1 files changed, 33 insertions, 0 deletions
diff --git a/node_modules/tsscmp/lib/index.js b/node_modules/tsscmp/lib/index.js
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+++ b/node_modules/tsscmp/lib/index.js
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+'use strict';
+
+// Implements Brad Hill's Double HMAC pattern from
+// https://www.nccgroup.trust/us/about-us/newsroom-and-events/blog/2011/february/double-hmac-verification/.
+// The approach is similar to the node's native implementation of timing safe buffer comparison that will be available on v6+.
+// https://github.com/nodejs/node/issues/3043
+// https://github.com/nodejs/node/pull/3073
+
+var crypto = require('crypto');
+
+function bufferEqual(a, b) {
+  if (a.length !== b.length) {
+    return false;
+  }
+  for (var i = 0; i < a.length; i++) {
+    if (a[i] !== b[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+function timeSafeCompare(a, b) {
+  var sa = String(a);
+  var sb = String(b);
+  var key = crypto.pseudoRandomBytes(32);
+  var ah = crypto.createHmac('sha256', key).update(sa).digest();
+  var bh = crypto.createHmac('sha256', key).update(sb).digest();
+
+  return bufferEqual(ah, bh) && a === b;
+}
+
+module.exports = timeSafeCompare;