conditionally use (un)blinding implementation from libgnunetutil

src/exchange/taler-exchange-httpd_recoup.c

@@ -438,7 +438,7 @@ verify_and_execute_recoup (struct MHD_Connection *connection,
                         sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey),
                         &c_hash);
     if (GNUNET_YES !=
-        GNUNET_CRYPTO_rsa_blind (&c_hash,
+        TALER_rsa_blind (&c_hash,
                          &coin_bks->bks,
                          dki->denom_pub.rsa_public_key,
                          &coin_ev,

src/include/taler_crypto_lib.h

@@ -1142,4 +1142,37 @@ TALER_merchant_wire_signature_make (
   struct TALER_MerchantSignatureP *merch_sig);
 
 
+/**
+ * Blinds the given message with the given blinding key
+ *
+ * @param hash hash of the message to sign
+ * @param bkey the blinding key
+ * @param pkey the public key of the signer
+ * @param[out] buf set to a buffer with the blinded message to be signed
+ * @param[out] buf_size number of bytes stored in @a buf
+ * @return #GNUNET_YES if successful, #GNUNET_NO if RSA key is malicious
+ */
+int
+TALER_rsa_blind (const struct GNUNET_HashCode *hash,
+                 const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks,
+                 struct GNUNET_CRYPTO_RsaPublicKey *pkey,
+                 void **buf,
+                 size_t *buf_size);
+
+
+/**
+ * Unblind a blind-signed signature.  The signature should have been generated
+ * with #GNUNET_CRYPTO_rsa_sign() using a hash that was blinded with
+ * #GNUNET_CRYPTO_rsa_blind().
+ *
+ * @param sig the signature made on the blinded signature purpose
+ * @param bks the blinding key secret used to blind the signature purpose
+ * @param pkey the public key of the signer
+ * @return unblinded signature on success, NULL if RSA key is bad or malicious.
+ */
+struct GNUNET_CRYPTO_RsaSignature *
+TALER_rsa_unblind (const struct GNUNET_CRYPTO_RsaSignature *sig,
+                   const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks,
+                   struct GNUNET_CRYPTO_RsaPublicKey *pkey);
+
 #endif

src/lib/exchange_api_link.c

@@ -123,7 +123,7 @@ parse_link_coin (const struct TALER_EXCHANGE_LinkHandle *lh,
   /* extract coin and signature */
   *coin_priv = fc.coin_priv;
   sig->rsa_signature
-    = GNUNET_CRYPTO_rsa_unblind (bsig,
+    = TALER_rsa_unblind (bsig,
                          &fc.blinding_key.bks,
                          rpub);
   /* verify link_sig */

src/util/crypto.c

@@ -25,6 +25,19 @@
 #include "taler_util.h"
 #include <gcrypt.h>
 
+/**
+ * Should we use the RSA blind signing implementation
+ * from libgnunetutil?  The blinding only works
+ * correctly with a current version of libgnunetutil.
+ *
+ * Only applies to blinding and unblinding, but
+ * not to blind signing.
+ *
+ * FIXME: Can we define some macro for this in configure.ac
+ * to detect the version?
+ */
+#define USE_GNUNET_RSA_BLINDING 1
+
 
 /**
  * Function called by libgcrypt on serious errors.
@@ -245,7 +258,7 @@ TALER_planchet_prepare (const struct TALER_DenominationPublicKey *dk,
                       sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey),
                       c_hash);
   if (GNUNET_YES !=
-      GNUNET_CRYPTO_rsa_blind (c_hash,
+      TALER_rsa_blind (c_hash,
                        &ps->blinding_key.bks,
                        dk->rsa_public_key,
                        &pd->coin_ev,
@@ -280,7 +293,7 @@ TALER_planchet_to_coin (const struct TALER_DenominationPublicKey *dk,
 {
   struct GNUNET_CRYPTO_RsaSignature *sig;
 
-  sig = GNUNET_CRYPTO_rsa_unblind (blind_sig,
+  sig = TALER_rsa_unblind (blind_sig,
                            &ps->blinding_key.bks,
                            dk->rsa_public_key);
   if (GNUNET_OK !=
@@ -381,4 +394,58 @@ TALER_refresh_get_commitment (struct TALER_RefreshCommitmentP *rc,
 }
 
 
+/**
+ * Blinds the given message with the given blinding key
+ *
+ * @param hash hash of the message to sign
+ * @param bkey the blinding key
+ * @param pkey the public key of the signer
+ * @param[out] buf set to a buffer with the blinded message to be signed
+ * @param[out] buf_size number of bytes stored in @a buf
+ * @return #GNUNET_YES if successful, #GNUNET_NO if RSA key is malicious
+ */
+int
+TALER_rsa_blind (const struct GNUNET_HashCode *hash,
+                 const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks,
+                 struct GNUNET_CRYPTO_RsaPublicKey *pkey,
+                 void **buf,
+                 size_t *buf_size)
+{
+#if USE_GNUNET_RSA_BLINDING
+  return GNUNET_CRYPTO_rsa_blind (hash,
+                                  bks,
+                                  pkey,
+                                  buf,
+                                  buf_size);
+#else
+# error "FIXME: implement"
+#endif
+}
+
+
+/**
+ * Unblind a blind-signed signature.  The signature should have been generated
+ * with #GNUNET_CRYPTO_rsa_sign() using a hash that was blinded with
+ * #GNUNET_CRYPTO_rsa_blind().
+ *
+ * @param sig the signature made on the blinded signature purpose
+ * @param bks the blinding key secret used to blind the signature purpose
+ * @param pkey the public key of the signer
+ * @return unblinded signature on success, NULL if RSA key is bad or malicious.
+ */
+struct GNUNET_CRYPTO_RsaSignature *
+TALER_rsa_unblind (const struct GNUNET_CRYPTO_RsaSignature *sig,
+                   const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks,
+                   struct GNUNET_CRYPTO_RsaPublicKey *pkey)
+{
+#if USE_GNUNET_RSA_BLINDING
+  return GNUNET_CRYPTO_rsa_unblind (sig,
+                                    bks,
+                                    pkey);
+#else
+# error "FIXME: implement"
+#endif
+}
+
+
 /* end of crypto.c */

src/util/test_helper_rsa.c

@@ -254,7 +254,7 @@ test_signing (struct TALER_CRYPTO_DenominationHelper *dh)
       void *buf;
       size_t buf_size;
       GNUNET_assert (GNUNET_YES ==
-                     GNUNET_CRYPTO_rsa_blind (&m_hash,
+                     TALER_rsa_blind (&m_hash,
                                       &bks,
                                       keys[i].denom_pub.rsa_public_key,
                                       &buf,
@@ -290,7 +290,7 @@ test_signing (struct TALER_CRYPTO_DenominationHelper *dh)
       {
         struct GNUNET_CRYPTO_RsaSignature *rs;
 
-        rs = GNUNET_CRYPTO_rsa_unblind (ds.rsa_signature,
+        rs = TALER_rsa_unblind (ds.rsa_signature,
                                 &bks,
                                 keys[i].denom_pub.rsa_public_key);
         if (NULL == rs)
@@ -409,7 +409,7 @@ perf_signing (struct TALER_CRYPTO_DenominationHelper *dh)
         size_t buf_size;
 
         GNUNET_assert (GNUNET_YES ==
-                       GNUNET_CRYPTO_rsa_blind (&m_hash,
+                       TALER_rsa_blind (&m_hash,
                                         &bks,
                                         keys[i].denom_pub.rsa_public_key,
                                         &buf,