crypto: add DecodeSignature and use SHA-256 with ECDSA.

This changes ECSignatureCreator to use the hash function that SPDY
expects (SHA-256). There are no other users of ECSignatureCreator in
the tree so I'm going to defer making these choices parameters until there's
a benefit to be had.

It also adds DecodeSignature to convert from ASN.1 signatures to the `raw'
form that SPDY needs.

BUG=none

Review URL: https://chromiumcodereview.appspot.com/10910226

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@157551 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 64 insertions, 13 deletions

diff --git a/crypto/ec_signature_creator.h b/crypto/ec_signature_creator.h
index b557daa..16e64f5 100644
--- a/crypto/ec_signature_creator.h
+++ b/crypto/ec_signature_creator.h
@@ -5,6 +5,7 @@
 #ifndef CRYPTO_EC_SIGNATURE_CREATOR_H_
 #define CRYPTO_EC_SIGNATURE_CREATOR_H_
 
+#include <string>
 #include <vector>
 
 #include "base/basictypes.h"
@@ -31,7 +32,7 @@ class CRYPTO_EXPORT ECSignatureCreator {
 
   // Create an instance. The caller must ensure that the provided PrivateKey
   // instance outlives the created ECSignatureCreator.
-  // TODO(rch):  This is currently hard coded to use SHA1. Ideally, we should
+  // TODO(rch):  This is currently hard coded to use SHA256. Ideally, we should
   // pass in the hash algorithm identifier.
   static ECSignatureCreator* Create(ECPrivateKey* key);
 
@@ -50,6 +51,14 @@ class CRYPTO_EXPORT ECSignatureCreator {
   virtual bool Sign(const uint8* data,
                     int data_len,
                     std::vector<uint8>* signature) = 0;
+
+  // DecodeSignature converts from a DER encoded ECDSA-Sig-Value (as produced
+  // by Sign) to a `raw' ECDSA signature which consists of a pair of
+  // big-endian, zero-padded, 256-bit integers, r and s. On success it returns
+  // true and puts the raw signature into |out_raw_sig|.
+  // (Only P-256 signatures are supported.)
+  virtual bool DecodeSignature(const std::vector<uint8>& signature,
+                               std::vector<uint8>* out_raw_sig) = 0;
 };
 
 }  // namespace crypto
diff --git a/crypto/ec_signature_creator_impl.h b/crypto/ec_signature_creator_impl.h
index f8baf86..8ef67cd 100644
--- a/crypto/ec_signature_creator_impl.h
+++ b/crypto/ec_signature_creator_impl.h
@@ -19,8 +19,12 @@ class ECSignatureCreatorImpl : public ECSignatureCreator {
                     int data_len,
                     std::vector<uint8>* signature) OVERRIDE;
 
+  virtual bool DecodeSignature(const std::vector<uint8>& der_sig,
+                               std::vector<uint8>* out_raw_sig) OVERRIDE;
+
  private:
   ECPrivateKey* key_;
+  size_t signature_len_;
 
   DISALLOW_COPY_AND_ASSIGN(ECSignatureCreatorImpl);
 };
diff --git a/crypto/ec_signature_creator_nss.cc b/crypto/ec_signature_creator_nss.cc
index a85b1e9..3e3626f 100644
--- a/crypto/ec_signature_creator_nss.cc
+++ b/crypto/ec_signature_creator_nss.cc
@@ -24,7 +24,8 @@ namespace {
 SECStatus SignData(SECItem* result,
                    SECItem* input,
                    SECKEYPrivateKey* key,
-                   HASH_HashType hash_type) {
+                   HASH_HashType hash_type,
+                   size_t* out_signature_len) {
   if (key->keyType != ecKey) {
     DLOG(FATAL) << "Should be using an EC key.";
     PORT_SetError(SEC_ERROR_INVALID_ARGS);
@@ -49,6 +50,8 @@ SECStatus SignData(SECItem* result,
   if (rv != SECSuccess)
     return rv;
 
+  *out_signature_len = sig.len;
+
   // DER encode the signature.
   return DSAU_EncodeDerSigWithLen(result, &sig, sig.len);
 }
@@ -56,7 +59,8 @@ SECStatus SignData(SECItem* result,
 }  // namespace
 
 ECSignatureCreatorImpl::ECSignatureCreatorImpl(ECPrivateKey* key)
-    : key_(key) {
+    : key_(key),
+      signature_len_(0) {
   EnsureNSSInit();
 }
 
@@ -79,7 +83,7 @@ bool ECSignatureCreatorImpl::Sign(const uint8* data,
 
   // Sign the secret data and save it to |result|.
   SECStatus rv =
-      SignData(&result, &secret, key_->key(), HASH_AlgSHA1);
+      SignData(&result, &secret, key_->key(), HASH_AlgSHA256, &signature_len_);
   if (rv != SECSuccess) {
     DLOG(ERROR) << "DerSignData: " << PORT_GetError();
     return false;
@@ -91,4 +95,20 @@ bool ECSignatureCreatorImpl::Sign(const uint8* data,
   return true;
 }
 
+bool ECSignatureCreatorImpl::DecodeSignature(
+    const std::vector<uint8>& der_sig,
+    std::vector<uint8>* out_raw_sig) {
+  SECItem der_sig_item;
+  der_sig_item.type = siBuffer;
+  der_sig_item.len = der_sig.size();
+  der_sig_item.data = const_cast<uint8*>(&der_sig[0]);
+
+  SECItem* raw_sig = DSAU_DecodeDerSigToLen(&der_sig_item, signature_len_);
+  if (!raw_sig)
+    return false;
+  out_raw_sig->assign(raw_sig->data, raw_sig->data + raw_sig->len);
+  SECITEM_FreeItem(raw_sig, PR_TRUE /* free SECItem structure itself. */);
+  return true;
+}
+
 }  // namespace crypto
diff --git a/crypto/ec_signature_creator_openssl.cc b/crypto/ec_signature_creator_openssl.cc
index ae443c4..8854f5e 100644
--- a/crypto/ec_signature_creator_openssl.cc
+++ b/crypto/ec_signature_creator_openssl.cc
@@ -22,4 +22,10 @@ bool ECSignatureCreatorImpl::Sign(const uint8* data,
   return false;
 }
 
+bool ECSignatureCreatorImpl::DecodeSignature(const std::vector<uint8>& der_sig,
+                                             std::vector<uint8>* out_raw_sig) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
 }  // namespace crypto
diff --git a/crypto/ec_signature_creator_unittest.cc b/crypto/ec_signature_creator_unittest.cc
index 407b278..df73bec 100644
--- a/crypto/ec_signature_creator_unittest.cc
+++ b/crypto/ec_signature_creator_unittest.cc
@@ -53,17 +53,17 @@ TEST(ECSignatureCreatorTest, BasicTest) {
   std::vector<uint8> public_key_info;
   ASSERT_TRUE(key_original->ExportPublicKey(&public_key_info));
 
-  // This is the algorithm ID for SHA-1 with EC encryption.
-  const uint8 kECDSAWithSHA1AlgorithmID[] = {
-    0x30, 0x0b,
-      0x06, 0x07,
-        0x2a, 0x86, 0x48, 0xce, 0x3d, 0x04, 0x01,
+  // This is the algorithm ID for SHA-256 with EC encryption.
+  const uint8 kECDSAWithSHA256AlgorithmID[] = {
+    0x30, 0x0c,
+      0x06, 0x08,
+        0x2a, 0x86, 0x48, 0xce, 0x3d, 0x04, 0x03, 0x02,
       0x05, 0x00
   };
   crypto::SignatureVerifier verifier;
   ASSERT_TRUE(verifier.VerifyInit(
-      kECDSAWithSHA1AlgorithmID, sizeof(kECDSAWithSHA1AlgorithmID),
-      &signature.front(), signature.size(),
+      kECDSAWithSHA256AlgorithmID, sizeof(kECDSAWithSHA256AlgorithmID),
+      &signature[0], signature.size(),
       &public_key_info.front(), public_key_info.size()));
 
   verifier.VerifyUpdate(reinterpret_cast<const uint8*>(data.c_str()),
diff --git a/net/spdy/spdy_credential_builder.cc b/net/spdy/spdy_credential_builder.cc
index accd33d..8ddda97 100644
--- a/net/spdy/spdy_credential_builder.cc
+++ b/net/spdy/spdy_credential_builder.cc
@@ -55,7 +55,7 @@ int SpdyCredentialBuilder::Build(const std::string& tls_unique,
   public_key = public_key.substr(2, public_key.length());
 
   // Convert the strings into a vector<unit8>
-  std::vector<uint8> proof_vector;
+  std::vector<uint8> der_signature;
   scoped_ptr<crypto::ECPrivateKey> private_key(
       crypto::ECPrivateKey::CreateFromEncryptedPrivateKeyInfo(
           ServerBoundCertService::kEPKIPassword,
@@ -63,7 +63,13 @@ int SpdyCredentialBuilder::Build(const std::string& tls_unique,
   scoped_ptr<crypto::ECSignatureCreator> creator(
       crypto::ECSignatureCreator::Create(private_key.get()));
   creator->Sign(reinterpret_cast<const unsigned char *>(secret.data()),
-                secret.length(), &proof_vector);
+                secret.length(), &der_signature);
+
+  std::vector<uint8> proof_vector;
+  if (!creator->DecodeSignature(der_signature, &proof_vector)) {
+    NOTREACHED();
+    return ERR_UNEXPECTED;
+  }
 
   credential->slot = slot;
   credential->certs.push_back(public_key.as_string());
diff --git a/net/spdy/spdy_test_util_spdy3.cc b/net/spdy/spdy_test_util_spdy3.cc
index cffd9eb..6598a49 100644
--- a/net/spdy/spdy_test_util_spdy3.cc
+++ b/net/spdy/spdy_test_util_spdy3.cc
@@ -63,6 +63,12 @@ class MockECSignatureCreator : public crypto::ECSignatureCreator {
     return true;
   }
 
+  virtual bool DecodeSignature(const std::vector<uint8>& signature,
+                               std::vector<uint8>* out_raw_sig) {
+    *out_raw_sig = signature;
+    return true;
+  }
+
  private:
   crypto::ECPrivateKey* key_;