Handle age restricted coin when minimum age was not required

When a customer pays with a coin that is age restricted while the
contract did not ask for a minimum age, it is required that the customer
provides 'h_age_commitment', the hash of the age commitment that went
into the FDH of the coin.  This is needed for the deposit of the age
restricted coin.

Fixes #7252

1 files changed, 44 insertions, 29 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
index 2e78c10d..43b68ff4 100644
--- a/src/backend/taler-merchant-httpd_post-orders-ID-pay.c
+++ b/src/backend/taler-merchant-httpd_post-orders-ID-pay.c
@@ -1131,7 +1131,7 @@ process_pay_with_exchange (
     const struct TALER_EXCHANGE_DenomPublicKey *denom_details;
     enum TALER_ErrorCode ec;
     unsigned int http_status;
-    bool age_verification_required = false;
+    bool is_age_restricted_denom = false;
     struct TALER_AgeCommitmentHash ach = {0};
     struct TALER_AgeCommitmentHash *achp = NULL;
 
@@ -1176,6 +1176,7 @@ process_pay_with_exchange (
               (json_t *) TALER_EXCHANGE_get_keys_raw (exchange_handle)))));
       return;
     }
+
     if (GNUNET_OK !=
         TMH_AUDITORS_check_dk (exchange_handle,
                                denom_details,
@@ -1210,15 +1211,18 @@ process_pay_with_exchange (
     /* Now that we have the details about the denomination, we can verify age
      * restriction requirements, if applicable. Note that denominations with an
      * age_mask equal to zero always pass the age verification.  */
-    age_verification_required = 0 < pc->minimum_age &&
-                                0 < denom_details->key.age_mask.bits;
+    is_age_restricted_denom =   0 < denom_details->key.age_mask.bits;
 
-    if (age_verification_required)
+    if (is_age_restricted_denom
+        && (0 < pc->minimum_age))
     {
+      /* Minimum age given and restricted coind provided: We need to verify the
+       * minimum age */
       unsigned int code = 0;
 
       if (dc->no_age_commitment)
       {
+        GNUNET_break_op (0);
         code = TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_AGE_COMMITMENT_MISSING;
         goto AGE_FAIL;
       }
@@ -1227,6 +1231,7 @@ process_pay_with_exchange (
       if ((dc->age_commitment.num + 1) !=
           __builtin_popcount (dc->age_commitment.mask.bits))
       {
+        GNUNET_break_op (0);
         code =
           TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_AGE_COMMITMENT_SIZE_MISMATCH;
         goto AGE_FAIL;
@@ -1242,6 +1247,7 @@ process_pay_with_exchange (
 AGE_FAIL:
       if (0 < code)
       {
+        GNUNET_free (dc->age_commitment.keys);
         resume_pay_with_response (
           pc,
           MHD_HTTP_BAD_REQUEST,
@@ -1256,9 +1262,31 @@ AGE_FAIL:
        * Calculate the hash of the age commitment. */
       TALER_age_commitment_hash (&dc->age_commitment,
                                  &ach);
-
+      GNUNET_free (dc->age_commitment.keys);
       achp = &ach;
     }
+    else if (is_age_restricted_denom)
+    {
+      /* The contract did not ask for a minimum_age but the client paid
+       * with a coin that has age restriction enabled.  We need the hash
+       * of the age commitment in this case in order to verify the coin
+       * and to deposit it with the exchange. */
+      if (dc->no_h_age_commitment)
+      {
+        GNUNET_break_op (0);
+        resume_pay_with_response (
+          pc,
+          MHD_HTTP_BAD_REQUEST,
+          TALER_MHD_MAKE_JSON_PACK (
+            TALER_JSON_pack_ec (
+              TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_AGE_COMMITMENT_HASH_MISSING),
+            GNUNET_JSON_pack_data_auto ("h_denom_pub",
+                                        &denom_details->h_key)));
+        return;
+      }
+
+      achp = &dc->h_age_commitment;
+    }
 
     dc->deposit_fee = denom_details->fees.deposit;
     dc->refund_fee = denom_details->fees.refund;
@@ -2066,7 +2094,6 @@ parse_pay (struct PayContext *pc)
     {
       struct DepositConfirmation *dc = &pc->dc[coins_index];
       const char *exchange_url;
-      bool no_minimum_age_sig;
       struct GNUNET_JSON_Specification ispec[] = {
         GNUNET_JSON_spec_fixed_auto ("coin_sig",
                                      &dc->coin_sig),
@@ -2086,7 +2113,7 @@ parse_pay (struct PayContext *pc)
         GNUNET_JSON_spec_mark_optional (
           GNUNET_JSON_spec_fixed_auto ("minimum_age_sig",
                                        &dc->minimum_age_sig),
-          &no_minimum_age_sig),
+          &dc->no_minimum_age_sig),
         GNUNET_JSON_spec_mark_optional (
           TALER_JSON_spec_age_commitment ("age_commitment",
                                           &dc->age_commitment),
@@ -2149,32 +2176,20 @@ parse_pay (struct PayContext *pc)
 
       // Check the consistency of the (potential) age restriction
       // information.
+      if (dc->no_age_commitment != dc->no_minimum_age_sig)
       {
-        char *error = NULL;
-
-        if (0 < dc->pc->minimum_age &&
-            dc->no_minimum_age_sig &&
-            dc->no_age_commitment)
-          error = "required: 'mininum_age_sig' and 'age_commitment'";
-
-        if (! dc->no_age_commitment &&
-            dc->no_h_age_commitment)
-          error = "only one allowed: 'age_commitment' vs. 'h_age_commitment'";
-
-        if (NULL != error)
-        {
-          GNUNET_break_op (0);
-          GNUNET_JSON_parse_free (spec);
-          return (MHD_YES ==
-                  TALER_MHD_reply_with_error (
-                    pc->connection,
-                    MHD_HTTP_BAD_REQUEST,
-                    TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                    error)
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return (MHD_YES ==
+                TALER_MHD_reply_with_error (
+                  pc->connection,
+                  MHD_HTTP_BAD_REQUEST,
+                  TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                  "inconsistent: 'age_commitment' vs. 'minimum_age_sig'"
                   )
+                )
               ? GNUNET_NO
               : GNUNET_SYSERR;
-        }
       }
     }
   }