Lax cookie parsing in http.cookies could be a security issue when combined

with non-standard cookie handling in some Web browsers.

Reported by Sergey Bobrov.

2 files changed, 11 insertions, 1 deletions

diff --git a/Lib/http/cookies.py b/Lib/http/cookies.py
index 24da5f4..556d101 100644
--- a/Lib/http/cookies.py
+++ b/Lib/http/cookies.py
@@ -431,6 +431,7 @@ class Morsel(dict):
 _LegalCharsPatt  = r"[\w\d!#%&'~_`><@,:/\$\*\+\-\.\^\|\)\(\?\}\{\=]"
 _CookiePattern = re.compile(r"""
     (?x)                           # This is a verbose pattern
+    \s*                            # Optional whitespace at start of cookie
     (?P<key>                       # Start of group 'key'
     """ + _LegalCharsPatt + r"""+?   # Any word of at least one letter
     )                              # End of group 'key'
@@ -534,7 +535,7 @@ class BaseCookie(dict):
 
         while 0 <= i < n:
             # Start looking for a cookie
-            match = patt.search(str, i)
+            match = patt.match(str, i)
             if not match:
                 # No more cookies
                 break
diff --git a/Lib/test/test_http_cookies.py b/Lib/test/test_http_cookies.py
index 1cfbe74..76e5e9c 100644
--- a/Lib/test/test_http_cookies.py
+++ b/Lib/test/test_http_cookies.py
@@ -179,6 +179,15 @@ class CookieTests(unittest.TestCase):
         </script>
         """)
 
+    def test_invalid_cookies(self):
+        # Accepting these could be a security issue
+        C = cookies.SimpleCookie()
+        for s in (']foo=x', '[foo=x', 'blah]foo=x', 'blah[foo=x'):
+            C.load(s)
+            self.assertEqual(dict(C), {})
+            self.assertEqual(C.output(), '')
+
+
 class MorselTests(unittest.TestCase):
     """Tests for the Morsel object."""