From: Nikos Mavrogiannopoulos <nmav@gnutls.org>
Date: Sun, 30 May 2010 22:52:27 +0000 (+0200)
Subject: Added gnutls_pubkey_get_preferred_hash_algorithm() and gnutls_x509_crt_get_preferred_... 
X-Git-Tag: gnutls_2_11_3~204
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5eeabed81dbfe7a2e4089e612db5c61e60edeb91;p=thirdparty%2Fgnutls.git

Added gnutls_pubkey_get_preferred_hash_algorithm() and gnutls_x509_crt_get_preferred_hash_algorithm()
to allow determining the hash algorithm to use during signing. This is needed in the case of DSA
that uses specific versions of SHA depending on the size of the parameters.
---

diff --git a/NEWS b/NEWS
index c92fae870f..3d947da787 100644
--- a/NEWS
+++ b/NEWS
@@ -43,6 +43,8 @@ pkcs11:token=Root%20CA%20Certificates;serial=1%3AROOTS%3ADEFAULT;model=1%2E0;man
 gnutls_certificate_set_server_retrieve_function: DEPRECATED
 gnutls_certificate_set_client_retrieve_function: DEPRECATED
 gnutls_sign_callback_set: DEPRECATED
+gnutls_pubkey_get_preferred_hash_algorithm: ADDED
+gnutls_x509_crt_get_preferred_hash_algorithm: ADDED
 gnutls_x509_privkey_export_rsa_raw2: ADDED
 gnutls_rnd: ADDED
 gnutls_sec_param_to_pk_bits: ADDED
diff --git a/lib/gnutls_pubkey.c b/lib/gnutls_pubkey.c
index 543a8d3443..4303ca76a2 100644
--- a/lib/gnutls_pubkey.c
+++ b/lib/gnutls_pubkey.c
@@ -183,6 +183,40 @@ int gnutls_pubkey_import_x509(gnutls_pubkey_t key, gnutls_x509_crt_t crt,
 	return 0;
 }
 
+/**
+ * gnutls_pubkey_get_preferred_hash_algorithm:
+ * @key: Holds the certificate
+ * @hash: The result of the call with the hash algorithm used for signature
+ *
+ * This function will read the certifcate and return the appropriate digest
+ * algorithm to use for signing with this certificate. Some certificates (i.e.
+ * DSA might not be able to sign without the preferred algorithm).
+ *
+ * Returns: the 0 if the hash algorithm is found. A negative value is
+ * returned on error.
+ *
+ * Since: 2.11.0
+ **/
+int
+gnutls_pubkey_get_preferred_hash_algorithm (gnutls_pubkey_t key,
+				      gnutls_digest_algorithm_t * hash)
+{
+  int ret;
+
+  if (key == NULL)
+    {
+      gnutls_assert ();
+      return GNUTLS_E_INVALID_REQUEST;
+    }
+
+  ret = _gnutls_x509_verify_algorithm ((gnutls_mac_algorithm_t *) hash,
+			NULL, key->pk_algorithm,
+			key->params, key->params_size);
+
+  return ret;
+}
+
+
 /**
  * gnutls_pubkey_import_pkcs11:
  * @key: The public key
diff --git a/lib/includes/gnutls/abstract.h b/lib/includes/gnutls/abstract.h
index 5e14890672..4731faa656 100644
--- a/lib/includes/gnutls/abstract.h
+++ b/lib/includes/gnutls/abstract.h
@@ -23,6 +23,9 @@ int gnutls_pubkey_import_openpgp(gnutls_pubkey_t pkey,
 				 gnutls_openpgp_keyid_t keyid,
 				 unsigned int flags);
 
+int gnutls_pubkey_get_preferred_hash_algorithm (gnutls_pubkey_t key,
+				      gnutls_digest_algorithm_t * hash);
+
 int gnutls_pubkey_get_pk_rsa_raw (gnutls_pubkey_t crt,
 				gnutls_datum_t * m, gnutls_datum_t * e);
 int gnutls_pubkey_get_pk_dsa_raw (gnutls_pubkey_t crt,
diff --git a/lib/includes/gnutls/x509.h b/lib/includes/gnutls/x509.h
index 308e7057be..b605870a0a 100644
--- a/lib/includes/gnutls/x509.h
+++ b/lib/includes/gnutls/x509.h
@@ -139,6 +139,8 @@ extern "C"
 				  unsigned int flags,
 				  unsigned char *output_data,
 				  size_t * output_data_size);
+  int gnutls_x509_crt_get_preferred_hash_algorithm (gnutls_x509_crt_t crt,
+				      gnutls_digest_algorithm_t * hash);
 
   int gnutls_x509_crt_set_authority_key_id (gnutls_x509_crt_t cert,
 					    const void *id, size_t id_size);
diff --git a/lib/libgnutls.map b/lib/libgnutls.map
index ffd44429e0..bd71a9125a 100644
--- a/lib/libgnutls.map
+++ b/lib/libgnutls.map
@@ -672,6 +672,8 @@ GNUTLS_2_11
 	gnutls_pkcs11_copy_x509_privkey;
 	gnutls_pkcs11_delete_url;
 	gnutls_x509_privkey_export_rsa_raw2;
+	gnutls_pubkey_get_preferred_hash_algorithm;
+	gnutls_x509_crt_get_preferred_hash_algorithm;
 
 	gnutls_sec_param_to_pk_bits;
 	gnutls_sec_param_get_name;
diff --git a/lib/x509/privkey.c b/lib/x509/privkey.c
index 7de84d22bc..2b8e213829 100644
--- a/lib/x509/privkey.c
+++ b/lib/x509/privkey.c
@@ -1624,6 +1624,9 @@ cleanup:
  * *@signature_size is updated and %GNUTLS_E_SHORT_MEMORY_BUFFER will
  * be returned.
  *
+ * Use gnutls_x509_crt_get_preferred_hash_algorithm() to determine
+ * the hash algorithm.
+ *
  * Returns: On success, %GNUTLS_E_SUCCESS is returned, otherwise a
  *   negative error value.
  **/
@@ -1734,6 +1737,9 @@ gnutls_x509_privkey_sign_hash (gnutls_x509_privkey_t key,
  * *@signature_size is updated and %GNUTLS_E_SHORT_MEMORY_BUFFER will
  * be returned.
  *
+ * Use gnutls_x509_crt_get_preferred_hash_algorithm() to determine
+ * the hash algorithm.
+ *
  * Returns: On success, %GNUTLS_E_SUCCESS is returned, otherwise a
  *   negative error value.
  **/
diff --git a/lib/x509/verify.c b/lib/x509/verify.c
index 81beea04aa..4f992eb27f 100644
--- a/lib/x509/verify.c
+++ b/lib/x509/verify.c
@@ -875,6 +875,10 @@ gnutls_digest_algorithm_t _gnutls_dsa_q_to_hash(bigint_t q)
   }
 }
 
+/* This will return the appropriate hash to verify the given signature.
+ * If signature is NULL it will return an (or the) appropriate hash for
+ * the given parameters.
+ */
 int
 _gnutls_x509_verify_algorithm (gnutls_mac_algorithm_t * hash,
 			       const gnutls_datum_t * signature,
@@ -896,6 +900,9 @@ _gnutls_x509_verify_algorithm (gnutls_mac_algorithm_t * hash,
       ret = 0;
       break;
     case GNUTLS_PK_RSA:
+      if (signature == NULL) /* return a sensible algorithm */
+        return GNUTLS_DIG_SHA256;
+
       ret =
 	_gnutls_pkcs1_rsa_decrypt (&decrypted, signature,
 				   issuer_params, issuer_params_size, 1);
diff --git a/lib/x509/x509.c b/lib/x509/x509.c
index 0a4229cdef..d6dddb2491 100644
--- a/lib/x509/x509.c
+++ b/lib/x509/x509.c
@@ -465,7 +465,8 @@ gnutls_x509_crt_get_dn_oid (gnutls_x509_crt_t cert,
  * @cert: should contain a #gnutls_x509_crt_t structure
  *
  * This function will return a value of the #gnutls_sign_algorithm_t
- * enumeration that is the signature algorithm.
+ * enumeration that is the signature algorithm that has been used to
+ * sign this certificate.
  *
  * Returns: a #gnutls_sign_algorithm_t value, or a negative value on
  *   error.
@@ -2532,6 +2533,57 @@ gnutls_x509_crt_get_verify_algorithm (gnutls_x509_crt_t crt,
   return ret;
 }
 
+/**
+ * gnutls_x509_crt_get_preferred_hash_algorithm:
+ * @crt: Holds the certificate
+ * @hash: The result of the call with the hash algorithm used for signature
+ *
+ * This function will read the certifcate and return the appropriate digest
+ * algorithm to use for signing with this certificate. Some certificates (i.e.
+ * DSA might not be able to sign without the preferred algorithm).
+ *
+ * Returns: the 0 if the hash algorithm is found. A negative value is
+ * returned on error.
+ *
+ * Since: 2.11.0
+ **/
+int
+gnutls_x509_crt_get_preferred_hash_algorithm (gnutls_x509_crt_t crt,
+				      gnutls_digest_algorithm_t * hash)
+{
+  bigint_t issuer_params[MAX_PUBLIC_PARAMS_SIZE];
+  int issuer_params_size;
+  int ret, i;
+
+  if (crt == NULL)
+    {
+      gnutls_assert ();
+      return GNUTLS_E_INVALID_REQUEST;
+    }
+
+  issuer_params_size = MAX_PUBLIC_PARAMS_SIZE;
+  ret =
+	_gnutls_x509_crt_get_mpis (crt, issuer_params,
+				   &issuer_params_size);
+  if (ret < 0)
+    {
+      gnutls_assert ();
+      return ret;
+    }
+
+  ret = _gnutls_x509_verify_algorithm ((gnutls_mac_algorithm_t *) hash,
+			NULL, gnutls_x509_crt_get_pk_algorithm (crt, NULL),
+			issuer_params, issuer_params_size);
+
+  /* release allocated mpis */
+  for (i = 0; i < issuer_params_size; i++)
+    {
+      _gnutls_mpi_release (&issuer_params[i]);
+    }
+
+  return ret;
+}
+
 /**
  * gnutls_x509_crt_verify_data:
  * @crt: Holds the certificate
diff --git a/src/certtool.c b/src/certtool.c
index 7a2a864d55..020a56879d 100644
--- a/src/certtool.c
+++ b/src/certtool.c
@@ -75,11 +75,10 @@ static void print_certificate_info (gnutls_x509_crt_t crt, FILE * out, unsigned
 
 static void print_hex_datum (gnutls_datum_t * dat);
 
-
 static gaainfo info;
 FILE *outfile;
 FILE *infile;
-gnutls_digest_algorithm_t dig = GNUTLS_DIG_SHA1;
+gnutls_digest_algorithm_t default_dig;
 
 /* non interactive operation if set
  */
@@ -698,8 +697,27 @@ generate_crl (gnutls_x509_crt_t ca_crt)
   return crl;
 }
 
-void
-generate_self_signed (void)
+static gnutls_digest_algorithm_t get_dig(gnutls_x509_crt crt)
+{
+gnutls_digest_algorithm_t dig;
+int result;
+
+  if (default_dig != GNUTLS_DIG_UNKNOWN)
+    dig = default_dig;
+  else
+    {
+      result = gnutls_x509_crt_get_preferred_hash_algorithm(crt, &dig);
+      if (result < 0)
+        {
+	    error (EXIT_FAILURE, 0, "crl_preferred_hash_algorithm: %s",
+	       gnutls_strerror (result));
+        }
+    }
+
+  return dig;
+}
+
+void generate_self_signed (void)
 {
   gnutls_x509_crt_t crt;
   gnutls_x509_privkey_t key;
@@ -729,7 +747,7 @@ generate_self_signed (void)
 
   fprintf (stderr, "\n\nSigning certificate...\n");
 
-  result = gnutls_x509_crt_sign2 (crt, crt, key, dig, 0);
+  result = gnutls_x509_crt_sign2 (crt, crt, key, get_dig(crt), 0);
   if (result < 0)
     error (EXIT_FAILURE, 0, "crt_sign: %s", gnutls_strerror (result));
 
@@ -771,7 +789,7 @@ generate_signed_certificate (void)
 
   fprintf (stderr, "\n\nSigning certificate...\n");
 
-  result = gnutls_x509_crt_sign2 (crt, ca_crt, ca_key, dig, 0);
+  result = gnutls_x509_crt_sign2 (crt, ca_crt, ca_key, get_dig(ca_crt), 0);
   if (result < 0)
     error (EXIT_FAILURE, 0, "crt_sign: %s", gnutls_strerror (result));
 
@@ -805,7 +823,7 @@ generate_proxy_certificate (void)
 
   fprintf (stderr, "\n\nSigning certificate...\n");
 
-  result = gnutls_x509_crt_sign2 (crt, eecrt, eekey, dig, 0);
+  result = gnutls_x509_crt_sign2 (crt, eecrt, eekey, get_dig(eecrt), 0);
   if (result < 0)
     error (EXIT_FAILURE, 0, "crt_sign: %s", gnutls_strerror (result));
 
@@ -874,7 +892,7 @@ update_signed_certificate (void)
 
   fprintf (stderr, "\n\nSigning certificate...\n");
 
-  result = gnutls_x509_crt_sign2 (crt, ca_crt, ca_key, dig, 0);
+  result = gnutls_x509_crt_sign2 (crt, ca_crt, ca_key, get_dig(ca_crt), 0);
   if (result < 0)
     error (EXIT_FAILURE, 0, "crt_sign: %s", gnutls_strerror (result));
 
@@ -949,24 +967,30 @@ gaa_parser (int argc, char **argv)
   else
     info.outcert_format = GNUTLS_X509_FMT_PEM;
 
+  default_dig = GNUTLS_DIG_UNKNOWN;
   if (info.hash != NULL)
     {
+      fprintf(stderr, "Warning: It is suggested that you do not use this parameter unless you know what you are doing. "
+      "It is not always possible to set specific algorithms, for example DSA keys are unable to use any algorithm and "
+      "thus using the defaults is highly recommended!\n");
+      sleep(2);
+
       if (strcasecmp (info.hash, "md5") == 0)
 	{
 	  fprintf (stderr,
 		   "Warning: MD5 is broken, and should not be used any more for digital signatures.\n");
-	  dig = GNUTLS_DIG_MD5;
+	  default_dig = GNUTLS_DIG_MD5;
 	}
       else if (strcasecmp (info.hash, "sha1") == 0)
-	dig = GNUTLS_DIG_SHA1;
+	default_dig = GNUTLS_DIG_SHA1;
       else if (strcasecmp (info.hash, "sha256") == 0)
-	dig = GNUTLS_DIG_SHA256;
+	default_dig = GNUTLS_DIG_SHA256;
       else if (strcasecmp (info.hash, "sha384") == 0)
-	dig = GNUTLS_DIG_SHA384;
+	default_dig = GNUTLS_DIG_SHA384;
       else if (strcasecmp (info.hash, "sha512") == 0)
-	dig = GNUTLS_DIG_SHA512;
+	default_dig = GNUTLS_DIG_SHA512;
       else if (strcasecmp (info.hash, "rmd160") == 0)
-	dig = GNUTLS_DIG_RMD160;
+	default_dig = GNUTLS_DIG_RMD160;
       else
 	error (EXIT_FAILURE, 0, "invalid hash: %s", info.hash);
     }