// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/renderer/webcrypto/webcrypto_impl.h"

#include <algorithm>
#include <functional>
#include <map>
#include "base/json/json_reader.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/strings/string_piece.h"
#include "base/values.h"
#include "content/renderer/webcrypto/webcrypto_util.h"
#include "third_party/WebKit/public/platform/WebCryptoAlgorithm.h"
#include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
#include "third_party/WebKit/public/platform/WebCryptoKey.h"
#include "third_party/WebKit/public/platform/WebString.h"

namespace content {

using webcrypto::Status;

namespace {

void CompleteWithError(const Status& status, blink::WebCryptoResult* result) {
  DCHECK(status.IsError());
  if (status.HasErrorDetails())
    result->completeWithError(blink::WebString::fromUTF8(status.ToString()));
  else
    result->completeWithError();
}

bool IsAlgorithmAsymmetric(const blink::WebCryptoAlgorithm& algorithm) {
  // TODO(padolph): include all other asymmetric algorithms once they are
  // defined, e.g. EC and DH.
  return (algorithm.id() == blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5 ||
          algorithm.id() == blink::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5 ||
          algorithm.id() == blink::WebCryptoAlgorithmIdRsaOaep);
}

typedef blink::WebCryptoAlgorithm (*AlgorithmCreationFunc)();

class JwkAlgorithmInfo {
 public:
  JwkAlgorithmInfo()
      : creation_func_(NULL),
        required_key_length_bytes_(NO_KEY_SIZE_REQUIREMENT) {

  }

  explicit JwkAlgorithmInfo(AlgorithmCreationFunc algorithm_creation_func)
      : creation_func_(algorithm_creation_func),
        required_key_length_bytes_(NO_KEY_SIZE_REQUIREMENT) {
  }

  JwkAlgorithmInfo(AlgorithmCreationFunc algorithm_creation_func,
                   unsigned int required_key_length_bits)
      : creation_func_(algorithm_creation_func),
        required_key_length_bytes_(required_key_length_bits / 8) {
    DCHECK((required_key_length_bits % 8) == 0);
  }

  bool CreateAlgorithm(blink::WebCryptoAlgorithm* algorithm) const {
    *algorithm = creation_func_();
    return !algorithm->isNull();
  }

  bool IsInvalidKeyByteLength(size_t byte_length) const {
    if (required_key_length_bytes_ == NO_KEY_SIZE_REQUIREMENT)
      return false;
    return required_key_length_bytes_  != byte_length;
  }

 private:
  enum { NO_KEY_SIZE_REQUIREMENT = UINT_MAX };

  AlgorithmCreationFunc creation_func_;

  // The expected key size for the algorithm or NO_KEY_SIZE_REQUIREMENT.
  unsigned int required_key_length_bytes_;

};

typedef std::map<std::string, JwkAlgorithmInfo> JwkAlgorithmInfoMap;

class JwkAlgorithmRegistry {
 public:
  JwkAlgorithmRegistry() {
    // TODO(eroman):
    // http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-20
    // says HMAC with SHA-2 should have a key size at least as large as the
    // hash output.
    alg_to_info_["HS256"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateHmacAlgorithmByHashId,
                        blink::WebCryptoAlgorithmIdSha256>);
    alg_to_info_["HS384"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateHmacAlgorithmByHashId,
                        blink::WebCryptoAlgorithmIdSha384>);
    alg_to_info_["HS512"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateHmacAlgorithmByHashId,
                         blink::WebCryptoAlgorithmIdSha512>);
    alg_to_info_["RS256"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateRsaSsaAlgorithm,
                         blink::WebCryptoAlgorithmIdSha256>);
    alg_to_info_["RS384"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateRsaSsaAlgorithm,
                         blink::WebCryptoAlgorithmIdSha384>);
    alg_to_info_["RS512"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateRsaSsaAlgorithm,
                         blink::WebCryptoAlgorithmIdSha512>);
    alg_to_info_["RSA1_5"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateAlgorithm,
                         blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5>);
    alg_to_info_["RSA-OAEP"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateRsaOaepAlgorithm,
                         blink::WebCryptoAlgorithmIdSha1>);
    // TODO(padolph): The Web Crypto spec does not enumerate AES-KW 128 yet
    alg_to_info_["A128KW"] =
        JwkAlgorithmInfo(&blink::WebCryptoAlgorithm::createNull, 128);
    // TODO(padolph): The Web Crypto spec does not enumerate AES-KW 256 yet
    alg_to_info_["A256KW"] =
        JwkAlgorithmInfo(&blink::WebCryptoAlgorithm::createNull, 256);
    alg_to_info_["A128GCM"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateAlgorithm,
                         blink::WebCryptoAlgorithmIdAesGcm>, 128);
    alg_to_info_["A256GCM"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateAlgorithm,
                         blink::WebCryptoAlgorithmIdAesGcm>, 256);
    alg_to_info_["A128CBC"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateAlgorithm,
                         blink::WebCryptoAlgorithmIdAesCbc>, 128);
    alg_to_info_["A192CBC"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateAlgorithm,
                         blink::WebCryptoAlgorithmIdAesCbc>, 192);
    alg_to_info_["A256CBC"] = JwkAlgorithmInfo(
        &BindAlgorithmId<webcrypto::CreateAlgorithm,
                         blink::WebCryptoAlgorithmIdAesCbc>, 256);
  }

  // Returns NULL if the algorithm name was not registered.
  const JwkAlgorithmInfo* GetAlgorithmInfo(const std::string& jwk_alg) const {
    const JwkAlgorithmInfoMap::const_iterator pos = alg_to_info_.find(jwk_alg);
    if (pos == alg_to_info_.end())
      return NULL;
    return &pos->second;
  }

 private:
  // Binds a WebCryptoAlgorithmId value to a compatible factory function.
  typedef blink::WebCryptoAlgorithm (*FuncWithWebCryptoAlgIdArg)(
      blink::WebCryptoAlgorithmId);
  template <FuncWithWebCryptoAlgIdArg func,
            blink::WebCryptoAlgorithmId algorithm_id>
  static blink::WebCryptoAlgorithm BindAlgorithmId() {
    return func(algorithm_id);
  }

  JwkAlgorithmInfoMap alg_to_info_;
};

base::LazyInstance<JwkAlgorithmRegistry> jwk_alg_registry =
    LAZY_INSTANCE_INITIALIZER;

bool WebCryptoAlgorithmsConsistent(const blink::WebCryptoAlgorithm& alg1,
                                   const blink::WebCryptoAlgorithm& alg2) {
  DCHECK(!alg1.isNull());
  DCHECK(!alg2.isNull());
  if (alg1.id() != alg2.id())
    return false;
  switch (alg1.id()) {
    case blink::WebCryptoAlgorithmIdHmac:
    case blink::WebCryptoAlgorithmIdRsaOaep:
    case blink::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5:
      if (WebCryptoAlgorithmsConsistent(
              webcrypto::GetInnerHashAlgorithm(alg1),
              webcrypto::GetInnerHashAlgorithm(alg2))) {
        return true;
      }
      break;
    case blink::WebCryptoAlgorithmIdRsaEsPkcs1v1_5:
    case blink::WebCryptoAlgorithmIdSha1:
    case blink::WebCryptoAlgorithmIdSha224:
    case blink::WebCryptoAlgorithmIdSha256:
    case blink::WebCryptoAlgorithmIdSha384:
    case blink::WebCryptoAlgorithmIdSha512:
    case blink::WebCryptoAlgorithmIdAesCbc:
    case blink::WebCryptoAlgorithmIdAesGcm:
    case blink::WebCryptoAlgorithmIdAesCtr:
      return true;
    default:
      NOTREACHED();  // Not a supported algorithm.
      break;
  }
  return false;
}

// Extracts the required string property with key |path| from |dict| and saves
// the result to |*result|. If the property does not exist or is not a string,
// returns an error.
Status GetJwkString(base::DictionaryValue* dict,
                    const std::string& path,
                    std::string* result) {
  base::Value* value = NULL;
  if (!dict->Get(path, &value))
    return Status::ErrorJwkPropertyMissing(path);
  if (!value->GetAsString(result))
    return Status::ErrorJwkPropertyWrongType(path, "string");
  return Status::Success();
}

// Extracts the optional string property with key |path| from |dict| and saves
// the result to |*result| if it was found. If the property exists and is not a
// string, returns an error. Otherwise returns success, and sets
// |*property_exists| if it was found.
Status GetOptionalJwkString(base::DictionaryValue* dict,
                            const std::string& path,
                            std::string* result,
                            bool* property_exists) {
  *property_exists = false;
  base::Value* value = NULL;
  if (!dict->Get(path, &value))
    return Status::Success();

  if (!value->GetAsString(result))
    return Status::ErrorJwkPropertyWrongType(path, "string");

  *property_exists = true;
  return Status::Success();
}

// Extracts the required string property with key |path| from |dict| and saves
// the base64-decoded bytes to |*result|. If the property does not exist or is
// not a string, or could not be base64-decoded, returns an error.
Status GetJwkBytes(base::DictionaryValue* dict,
                   const std::string& path,
                   std::string* result) {
  std::string base64_string;
  Status status = GetJwkString(dict, path, &base64_string);
  if (status.IsError())
    return status;

  if (!webcrypto::Base64DecodeUrlSafe(base64_string, result))
    return Status::ErrorJwkBase64Decode(path);

  return Status::Success();
}

// Extracts the optional boolean property with key |path| from |dict| and saves
// the result to |*result| if it was found. If the property exists and is not a
// boolean, returns an error. Otherwise returns success, and sets
// |*property_exists| if it was found.
Status GetOptionalJwkBool(base::DictionaryValue* dict,
                          const std::string& path,
                          bool* result,
                          bool* property_exists) {
  *property_exists = false;
  base::Value* value = NULL;
  if (!dict->Get(path, &value))
    return Status::Success();

  if (!value->GetAsBoolean(result))
    return Status::ErrorJwkPropertyWrongType(path, "boolean");

  *property_exists = true;
  return Status::Success();
}

}  // namespace

WebCryptoImpl::WebCryptoImpl() {
  Init();
}

void WebCryptoImpl::encrypt(
    const blink::WebCryptoAlgorithm& algorithm,
    const blink::WebCryptoKey& key,
    const unsigned char* data,
    unsigned int data_size,
    blink::WebCryptoResult result) {
  DCHECK(!algorithm.isNull());
  blink::WebArrayBuffer buffer;
  Status status = EncryptInternal(algorithm, key, data, data_size, &buffer);
  if (status.IsError())
    CompleteWithError(status, &result);
  else
    result.completeWithBuffer(buffer);
}

void WebCryptoImpl::decrypt(
    const blink::WebCryptoAlgorithm& algorithm,
    const blink::WebCryptoKey& key,
    const unsigned char* data,
    unsigned int data_size,
    blink::WebCryptoResult result) {
  DCHECK(!algorithm.isNull());
  blink::WebArrayBuffer buffer;
  Status status = DecryptInternal(algorithm, key, data, data_size, &buffer);
  if (status.IsError())
    CompleteWithError(status, &result);
  else
    result.completeWithBuffer(buffer);
}

void WebCryptoImpl::digest(
    const blink::WebCryptoAlgorithm& algorithm,
    const unsigned char* data,
    unsigned int data_size,
    blink::WebCryptoResult result) {
  DCHECK(!algorithm.isNull());
  blink::WebArrayBuffer buffer;
  Status status = DigestInternal(algorithm, data, data_size, &buffer);
  if (status.IsError())
    CompleteWithError(status, &result);
  else
    result.completeWithBuffer(buffer);
}

void WebCryptoImpl::generateKey(
    const blink::WebCryptoAlgorithm& algorithm,
    bool extractable,
    blink::WebCryptoKeyUsageMask usage_mask,
    blink::WebCryptoResult result) {
  DCHECK(!algorithm.isNull());
  if (IsAlgorithmAsymmetric(algorithm)) {
    blink::WebCryptoKey public_key = blink::WebCryptoKey::createNull();
    blink::WebCryptoKey private_key = blink::WebCryptoKey::createNull();
    Status status = GenerateKeyPairInternal(
        algorithm, extractable, usage_mask, &public_key, &private_key);
    if (status.IsError()) {
      CompleteWithError(status, &result);
    } else {
      DCHECK(public_key.handle());
      DCHECK(private_key.handle());
      DCHECK_EQ(algorithm.id(), public_key.algorithm().id());
      DCHECK_EQ(algorithm.id(), private_key.algorithm().id());
      DCHECK_EQ(true, public_key.extractable());
      DCHECK_EQ(extractable, private_key.extractable());
      DCHECK_EQ(usage_mask, public_key.usages());
      DCHECK_EQ(usage_mask, private_key.usages());
      result.completeWithKeyPair(public_key, private_key);
    }
  } else {
    blink::WebCryptoKey key = blink::WebCryptoKey::createNull();
    Status status = GenerateSecretKeyInternal(
        algorithm, extractable, usage_mask, &key);
    if (status.IsError()) {
      CompleteWithError(status, &result);
    } else {
      DCHECK(key.handle());
      DCHECK_EQ(algorithm.id(), key.algorithm().id());
      DCHECK_EQ(extractable, key.extractable());
      DCHECK_EQ(usage_mask, key.usages());
      result.completeWithKey(key);
    }
  }
}

void WebCryptoImpl::importKey(
    blink::WebCryptoKeyFormat format,
    const unsigned char* key_data,
    unsigned int key_data_size,
    const blink::WebCryptoAlgorithm& algorithm_or_null,
    bool extractable,
    blink::WebCryptoKeyUsageMask usage_mask,
    blink::WebCryptoResult result) {
  blink::WebCryptoKey key = blink::WebCryptoKey::createNull();
  Status status = Status::Error();
  if (format == blink::WebCryptoKeyFormatJwk) {
    status = ImportKeyJwk(key_data,
                          key_data_size,
                          algorithm_or_null,
                          extractable,
                          usage_mask,
                          &key);
  } else {
    status = ImportKeyInternal(format,
                               key_data,
                               key_data_size,
                               algorithm_or_null,
                               extractable,
                               usage_mask,
                               &key);
  }
  if (status.IsError()) {
    CompleteWithError(status, &result);
  } else {
    DCHECK(key.handle());
    DCHECK(!key.algorithm().isNull());
    DCHECK_EQ(extractable, key.extractable());
    result.completeWithKey(key);
  }
}

void WebCryptoImpl::exportKey(
    blink::WebCryptoKeyFormat format,
    const blink::WebCryptoKey& key,
    blink::WebCryptoResult result) {
  blink::WebArrayBuffer buffer;
  Status status = ExportKeyInternal(format, key, &buffer);
  if (status.IsError())
    CompleteWithError(status, &result);
  else
    result.completeWithBuffer(buffer);
}

void WebCryptoImpl::sign(
    const blink::WebCryptoAlgorithm& algorithm,
    const blink::WebCryptoKey& key,
    const unsigned char* data,
    unsigned int data_size,
    blink::WebCryptoResult result) {
  DCHECK(!algorithm.isNull());
  blink::WebArrayBuffer buffer;
  Status status = SignInternal(algorithm, key, data, data_size, &buffer);
  if (status.IsError())
    CompleteWithError(status, &result);
  else
    result.completeWithBuffer(buffer);
}

void WebCryptoImpl::verifySignature(
    const blink::WebCryptoAlgorithm& algorithm,
    const blink::WebCryptoKey& key,
    const unsigned char* signature,
    unsigned int signature_size,
    const unsigned char* data,
    unsigned int data_size,
    blink::WebCryptoResult result) {
  DCHECK(!algorithm.isNull());
  bool signature_match = false;
  Status status = VerifySignatureInternal(algorithm,
                                          key,
                                          signature,
                                          signature_size,
                                          data,
                                          data_size,
                                          &signature_match);
  if (status.IsError())
    CompleteWithError(status, &result);
  else
    result.completeWithBoolean(signature_match);
}

Status WebCryptoImpl::ImportKeyJwk(
    const unsigned char* key_data,
    unsigned int key_data_size,
    const blink::WebCryptoAlgorithm& algorithm_or_null,
    bool extractable,
    blink::WebCryptoKeyUsageMask usage_mask,
    blink::WebCryptoKey* key) {

  // The goal of this method is to extract key material and meta data from the
  // incoming JWK, combine them with the input parameters, and ultimately import
  // a Web Crypto Key.
  //
  // JSON Web Key Format (JWK)
  // http://tools.ietf.org/html/draft-ietf-jose-json-web-key-16
  // TODO(padolph): Not all possible values are handled by this code right now
  //
  // A JWK is a simple JSON dictionary with the following entries
  // - "kty" (Key Type) Parameter, REQUIRED
  // - <kty-specific parameters, see below>, REQUIRED
  // - "use" (Key Use) Parameter, OPTIONAL
  // - "alg" (Algorithm) Parameter, OPTIONAL
  // - "extractable" (Key Exportability), OPTIONAL [NOTE: not yet part of JOSE,
  //   see https://www.w3.org/Bugs/Public/show_bug.cgi?id=23796]
  // (all other entries are ignored)
  //
  // OPTIONAL here means that this code does not require the entry to be present
  // in the incoming JWK, because the method input parameters contain similar
  // information. If the optional JWK entry is present, it will be validated
  // against the corresponding input parameter for consistency and combined with
  // it according to rules defined below. A special case is that the method
  // input parameter 'algorithm' is also optional. If it is null, the JWK 'alg'
  // value (if present) is used as a fallback.
  //
  // Input 'key_data' contains the JWK. To build a Web Crypto Key, the JWK
  // values are parsed out and combined with the method input parameters to
  // build a Web Crypto Key:
  // Web Crypto Key type            <-- (deduced)
  // Web Crypto Key extractable     <-- JWK extractable + input extractable
  // Web Crypto Key algorithm       <-- JWK alg + input algorithm
  // Web Crypto Key keyUsage        <-- JWK use + input usage_mask
  // Web Crypto Key keying material <-- kty-specific parameters
  //
  // Values for each JWK entry are case-sensitive and defined in
  // http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-16.
  // Note that not all values specified by JOSE are handled by this code. Only
  // handled values are listed.
  // - kty (Key Type)
  //   +-------+--------------------------------------------------------------+
  //   | "RSA" | RSA [RFC3447]                                                |
  //   | "oct" | Octet sequence (used to represent symmetric keys)            |
  //   +-------+--------------------------------------------------------------+
  // - use (Key Use)
  //   +-------+--------------------------------------------------------------+
  //   | "enc" | encrypt and decrypt operations                               |
  //   | "sig" | sign and verify (MAC) operations                             |
  //   | "wrap"| key wrap and unwrap [not yet part of JOSE]                   |
  //   +-------+--------------------------------------------------------------+
  // - extractable (Key Exportability)
  //   +-------+--------------------------------------------------------------+
  //   | true  | Key may be exported from the trusted environment             |
  //   | false | Key cannot exit the trusted environment                      |
  //   +-------+--------------------------------------------------------------+
  // - alg (Algorithm)
  //   See http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-16
  //   +--------------+-------------------------------------------------------+
  //   | Digital Signature or MAC Algorithm                                   |
  //   +--------------+-------------------------------------------------------+
  //   | "HS256"      | HMAC using SHA-256 hash algorithm                     |
  //   | "HS384"      | HMAC using SHA-384 hash algorithm                     |
  //   | "HS512"      | HMAC using SHA-512 hash algorithm                     |
  //   | "RS256"      | RSASSA using SHA-256 hash algorithm                   |
  //   | "RS384"      | RSASSA using SHA-384 hash algorithm                   |
  //   | "RS512"      | RSASSA using SHA-512 hash algorithm                   |
  //   +--------------+-------------------------------------------------------|
  //   | Key Management Algorithm                                             |
  //   +--------------+-------------------------------------------------------+
  //   | "RSA1_5"     | RSAES-PKCS1-V1_5 [RFC3447]                            |
  //   | "RSA-OAEP"   | RSAES using Optimal Asymmetric Encryption Padding     |
  //   |              | (OAEP) [RFC3447], with the default parameters         |
  //   |              | specified by RFC3447 in Section A.2.1                 |
  //   | "A128KW"     | Advanced Encryption Standard (AES) Key Wrap Algorithm |
  //   |              | [RFC3394] using 128 bit keys                          |
  //   | "A256KW"     | AES Key Wrap Algorithm using 256 bit keys             |
  //   | "A128GCM"    | AES in Galois/Counter Mode (GCM) [NIST.800-38D] using |
  //   |              | 128 bit keys                                          |
  //   | "A256GCM"    | AES GCM using 256 bit keys                            |
  //   | "A128CBC"    | AES in Cipher Block Chaining Mode (CBC) with PKCS #5  |
  //   |              | padding [NIST.800-38A] [not yet part of JOSE, see     |
  //   |              | https://www.w3.org/Bugs/Public/show_bug.cgi?id=23796  |
  //   | "A192CBC"    | AES CBC using 192 bit keys [not yet part of JOSE]     |
  //   | "A256CBC"    | AES CBC using 256 bit keys [not yet part of JOSE]     |
  //   +--------------+-------------------------------------------------------+
  //
  // kty-specific parameters
  // The value of kty determines the type and content of the keying material
  // carried in the JWK to be imported. Currently only two possibilities are
  // supported: a raw key or an RSA public key. RSA private keys are not
  // supported because typical applications seldom need to import a private key,
  // and the large number of JWK parameters required to describe one.
  // - kty == "oct" (symmetric or other raw key)
  //   +-------+--------------------------------------------------------------+
  //   | "k"   | Contains the value of the symmetric (or other single-valued) |
  //   |       | key.  It is represented as the base64url encoding of the     |
  //   |       | octet sequence containing the key value.                     |
  //   +-------+--------------------------------------------------------------+
  // - kty == "RSA" (RSA public key)
  //   +-------+--------------------------------------------------------------+
  //   | "n"   | Contains the modulus value for the RSA public key.  It is    |
  //   |       | represented as the base64url encoding of the value's         |
  //   |       | unsigned big endian representation as an octet sequence.     |
  //   +-------+--------------------------------------------------------------+
  //   | "e"   | Contains the exponent value for the RSA public key.  It is   |
  //   |       | represented as the base64url encoding of the value's         |
  //   |       | unsigned big endian representation as an octet sequence.     |
  //   +-------+--------------------------------------------------------------+
  //
  // Consistency and conflict resolution
  // The 'algorithm_or_null', 'extractable', and 'usage_mask' input parameters
  // may be different than the corresponding values inside the JWK. The Web
  // Crypto spec says that if a JWK value is present but is inconsistent with
  // the input value, it is an error and the operation must fail. If no
  // inconsistency is found, the input and JWK values are combined as follows:
  //
  // algorithm
  //   If an algorithm is provided by both the input parameter and the JWK,
  //   consistency between the two is based only on algorithm ID's (including an
  //   inner hash algorithm if present). In this case if the consistency
  //   check is passed, the input algorithm is used. If only one of either the
  //   input algorithm and JWK alg is provided, it is used as the final
  //   algorithm.
  //
  // extractable
  //   If the JWK extractable is true but the input parameter is false, make the
  //   Web Crypto Key non-extractable. Conversely, if the JWK extractable is
  //   false but the input parameter is true, it is an inconsistency. If both
  //   are true or both are false, use that value.
  //
  // usage_mask
  //   The input usage_mask must be a strict subset of the interpreted JWK use
  //   value, else it is judged inconsistent. In all cases the input usage_mask
  //   is used as the final usage_mask.
  //

  if (!key_data_size)
    return Status::ErrorImportEmptyKeyData();
  DCHECK(key);

  // Parse the incoming JWK JSON.
  base::StringPiece json_string(reinterpret_cast<const char*>(key_data),
                                key_data_size);
  scoped_ptr<base::Value> value(base::JSONReader::Read(json_string));
  // Note, bare pointer dict_value is ok since it points into scoped value.
  base::DictionaryValue* dict_value = NULL;
  if (!value.get() || !value->GetAsDictionary(&dict_value) || !dict_value)
    return Status::ErrorJwkNotDictionary();

  // JWK "kty". Exit early if this required JWK parameter is missing.
  std::string jwk_kty_value;
  Status status = GetJwkString(dict_value, "kty", &jwk_kty_value);
  if (status.IsError())
    return status;

  // JWK "extractable" (optional) --> extractable parameter
  {
    bool jwk_extractable_value = false;
    bool has_jwk_extractable;
    status = GetOptionalJwkBool(dict_value,
                                "extractable",
                                &jwk_extractable_value,
                                &has_jwk_extractable);
    if (status.IsError())
      return status;
    if (has_jwk_extractable && !jwk_extractable_value && extractable)
      return Status::ErrorJwkExtractableInconsistent();
  }

  // JWK "alg" (optional) --> algorithm parameter
  // Note: input algorithm is also optional, so we have six cases to handle.
  // 1. JWK alg present but unrecognized: error
  // 2. JWK alg valid AND input algorithm isNull: use JWK value
  // 3. JWK alg valid AND input algorithm specified, but JWK value
  //      inconsistent with input: error
  // 4. JWK alg valid AND input algorithm specified, both consistent: use
  //      input value (because it has potentially more details)
  // 5. JWK alg missing AND input algorithm isNull: error
  // 6. JWK alg missing AND input algorithm specified: use input value
  blink::WebCryptoAlgorithm algorithm = blink::WebCryptoAlgorithm::createNull();
  const JwkAlgorithmInfo* algorithm_info = NULL;
  std::string jwk_alg_value;
  bool has_jwk_alg;
  status =
      GetOptionalJwkString(dict_value, "alg", &jwk_alg_value, &has_jwk_alg);
  if (status.IsError())
    return status;

  if (has_jwk_alg) {
    // JWK alg present

    // TODO(padolph): Validate alg vs kty. For example kty="RSA" implies alg can
    // only be from the RSA family.

    blink::WebCryptoAlgorithm jwk_algorithm =
        blink::WebCryptoAlgorithm::createNull();
    algorithm_info = jwk_alg_registry.Get().GetAlgorithmInfo(jwk_alg_value);
    if (!algorithm_info || !algorithm_info->CreateAlgorithm(&jwk_algorithm))
      return Status::ErrorJwkUnrecognizedAlgorithm();  // case 1

    // JWK alg valid
    if (algorithm_or_null.isNull()) {
      // input algorithm not specified
      algorithm = jwk_algorithm;  // case 2
    } else {
      // input algorithm specified
      if (!WebCryptoAlgorithmsConsistent(jwk_algorithm, algorithm_or_null))
        return Status::ErrorJwkAlgorithmInconsistent();  // case 3
      algorithm = algorithm_or_null;  // case 4
    }
  } else {
    // JWK alg missing
    if (algorithm_or_null.isNull())
      return Status::ErrorJwkAlgorithmMissing();  // case 5
    algorithm = algorithm_or_null;  // case 6
  }
  DCHECK(!algorithm.isNull());

  // JWK "use" (optional) --> usage_mask parameter
  std::string jwk_use_value;
  bool has_jwk_use;
  status =
      GetOptionalJwkString(dict_value, "use", &jwk_use_value, &has_jwk_use);
  if (status.IsError())
    return status;
  if (has_jwk_use) {
    blink::WebCryptoKeyUsageMask jwk_usage_mask = 0;
    if (jwk_use_value == "enc") {
      jwk_usage_mask =
          blink::WebCryptoKeyUsageEncrypt | blink::WebCryptoKeyUsageDecrypt;
    } else if (jwk_use_value == "sig") {
      jwk_usage_mask =
          blink::WebCryptoKeyUsageSign | blink::WebCryptoKeyUsageVerify;
    } else if (jwk_use_value == "wrap") {
      jwk_usage_mask =
          blink::WebCryptoKeyUsageWrapKey | blink::WebCryptoKeyUsageUnwrapKey;
    } else {
      return Status::ErrorJwkUnrecognizedUsage();
    }
    if ((jwk_usage_mask & usage_mask) != usage_mask) {
      // A usage_mask must be a subset of jwk_usage_mask.
      return Status::ErrorJwkUsageInconsistent();
    }
  }

  // JWK keying material --> ImportKeyInternal()
  if (jwk_kty_value == "oct") {

    std::string jwk_k_value;
    status = GetJwkBytes(dict_value, "k", &jwk_k_value);
    if (status.IsError())
      return status;

    // Some JWK alg ID's embed information about the key length in the alg ID
    // string. For example "A128CBC" implies the JWK carries 128 bits
    // of key material. For such keys validate that enough bytes were provided.
    // If this validation is not done, then it would be possible to select a
    // different algorithm by passing a different lengthed key, since that is
    // how WebCrypto interprets things.
    if (algorithm_info &&
        algorithm_info->IsInvalidKeyByteLength(jwk_k_value.size())) {
      return Status::ErrorJwkIncorrectKeyLength();
    }

    return ImportKeyInternal(blink::WebCryptoKeyFormatRaw,
                             reinterpret_cast<const uint8*>(jwk_k_value.data()),
                             jwk_k_value.size(),
                             algorithm,
                             extractable,
                             usage_mask,
                             key);
  } else if (jwk_kty_value == "RSA") {

    // An RSA public key must have an "n" (modulus) and an "e" (exponent) entry
    // in the JWK, while an RSA private key must have those, plus at least a "d"
    // (private exponent) entry.
    // See http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-18,
    // section 6.3.

    // RSA private key import is not currently supported, so fail here if a "d"
    // entry is found.
    // TODO(padolph): Support RSA private key import.
    if (dict_value->HasKey("d"))
      return Status::ErrorJwkRsaPrivateKeyUnsupported();

    std::string jwk_n_value;
    status = GetJwkBytes(dict_value, "n", &jwk_n_value);
    if (status.IsError())
      return status;
    std::string jwk_e_value;
    status = GetJwkBytes(dict_value, "e", &jwk_e_value);
    if (status.IsError())
      return status;

    return ImportRsaPublicKeyInternal(
        reinterpret_cast<const uint8*>(jwk_n_value.data()),
        jwk_n_value.size(),
        reinterpret_cast<const uint8*>(jwk_e_value.data()),
        jwk_e_value.size(),
        algorithm,
        extractable,
        usage_mask,
        key);

  } else {
    return Status::ErrorJwkUnrecognizedKty();
  }

  return Status::Success();
}

}  // namespace content