crypto: fix default encoding of LazyTransform

PullRequest nodejs#5522 and nodejs#5500 described the change
of the default encoding into UTF8 in crypto functions.

This however was only changed for the non-streaming API.
The streaming API still used binary as the default encoding.

This commit will change the default streaming API encoding to UTF8
to make both APIs behave the same.

It will also add tests to validate the behavior.

Refs: nodejs#5522
Refs: nodejs#5500
PR-URL: nodejs#8611
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: Lukas Möller

lib/internal/streams/lazy_transform.js

@@ -5,6 +5,7 @@
 
 const stream = require('stream');
 const util = require('util');
+const crypto = require('crypto');
 
 module.exports = LazyTransform;
 
@@ -22,7 +23,11 @@ util.inherits(LazyTransform, stream.Transform);
     get: function() {
       stream.Transform.call(this, this._options);
       this._writableState.decodeStrings = false;
-      this._writableState.defaultEncoding = 'latin1';
+
+      if (!this._options || !this._options.defaultEncoding) {
+        this._writableState.defaultEncoding = crypto.DEFAULT_ENCODING;
+      }
+
       return this[prop];
     },
     set: function(val) {

test/parallel/test-crypto.js

@@ -189,3 +189,42 @@ console.log(crypto.randomBytes(16));
 assert.throws(function() {
   tls.createSecureContext({ crl: 'not a CRL' });
 }, /^Error: Failed to parse CRL$/);
+
+/**
+ * Check if the stream function uses utf8 as a default encoding.
+ **/
+
+function testEncoding(options, assertionHash) {
+  const hash = crypto.createHash('sha256', options);
+  let hashValue = '';
+
+  hash.on('data', (data) => {
+    hashValue += data.toString('hex');
+  });
+
+  hash.on('end', common.mustCall(() => {
+    assert.strictEqual(hashValue, assertionHash);
+  }));
+
+  hash.write('öäü');
+  hash.end();
+}
+
+// Hash of "öäü" in utf8 format
+const assertionHashUtf8 =
+  '4f53d15bee524f082380e6d7247cc541e7cb0d10c64efdcc935ceeb1e7ea345c';
+
+// Hash of "öäü" in latin1 format
+const assertionHashLatin1 =
+  'cd37bccd5786e2e76d9b18c871e919e6eb11cc12d868f5ae41c40ccff8e44830';
+
+testEncoding(undefined, assertionHashUtf8);
+testEncoding({}, assertionHashUtf8);
+
+testEncoding({
+  defaultEncoding: 'utf8'
+}, assertionHashUtf8);
+
+testEncoding({
+  defaultEncoding: 'latin1'
+}, assertionHashLatin1);