Transplant of rev 544b654d000c: directory traversal attack in CGIHttpRequestHandler.

Lib/http/server.py

@@ -987,18 +987,17 @@ class CGIHTTPRequestHandler(SimpleHTTPRequestHandler):
 
     def run_cgi(self):
         """Execute a CGI script."""
-        path = self.path
         dir, rest = self.cgi_info
 
-        i = path.find('/', len(dir) + 1)
+        i = rest.find('/')
         while i >= 0:
-            nextdir = path[:i]
-            nextrest = path[i+1:]
+            nextdir = rest[:i]
+            nextrest = rest[i+1:]
 
             scriptdir = self.translate_path(nextdir)
             if os.path.isdir(scriptdir):
                 dir, rest = nextdir, nextrest
-                i = path.find('/', len(dir) + 1)
+                i = rest.find('/')
             else:
                 break
 

Lib/test/test_httpservers.py

@@ -325,6 +325,7 @@ class CGIHTTPServerTestCase(BaseTestCase):
         self.parent_dir = tempfile.mkdtemp()
         self.cgi_dir = os.path.join(self.parent_dir, 'cgi-bin')
         os.mkdir(self.cgi_dir)
+        self.nocgi_path = None
         self.file1_path = None
         self.file2_path = None
 
@@ -345,6 +346,11 @@ class CGIHTTPServerTestCase(BaseTestCase):
             self.tearDown()
             self.skipTest("Python executable path is not encodable to utf-8")
 
+        self.nocgi_path = os.path.join(self.parent_dir, 'nocgi.py')
+        with open(self.nocgi_path, 'w') as fp:
+            fp.write(cgi_file1 % self.pythonexe)
+        os.chmod(self.nocgi_path, 0o777)
+
         self.file1_path = os.path.join(self.cgi_dir, 'file1.py')
         with open(self.file1_path, 'w', encoding='utf-8') as file1:
             file1.write(cgi_file1 % self.pythonexe)
@@ -362,6 +368,8 @@ class CGIHTTPServerTestCase(BaseTestCase):
             os.chdir(self.cwd)
             if self.pythonexe != sys.executable:
                 os.remove(self.pythonexe)
+            if self.nocgi_path:
+                os.remove(self.nocgi_path)
             if self.file1_path:
                 os.remove(self.file1_path)
             if self.file2_path:
@@ -418,6 +426,10 @@ class CGIHTTPServerTestCase(BaseTestCase):
         self.assertEqual((b'Hello World' + self.linesep, 'text/html', 200),
             (res.read(), res.getheader('Content-type'), res.status))
 
+    def test_issue19435(self):
+        res = self.request('///////////nocgi.py/../cgi-bin/nothere.sh')
+        self.assertEqual(res.status, 404)
+
     def test_post(self):
         params = urllib.parse.urlencode(
             {'spam' : 1, 'eggs' : 'python', 'bacon' : 123456})

Misc/NEWS

@@ -7,6 +7,11 @@ What's New in Python 3.3.3?
 
 *Release date: XX-Nov-2013*
 
+Library
+-------
+
+- Issue #19435: Fix directory traversal attack on CGIHttpRequestHandler.
+
 Tests
 -----