tls: copy the Buffer object before using

`convertNPNProtocols` and `convertALPNProtocols' uses the `protocols`
buffer object as it is, and if it is modified outside of core, it
might have an impact. This patch makes a copy of the buffer object,
before using it.

PR-URL: https://github.com/nodejs/node/pull/8055
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

1 files changed, 7 insertions, 10 deletions

diff --git a/lib/tls.js b/lib/tls.js
index 849daeb07f3..765e1658ea9 100644
--- a/lib/tls.js
+++ b/lib/tls.js
@@ -49,22 +49,19 @@ function convertProtocols(protocols) {
 exports.convertNPNProtocols = function(protocols, out) {
   // If protocols is Array - translate it into buffer
   if (Array.isArray(protocols)) {
-    protocols = convertProtocols(protocols);
-  }
-  // If it's already a Buffer - store it
-  if (protocols instanceof Buffer) {
-    out.NPNProtocols = protocols;
+    out.NPNProtocols = convertProtocols(protocols);
+  } else if (protocols instanceof Buffer) {
+    // Copy new buffer not to be modified by user.
+    out.NPNProtocols = Buffer.from(protocols);
   }
 };
 
 exports.convertALPNProtocols = function(protocols, out) {
   // If protocols is Array - translate it into buffer
   if (Array.isArray(protocols)) {
-    protocols = convertProtocols(protocols);
-  }
-  // If it's already a Buffer - store it
-  if (protocols instanceof Buffer) {
-    // copy new buffer not to be modified by user
+    out.ALPNProtocols = convertProtocols(protocols);
+  } else if (protocols instanceof Buffer) {
+    // Copy new buffer not to be modified by user.
     out.ALPNProtocols = Buffer.from(protocols);
   }
 };