From 0a0feeea8679d96cf2b5679562654512d467f0c2 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Wed, 15 Apr 2015 18:34:14 +0200
Subject: [PATCH] finish #3777 including testing

---
 src/include/taler_crypto_lib.h | 18 ++++++++++
 src/util/crypto.c              | 40 ++++++++++++++++++++-
 src/util/test_crypto.c         | 66 +++++++++++++++++++++++++++++++---
 3 files changed, 119 insertions(+), 5 deletions(-)

diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index dedeef5b0..752d2bfd8 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -441,6 +441,24 @@ TALER_link_decrypt_secret (const struct TALER_EncryptedLinkSecretP *secret_enc,
 			   struct TALER_LinkSecretP *secret);
 
 
+/**
+ * Decrypt the shared @a secret from the information in the
+ * encrypted link secret @e secret_enc using the transfer
+ * public key and the coin's private key.
+ * 
+ * @param secret_enc encrypted link secret
+ * @param transfer_pub transfer public key
+ * @param coin_priv coin private key
+ * @param[out] secret set to the shared secret
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+int
+TALER_link_decrypt_secret2 (const struct TALER_EncryptedLinkSecretP *secret_enc,
+			    const struct TALER_TransferPublicKeyP *trans_pub,
+			    const union TALER_CoinSpendPrivateKeyP *coin_priv,
+			    struct TALER_LinkSecretP *secret);
+
+
 /**
  * Encrypt the shared @a secret to generate the encrypted link secret.
  * Also creates the transfer key.
diff --git a/src/util/crypto.c b/src/util/crypto.c
index 158bb9511..14c14ebce 100644
--- a/src/util/crypto.c
+++ b/src/util/crypto.c
@@ -333,7 +333,6 @@ TALER_test_coin_valid (const struct TALER_CoinPublicInfo *coin_public_info)
 }
 
 
-
 /**
  * Decrypt the shared @a secret from the information in the
  * encrypted link secret @e secret_enc using the transfer
@@ -373,6 +372,45 @@ TALER_link_decrypt_secret (const struct TALER_EncryptedLinkSecretP *secret_enc,
 }
 
 
+/**
+ * Decrypt the shared @a secret from the information in the
+ * encrypted link secret @e secret_enc using the transfer
+ * public key and the coin's private key.
+ * 
+ * @param secret_enc encrypted link secret
+ * @param transfer_pub transfer public key
+ * @param coin_priv coin private key
+ * @param[out] secret set to the shared secret
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+int
+TALER_link_decrypt_secret2 (const struct TALER_EncryptedLinkSecretP *secret_enc,
+			    const struct TALER_TransferPublicKeyP *trans_pub,
+			    const union TALER_CoinSpendPrivateKeyP *coin_priv,
+			    struct TALER_LinkSecretP *secret)
+{
+  struct TALER_TransferSecretP transfer_secret;
+
+  if (GNUNET_OK !=
+      GNUNET_CRYPTO_ecc_ecdh (&coin_priv->ecdhe_priv,
+			      &trans_pub->ecdhe_pub,			      
+			      &transfer_secret.key))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  if (GNUNET_OK !=
+      TALER_transfer_decrypt (secret_enc,
+			      &transfer_secret,
+			      secret))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
 /**
  * Encrypt the shared @a secret to generate the encrypted link secret.
  * Also creates the transfer key.
diff --git a/src/util/test_crypto.c b/src/util/test_crypto.c
index 032127706..e95f25e90 100644
--- a/src/util/test_crypto.c
+++ b/src/util/test_crypto.c
@@ -24,9 +24,8 @@
 #include "taler_crypto_lib.h"
 
 
-int
-main(int argc,
-     const char *const argv[])
+static int
+test_basics ()
 {
   struct TALER_EncryptedLinkSecretP secret_enc;
   struct TALER_TransferSecretP trans_sec;
@@ -39,7 +38,6 @@ main(int argc,
   GNUNET_log_setup ("test-crypto",
 		    "WARNING",
 		    NULL);
-  /* FIXME: implement test... */
   GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_WEAK,
 			      &secret,
 			      sizeof (secret));
@@ -78,4 +76,64 @@ main(int argc,
   return 0;
 }
 
+
+static int
+test_high_level ()
+{
+  struct GNUNET_CRYPTO_EcdsaPrivateKey *pk;
+  struct TALER_LinkSecretP secret;
+  struct TALER_LinkSecretP secret2;
+  union TALER_CoinSpendPublicKeyP coin_pub;
+  union TALER_CoinSpendPrivateKeyP coin_priv;
+  struct TALER_TransferPrivateKeyP trans_priv;
+  struct TALER_TransferPublicKeyP trans_pub;
+  struct TALER_EncryptedLinkSecretP secret_enc;
+
+  pk = GNUNET_CRYPTO_ecdsa_key_create ();
+  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_WEAK,
+			      &secret,
+			      sizeof (secret));
+  GNUNET_CRYPTO_ecdsa_key_get_public (pk,
+				      &coin_pub.ecdsa_pub);
+  GNUNET_assert (GNUNET_OK == 
+		 TALER_link_encrypt_secret (&secret,
+					    &coin_pub,
+					    &trans_priv,
+					    &trans_pub,
+					    &secret_enc));
+  GNUNET_assert (GNUNET_OK == 
+		 TALER_link_decrypt_secret (&secret_enc,
+					    &trans_priv,
+					    &coin_pub,
+					    &secret2));
+  GNUNET_assert (0 ==
+		 memcmp (&secret,
+			 &secret2,
+			 sizeof (secret)));
+  coin_priv.ecdsa_priv = *pk;
+  GNUNET_assert (GNUNET_OK == 
+		 TALER_link_decrypt_secret2 (&secret_enc,
+					     &trans_pub,
+					     &coin_priv,
+					     &secret2));
+  GNUNET_assert (0 ==
+		 memcmp (&secret,
+			 &secret2,
+			 sizeof (secret)));
+  GNUNET_free (pk);
+  return 0;
+}
+
+
+int
+main(int argc,
+     const char *const argv[])
+{
+  if (0 != test_basics ())
+    return 1;
+  if (0 != test_high_level ())
+    return 1;
+  return 0;  
+}
+
 /* end of test_crypto.c */