Bug 1050202 - Take length parameter into account when deriving HMAC keys r=rbarnes,smaug

dom/crypto/WebCryptoTask.cpp

@@ -202,8 +202,8 @@ MapHashAlgorithmNameToBlockSize(const nsString& aName)
 }
 
 inline nsresult
-GetKeySizeForAlgorithm(JSContext* aCx, const ObjectOrString& aAlgorithm,
-                       size_t& aLength)
+GetKeyLengthForAlgorithm(JSContext* aCx, const ObjectOrString& aAlgorithm,
+                         size_t& aLength)
 {
   aLength = 0;
 
@@ -218,7 +218,7 @@ GetKeySizeForAlgorithm(JSContext* aCx, const ObjectOrString& aAlgorithm,
       algName.EqualsLiteral(WEBCRYPTO_ALG_AES_CTR) ||
       algName.EqualsLiteral(WEBCRYPTO_ALG_AES_GCM) ||
       algName.EqualsLiteral(WEBCRYPTO_ALG_AES_KW)) {
-    RootedDictionary<AesKeyGenParams> params(aCx);
+    RootedDictionary<AesDerivedKeyParams> params(aCx);
     if (NS_FAILED(Coerce(aCx, params, aAlgorithm)) ||
         !params.mLength.WasPassed()) {
       return NS_ERROR_DOM_SYNTAX_ERR;
@@ -233,19 +233,27 @@ GetKeySizeForAlgorithm(JSContext* aCx, const ObjectOrString& aAlgorithm,
     return NS_OK;
   }
 
-  // Determine HMAC key length as the block size of the given hash.
+  // Read HMAC key length from given algorithm object or
+  // determine key length as the block size of the given hash.
   if (algName.EqualsLiteral(WEBCRYPTO_ALG_HMAC)) {
-    RootedDictionary<HmacImportParams> params(aCx);
+    RootedDictionary<HmacDerivedKeyParams> params(aCx);
     if (NS_FAILED(Coerce(aCx, params, aAlgorithm)) ||
         !params.mHash.WasPassed()) {
       return NS_ERROR_DOM_SYNTAX_ERR;
     }
 
+    // Return the passed length, if any.
+    if (params.mLength.WasPassed()) {
+      aLength = params.mLength.Value();
+      return NS_OK;
+    }
+
     nsString hashName;
     if (NS_FAILED(GetAlgorithmName(aCx, params.mHash.Value(), hashName))) {
       return NS_ERROR_DOM_SYNTAX_ERR;
     }
 
+    // Return the given hash algorithm's block size as the key length.
     size_t length = MapHashAlgorithmNameToBlockSize(hashName);
     if (length == 0) {
       return NS_ERROR_DOM_SYNTAX_ERR;
@@ -1942,7 +1950,7 @@ public:
         algName.EqualsLiteral(WEBCRYPTO_ALG_AES_CTR) ||
         algName.EqualsLiteral(WEBCRYPTO_ALG_AES_GCM) ||
         algName.EqualsLiteral(WEBCRYPTO_ALG_AES_KW)) {
-      mEarlyRv = GetKeySizeForAlgorithm(aCx, aAlgorithm, mLength);
+      mEarlyRv = GetKeyLengthForAlgorithm(aCx, aAlgorithm, mLength);
       if (NS_FAILED(mEarlyRv)) {
         return;
       }
@@ -2267,7 +2275,7 @@ public:
     : mSymKey(aKey.GetSymKey())
   {
     size_t length;
-    mEarlyRv = GetKeySizeForAlgorithm(aCx, aTargetAlgorithm, length);
+    mEarlyRv = GetKeyLengthForAlgorithm(aCx, aTargetAlgorithm, length);
 
     if (NS_SUCCEEDED(mEarlyRv)) {
       Init(aCx, aAlgorithm, aKey, length);
@@ -2426,7 +2434,7 @@ public:
                      CryptoKey& aKey, const ObjectOrString& aTargetAlgorithm)
     : mPrivKey(aKey.GetPrivateKey())
   {
-    mEarlyRv = GetKeySizeForAlgorithm(aCx, aTargetAlgorithm, mLength);
+    mEarlyRv = GetKeyLengthForAlgorithm(aCx, aTargetAlgorithm, mLength);
     if (NS_SUCCEEDED(mEarlyRv)) {
       Init(aCx, aAlgorithm, aKey);
     }

dom/crypto/test/tests.js

@@ -1143,6 +1143,33 @@ TestArray.addTest(
   }
 );
 
+// -----------------------------------------------------------------------------
+TestArray.addTest(
+  "Import raw PBKDF2 key and derive a new key using HMAC-SHA-1 with custom length",
+  function() {
+    var that = this;
+
+    function doDerive(x) {
+      var alg = {
+        name: "PBKDF2",
+        hash: "SHA-1",
+        salt: tv.pbkdf2_sha1.salt,
+        iterations: tv.pbkdf2_sha1.iterations
+      };
+
+      var algDerived = {name: "HMAC", hash: "SHA-1", length: 128};
+      return crypto.subtle.deriveKey(alg, x, algDerived, false, ["sign"]);
+    }
+
+    var password = crypto.getRandomValues(new Uint8Array(8));
+    crypto.subtle.importKey("raw", password, "PBKDF2", false, ["deriveKey"])
+      .then(doDerive)
+      .then(complete(that, function (x) {
+        return hasKeyFields(x) && x.algorithm.length == 128;
+      }), error(that));
+  }
+);
+
 // -----------------------------------------------------------------------------
 /*TestArray.addTest(
   "Import raw PBKDF2 key and derive bits using HMAC-SHA-256",

dom/webidl/SubtleCrypto.webidl

@@ -114,6 +114,14 @@ dictionary EcKeyGenParams : Algorithm {
   NamedCurve namedCurve;
 };
 
+dictionary AesDerivedKeyParams : Algorithm {
+  [EnforceRange] unsigned long length;
+};
+
+dictionary HmacDerivedKeyParams : HmacImportParams {
+  [EnforceRange] unsigned long length;
+};
+
 dictionary EcdhKeyDeriveParams : Algorithm {
   CryptoKey public;
 };