fix regex in utils.stackTraceFilter to prevent ReDoS mochajs#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)`.
cyjake · Jan 30, 2019 · f6d9635 · f6d9635
1 parent 7fee3a3
commit f6d9635
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Showing 2 changed files with 55 additions and 3 deletions.
diff --git 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
@@ -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() {