From e8465350fc2d1f4c09f25f18118bfb8fdf7fb1b4 Mon Sep 17 00:00:00 2001
From: Bart Butler <bart.c.butler@gmail.com>
Date: Sat, 28 Feb 2015 03:43:39 -0800
Subject: [PATCH] Support for crypto API keygen in IE11 on Windows 7 and 8

---
 src/crypto/public_key/rsa.js | 58 +++++++++++++++++++++++++-----------
 src/util.js                  |  9 ++++--
 2 files changed, 47 insertions(+), 20 deletions(-)

diff --git a/src/crypto/public_key/rsa.js b/src/crypto/public_key/rsa.js
index fe293897..1d92216e 100644
--- a/src/crypto/public_key/rsa.js
+++ b/src/crypto/public_key/rsa.js
@@ -140,12 +140,33 @@ function RSA() {
     // Native RSA keygen using Web Crypto
     //
 
+    function convertKeyOperation(keyop, errmsg) {
+      return new Promise(function(resolve, reject) {
+        keyop.onerror = function (err) { 
+          reject(new Error(errmsg));
+        }
+        keyop.oncomplete = function (e) {
+          resolve(e.target.result);
+        }
+      });
+    }
+
     if (webCrypto) {
       var Euint32 = new Uint32Array([parseInt(E, 16)]); // get integer of exponent
       var Euint8 = new Uint8Array(Euint32.buffer); // get bytes of exponent
       var keyGenOpt;
 
-      if (window.crypto.subtle) {
+      var keys;
+      if (window.crypto && window.crypto.webkitSubtle) {
+        // outdated spec implemented by Webkit
+        keyGenOpt = {
+          name: 'RSA-OAEP',
+          modulusLength: B, // the specified keysize in bits
+          publicExponent: Euint8.subarray(0, 3), // take three bytes (max 65537)
+        };
+        keys = webCrypto.generateKey(keyGenOpt, true, ['encrypt', 'decrypt']);
+      }
+      else {
         // current standard spec
         keyGenOpt = {
           name: 'RSASSA-PKCS1-v1_5',
@@ -155,29 +176,30 @@ function RSA() {
             name: 'SHA-1' // not required for actual RSA keys, but for crypto api 'sign' and 'verify'
           }
         };
-        return webCrypto.generateKey(keyGenOpt, true, ['sign', 'verify']).then(exportKey).then(decodeKey);
-
-      } else if (window.crypto.webkitSubtle) {
-        // outdated spec implemented by Webkit
-        keyGenOpt = {
-          name: 'RSA-OAEP',
-          modulusLength: B, // the specified keysize in bits
-          publicExponent: Euint8.subarray(0, 3), // take three bytes (max 65537)
-        };
-        return webCrypto.generateKey(keyGenOpt, true, ['encrypt', 'decrypt']).then(exportKey).then(function(key) {
-          if (key instanceof ArrayBuffer) {
-            // parse raw ArrayBuffer bytes to jwk/json (WebKit/Safari quirk)
-            return decodeKey(JSON.parse(String.fromCharCode.apply(null, new Uint8Array(key))));
-          }
-          return decodeKey(key);
-        });
+        
+        keys = webCrypto.generateKey(keyGenOpt, true, ['sign', 'verify']);
+        if(!(keys instanceof Promise)) { // IE11 KeyOperation
+          keys = convertKeyOperation(keys, 'Error generating RSA key pair.');
+        }
       }
+
+      return keys.then(exportKey).then(function(key) {
+        if (key instanceof ArrayBuffer) {
+          // parse raw ArrayBuffer bytes to jwk/json (WebKit/Safari/IE11 quirk)
+          return decodeKey(JSON.parse(String.fromCharCode.apply(null, new Uint8Array(key))));
+        }
+        return decodeKey(key);
+      });
     }
 
     function exportKey(keypair) {
       // export the generated keys as JsonWebKey (JWK)
       // https://tools.ietf.org/html/draft-ietf-jose-json-web-key-33
-      return webCrypto.exportKey('jwk', keypair.privateKey);
+      key = webCrypto.exportKey('jwk', keypair.privateKey);
+      if(!(key instanceof Promise)) { // IE11 KeyOperation
+        key = convertKeyOperation(key, 'Error exporting RSA key pair.');
+      }
+      return key;
     }
 
     function decodeKey(jwk) {
diff --git a/src/util.js b/src/util.js
index 89a08387..c2f9c386 100644
--- a/src/util.js
+++ b/src/util.js
@@ -320,8 +320,13 @@ module.exports = {
       return;
     }
 
-    if (typeof window !== 'undefined' && window.crypto) {
-      return window.crypto.subtle || window.crypto.webkitSubtle;
+    if (typeof window !== 'undefined') {
+      if(window.crypto) {
+        return window.crypto.subtle || window.crypto.webkitSubtle;
+      }
+      if(window.msCrypto) {
+        return window.msCrypto.subtle;
+      }
     }
   }
 };