crypto,tls: fix mutability of return values

If you alter the array returned by `tls.getCiphers()`,
`crypto.getCiphers()`, `crypto.getHashes()`, or `crypto.getCurves()`, it
will alter subsequent return values from those functions.

```js
'use strict';

const crypto = require('crypto');

var hashes = crypto.getHashes();

hashes.splice(0, hashes.length);

hashes.push('some-arbitrary-value');

console.log(crypto.getHashes()); // "['some-arbitrary-value']"
```

This is surprising. Change functions to return copy of array instead.

PR-URL: https://github.com/nodejs/node/pull/10795
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/internal/util.js b/lib/internal/util.js
index b7facfbbbf..5384d59fc5 100644
--- a/lib/internal/util.js
+++ b/lib/internal/util.js
@@ -158,7 +158,7 @@ exports.cachedResult = function cachedResult(fn) {
   return () => {
     if (result === undefined)
       result = fn();
-    return result;
+    return result.slice();
   };
 };