Refactor WebCrypto code

content/child/webcrypto/webcrypto_util.cc

Index: content/child/webcrypto/webcrypto_util.cc
diff --git a/content/child/webcrypto/webcrypto_util.cc b/content/child/webcrypto/webcrypto_util.cc
index 87ac17465e8639fa40b879cbdaa3d5caa91cbb30..4cc8c857483a2bc461abad03b805a81a1c4077dd 100644
--- a/content/child/webcrypto/webcrypto_util.cc
+++ b/content/child/webcrypto/webcrypto_util.cc
@@ -160,37 +160,17 @@ blink::WebCryptoAlgorithm CreateRsaHashedImportAlgorithm(
       id, new blink::WebCryptoRsaHashedImportParams(CreateAlgorithm(hash_id)));
 }
 
-bool CreateSecretKeyAlgorithm(const blink::WebCryptoAlgorithm& algorithm,
-                              unsigned int keylen_bytes,
-                              blink::WebCryptoKeyAlgorithm* key_algorithm) {
-  switch (algorithm.id()) {
-    case blink::WebCryptoAlgorithmIdHmac: {
-      blink::WebCryptoAlgorithm hash = GetInnerHashAlgorithm(algorithm);
-      if (hash.isNull())
-        return false;
-      if (keylen_bytes > UINT_MAX / 8)
-        return false;
-      *key_algorithm =
-          blink::WebCryptoKeyAlgorithm::createHmac(hash.id(), keylen_bytes * 8);
-      return true;
-    }
-    case blink::WebCryptoAlgorithmIdAesKw:
-    case blink::WebCryptoAlgorithmIdAesCbc:
-    case blink::WebCryptoAlgorithmIdAesCtr:
-    case blink::WebCryptoAlgorithmIdAesGcm:
-      *key_algorithm = blink::WebCryptoKeyAlgorithm::createAes(
-          algorithm.id(), keylen_bytes * 8);
-      return true;
-    default:
-      return false;
-  }
-}
-
 bool ContainsKeyUsages(blink::WebCryptoKeyUsageMask a,
                        blink::WebCryptoKeyUsageMask b) {
   return (a & b) == b;
 }
 
+// TODO(eroman): Move this helper to WebCryptoKey.
+bool KeyUsageAllows(const blink::WebCryptoKey& key,
+                    const blink::WebCryptoKeyUsage usage) {
+  return ((key.usages() & usage) != 0);
+}
+
 bool IsAlgorithmRsa(blink::WebCryptoAlgorithmId alg_id) {
   return alg_id == blink::WebCryptoAlgorithmIdRsaOaep ||
          alg_id == blink::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5;
@@ -202,6 +182,80 @@ bool IsAlgorithmAsymmetric(blink::WebCryptoAlgorithmId alg_id) {
   return IsAlgorithmRsa(alg_id);
 }
 
+Status GetAesGcmTagLength(const blink::WebCryptoAesGcmParams* params,
+                          unsigned int* tag_length_bits) {
+  *tag_length_bits = 128;
+  if (params->hasTagLengthBits())
+    *tag_length_bits = params->optionalTagLengthBits();
+
+  if (*tag_length_bits != 32 && *tag_length_bits != 64 &&
+      *tag_length_bits != 96 && *tag_length_bits != 104 &&
+      *tag_length_bits != 112 && *tag_length_bits != 120 &&
+      *tag_length_bits != 128)

[Ryan Sleevi, 2014/07/17 00:06:55]

Document where these values come from.

[eroman, 2014/07/17 20:37:27]

Done. Documented as:

// The WebCrypto spec defines the default value for the tag length, as well as
// the allowed values for tag length.

+    return Status::ErrorInvalidAesGcmTagLength();
+
+  return Status::Success();
+}
+
+Status GetAesKeyGenLength(const blink::WebCryptoAesKeyGenParams* params,
+                          unsigned int* keylen_bits) {
+  *keylen_bits = params->lengthBits();
+
+  if (*keylen_bits == 128 || *keylen_bits == 256)
+    return Status::Success();
+
+  if (*keylen_bits == 192)

[Ryan Sleevi, 2014/07/17 00:06:54]

Document why.

[eroman, 2014/07/17 20:37:27]

Done. Documented as:

// BoringSSL does not support 192-bit AES.

+    return Status::ErrorAes192BitUnsupported();
+
+  return Status::ErrorGenerateKeyLength();
+}
+
+Status GetHmacKeyGenLength(const blink::WebCryptoHmacKeyGenParams* params,
+                           unsigned int* keylen_bits) {

[Ryan Sleevi, 2014/07/17 00:06:55]

GetHmacKeyGenLengthInBits?

keylen_bits won't be a variable at the callsite.

[eroman, 2014/07/17 20:37:27]

Done.

+  if (!params->hasLengthBits()) {
+    switch (params->hash().id()) {
+      case blink::WebCryptoAlgorithmIdSha1:
+      case blink::WebCryptoAlgorithmIdSha256:
+        *keylen_bits = 512;
+        return Status::Success();
+      case blink::WebCryptoAlgorithmIdSha384:
+      case blink::WebCryptoAlgorithmIdSha512:
+        *keylen_bits = 1024;
+        return Status::Success();
+      default:
+        return Status::ErrorUnsupported();
+    }
+  }
+
+  if (params->optionalLengthBits() % 8)
+    return Status::ErrorGenerateKeyLength();
+
+  *keylen_bits = params->optionalLengthBits();
+
+  // TODO(eroman): NSS fails when generating a zero-length secret key.
+  if (*keylen_bits == 0)
+    return Status::ErrorGenerateKeyLength();
+
+  return Status::Success();
+}
+
+Status VerifyAesKeyLengthForImport(unsigned int keylen_bytes) {
+  if (keylen_bytes == 16 || keylen_bytes == 32)
+    return Status::Success();
+
+  if (keylen_bytes == 24)
+    return Status::ErrorAes192BitUnsupported();
+
+  return Status::ErrorImportAesKeyLength();
+}
+
+Status CheckKeyCreationUsages(blink::WebCryptoKeyUsageMask all_possible_usages,
+                              blink::WebCryptoKeyUsageMask actual_usages) {
+  if (!ContainsKeyUsages(all_possible_usages, actual_usages))
+    return Status::ErrorCreateKeyBadUsages();
+  return Status::Success();
+}
+
 }  // namespace webcrypto
 
 }  // namespace content