Fixed allocation bug and overwrite in ed25519_sha512_public_key.

ChangeLog

+2015-03-25  Niels Möller  <nisse@diamant.hack.org>
+
+	* ed25519-sha512-pubkey.c: Fix stack overwrite. The digest array
+	must have room for a complete sha512 digest.
+
 2015-03-19  Niels Möller  <nisse@diamant.hack.org>
 
 	* Makefile.in (OPT_HOGWEED_SOURCES): Deleted make variable.

ed25519-sha512-pubkey.c

@@ -43,7 +43,7 @@ ed25519_sha512_public_key (uint8_t *pub, const uint8_t *priv)
 {
   const struct ecc_curve *ecc = &_nettle_curve25519;
   struct sha512_ctx ctx;
-  uint8_t digest[ED25519_KEY_SIZE];
+  uint8_t digest[SHA512_DIGEST_SIZE];
   mp_size_t itch = ecc->q.size + _eddsa_public_key_itch (ecc);
   mp_limb_t *scratch = gmp_alloc_limbs (itch);