update: support RSA-PSS in WebCrypto (#171)

Author: linuxwolf

lib/algorithms/rsassa.js

@@ -155,14 +155,20 @@ function rsassaV15VerifyFn(name) {
 }
 
 // ### RSA-PSS
-// NOTE: no WebCryptoAPI variant -- too many browsers don't
-// implement it yet (e.g., Firefox, Safari)
-
 function rsassaPssSignFn(name) {
   var md = name.replace("PS", "SHA").toLowerCase(),
       hash = name.replace("PS", "SHA-");
 
-  return function(key, pdata) {
+  var alg = {
+    name: "RSA-PSS",
+    hash: {
+      name: hash
+    },
+    saltLength: CONSTANTS.HASHLENGTH[hash] / 8
+  };
+
+  // ### Fallback implementation -- uses forge
+  var fallback = function (key, pdata) {
     // create the digest
     var digest = forge.md[md].create();
     digest.start();
@@ -185,14 +191,43 @@ function rsassaPssSignFn(name) {
       mac: sig
     });
   };
+
+  // ### WebCryptoAPI Implementation
+  var webcrypto = function(key, pdata) {
+    key = rsaUtil.convertToJWK(key, false);
+    var promise;
+    promise = helpers.subtleCrypto.importKey("jwk", key, alg, true, ["sign"]);
+    promise = promise.then(function (key) {
+      return helpers.subtleCrypto.sign(alg, key, pdata);
+    });
+    promise = promise.then(function (result) {
+      var sig = new Buffer(result);
+      return {
+        data: pdata,
+        mac: sig
+      };
+    });
+
+    return promise;
+  };
+
+  return helpers.setupFallback(null, webcrypto, fallback);
 }
 
 function rsassaPssVerifyFn(name) {
   var md = name.replace("PS", "SHA").toLowerCase(),
       hash = name.replace("PS", "SHA-");
 
+  var alg = {
+    name: "RSA-PSS",
+    hash: {
+      name: hash
+    },
+    saltLength: CONSTANTS.HASHLENGTH[hash] / 8
+  };
+
   // ### Fallback implementation -- uses forge
-  return function(key, pdata, mac) {
+  var fallback = function (key, pdata, mac) {
     // create the digest
     var digest = forge.md[md].create();
     digest.start();
@@ -219,6 +254,31 @@ function rsassaPssVerifyFn(name) {
       valid: true
     });
   };
+
+  // ### WebCryptoAPI Implementation
+  var webcrypto = function(key, pdata, mac) {
+    key = rsaUtil.convertToJWK(key, true);
+    var promise;
+    promise = helpers.subtleCrypto.importKey("jwk", key, alg, true, ["verify"]);
+    promise = promise.then(function (key) {
+      return helpers.subtleCrypto.verify(alg, key, mac, pdata);
+    });
+    promise = promise.then(function (result) {
+      if (!result) {
+        return Promise.reject(new Error("verification failed"));
+      }
+
+      return {
+        data: pdata,
+        mac: mac,
+        valid: true
+      };
+    });
+
+    return promise;
+  };
+
+  return helpers.setupFallback(null, webcrypto, fallback);
 }
 
 // ### Public API