[webcrypto] Add JWK import for HMAC and AES-CBC key.

content/renderer/webcrypto/webcrypto_impl.cc

Index: content/renderer/webcrypto/webcrypto_impl.cc
diff --git a/content/renderer/webcrypto/webcrypto_impl.cc b/content/renderer/webcrypto/webcrypto_impl.cc
index 6eeb3daf5a0cb07de9dc19128ed3e2913338054b..d4562f8fcc67ee8f46243bc50eb3bf9b6537b95b 100644
--- a/content/renderer/webcrypto/webcrypto_impl.cc
+++ b/content/renderer/webcrypto/webcrypto_impl.cc
@@ -4,15 +4,242 @@
 
 #include "content/renderer/webcrypto/webcrypto_impl.h"
 
+#include <algorithm>
+#include <map>
+#include "base/base64.h"
+#include "base/json/json_reader.h"
+#include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/strings/string_piece.h"
+#include "base/values.h"
 #include "third_party/WebKit/public/platform/WebArrayBuffer.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"
 
 namespace content {
 
+namespace {
+
+// TODO(padolph) Similar Create*Algorithm() methods are in
+// webcrypto_impl_unittest.cc. Find a common place to put these.
+
+WebKit::WebCryptoAlgorithm CreateAlgorithm(WebKit::WebCryptoAlgorithmId id) {
+  return WebKit::WebCryptoAlgorithm::adoptParamsAndCreate(id, NULL);
+}
+
+WebKit::WebCryptoAlgorithm CreateAlgorithmWithInnerHash(
+    WebKit::WebCryptoAlgorithmId algorithm_id,
+    unsigned short hash_key_length) {
+  WebKit::WebCryptoAlgorithmId hashId;
+  switch (hash_key_length) {
+    case 160:
+      hashId = WebKit::WebCryptoAlgorithmIdSha1;
+      break;
+    case 224:
+      hashId = WebKit::WebCryptoAlgorithmIdSha224;
+      break;
+    case 256:
+      hashId = WebKit::WebCryptoAlgorithmIdSha256;
+      break;
+    case 384:
+      hashId = WebKit::WebCryptoAlgorithmIdSha384;
+      break;
+    case 512:
+      hashId = WebKit::WebCryptoAlgorithmIdSha384;
+      break;
+  }
+  return WebKit::WebCryptoAlgorithm::adoptParamsAndCreate(
+      algorithm_id,
+      new WebKit::WebCryptoHmacParams(CreateAlgorithm(hashId)));
+}
+
+WebKit::WebCryptoAlgorithm CreateHmacAlgorithm(unsigned short hash_key_length) {
+  return CreateAlgorithmWithInnerHash(
+      WebKit::WebCryptoAlgorithmIdHmac,
+      hash_key_length);
+}
+
+WebKit::WebCryptoAlgorithm CreateRsaSsaAlgorithm(
+    unsigned short hash_key_length) {
+  return CreateAlgorithmWithInnerHash(
+      WebKit::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5,
+      hash_key_length);
+}
+
+WebKit::WebCryptoAlgorithm CreateRsaOaepAlgorithm(
+    unsigned short hash_key_length) {
+  return CreateAlgorithmWithInnerHash(
+      WebKit::WebCryptoAlgorithmIdRsaOaep,
+      hash_key_length);
+}
+
+WebKit::WebCryptoAlgorithm CreateAesAlgorithm(
+    WebKit::WebCryptoAlgorithmId aes_alg_id,
+    unsigned short length) {
+  return WebKit::WebCryptoAlgorithm::adoptParamsAndCreate(
+      aes_alg_id,
+      new WebKit::WebCryptoAesKeyGenParams(length));
+}
+
+WebKit::WebCryptoAlgorithm CreateAesCbcAlgorithm(unsigned short length) {
+  return CreateAesAlgorithm(WebKit::WebCryptoAlgorithmIdAesCbc, length);
+}
+
+WebKit::WebCryptoAlgorithm CreateAesGcmAlgorithm(unsigned short length) {
+  return CreateAesAlgorithm(WebKit::WebCryptoAlgorithmIdAesGcm, length);
+}
+
+bool Base64DecodeUrlSafe(const std::string& input, std::string* output) {
+  std::string base64EncodedText(input);
+  std::replace(base64EncodedText.begin(), base64EncodedText.end(), '-', '+');
+  std::replace(base64EncodedText.begin(), base64EncodedText.end(), '_', '/');
+  base64EncodedText.append((4 - base64EncodedText.size() % 4) % 4, '=');
+  return base::Base64Decode(base64EncodedText, output);
+}
+
+// Identifiers for all JWK "alg" (algorithm) values handled by this code. The
+// "enum trick" is used to force int type, so a user type is not required in
+// web_crypto_impl.h
+enum {
+  kJwkAlgorithmHs256,
+  kJwkAlgorithmHs384,
+  kJwkAlgorithmHs512,
+  kJwkAlgorithmRs256,
+  kJwkAlgorithmRs384,
+  kJwkAlgorithmRs512,
+  kJwkAlgorithmRsa1_5,
+  kJwkAlgorithmRsaOaep,
+  kJwkAlgorithmA128Kw,
+  kJwkAlgorithmA256Kw,
+  kJwkAlgorithmA128Gcm,
+  kJwkAlgorithmA256Gcm,
+  kJwkAlgorithmA128Cbc,
+  kJwkAlgorithmA256Cbc,
+  kJwkAlgorithmA384Cbc,
+  kJwkAlgorithmA512Cbc
+};
+
+WebKit::WebCryptoAlgorithmId JwkAlgIdToWebCryptoAlgId(int jwk_algorithm_id) {
+  switch (jwk_algorithm_id) {
+    case kJwkAlgorithmHs256:
+    case kJwkAlgorithmHs384:
+    case kJwkAlgorithmHs512:
+      return WebKit::WebCryptoAlgorithmIdHmac;
+    case kJwkAlgorithmRs256:
+    case kJwkAlgorithmRs384:
+    case kJwkAlgorithmRs512:
+      return WebKit::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5;
+    case kJwkAlgorithmRsa1_5:
+      return WebKit::WebCryptoAlgorithmIdRsaEsPkcs1v1_5;
+    case kJwkAlgorithmRsaOaep:
+      return WebKit::WebCryptoAlgorithmIdRsaOaep;
+    case kJwkAlgorithmA128Kw:
+    case kJwkAlgorithmA256Kw:
+      // TODO(padolph) Support AES keywrap algorithm, required for JWK but not
+      // present in the Web Crypto spec.
+      return WebKit::WebCryptoAlgorithmIdNone;
+    case kJwkAlgorithmA128Gcm:
+    case kJwkAlgorithmA256Gcm:
+      return WebKit::WebCryptoAlgorithmIdAesGcm;
+    case kJwkAlgorithmA128Cbc:
+    case kJwkAlgorithmA256Cbc:
+    case kJwkAlgorithmA384Cbc:
+    case kJwkAlgorithmA512Cbc:
+      return WebKit::WebCryptoAlgorithmIdAesCbc;
+    default:
+      DCHECK(false);
+      return WebKit::WebCryptoAlgorithmIdNone;
+  }
+}
+
+unsigned short JwkAlgIdToKeyLengthBits(int jwk_algorithm_id) {
+  switch (jwk_algorithm_id) {
+    case kJwkAlgorithmA128Kw:
+    case kJwkAlgorithmA128Gcm:
+    case kJwkAlgorithmA128Cbc:
+      return 128;
+    case kJwkAlgorithmHs256:
+    case kJwkAlgorithmA256Kw:
+    case kJwkAlgorithmRs256:
+    case kJwkAlgorithmA256Gcm:
+    case kJwkAlgorithmA256Cbc:
+      return 256;
+    case kJwkAlgorithmHs384:
+    case kJwkAlgorithmRs384:
+    case kJwkAlgorithmA384Cbc:
+      return 384;
+    case kJwkAlgorithmHs512:
+    case kJwkAlgorithmRs512:
+    case kJwkAlgorithmA512Cbc:
+      return 512;
+    default:
+      return 0;
+  }
+}
+
+typedef std::map<std::string, int> StringIntMap;
+
+// Syntactic sugar to make runtime initialization of a std::map more palatable,
+// similar to what you can do in C++11 or with Boost.Assign.
+// Example:
+//  StringIntMap my_map;
+//  // instead of this
+//  my_map.insert(std::make_pair("a", 1);
+//  my_map.insert(std::make_pair("b", 2);
+//  my_map.insert(std::make_pair("c", 3);
+//  my_map.insert(std::make_pair("d", 4);
+//  // do this
+//  map_fill<StringIntMap>
+//    ("a", 1)
+//    ("b", 2)
+//    ("c", 3)
+//    ("d", 4)
+//    .to(my_map);

[Ryan Sleevi, 2013/10/04 23:19:11]

Why is this syntactic sugar needed, when

my_map["a"] = 1 is 'just as' good.

I note 'just as' because it "technically" is equiv to my_map.insert("a",
int()).second->second = 1, but in terms of compiler generated code, my
experience is it all collapses the same, and avoids the added syntactic sugars.

[padolph, 2013/10/05 02:57:42]

Done.

+template <typename MapType>
+class FillMap {
+ public:
+  typedef typename MapType::key_type KeyType;
+  typedef typename MapType::mapped_type MappedType;
+  FillMap(const KeyType& key, const MappedType& val) { operator()(key, val); }
+  FillMap& operator()(const KeyType& key, const MappedType& val) {
+    map_.insert(std::make_pair(key, val));
+    return *this;
+  }
+  void to(MapType& map) { map.swap(map_); }
+ private:
+  MapType map_;
+};
+
+void InitJwkAlgorithmMap(StringIntMap& jwk_algorithm_map)
+{
+  // Note: A*CBC are not yet present in the JOSE JWA spec
+  // http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-16
+  FillMap<StringIntMap>
+    ("HS256"   , kJwkAlgorithmHs256  )
+    ("HS384"   , kJwkAlgorithmHs384  )
+    ("HS512"   , kJwkAlgorithmHs512  )
+    ("RS256"   , kJwkAlgorithmRs256  )
+    ("RS384"   , kJwkAlgorithmRs384  )
+    ("RS512"   , kJwkAlgorithmRs512  )
+    ("RSA1_5"  , kJwkAlgorithmRsa1_5 )
+    ("RSA-OAEP", kJwkAlgorithmRsaOaep)
+    ("A128KW"  , kJwkAlgorithmA128Kw )
+    ("A256KW"  , kJwkAlgorithmA256Kw )
+    ("A128GCM" , kJwkAlgorithmA128Gcm)
+    ("A256GCM" , kJwkAlgorithmA256Gcm)
+    ("A128CBC" , kJwkAlgorithmA128Cbc)
+    ("A256CBC" , kJwkAlgorithmA256Cbc)
+    ("A384CBC" , kJwkAlgorithmA384Cbc)
+    ("A512CBC" , kJwkAlgorithmA512Cbc)
+    .to(jwk_algorithm_map);
+}
+
+}  // namespace
+
 WebCryptoImpl::WebCryptoImpl() {
   Init();
+  InitJwkAlgorithmMap(jwk_algorithm_map_);
 }
 
 void WebCryptoImpl::encrypt(
@@ -66,21 +293,32 @@ void WebCryptoImpl::importKey(
     WebKit::WebCryptoResult result) {
   WebKit::WebCryptoKeyType type;
   scoped_ptr<WebKit::WebCryptoKeyHandle> handle;
+  WebKit::WebCryptoAlgorithm modified_algorithm = algorithm;
 
-  if (!ImportKeyInternal(format,
-                         key_data,
-                         key_data_size,
-                         algorithm,
-                         usage_mask,
-                         &handle,
-                         &type)) {
-    result.completeWithError();
-    return;
+  if (format == WebKit::WebCryptoKeyFormatJwk) {
+    if (!ImportKeyJwk(key_data,
+                      key_data_size,
+                      &handle,
+                      &type,
+                      &extractable,
+                      &modified_algorithm,
+                      &usage_mask)) {
+      result.completeWithError();
+    }
+  } else {
+    if (!ImportKeyInternal(format,
+                           key_data,
+                           key_data_size,
+                           modified_algorithm,
+                           usage_mask,
+                           &handle,
+                           &type)) {
+      result.completeWithError();
+    }
   }
 
-  WebKit::WebCryptoKey key(
-      WebKit::WebCryptoKey::create(
-          handle.release(), type, extractable, algorithm, usage_mask));
+  WebKit::WebCryptoKey key(WebKit::WebCryptoKey::create(
+      handle.release(), type, extractable, modified_algorithm, usage_mask));
 
   result.completeWithKey(key);
 }
@@ -121,4 +359,214 @@ void WebCryptoImpl::verifySignature(
   }
 }
 
+bool WebCryptoImpl::ImportKeyJwk(
+    const unsigned char* key_data,
+    unsigned key_data_size,
+    scoped_ptr<WebKit::WebCryptoKeyHandle>* handle,
+    WebKit::WebCryptoKeyType* type,
+    bool* extractable,
+    WebKit::WebCryptoAlgorithm* algorithm,
+    WebKit::WebCryptoKeyUsageMask* usage_mask) {
+
+  // JSON Web Key Format (JWK)
+  // http://self-issued.info/docs/draft-ietf-jose-json-web-key.html (JOSE)

[Ryan Sleevi, 2013/10/04 23:19:11]

Let's refer to a canonical draft URL at the IETF, rather than Mike's homepage.

http://tools.ietf.org/html/draft-ietf-jose-json-web-key-16 (for example)

[padolph, 2013/10/05 02:57:42]

Done.

+  // 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]
+  // (all other entries are ignored)
+  //
+  // Input key_data contains the JWK. To build a Web Crypto Key, the JWK values
+  // are parsed out and used as follows:
+  // Web Crypto Key type            <-- (deduced)
+  // Web Crypto Key extractable     <-- extractable
+  // Web Crypto Key algorithm       <-- alg
+  // Web Crypto Key keyUsage        <-- usage
+  // Web Crypto Key keying material <-- kty-specific parameters
+  //
+  // Values for each 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]         |
+  //   | "A256CBC"    | AES CBC using 256 bit keys [not yet part of JOSE]     |
+  //   | "A384CBC"    | AES CBC using 384 bit keys [not yet part of JOSE]     |
+  //   | "A512CBC"    | AES CBC using 512 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.     |
+  //   +-------+--------------------------------------------------------------+
+  //
+  // Conflict resolution
+  // The type, algorithm, extractable, and usage_mask input parameters may be
+  // different from similar values inside the JWK. Conflicts are resolved as
+  // follows:
+  // type:        Deduce value from JWK contents only, ignore input value
+  // algorithm:   Use JWK value if present, otherwise use input value
+  // extractable: If JWK value present, logical AND of the input and JWK values,
+  //              otherwise use input value
+  // keyUsage:    Use JWK value if present, otherwise use input value

[Ryan Sleevi, 2013/10/04 23:19:11]

These are all things that should be in the spec before we ship something.

I'm updating it this weekend, but per the WebCrypto mailing list, if a JWK value
is present, and it is inconsistent with the input value, it's an error and the
op fails. We should be sure to implement that algorithm.

http://lists.w3.org/Archives/Public/public-webcrypto/2013Sep/0042.html

[padolph, 2013/10/05 02:57:42]

The other parameters are easy, but can you please define "consistent" for
algorithm? I assume this is just the general algorithm type, plus the inner hash
type if the algorithm has one, but does not check consistency of other
parameters like key length, exponent, etc.

I'm concerned this requires the user knowing ahead of time the exact details of
the JWK he is importing which seems like a big burden, especially if say it is
inside a JWE received from a remote site. 

For example, the client does not normally have to know if a public key from a
remote site is RSAES-PKCS1-v1_5 or RSA-OEAP to use it to encrypt something. Is
that the kind of consistency my code needs to be aware of, so the API user can
guess and use either one as the input algorithm?

+
+  std::string jsonStr(key_data, key_data + key_data_size);

[Ryan Sleevi, 2013/10/04 23:19:11]

json_str

However, you don't need to use std::string, but can use base::StringPiece
instead to avoid the copy.

[padolph, 2013/10/05 02:57:42]

Done.

+  scoped_ptr<base::Value> value(base::JSONReader::Read(jsonStr));
+  // 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 false;
+
+  // JWK "kty". Exit early if this required JWK parameter is missing.
+  std::string jwk_kty_value;
+  if (!dict_value->GetString("kty", &jwk_kty_value))
+    return false;
+
+  // JWK "extractable" --> extractable parameter
+  bool jwk_extractable_value;
+  if (dict_value->GetBoolean("extractable", &jwk_extractable_value)) {
+    *extractable &= jwk_extractable_value;
+  }
+
+  // JWK "alg" --> algorithm parameter
+  std::string jwk_alg_value;
+  if (dict_value->GetString("alg", &jwk_alg_value)) {
+    const StringIntMap::iterator pos = jwk_algorithm_map_.find(jwk_alg_value);
+    if (pos == jwk_algorithm_map_.end())
+      return false;
+    const int jwk_algorithm_id = pos->second;
+    const unsigned short key_length_bits =
+        JwkAlgIdToKeyLengthBits(jwk_algorithm_id);
+    const WebKit::WebCryptoAlgorithmId webcrypto_algorithm_id =
+        JwkAlgIdToWebCryptoAlgId(jwk_algorithm_id);
+    switch (webcrypto_algorithm_id) {
+      case WebKit::WebCryptoAlgorithmIdHmac:
+        *algorithm = CreateHmacAlgorithm(key_length_bits);
+        break;
+      case WebKit::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5:
+        *algorithm = CreateRsaSsaAlgorithm(key_length_bits);
+        break;
+      case WebKit::WebCryptoAlgorithmIdRsaEsPkcs1v1_5:
+        *algorithm = CreateAlgorithm(webcrypto_algorithm_id);
+        break;
+      case WebKit::WebCryptoAlgorithmIdRsaOaep:
+        *algorithm = CreateRsaOaepAlgorithm(key_length_bits);
+        break;
+      case WebKit::WebCryptoAlgorithmIdAesGcm:
+        *algorithm = CreateAesGcmAlgorithm(key_length_bits);
+        break;
+      case WebKit::WebCryptoAlgorithmIdAesCbc:
+        *algorithm = CreateAesCbcAlgorithm(key_length_bits);
+        break;
+      default:
+        return false;
+    }
+  }
+
+  // JWK "use" --> usage_mask parameter
+  std::string jwk_use_value;
+  if (dict_value->GetString("use", &jwk_use_value)) {
+    if (jwk_use_value == "enc") {
+      *usage_mask =
+          WebKit::WebCryptoKeyUsageEncrypt | WebKit::WebCryptoKeyUsageDecrypt;
+    } else if (jwk_use_value == "sig") {
+      *usage_mask =
+          WebKit::WebCryptoKeyUsageSign | WebKit::WebCryptoKeyUsageVerify;
+    } else if (jwk_use_value == "wrap") {
+      *usage_mask =
+          WebKit::WebCryptoKeyUsageWrapKey | WebKit::WebCryptoKeyUsageUnwrapKey;
+    } else {
+      return false;
+    }
+  }
+
+  // JWK keying material --> ImportKeyInternal()
+  if (jwk_kty_value == "oct") {
+    std::string jwk_k_value_url64;
+    if (!dict_value->GetString("k", &jwk_k_value_url64))
+      return false;
+    std::string jwk_k_value;
+    if (!Base64DecodeUrlSafe(jwk_k_value_url64, &jwk_k_value))
+      return false;
+    const std::vector<uint8> data(jwk_k_value.begin(), jwk_k_value.end());
+    if (!ImportKeyInternal(WebKit::WebCryptoKeyFormatRaw,
+                           &data[0],
+                           data.size(),
+                           *algorithm,
+                           *usage_mask,
+                           handle,
+                           type))
+      return false;
+  } else if (jwk_kty_value == "RSA") {
+    // TODO(padolph): RSA public key
+    return false;
+  } else {
+    return false;
+  }
+
+  return true;
+}
+
 }  // namespace content