[webcrypto] Add JWK symmetric key AES-KW unwrap for NSS.

content/child/webcrypto/shared_crypto.cc

Index: content/child/webcrypto/shared_crypto.cc
diff --git a/content/child/webcrypto/shared_crypto.cc b/content/child/webcrypto/shared_crypto.cc
index b0097c1cad593c903258e167bf641a44c76f8aa1..7d54bdf26168614cdc5cdcf73f04fafcb58c6211 100644
--- a/content/child/webcrypto/shared_crypto.cc
+++ b/content/child/webcrypto/shared_crypto.cc
@@ -26,6 +26,11 @@ bool KeyUsageAllows(const blink::WebCryptoKey& key,
   return ((key.usages() & usage) != 0);
 }
 
+bool KeyUsageAllowsAnyOf(const blink::WebCryptoKey& key,
+                         const blink::WebCryptoKeyUsageMask usage_mask) {
+  return ((key.usages() & usage_mask) != 0);
+}
+
 bool IsValidAesKeyLengthBits(unsigned int length_bits) {
   return length_bits == 128 || length_bits == 192 || length_bits == 256;
 }
@@ -233,6 +238,104 @@ Status ImportKeyRaw(const CryptoData& key_data,
   }
 }
 
+// Validates the size of data input to AES-KW. AES-KW requires the input data
+// size to be at least 24 bytes and a multiple of 8 bytes.
+Status CheckAesKwInputSize(const CryptoData& aeskw_input_data) {
+  if (aeskw_input_data.byte_length() < 24)
+    return Status::ErrorDataTooSmall();
+  if (aeskw_input_data.byte_length() % 8)
+    return Status::ErrorInvalidAesKwDataLength();
+  return Status::Success();
+}
+
+Status UnwrapKeyRaw(const CryptoData& wrapped_key_data,
+                    const blink::WebCryptoKey& wrapping_key,
+                    const blink::WebCryptoAlgorithm& wrapping_algorithm,
+                    const blink::WebCryptoAlgorithm& algorithm_or_null,
+                    bool extractable,
+                    blink::WebCryptoKeyUsageMask usage_mask,
+                    blink::WebCryptoKey* key) {
+  // Must provide an algorithm when unwrapping a raw key
+  if (algorithm_or_null.isNull())
+    return Status::ErrorMissingAlgorithmUnwrapRawKey();
+
+  // TODO(padolph): Handle other wrapping algorithms
+  switch (wrapping_algorithm.id()) {
+    case blink::WebCryptoAlgorithmIdAesKw: {
+      platform::SymKey* platform_wrapping_key;
+      Status status = ToPlatformSymKey(wrapping_key, &platform_wrapping_key);
+      if (status.IsError())
+        return status;
+      status = CheckAesKwInputSize(wrapped_key_data);
+      if (status.IsError())
+        return status;
+      return platform::UnwrapSymKeyAesKw(wrapped_key_data,
+                                         platform_wrapping_key,
+                                         algorithm_or_null,
+                                         extractable,
+                                         usage_mask,
+                                         key);
+    }
+    case blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5: {
+      platform::PrivateKey* platform_wrapping_key;
+      Status status =
+          ToPlatformPrivateKey(wrapping_key, &platform_wrapping_key);
+      if (status.IsError())
+        return status;
+      if (!wrapped_key_data.byte_length())
+        return Status::ErrorDataTooSmall();
+      return platform::UnwrapSymKeyRsaEs(wrapped_key_data,
+                                         platform_wrapping_key,
+                                         algorithm_or_null,
+                                         extractable,
+                                         usage_mask,
+                                         key);
+    }
+    default:
+      return Status::ErrorUnsupported();
+  }
+}
+
+Status UnwrapKeyDecryptAndImport(
+    blink::WebCryptoKeyFormat format,
+    const CryptoData& wrapped_key_data,
+    const blink::WebCryptoKey& wrapping_key,
+    const blink::WebCryptoAlgorithm& wrapping_algorithm,
+    const blink::WebCryptoAlgorithm& algorithm_or_null,
+    bool extractable,
+    blink::WebCryptoKeyUsageMask usage_mask,
+    blink::WebCryptoKey* key) {
+  blink::WebArrayBuffer buffer;
+  Status status =
+      Decrypt(wrapping_algorithm, wrapping_key, wrapped_key_data, &buffer);
+  if (status.IsError())
+    return status;
+  status = ImportKey(format,
+                     CryptoData(buffer),
+                     algorithm_or_null,
+                     extractable,
+                     usage_mask,
+                     key);
+  // NOTE! Returning the details of any ImportKey() failure here would leak
+  // information about the plaintext internals of the encrypted key. Instead,
+  // collapse any error into the generic Status::Error().
+  return status.IsError() ? Status::Error() : Status::Success();
+}
+
+Status DecryptAesKw(const blink::WebCryptoAlgorithm& algorithm,
+                    const blink::WebCryptoKey& key,
+                    const CryptoData& data,
+                    blink::WebArrayBuffer* buffer) {
+  platform::SymKey* sym_key;
+  Status status = ToPlatformSymKey(key, &sym_key);
+  if (status.IsError())
+    return status;
+  status = CheckAesKwInputSize(data);
+  if (status.IsError())
+    return status;
+  return platform::DecryptAesKw(sym_key, data, buffer);
+}
+
 }  // namespace
 
 void Init() { platform::Init(); }
@@ -262,18 +365,38 @@ Status Decrypt(const blink::WebCryptoAlgorithm& algorithm,
                const blink::WebCryptoKey& key,
                const CryptoData& data,
                blink::WebArrayBuffer* buffer) {
-  if (!KeyUsageAllows(key, blink::WebCryptoKeyUsageDecrypt))
-    return Status::ErrorUnexpected();
   if (algorithm.id() != key.algorithm().id())
     return Status::ErrorUnexpected();
 
   switch (algorithm.id()) {
     case blink::WebCryptoAlgorithmIdAesCbc:
+    case blink::WebCryptoAlgorithmIdAesGcm:
+      if (!KeyUsageAllows(key, blink::WebCryptoKeyUsageDecrypt))

[eroman, 2014/03/17 19:47:47]

I don't like having an extra switch for verifying the usage.

How about instead having different entry points, like:

DecryptForUnwrap() --> or add the check directly into
UnwrapKeyDecryptAndImport()
Decrypt()
DecryptDontCheckUsages()

[padolph, 2014/03/17 22:12:49]

Done.

+        return Status::ErrorUnexpected();
+      break;
+    case blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5:
+      if (!KeyUsageAllowsAnyOf(key,
+                               blink::WebCryptoKeyUsageDecrypt |
+                                   blink::WebCryptoKeyUsageUnwrapKey))
+        return Status::ErrorUnexpected();
+      break;
+    case blink::WebCryptoAlgorithmIdAesKw:
+      if (!KeyUsageAllows(key, blink::WebCryptoKeyUsageUnwrapKey))
+        return Status::ErrorUnexpected();
+      break;
+    default:
+      return Status::ErrorUnsupported();
+  }
+
+  switch (algorithm.id()) {
+    case blink::WebCryptoAlgorithmIdAesCbc:
       return EncryptDecryptAesCbc(DECRYPT, algorithm, key, data, buffer);
     case blink::WebCryptoAlgorithmIdAesGcm:
       return EncryptDecryptAesGcm(DECRYPT, algorithm, key, data, buffer);
     case blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5:
       return DecryptRsaEsPkcs1v1_5(algorithm, key, data, buffer);
+    case blink::WebCryptoAlgorithmIdAesKw:
+      return DecryptAesKw(algorithm, key, data, buffer);
     default:
       return Status::ErrorUnsupported();
   }
@@ -424,8 +547,9 @@ Status ExportKey(blink::WebCryptoKeyFormat format,
         return status;
       return platform::ExportKeySpki(public_key, buffer);
     }
-    case blink::WebCryptoKeyFormatPkcs8:
     case blink::WebCryptoKeyFormatJwk:
+      return ExportKeyJwk(key, buffer);
+    case blink::WebCryptoKeyFormatPkcs8:
       // TODO(eroman):
       return Status::ErrorUnsupported();
     default:
@@ -539,50 +663,29 @@ Status UnwrapKey(blink::WebCryptoKeyFormat format,
   if (wrapping_algorithm.id() != wrapping_key.algorithm().id())
     return Status::ErrorUnexpected();
 
-  // TODO(padolph): Handle formats other than raw
-  if (format != blink::WebCryptoKeyFormatRaw)
-    return Status::ErrorUnsupported();
-
-  // Must provide an algorithm when unwrapping a raw key
-  if (format == blink::WebCryptoKeyFormatRaw && algorithm_or_null.isNull())
-    return Status::ErrorMissingAlgorithmUnwrapRawKey();
-
-  // TODO(padolph): Handle other wrapping algorithms
-  switch (wrapping_algorithm.id()) {
-    case blink::WebCryptoAlgorithmIdAesKw: {
-      platform::SymKey* platform_wrapping_key;
-      Status status = ToPlatformSymKey(wrapping_key, &platform_wrapping_key);
-      if (status.IsError())
-        return status;
-      // AES-KW requires the wrapped key data size must be at least 24 bytes and
-      // also a multiple of 8 bytes.
-      if (wrapped_key_data.byte_length() < 24)
-        return Status::ErrorDataTooSmall();
-      if (wrapped_key_data.byte_length() % 8)
-        return Status::ErrorInvalidAesKwDataLength();
-      return platform::UnwrapSymKeyAesKw(wrapped_key_data,
-                                         platform_wrapping_key,
-                                         algorithm_or_null,
-                                         extractable,
-                                         usage_mask,
-                                         key);
-    }
-    case blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5: {
-      platform::PrivateKey* platform_wrapping_key;
-      Status status =
-          ToPlatformPrivateKey(wrapping_key, &platform_wrapping_key);
-      if (status.IsError())
-        return status;
-      if (!wrapped_key_data.byte_length())
-        return Status::ErrorDataTooSmall();
-      return platform::UnwrapSymKeyRsaEs(wrapped_key_data,
-                                         platform_wrapping_key,
-                                         algorithm_or_null,
-                                         extractable,
-                                         usage_mask,
-                                         key);
-    }
+  switch (format) {
+    case blink::WebCryptoKeyFormatRaw:
+      return UnwrapKeyRaw(wrapped_key_data,
+                          wrapping_key,
+                          wrapping_algorithm,
+                          algorithm_or_null,
+                          extractable,
+                          usage_mask,
+                          key);
+    case blink::WebCryptoKeyFormatJwk:
+      return UnwrapKeyDecryptAndImport(format,
+                                       wrapped_key_data,
+                                       wrapping_key,
+                                       wrapping_algorithm,
+                                       algorithm_or_null,
+                                       extractable,
+                                       usage_mask,
+                                       key);
+    case blink::WebCryptoKeyFormatSpki:
+    case blink::WebCryptoKeyFormatPkcs8:
+      return Status::ErrorUnsupported();  // TODO(padolph)
     default:
+      NOTREACHED();
       return Status::ErrorUnsupported();
   }
 }