next output once we've output all tokens for the current one. */
+  pc->output_token_cnt++;
+  if (pc->output_token_cnt >= cnt)
+  {
+    pc->output_token_cnt = 0;
+    pc->output_index_gen++;
+  }
 }