[webcrypto] Reject failed operations with a DOMException rather than null.

Source/modules/crypto/NormalizeAlgorithm.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 378 matching lines @@
     return true;
 }
 
 const AlgorithmInfo* lookupAlgorithmInfo(blink::WebCryptoAlgorithmId id)
 {
     if (id < 0 || id >= WTF_ARRAY_LENGTH(algorithmIdToInfo))
         return 0;
     return &algorithmIdToInfo[id];
 }
 
+void completeWithSyntaxError(const String& message, CryptoResult* result)
+{
+    result->completeWithError(blink::WebCryptoErrorTypeSyntax, message);
+}
+
+void completeWithNotSupportedError(const String& message, CryptoResult* result)
+{
+    result->completeWithError(blink::WebCryptoErrorTypeNotSupported, message);
+}
+
+void completeWithDataError(const String& message, CryptoResult* result)
+{
+    result->completeWithError(blink::WebCryptoErrorTypeData, message);
+}
+
 // ErrorContext holds a stack of string literals which describe what was
 // happening at the time the error occurred. This is helpful because
 // parsing of the algorithm dictionary can be recursive and it is difficult to
 // tell what went wrong from a failure alone.
 class ErrorContext {
 public:
     void add(const char* message)
     {
         m_messages.append(message);
     }
 
+    void removeLast()
+    {
+        m_messages.removeLast();
+    }
+
     // Join all of the string literals into a single String.
     String toString() const
     {
         if (m_messages.isEmpty())
             return String();
 
         StringBuilder result;
         const char* Separator = ": ";
 
         size_t length = (m_messages.size() - 1) * strlen(Separator);
@@ skipping 29 matching lines @@
     // This inline size is large enough to avoid having to grow the Vector in
     // the majority of cases (up to 1 nested algorithm identifier).
     Vector<const char*, 10> m_messages;
 };
 
 // Defined by the WebCrypto spec as:
 //
 //     typedef (ArrayBuffer or ArrayBufferView) CryptoOperationData;
 //
 // FIXME: Currently only supports ArrayBufferView.
-bool getOptionalCryptoOperationData(const Dictionary& raw, const char* propertyName, bool& hasProperty, RefPtr<ArrayBufferView>& buffer, const ErrorContext& context, String& errorDetails)
+bool getOptionalCryptoOperationData(const Dictionary& raw, const char* propertyName, bool& hasProperty, RefPtr<ArrayBufferView>& buffer, const ErrorContext& context, CryptoResult* result)
 {
     if (!raw.get(propertyName, buffer)) {
         hasProperty = false;
         return true;
     }
 
     hasProperty = true;
 
     if (!buffer) {
-        errorDetails = context.toString(propertyName, "Not an ArrayBufferView");
+        completeWithSyntaxError(context.toString(propertyName, "Not an ArrayBufferView"), result);
         return false;
     }
 
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //     typedef (ArrayBuffer or ArrayBufferView) CryptoOperationData;
 //
 // FIXME: Currently only supports ArrayBufferView.
-bool getCryptoOperationData(const Dictionary& raw, const char* propertyName, RefPtr<ArrayBufferView>& buffer, const ErrorContext& context, String& errorDetails)
+bool getCryptoOperationData(const Dictionary& raw, const char* propertyName, RefPtr<ArrayBufferView>& buffer, const ErrorContext& context, CryptoResult* result)
 {
     bool hasProperty;
-    bool ok = getOptionalCryptoOperationData(raw, propertyName, hasProperty, buffer, context, errorDetails);
+    bool ok = getOptionalCryptoOperationData(raw, propertyName, hasProperty, buffer, context, result);
     if (!hasProperty) {
-        errorDetails = context.toString(propertyName, "Missing required property");
+        completeWithSyntaxError(context.toString(propertyName, "Missing required property"), result);
         return false;
     }
     return ok;
 }
 
-bool getUint8Array(const Dictionary& raw, const char* propertyName, RefPtr<Uint8Array>& array, const ErrorContext& context, String& errorDetails)
+bool getUint8Array(const Dictionary& raw, const char* propertyName, RefPtr<Uint8Array>& array, const ErrorContext& context, CryptoResult* result)
 {
     if (!raw.get(propertyName, array) || !array) {
-        errorDetails = context.toString(propertyName, "Missing or not a Uint8Array");
+        completeWithSyntaxError(context.toString(propertyName, "Missing or not a Uint8Array"), result);
         return false;
     }
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //     typedef Uint8Array BigInteger;
-bool getBigInteger(const Dictionary& raw, const char* propertyName, RefPtr<Uint8Array>& array, const ErrorContext& context, String& errorDetails)
+bool getBigInteger(const Dictionary& raw, const char* propertyName, RefPtr<Uint8Array>& array, const ErrorContext& context, CryptoResult* result)
 {
-    if (!getUint8Array(raw, propertyName, array, context, errorDetails))
+    if (!getUint8Array(raw, propertyName, array, context, result))
         return false;
 
     if (!array->byteLength()) {
-        errorDetails = context.toString(propertyName, "BigInteger should not be empty");
+        completeWithSyntaxError(context.toString(propertyName, "BigInteger should not be empty"), result);
         return false;
     }
 
     if (!raw.get(propertyName, array) || !array) {
-        errorDetails = context.toString(propertyName, "Missing or not a Uint8Array");
+        completeWithSyntaxError(context.toString(propertyName, "Missing or not a Uint8Array"), result);
         return false;
     }
     return true;
 }
 
 // Gets an integer according to WebIDL's [EnforceRange].
-bool getOptionalInteger(const Dictionary& raw, const char* propertyName, bool& hasProperty, double& value, double minValue, double maxValue, const ErrorContext& context, String& errorDetails)
+bool getOptionalInteger(const Dictionary& raw, const char* propertyName, bool& hasProperty, double& value, double minValue, double maxValue, const ErrorContext& context, CryptoResult* result)
 {
     double number;
     bool ok = raw.get(propertyName, number, hasProperty);
 
     if (!hasProperty)
         return true;
 
     if (!ok || std::isnan(number)) {
-        errorDetails = context.toString(propertyName, "Is not a number");
+        completeWithSyntaxError(context.toString(propertyName, "Is not a number"), result);
         return false;
     }
 
     number = trunc(number);
 
     if (std::isinf(number) || number < minValue || number > maxValue) {
-        errorDetails = context.toString(propertyName, "Outside of numeric range");
+        completeWithSyntaxError(context.toString(propertyName, "Outside of numeric range"), result);
         return false;
     }
 
     value = number;
     return true;
 }
 
-bool getInteger(const Dictionary& raw, const char* propertyName, double& value, double minValue, double maxValue, const ErrorContext& context, String& errorDetails)
+bool getInteger(const Dictionary& raw, const char* propertyName, double& value, double minValue, double maxValue, const ErrorContext& context, CryptoResult* result)
 {
     bool hasProperty;
-    if (!getOptionalInteger(raw, propertyName, hasProperty, value, minValue, maxValue, context, errorDetails))
+    if (!getOptionalInteger(raw, propertyName, hasProperty, value, minValue, maxValue, context, result))
         return false;
 
     if (!hasProperty) {
-        errorDetails = context.toString(propertyName, "Missing required property");
+        completeWithSyntaxError(context.toString(propertyName, "Missing required property"), result);
         return false;
     }
 
     return true;
 }
 
-bool getUint32(const Dictionary& raw, const char* propertyName, uint32_t& value, const ErrorContext& context, String& errorDetails)
+bool getUint32(const Dictionary& raw, const char* propertyName, uint32_t& value, const ErrorContext& context, CryptoResult* result)
 {
     double number;
-    if (!getInteger(raw, propertyName, number, 0, 0xFFFFFFFF, context, errorDetails))
+    if (!getInteger(raw, propertyName, number, 0, 0xFFFFFFFF, context, result))
         return false;
     value = number;
     return true;
 }
 
-bool getUint16(const Dictionary& raw, const char* propertyName, uint16_t& value, const ErrorContext& context, String& errorDetails)
+bool getUint16(const Dictionary& raw, const char* propertyName, uint16_t& value, const ErrorContext& context, CryptoResult* result)
 {
     double number;
-    if (!getInteger(raw, propertyName, number, 0, 0xFFFF, context, errorDetails))
+    if (!getInteger(raw, propertyName, number, 0, 0xFFFF, context, result))
         return false;
     value = number;
     return true;
 }
 
-bool getUint8(const Dictionary& raw, const char* propertyName, uint8_t& value, const ErrorContext& context, String& errorDetails)
+bool getUint8(const Dictionary& raw, const char* propertyName, uint8_t& value, const ErrorContext& context, CryptoResult* result)
 {
     double number;
-    if (!getInteger(raw, propertyName, number, 0, 0xFF, context, errorDetails))
+    if (!getInteger(raw, propertyName, number, 0, 0xFF, context, result))
         return false;
     value = number;
     return true;
 }
 
-bool getOptionalUint32(const Dictionary& raw, const char* propertyName, bool& hasValue, uint32_t& value, const ErrorContext& context, String& errorDetails)
+bool getOptionalUint32(const Dictionary& raw, const char* propertyName, bool& hasValue, uint32_t& value, const ErrorContext& context, CryptoResult* result)
 {
     double number;
-    if (!getOptionalInteger(raw, propertyName, hasValue, number, 0, 0xFFFFFFFF, context, errorDetails))
+    if (!getOptionalInteger(raw, propertyName, hasValue, number, 0, 0xFFFFFFFF, context, result))
         return false;
     if (hasValue)
         value = number;
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary AesCbcParams : Algorithm {
 //      CryptoOperationData iv;
 //    };
-bool parseAesCbcParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseAesCbcParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     RefPtr<ArrayBufferView> iv;
-    if (!getCryptoOperationData(raw, "iv", iv, context, errorDetails))
+    if (!getCryptoOperationData(raw, "iv", iv, context, result))
         return false;
 
     if (iv->byteLength() != 16) {
-        errorDetails = context.toString("iv", "Must be 16 bytes");
+        completeWithDataError(context.toString("iv", "Must be 16 bytes"), result);
         return false;
     }
 
     params = adoptPtr(new blink::WebCryptoAesCbcParams(static_cast<unsigned char*>(iv->baseAddress()), iv->byteLength()));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary AesKeyGenParams : Algorithm {
 //      [EnforceRange] unsigned short length;
 //    };
-bool parseAesKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseAesKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     uint16_t length;
-    if (!getUint16(raw, "length", length, context, errorDetails))
+    if (!getUint16(raw, "length", length, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoAesKeyGenParams(length));
     return true;
 }
 
-bool parseAlgorithm(const Dictionary&, AlgorithmOperation, blink::WebCryptoAlgorithm&, ErrorContext, String&);
+bool parseAlgorithm(const Dictionary&, AlgorithmOperation, blink::WebCryptoAlgorithm&, ErrorContext, CryptoResult*);
 
-bool parseHash(const Dictionary& raw, blink::WebCryptoAlgorithm& hash, ErrorContext context, String& errorDetails)
+bool parseHash(const Dictionary& raw, blink::WebCryptoAlgorithm& hash, ErrorContext context, CryptoResult* result)
 {
     Dictionary rawHash;
     if (!raw.get("hash", rawHash)) {
-        errorDetails = context.toString("hash", "Missing or not a dictionary");
+        completeWithSyntaxError(context.toString("hash", "Missing or not a dictionary"), result);
         return false;
     }
 
     context.add("hash");
-    return parseAlgorithm(rawHash, Digest, hash, context, errorDetails);
+    return parseAlgorithm(rawHash, Digest, hash, context, result);
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary HmacImportParams : Algorithm {
 //      AlgorithmIdentifier hash;
 //    };
-bool parseHmacImportParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseHmacImportParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     blink::WebCryptoAlgorithm hash;
-    if (!parseHash(raw, hash, context, errorDetails))
+    if (!parseHash(raw, hash, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoHmacImportParams(hash));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary HmacKeyGenParams : Algorithm {
 //      AlgorithmIdentifier hash;
 //      // The length (in bits) of the key to generate. If unspecified, the
 //      // recommended length will be used, which is the size of the associated hash function's block
 //      // size.
 //      unsigned long length;
 //    };
-bool parseHmacKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseHmacKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     blink::WebCryptoAlgorithm hash;
-    if (!parseHash(raw, hash, context, errorDetails))
+    if (!parseHash(raw, hash, context, result))
         return false;
 
     bool hasLength;
     uint32_t length = 0;
-    if (!getOptionalUint32(raw, "length", hasLength, length, context, errorDetails))
+    if (!getOptionalUint32(raw, "length", hasLength, length, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoHmacKeyGenParams(hash, hasLength, length));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary RsaHashedImportParams {
 //      AlgorithmIdentifier hash;
 //    };
-bool parseRsaHashedImportParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseRsaHashedImportParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     blink::WebCryptoAlgorithm hash;
-    if (!parseHash(raw, hash, context, errorDetails))
+    if (!parseHash(raw, hash, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoRsaHashedImportParams(hash));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary RsaKeyGenParams : Algorithm {
 //      unsigned long modulusLength;
 //      BigInteger publicExponent;
 //    };
-bool parseRsaKeyGenParams(const Dictionary& raw, uint32_t& modulusLength, RefPtr<Uint8Array>& publicExponent, const ErrorContext& context, String& errorDetails)
+bool parseRsaKeyGenParams(const Dictionary& raw, uint32_t& modulusLength, RefPtr<Uint8Array>& publicExponent, const ErrorContext& context, CryptoResult* result)
 {
-    if (!getUint32(raw, "modulusLength", modulusLength, context, errorDetails))
+    if (!getUint32(raw, "modulusLength", modulusLength, context, result))
         return false;
 
-    if (!getBigInteger(raw, "publicExponent", publicExponent, context, errorDetails))
+    if (!getBigInteger(raw, "publicExponent", publicExponent, context, result))
         return false;
 
     return true;
 }
 
-bool parseRsaKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseRsaKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     uint32_t modulusLength;
     RefPtr<Uint8Array> publicExponent;
-    if (!parseRsaKeyGenParams(raw, modulusLength, publicExponent, context, errorDetails))
+    if (!parseRsaKeyGenParams(raw, modulusLength, publicExponent, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoRsaKeyGenParams(modulusLength, static_cast<const unsigned char*>(publicExponent->baseAddress()), publicExponent->byteLength()));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary RsaHashedKeyGenParams : RsaKeyGenParams {
 //      AlgorithmIdentifier hash;
 //    };
-bool parseRsaHashedKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseRsaHashedKeyGenParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     uint32_t modulusLength;
     RefPtr<Uint8Array> publicExponent;
-    if (!parseRsaKeyGenParams(raw, modulusLength, publicExponent, context, errorDetails))
+    if (!parseRsaKeyGenParams(raw, modulusLength, publicExponent, context, result))
         return false;
 
     blink::WebCryptoAlgorithm hash;
-    if (!parseHash(raw, hash, context, errorDetails))
+    if (!parseHash(raw, hash, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoRsaHashedKeyGenParams(hash, modulusLength, static_cast<const unsigned char*>(publicExponent->baseAddress()), publicExponent->byteLength()));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //    dictionary AesCtrParams : Algorithm {
 //      CryptoOperationData counter;
 //      [EnforceRange] octet length;
 //    };
-bool parseAesCtrParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseAesCtrParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     RefPtr<ArrayBufferView> counter;
-    if (!getCryptoOperationData(raw, "counter", counter, context, errorDetails))
+    if (!getCryptoOperationData(raw, "counter", counter, context, result))
         return false;
 
     uint8_t length;
-    if (!getUint8(raw, "length", length, context, errorDetails))
+    if (!getUint8(raw, "length", length, context, result))
         return false;
 
     params = adoptPtr(new blink::WebCryptoAesCtrParams(length, static_cast<const unsigned char*>(counter->baseAddress()), counter->byteLength()));
     return true;
 }
 
 // Defined by the WebCrypto spec as:
 //
 //     dictionary AesGcmParams : Algorithm {
 //       CryptoOperationData iv;
 //       CryptoOperationData? additionalData;
 //       [EnforceRange] octet? tagLength;  // May be 0-128
 //     }
-bool parseAesGcmParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, String& errorDetails)
+bool parseAesGcmParams(const Dictionary& raw, OwnPtr<blink::WebCryptoAlgorithmParams>& params, const ErrorContext& context, CryptoResult* result)
 {
     RefPtr<ArrayBufferView> iv;
-    if (!getCryptoOperationData(raw, "iv", iv, context, errorDetails))
+    if (!getCryptoOperationData(raw, "iv", iv, context, result))
         return false;
 
     bool hasAdditionalData;
     RefPtr<ArrayBufferView> additionalData;
-    if (!getOptionalCryptoOperationData(raw, "additionalData", hasAdditionalData, additionalData, context, errorDetails))
+    if (!getOptionalCryptoOperationData(raw, "additionalData", hasAdditionalData, additionalData, context, result))
         return false;
 
     double tagLength;
     bool hasTagLength;
-    if (!getOptionalInteger(raw, "tagLength", hasTagLength, tagLength, 0, 128, context, errorDetails))
+    if (!getOptionalInteger(raw, "tagLength", hasTagLength, tagLength, 0, 128, context, result))
         return false;
 
     const unsigned char* ivStart = static_cast<const unsigned char*>(iv->baseAddress());
     unsigned ivLength = iv->byteLength();
 
     const unsigned char* additionalDataStart = hasAdditionalData ? static_cast<const unsigned char*>(additionalData->baseAddress()) : 0;
     unsigned additionalDataLength = hasAdditionalData ? additionalData->byteLength() : 0;
 
     params = adoptPtr(new blink::WebCryptoAesGcmParams(ivStart, ivLength, hasAdditionalData, additionalDataStart, additionalDataLength, hasTagLength, tagLength));
     return true;
 }
 
-bool parseAlgorithmParams(const Dictionary& raw, blink::WebCryptoAlgorithmParamsType type, OwnPtr<blink::WebCryptoAlgorithmParams>& params, ErrorContext& context, String& errorDetails)
+bool parseAlgorithmParams(const Dictionary& raw, blink::WebCryptoAlgorithmParamsType type, OwnPtr<blink::WebCryptoAlgorithmParams>& params, ErrorContext& context, CryptoResult* result)
 {
     switch (type) {
     case blink::WebCryptoAlgorithmParamsTypeNone:
         return true;
     case blink::WebCryptoAlgorithmParamsTypeAesCbcParams:
         context.add("AesCbcParams");
-        return parseAesCbcParams(raw, params, context, errorDetails);
+        return parseAesCbcParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeAesKeyGenParams:
         context.add("AesKeyGenParams");
-        return parseAesKeyGenParams(raw, params, context, errorDetails);
+        return parseAesKeyGenParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeHmacImportParams:
         context.add("HmacImportParams");
-        return parseHmacImportParams(raw, params, context, errorDetails);
+        return parseHmacImportParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeHmacKeyGenParams:
         context.add("HmacKeyGenParams");
-        return parseHmacKeyGenParams(raw, params, context, errorDetails);
+        return parseHmacKeyGenParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeRsaHashedKeyGenParams:
         context.add("RsaHashedKeyGenParams");
-        return parseRsaHashedKeyGenParams(raw, params, context, errorDetails);
+        return parseRsaHashedKeyGenParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeRsaHashedImportParams:
         context.add("RsaHashedImportParams");
-        return parseRsaHashedImportParams(raw, params, context, errorDetails);
+        return parseRsaHashedImportParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeRsaKeyGenParams:
         context.add("RsaKeyGenParams");
-        return parseRsaKeyGenParams(raw, params, context, errorDetails);
+        return parseRsaKeyGenParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeAesCtrParams:
         context.add("AesCtrParams");
-        return parseAesCtrParams(raw, params, context, errorDetails);
+        return parseAesCtrParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeAesGcmParams:
         context.add("AesGcmParams");
-        return parseAesGcmParams(raw, params, context, errorDetails);
+        return parseAesGcmParams(raw, params, context, result);
     case blink::WebCryptoAlgorithmParamsTypeRsaOaepParams:
         // TODO
         notImplemented();
         break;
     }
     ASSERT_NOT_REACHED();
     return false;
 }
 
-bool parseAlgorithm(const Dictionary& raw, AlgorithmOperation op, blink::WebCryptoAlgorithm& algorithm, ErrorContext context, String& errorDetails)
+const char* operationToString(AlgorithmOperation op)
+{
+    switch (op) {
+    case Encrypt:
+        return "encrypt";
+    case Decrypt:
+        return "decrypt";
+    case Sign:
+        return "sign";
+    case Verify:
+        return "verify";
+    case Digest:
+        return "digest";
+    case GenerateKey:
+        return "generateKey";
+    case ImportKey:
+        return "importKey";
+    case DeriveKey:
+        return "deriveKey";
+    case DeriveBits:
+        return "deriveBits";
+    case WrapKey:
+        return "wrapKey";
+    case UnwrapKey:
+        return "unwrapKey";
+    }
+    return 0;
+}
+
+bool parseAlgorithm(const Dictionary& raw, AlgorithmOperation op, blink::WebCryptoAlgorithm& algorithm, ErrorContext context, CryptoResult* result)
 {
     context.add("Algorithm");
 
     if (!raw.isObject()) {
-        errorDetails = context.toString("Not an object");
+        completeWithSyntaxError(context.toString("Not an object"), result);
         return false;
     }
 
     String algorithmName;
     if (!raw.get("name", algorithmName)) {
-        errorDetails = context.toString("name", "Missing or not a string");
+        completeWithSyntaxError(context.toString("name", "Missing or not a string"), result);
         return false;
     }
 
     blink::WebCryptoAlgorithmId algorithmId;
     if (!lookupAlgorithmIdByName(algorithmName, algorithmId)) {
-        errorDetails = context.toString("Unrecognized algorithm name");
+        // FIXME: The spec says to return a SyntaxError if the input contains
+        //        any non-ASCII characters.
+        completeWithNotSupportedError(context.toString("Unrecognized name"), result);
         return false;
     }
 
+    // Remove the "Algorithm:" prefix for all subsequent errors.
+    context.removeLast();
+
     const AlgorithmInfo* algorithmInfo = lookupAlgorithmInfo(algorithmId);
-    context.add(algorithmInfo->name);
 
     if (algorithmInfo->operationToParamsType[op] == Undefined) {
-        errorDetails = context.toString("Unsupported operation");
+        context.add(algorithmIdToName(algorithmId));
+        completeWithNotSupportedError(context.toString("Unsupported operation", operationToString(op)), result);
         return false;
     }
 
     blink::WebCryptoAlgorithmParamsType paramsType = static_cast<blink::WebCryptoAlgorithmParamsType>(algorithmInfo->operationToParamsType[op]);
 
     OwnPtr<blink::WebCryptoAlgorithmParams> params;
-    if (!parseAlgorithmParams(raw, paramsType, params, context, errorDetails))
+    if (!parseAlgorithmParams(raw, paramsType, params, context, result))
         return false;
 
     algorithm = blink::WebCryptoAlgorithm(algorithmId, params.release());
     return true;
 }
 
 } // namespace
 
 bool parseAlgorithm(const Dictionary& raw, AlgorithmOperation op, blink::WebCryptoAlgorithm& algorithm, CryptoResult* result)
 {
-    String errorDetails;
-    if (!parseAlgorithm(raw, op, algorithm, ErrorContext(), errorDetails)) {
-        result->completeWithError(errorDetails);
-        return false;
-    }
-    return true;
+    return parseAlgorithm(raw, op, algorithm, ErrorContext(), result);
 }
 
 const char* algorithmIdToName(blink::WebCryptoAlgorithmId id)
 {
     return lookupAlgorithmInfo(id)->name;
 }
 
 } // namespace WebCore