There was an unnecessary quadratic loop in idna decoding. This restores
the behavior to linear.
This also adds an early length check in IDNA decoding to outright reject
huge inputs early on given the ultimate result is defined to be 63 or fewer
characters.
Linux abstract sockets are insecure as they lack any form of filesystem
permissions so their use allows anyone on the system to inject code into
the process.
This removes the default preference for abstract sockets in
multiprocessing introduced in Python 3.9+ via
https://github.com/python/cpython/pull/18866 while fixing
https://github.com/python/cpython/issues/84031.
Explicit use of an abstract socket by a user now generates a
RuntimeWarning. If we choose to keep this warning, it should be
backported to the 3.7 and 3.8 branches.
Fix a shell code injection vulnerability in the
get-remote-certificate.py example script. The script no longer uses a
shell to run "openssl" commands. Issue reported and initial fix by
Caleb Shortt.
Remove the Windows code path to send "quit" on stdin to the "openssl
s_client" command: use DEVNULL on all platforms instead.
Co-authored-by: Caleb Shortt <caleb@rgauge.com>
Fix multiplying a list by an integer (list *= int): detect the
integer overflow when the new allocated length is close to the
maximum size. Issue reported by Jordan Limor.
list_resize() now checks for integer overflow before multiplying the
new allocated length by the list item size (sizeof(PyObject*)).
Converting a large enough `int` to a decimal string raises `ValueError` as expected. However, the raise comes _after_ the quadratic-time base-conversion algorithm has run to completion. For effective DOS prevention, we need some kind of check before entering the quadratic-time loop. Oops! =)
The quick fix: essentially we catch _most_ values that exceed the threshold up front. Those that slip through will still be on the small side (read: sufficiently fast), and will get caught by the existing check so that the limit remains exact.
The justification for the current check. The C code check is:
```c
max_str_digits / (3 * PyLong_SHIFT) <= (size_a - 11) / 10
```
In GitHub markdown math-speak, writing $M$ for `max_str_digits`, $L$ for `PyLong_SHIFT` and $s$ for `size_a`, that check is:
$$\left\lfloor\frac{M}{3L}\right\rfloor \le \left\lfloor\frac{s - 11}{10}\right\rfloor$$
From this it follows that
$$\frac{M}{3L} < \frac{s-1}{10}$$
hence that
$$\frac{L(s-1)}{M} > \frac{10}{3} > \log_2(10).$$
So
$$2^{L(s-1)} > 10^M.$$
But our input integer $a$ satisfies $|a| \ge 2^{L(s-1)}$, so $|a|$ is larger than $10^M$. This shows that we don't accidentally capture anything _below_ the intended limit in the check.
<!-- gh-issue-number: gh-95778 -->
* Issue: gh-95778
<!-- /gh-issue-number -->
Co-authored-by: Gregory P. Smith [Google LLC] <greg@krypto.org>
Integer to and from text conversions via CPython's bignum `int` type is not safe against denial of service attacks due to malicious input. Very large input strings with hundred thousands of digits can consume several CPU seconds.
This PR comes fresh from a pile of work done in our private PSRT security response team repo.
Signed-off-by: Christian Heimes [Red Hat] <christian@python.org>
Tons-of-polishing-up-by: Gregory P. Smith [Google] <greg@krypto.org>
Reviews via the private PSRT repo via many others (see the NEWS entry in the PR).
<!-- gh-issue-number: gh-95778 -->
* Issue: gh-95778
<!-- /gh-issue-number -->
I wrote up [a one pager for the release managers](https://docs.google.com/document/d/1KjuF_aXlzPUxTK4BMgezGJ2Pn7uevfX7g0_mvgHlL7Y/edit#). Much of that text wound up in the Issue. Backports PRs already exist. See the issue for links.
Fix an open redirection vulnerability in the `http.server` module when
an URI path starts with `//` that could produce a 301 Location header
with a misleading target. Vulnerability discovered, and logic fix
proposed, by Hamza Avvan (@hamzaavvan).
Test and comments authored by Gregory P. Smith [Google].
Note: This change is not effective on Microsoft Windows.
Cookies can store sensitive information and should therefore be protected
against unauthorized third parties. This is also described in issue #79096.
The filesystem permissions are currently set to 644, everyone can read the
file. This commit changes the permissions to 600, only the creater of the file
can read and modify it. This improves security, because it reduces the attack
surface. Now the attacker needs control of the user that created the cookie or
a ways to circumvent the filesystems permissions.
This change is backwards incompatible. Systems that rely on world-readable
cookies will breake. However, one could argue that those are misconfigured in
the first place.
Add the -P command line option and the PYTHONSAFEPATH environment
variable to not prepend a potentially unsafe path to sys.path.
* Add sys.flags.safe_path flag.
* Add PyConfig.safe_path member.
* Programs/_bootstrap_python.c uses config.safe_path=0.
* Update subprocess._optim_args_from_interpreter_flags() to handle
the -P command line option.
* Modules/getpath.py sets safe_path to 1 if a "._pth" file is
present.
Update the vendored copy of libexpat to 2.4.1 (from 2.2.8) to get the
fix for the CVE-2013-0340 "Billion Laughs" vulnerability. This copy
is most used on Windows and macOS.
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Fixes http.client potential denial of service where it could get stuck reading lines from a malicious server after a 100 Continue response.
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Reverts commit e653d4d8e8 and makes
parsing even more strict. Like socket.inet_pton() any leading zero
is now treated as invalid input.
Signed-off-by: Christian Heimes <christian@python.org>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Accessing the following attributes will now fire PEP 578 style audit hooks as ("object.__getattr__", obj, name):
* PyTracebackObject: tb_frame
* PyFrameObject: f_code
* PyGenObject: gi_code, gi_frame
* PyCoroObject: cr_code, cr_frame
* PyAsyncGenObject: ag_code, ag_frame
Add an AUDIT_READ attribute flag aliased to READ_RESTRICTED.
Update obsolete flag documentation.
Commit 93d50a6a8d / GH-21855 changed the
order of variable definitions, which introduced a potential invalid free
bug. Py_buffer object is now initialized earlier and the result of
Keccak initialize is verified.
Co-authored-by: Alex Henrie <alexhenrie24@gmail.com>
Signed-off-by: Christian Heimes <christian@python.org>
Co-authored-by: Alex Henrie <alexhenrie24@gmail.com>
Fix Regular Expression Denial of Service (ReDoS) vulnerability in
urllib.request.AbstractBasicAuthHandler. The ReDoS-vulnerable regex
has quadratic worst-case complexity and it allows cause a denial of
service when identifying crafted invalid RFCs. This ReDoS issue is on
the client side and needs remote attackers to control the HTTP server.
CVE-2021-3426: Remove the "getfile" feature of the pydoc module which
could be abused to read arbitrary files on the disk (directory
traversal vulnerability). Moreover, even source code of Python
modules can contain sensitive data like passwords. Vulnerability
reported by David Schwörer.
bpo-43285: Make ftplib not trust the PASV response.
The IPv4 address value returned from the server in response to the PASV command
should not be trusted. This prevents a malicious FTP server from using the
response to probe IPv4 address and port combinations on the client network.
Instead of using the returned address, we use the IP address we're
already connected to. This is the strategy other ftp clients adopted,
and matches the only strategy available for the modern IPv6 EPSV command
where the server response must return a port number and nothing else.
For the rare user who _wants_ this ugly behavior, set a `trust_server_pasv_ipv4_address`
attribute on your `ftplib.FTP` instance to True.
bpo-42967: [security] Address a web cache-poisoning issue reported in urllib.parse.parse_qsl().
urllib.parse will only us "&" as query string separator by default instead of both ";" and "&" as allowed in earlier versions. An optional argument seperator with default value "&" is added to specify the separator.
Co-authored-by: Éric Araujo <merwok@netwok.org>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
Co-authored-by: Éric Araujo <merwok@netwok.org>
* bpo-40791: Make compare_digest more constant-time.
The existing volatile `left`/`right` pointers guarantee that the reads will all occur, but does not guarantee that they will be _used_. So a compiler can still short-circuit the loop, saving e.g. the overhead of doing the xors and especially the overhead of the data dependency between `result` and the reads. That would change performance depending on where the first unequal byte occurs. This change removes that optimization.
(This is change #1 from https://bugs.python.org/issue40791 .)
* Prevent some possible DoS attacks via providing invalid Plist files
with extremely large number of objects or collection sizes.
* Raise InvalidFileException for too large bytes and string size instead of returning garbage.
* Raise InvalidFileException instead of ValueError for specific invalid datetime (NaN).
* Raise InvalidFileException instead of TypeError for non-hashable dict keys.
* Add more tests for invalid Plist files.
