Fix and test dummy key conversion (#1172)

Keys converted using makeDummy() were not serialised correctly as they were
treated as unencrypted keys.

src/packet/secret_key.js

@@ -280,11 +280,14 @@ SecretKey.prototype.makeDummy = function () {
     throw new Error("Key is not decrypted");
   }
   this.clearPrivateParams();
+  this.keyMaterial = null;
   this.isEncrypted = false;
   this.s2k = new type_s2k();
   this.s2k.algorithm = 0;
   this.s2k.c = 0;
   this.s2k.type = 'gnu-dummy';
+  this.s2k_usage = 254;
+  this.symmetric = 'aes256';
 };
 
 /**

test/general/key.js

@@ -2817,6 +2817,24 @@ describe('Key', function() {
     await expect(key.validate()).to.be.rejectedWith('Key is invalid');
   });
 
+  it('makeDummy() - the converted key can be parsed', async function() {
+    const { key: key } = await openpgp.generateKey({ userIds: 'dummy <[email protected]>' });
+    key.primaryKey.makeDummy();
+    const parsedKeys = (await openpgp.key.readArmored(key.armor())).keys;
+    expect(parsedKeys).to.not.be.empty;
+  });
+
+  it('makeDummy() - the converted key can be encrypted and decrypted', async function() {
+    const { key: key } = await openpgp.generateKey({ userIds: 'dummy <[email protected]>' });
+    const passphrase = 'passphrase';
+    key.primaryKey.makeDummy();
+    expect(key.isDecrypted()).to.be.true;
+    await key.encrypt(passphrase);
+    expect(key.isDecrypted()).to.be.false;
+    await key.decrypt(passphrase);
+    expect(key.isDecrypted()).to.be.true;
+  });
+
   it('makeDummy() - the converted key is valid but can no longer sign', async function() {
     const { keys: [key] } = await openpgp.key.readArmored(priv_key_rsa);
     await key.decrypt('hello world');