From f6d96352fb4af965225e1795816512425aa7f65d Mon Sep 17 00:00:00 2001
From: Chen Yangjian <252317+dotnil@users.noreply.github.com>
Date: Thu, 24 Jan 2019 11:21:09 +0800
Subject: [PATCH] fix regex in utils.stackTraceFilter to prevent ReDoS #3416

if the stack trace begins with a large error message (>= 20k charactors), and user leaves `--full-trace` disabled, `utils.stackTraceFilter()` takes ages to finish. Large error messages is quite possible when user makes containment assertions such as `expect(content).to.contain(word)`.
---
 lib/utils.js             |  4 +--
 test/unit/runner.spec.js | 54 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/lib/utils.js b/lib/utils.js
index 8dc41bc924..bf50ee8ee9 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -671,8 +671,6 @@ exports.stackTraceFilter = function() {
   function isMochaInternal(line) {
     return (
       ~line.indexOf('node_modules' + slash + 'mocha' + slash) ||
-      ~line.indexOf('node_modules' + slash + 'mocha.js') ||
-      ~line.indexOf('bower_components' + slash + 'mocha.js') ||
       ~line.indexOf(slash + 'mocha.js')
     );
   }
@@ -701,7 +699,7 @@ exports.stackTraceFilter = function() {
       }
 
       // Clean up cwd(absolute)
-      if (/\(?.+:\d+:\d+\)?$/.test(line)) {
+      if (/:\d+:\d+\)?$/.test(line)) {
         line = line.replace('(' + cwd, '(');
       }
 
diff --git a/test/unit/runner.spec.js b/test/unit/runner.spec.js
index 7ae4984117..7f212d9c59 100644
--- a/test/unit/runner.spec.js
+++ b/test/unit/runner.spec.js
@@ -496,6 +496,60 @@ describe('Runner', function() {
         runner.failHook(hook, err);
       });
     });
+
+    describe('hugeStackTrace', function() {
+      beforeEach(function() {
+        if (path.sep !== '/') {
+          this.skip();
+        }
+      });
+
+      it('should not hang if the error message is ridiculously long single line', function(done) {
+        var hook = new Hook();
+        var data = [];
+        // mock a long message
+        for (var i = 0; i < 10000; i++) data[i] = {a: 1};
+        var message = JSON.stringify(data);
+        var err = new Error();
+        // Fake stack-trace
+        err.stack = [message].concat(stack).join('\n');
+
+        runner.on('fail', function(hook, err) {
+          expect(
+            err.stack
+              .split('\n')
+              .slice(1)
+              .join('\n'),
+            'to be',
+            stack.slice(0, 3).join('\n')
+          );
+          done();
+        });
+        runner.failHook(hook, err);
+      });
+
+      it('should not hang if error message is ridiculously long multiple lines either', function(done) {
+        var hook = new Hook();
+        var fpath = require('path').join(__dirname, '../../mocha.js');
+        var message = require('fs').readFileSync(fpath, 'utf8');
+        var err = new Error();
+        // Fake stack-trace
+        err.stack = [message].concat(stack).join('\n');
+
+        runner.on('fail', function(hook, err) {
+          expect(
+            err.stack
+              .split('\n')
+              .slice(-3)
+              .join('\n'),
+            'to be',
+            stack.slice(0, 3).join('\n')
+          );
+          done();
+        });
+        runner.failHook(hook, err);
+      });
+    });
   });
 
   describe('abort', function() {