Add PGP api for changing a user's passphrase

src/js/crypto/pgp.js

@@ -184,6 +184,55 @@ define(function(require) {
         });
     };
 
+    /**
+     * Change the passphrase of an ascii armored private key.
+     */
+    PGP.prototype.changePassphrase = function(options, callback) {
+        var privKey, packets;
+
+        if (!options.privateKeyArmored ||
+            typeof options.oldPassphrase !== 'string' ||
+            typeof options.newPassphrase !== 'string') {
+            callback({
+                errMsg: 'Could not export keys!'
+            });
+            return;
+        }
+
+        // read armored key
+        try {
+            privKey = openpgp.key.readArmored(options.privateKeyArmored).keys[0];
+        } catch (e) {
+            callback({
+                errMsg: 'Importing key failed. Parsing error!'
+            });
+            return;
+        }
+
+        // decrypt private key with passphrase
+        if (!privKey.decrypt(options.oldPassphrase)) {
+            callback({
+                errMsg: 'Old passphrase incorrect!'
+            });
+            return;
+        }
+
+        // encrypt key with new passphrase
+        try {
+            packets = privKey.getAllKeyPackets();
+            for (var i = 0; i < packets.length; i++) {
+                packets[i].encrypt(options.newPassphrase);
+            }
+        } catch (e) {
+            callback({
+                errMsg: 'Setting new passphrase failed!'
+            });
+            return;
+        }
+
+        callback(null, privKey.armor());
+    };
+
     /**
      * Encrypt and sign a pgp message for a list of receivers
      */

test/new-unit/pgp-test.js

@@ -120,6 +120,28 @@ define(function(require) {
             });
         });
 
+        describe('Change passphrase of private key', function() {
+            it('should work', function(done) {
+                pgp.changePassphrase({
+                    privateKeyArmored: privkey,
+                    oldPassphrase: passphrase,
+                    newPassphrase: 'yxcv'
+                }, function(err, reEncryptedKey) {
+                    expect(err).to.not.exist;
+                    expect(reEncryptedKey).to.exist;
+
+                    pgp.importKeys({
+                        passphrase: 'yxcv',
+                        privateKeyArmored: reEncryptedKey,
+                        publicKeyArmored: pubkey
+                    }, function(err) {
+                        expect(err).to.not.exist;
+                        done();
+                    });
+                });
+            });
+        });
+
         describe('Encrypt/Sign/Decrypt/Verify', function() {
             var message = 'asdfs\n\nThursday, Nov 21, 2013 7:38 PM asdf@example.com wrote:\n' +
                 '> asdf\n' +