deal with empty encrypted data correctly

src/message.js

@@ -219,21 +219,21 @@ Message.prototype.getText = function() {
 Message.prototype.encrypt = function(keys, passwords, sessionKey) {
   let symAlgo, msg, symEncryptedPacket;
   return Promise.resolve().then(() => {
-    if (keys) {
-      symAlgo = enums.read(enums.symmetric, keyModule.getPreferredSymAlgo(keys));
-    } else if (passwords) {
-      symAlgo = enums.read(enums.symmetric, config.encryption_cipher);
-    } else {
-      throw new Error('No keys or passwords');
-    }
-
     if (sessionKey) {
       if (!util.isUint8Array(sessionKey.data) || !util.isString(sessionKey.algorithm)) {
         throw new Error('Invalid session key for encryption.');
       }
       symAlgo = sessionKey.algorithm;
       sessionKey = sessionKey.data;
+    } else if (keys && keys.length) {
+      symAlgo = enums.read(enums.symmetric, keyModule.getPreferredSymAlgo(keys));
+    } else if (passwords && passwords.length) {
+      symAlgo = enums.read(enums.symmetric, config.encryption_cipher);
     } else {
+      throw new Error('No keys, passwords, or session key provided.');
+    }
+
+    if (!sessionKey) {
       sessionKey = crypto.generateSessionKey(symAlgo);
     }
 

src/openpgp.js

@@ -252,17 +252,17 @@ export function decrypt({ message, privateKey, publicKeys, sessionKey, password,
   return message.decrypt(privateKey, sessionKey, password).then(message => {
 
     const result = parseMessage(message, format);
-    if (result.data) { // verify
-      if (!publicKeys) {
-        publicKeys = [];
-      }
-      if (signature) {
-        //detached signature
-        result.signatures = message.verifyDetached(signature, publicKeys);
-      } else {
-        result.signatures = message.verify(publicKeys);
-      }
+
+    if (!publicKeys) {
+      publicKeys = [];
     }
+    if (signature) {
+      //detached signature
+      result.signatures = message.verifyDetached(signature, publicKeys);
+    } else {
+      result.signatures = message.verify(publicKeys);
+    }
+
     return result;
 
   }).catch(onError.bind(null, 'Error decrypting message'));

test/general/openpgp.js

@@ -715,6 +715,27 @@ describe('OpenPGP.js public api tests', function() {
           });
         });
 
+        it('should encrypt/sign and decrypt/verify with null string input', function() {
+          var encOpt = {
+            data: '',
+            publicKeys: publicKey.keys,
+            privateKeys: privateKey.keys
+          };
+          var decOpt = {
+            privateKey: privateKey.keys[0],
+            publicKeys: publicKey.keys
+          };
+          return openpgp.encrypt(encOpt).then(function(encrypted) {
+            decOpt.message = openpgp.message.readArmored(encrypted.data);
+            return openpgp.decrypt(decOpt);
+          }).then(function(decrypted) {
+            expect(decrypted.data).to.equal('');
+            expect(decrypted.signatures[0].valid).to.be.true;
+            expect(decrypted.signatures[0].keyid.toHex()).to.equal(privateKey.keys[0].getSigningKeyPacket().getKeyId().toHex());
+            expect(decrypted.signatures[0].signature.packets.length).to.equal(1);
+          });
+        });
+
         it('should encrypt/sign and decrypt/verify with detached signatures', function() {
           var encOpt = {
             data: plaintext,
@@ -1242,7 +1263,7 @@ describe('OpenPGP.js public api tests', function() {
             throw new Error('Error expected.');
           })
           .catch(function(error) {
-            expect(error.message).to.match(/No keys or passwords/);
+            expect(error.message).to.match(/No keys, passwords, or session key provided/);
           });
         });