Add abstractions: TALER_exchange_deposit_{sign,verify}

This change also removes ‘struct TALER_DepositTrackPS’
from the public API.

* src/include/taler_signatures.h (struct TALER_DepositTrackPS): Delete.

* src/util/exchange_signatures.c (struct TALER_DepositTrackPS): New.
  (TALER_exchange_deposit_sign): New func.
  (TALER_exchange_deposit_verify): New func.

* src/include/taler_crypto_lib.h
  (TALER_exchange_deposit_sign): New func decl.
  (TALER_exchange_deposit_verify): New func decl.

* src/exchange/taler-exchange-httpd_deposits_get.c
  (TEH_handler_deposits_get): Rework to use ‘TALER_exchange_deposit_verify’.

* src/lib/exchange_api_deposits_get.c
  (TALER_EXCHANGE_deposits_get): Rework to use ‘taler_exchange_deposit_sign’.

src/exchange/taler-exchange-httpd_deposits_get.c

@@ -328,20 +328,12 @@ TEH_handler_deposits_get (struct TEH_RequestContext *rc,
     return MHD_YES; /* parse error */
   TEH_METRICS_num_verifications[TEH_MT_SIGNATURE_EDDSA]++;
   {
-    struct TALER_DepositTrackPS tps = {
-      .purpose.size = htonl (sizeof (tps)),
-      .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION),
-      .merchant = ctx.merchant,
-      .coin_pub = ctx.coin_pub,
-      .h_contract_terms = ctx.h_contract_terms,
-      .h_wire = ctx.h_wire
-    };
-
     if (GNUNET_OK !=
-        GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION,
+        TALER_exchange_deposit_verify (&ctx.merchant,
-                                    &tps,
+                                       &ctx.coin_pub,
-                                    &merchant_sig.eddsa_sig,
+                                       &ctx.h_contract_terms,
-                                    &tps.merchant.eddsa_pub))
+                                       &ctx.h_wire,
+                                       &merchant_sig))
     {
       GNUNET_break_op (0);
       return TALER_MHD_reply_with_error (rc->connection,

src/include/taler_crypto_lib.h

@@ -3370,6 +3370,46 @@ TALER_merchant_refund_verify (
   const struct TALER_MerchantSignatureP *merchant_sig);
 
 
+/* ********************* exchange deposit signing ************************* */
+
+/**
+ * Sign a deposit.
+ *
+ * @param h_contract_terms hash of contract terms
+ * @param h_wire hash of the merchant account details
+ * @param coin_pub coin to be deposited
+ * @param merchant_pub merchant public key
+ * @param merchant_priv private key to sign with
+ * @param[out] merchant_sig where to write the signature
+ */
+void
+TALER_exchange_deposit_sign (
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_MerchantWireHashP *h_wire,
+  const struct TALER_CoinSpendPublicKeyP *coin_pub,
+  const struct TALER_MerchantPublicKeyP *merchant_pub,
+  const struct TALER_MerchantPrivateKeyP *merchant_priv,
+  struct TALER_MerchantSignatureP *merchant_sig);
+
+/**
+ * Verify a deposit.
+ *
+ * @param merchant merchant public key
+ * @param public key of the deposited coin
+ * @param h_contract_terms hash of contract terms
+ * @param h_wire hash of the merchant account details
+ * @param merchant_sig signature of the merchant
+ * @return #GNUNET_OK if the signature is valid
+ */
+enum GNUNET_GenericReturnValue
+TALER_exchange_deposit_verify (
+  const struct TALER_MerchantPublicKeyP *merchant,
+  const struct TALER_CoinSpendPublicKeyP *coin_pub,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_MerchantWireHashP *h_wire,
+  const struct TALER_MerchantSignatureP *merchant_sig);
+
+
 /* ********************* exchange online signing ************************** */
 
 

src/include/taler_signatures.h

@@ -386,42 +386,6 @@
 GNUNET_NETWORK_STRUCT_BEGIN
 
 
-/**
- * @brief Format used to generate the signature on a request to obtain
- * the wire transfer identifier associated with a deposit.
- */
-struct TALER_DepositTrackPS
-{
-  /**
-   * Purpose must be #TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION.
-   */
-  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
-
-  /**
-   * Hash over the proposal data of the contract for which this deposit is made.
-   */
-  struct TALER_PrivateContractHashP h_contract_terms GNUNET_PACKED;
-
-  /**
-   * Hash over the wiring information of the merchant.
-   */
-  struct TALER_MerchantWireHashP h_wire GNUNET_PACKED;
-
-  /**
-   * The Merchant's public key.  The deposit inquiry request is to be
-   * signed by the corresponding private key (using EdDSA).
-   */
-  struct TALER_MerchantPublicKeyP merchant;
-
-  /**
-   * The coin's public key.  This is the value that must have been
-   * signed (blindly) by the Exchange.
-   */
-  struct TALER_CoinSpendPublicKeyP coin_pub;
-
-};
-
-
 GNUNET_NETWORK_STRUCT_END
 
 #endif

src/lib/exchange_api_deposits_get.c

@@ -301,7 +301,7 @@ TALER_EXCHANGE_deposits_get (
   TALER_EXCHANGE_DepositGetCallback cb,
   void *cb_cls)
 {
-  struct TALER_DepositTrackPS dtp;
+  struct TALER_MerchantPublicKeyP merchant;
   struct TALER_MerchantSignatureP merchant_sig;
   struct TALER_EXCHANGE_DepositGetHandle *dwh;
   struct GNUNET_CURL_Context *ctx;
@@ -318,18 +318,14 @@ TALER_EXCHANGE_deposits_get (
     GNUNET_break (0);
     return NULL;
   }
-  // FIXME: move to helper!
-  dtp.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION);
-  dtp.purpose.size = htonl (sizeof (dtp));
-  dtp.h_contract_terms = *h_contract_terms;
-  dtp.h_wire = *h_wire;
   GNUNET_CRYPTO_eddsa_key_get_public (&merchant_priv->eddsa_priv,
-                                      &dtp.merchant.eddsa_pub);
+                                      &merchant.eddsa_pub);
-
+  TALER_exchange_deposit_sign (h_contract_terms,
-  dtp.coin_pub = *coin_pub;
+                               h_wire,
-  GNUNET_CRYPTO_eddsa_sign (&merchant_priv->eddsa_priv,
+                               coin_pub,
-                            &dtp,
+                               &merchant,
-                            &merchant_sig.eddsa_sig);
+                               merchant_priv,
+                               &merchant_sig);
   {
     char cpub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
     char mpub_str[sizeof (struct TALER_MerchantPublicKeyP) * 2];
@@ -343,8 +339,8 @@ TALER_EXCHANGE_deposits_get (
                                          whash_str,
                                          sizeof (whash_str));
     *end = '\0';
-    end = GNUNET_STRINGS_data_to_string (&dtp.merchant,
+    end = GNUNET_STRINGS_data_to_string (&merchant,
-                                         sizeof (dtp.merchant),
+                                         sizeof (merchant),
                                          mpub_str,
                                          sizeof (mpub_str));
     *end = '\0';

src/util/exchange_signatures.c

@@ -23,6 +23,93 @@
 #include "taler_signatures.h"
 
 
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * @brief Format used to generate the signature on a request to obtain
+ * the wire transfer identifier associated with a deposit.
+ */
+struct TALER_DepositTrackPS
+{
+  /**
+   * Purpose must be #TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION.
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * Hash over the proposal data of the contract for which this deposit is made.
+   */
+  struct TALER_PrivateContractHashP h_contract_terms GNUNET_PACKED;
+
+  /**
+   * Hash over the wiring information of the merchant.
+   */
+  struct TALER_MerchantWireHashP h_wire GNUNET_PACKED;
+
+  /**
+   * The Merchant's public key.  The deposit inquiry request is to be
+   * signed by the corresponding private key (using EdDSA).
+   */
+  struct TALER_MerchantPublicKeyP merchant;
+
+  /**
+   * The coin's public key.  This is the value that must have been
+   * signed (blindly) by the Exchange.
+   */
+  struct TALER_CoinSpendPublicKeyP coin_pub;
+
+};
+
+GNUNET_NETWORK_STRUCT_END
+
+
+void
+TALER_exchange_deposit_sign (
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_MerchantWireHashP *h_wire,
+  const struct TALER_CoinSpendPublicKeyP *coin_pub,
+  const struct TALER_MerchantPublicKeyP *merchant_pub,
+  const struct TALER_MerchantPrivateKeyP *merchant_priv,
+  struct TALER_MerchantSignatureP *merchant_sig)
+{
+  struct TALER_DepositTrackPS dtp = {
+    .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION),
+    .purpose.size = htonl (sizeof (dtp)),
+    .h_contract_terms = *h_contract_terms,
+    .h_wire = *h_wire,
+    .merchant = *merchant_pub,
+    .coin_pub = *coin_pub
+  };
+  GNUNET_CRYPTO_eddsa_sign (&merchant_priv->eddsa_priv,
+                            &dtp,
+                            &merchant_sig->eddsa_sig);
+}
+
+enum GNUNET_GenericReturnValue
+TALER_exchange_deposit_verify (
+  const struct TALER_MerchantPublicKeyP *merchant,
+  const struct TALER_CoinSpendPublicKeyP *coin_pub,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_MerchantWireHashP *h_wire,
+  const struct TALER_MerchantSignatureP *merchant_sig)
+{
+  struct TALER_DepositTrackPS tps = {
+    .purpose.size = htonl (sizeof (tps)),
+    .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION),
+    .merchant = *merchant,
+    .coin_pub = *coin_pub,
+    .h_contract_terms = *h_contract_terms,
+    .h_wire = *h_wire
+  };
+
+  return
+    GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION,
+                                &tps,
+                                &merchant_sig->eddsa_sig,
+                                &tps.merchant.eddsa_pub);
+}
+
+
 GNUNET_NETWORK_STRUCT_BEGIN
 
 /**