returnSessionKey flag in encrypt function

src/message.js

@@ -253,7 +253,13 @@ Message.prototype.encrypt = function(keys, passwords, sessionKey) {
   }).then(() => {
     msg.packets.push(symEncryptedPacket);
     symEncryptedPacket.packets = new packet.List(); // remove packets after encryption
-    return msg;
+    return {
+      message: msg,
+      sessionKey: {
+        data: sessionKey,
+        algorithm: enums.read(enums.symmetric, symAlgo)
+      }
+    };
   });
 };
 

src/openpgp.js

@@ -187,11 +187,11 @@ export function decryptKey({ privateKey, passphrase }) {
  *                                                message: full Message object if 'armor' is false, signature: detached signature if 'detached' is true}
  * @static
  */
-export function encrypt({ data, publicKeys, privateKeys, passwords, sessionKey, filename, armor=true, detached=false, signature=null }) {
+export function encrypt({ data, publicKeys, privateKeys, passwords, sessionKey, filename, armor=true, detached=false, signature=null, returnSessionKey=false}) {
   checkData(data); publicKeys = toArray(publicKeys); privateKeys = toArray(privateKeys); passwords = toArray(passwords);
 
   if (!nativeAEAD() && asyncProxy) { // use web worker if web crypto apis are not supported
-    return asyncProxy.delegate('encrypt', { data, publicKeys, privateKeys, passwords, sessionKey, filename, armor, detached, signature });
+    return asyncProxy.delegate('encrypt', { data, publicKeys, privateKeys, passwords, sessionKey, filename, armor, detached, signature, returnSessionKey });
   }
   var result = {};
   return Promise.resolve().then(() => {
@@ -214,11 +214,14 @@ export function encrypt({ data, publicKeys, privateKeys, passwords, sessionKey,
     }
     return message.encrypt(publicKeys, passwords, sessionKey);
 
-  }).then(message => {
+  }).then(encrypted => {
     if (armor) {
-      result.data = message.armor();
+      result.data = encrypted.message.armor();
     } else {
-      result.message = message;
+      result.message = encrypted.message;
+    }
+    if (returnSessionKey) {
+      result.sessionKey = encrypted.sessionKey;
     }
     return result;
   }).catch(onError.bind(null, 'Error encrypting message'));

test/general/key.js

@@ -931,7 +931,7 @@ describe('Key', function() {
       key = newKey;
       return openpgp.message.fromText('hello').encrypt([key.key]);
     }).then(function(msg) {
-      return msg.decrypt(key.key);
+      return msg.message.decrypt(key.key);
     }).catch(function(err) {
       expect(err.message).to.equal('Private key is not decrypted.');
     });

test/general/openpgp.js

@@ -629,6 +629,27 @@ describe('OpenPGP.js public api tests', function() {
           });
         });
 
+        it('should encrypt then decrypt using returned session key', function() {
+          var encOpt = {
+            data: plaintext,
+            publicKeys: publicKey.keys,
+            returnSessionKey: true
+          };
+
+          return openpgp.encrypt(encOpt).then(function(encrypted) {
+            expect(encrypted.data).to.match(/^-----BEGIN PGP MESSAGE/);
+            var decOpt = {
+              sessionKey: encrypted.sessionKey,
+              message: openpgp.message.readArmored(encrypted.data)
+            };
+            return openpgp.decrypt(decOpt);
+          }).then(function(decrypted) {
+            expect(decrypted.data).to.equal(plaintext);
+            expect(decrypted.signatures).to.exist;
+            expect(decrypted.signatures.length).to.equal(0);
+          });
+        });
+
         it('should encrypt using custom session key and decrypt using session key', function() {
           var sessionKey = {
             data: openpgp.crypto.generateSessionKey('aes256'),