test_aead_aes_gcm fails on Kernel 4.9

[tiran]

BPO	29324
Nosy	@warsaw, @nascheme, @vstinner, @tiran, @matejcik, @stratakis
PRs	bpo-29324 update test_socket AEAD test for kernel 4.9 and up #133
Files	test_socket_aead_kernel49.patch: updating AEAD test for kernel 4.9

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/tiran'
closed_at = <Date 2017-06-09.21:30:06.580>
created_at = <Date 2017-01-19.15:01:06.592>
labels = ['extension-modules', 'type-bug', '3.7']
title = 'test_aead_aes_gcm fails on Kernel 4.9'
updated_at = <Date 2017-10-09.15:28:12.017>
user = 'https://github.com/tiran'

bugs.python.org fields:

activity = <Date 2017-10-09.15:28:12.017>
actor = 'vstinner'
assignee = 'christian.heimes'
closed = True
closed_date = <Date 2017-06-09.21:30:06.580>
closer = 'nascheme'
components = ['Extension Modules']
creation = <Date 2017-01-19.15:01:06.592>
creator = 'christian.heimes'
dependencies = []
files = ['46494']
hgrepos = []
issue_num = 29324
keywords = ['patch']
message_count = 14.0
messages = ['285794', '285797', '286808', '286811', '287509', '287614', '287616', '287902', '287943', '295561', '295569', '295583', '295621', '303976']
nosy_count = 6.0
nosy_names = ['barry', 'nascheme', 'vstinner', 'christian.heimes', 'matejcik', 'cstratak']
pr_nums = ['133']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29324'
versions = ['Python 3.6', 'Python 3.7']

[tiran]

$ ./python -m test -m test_aead_aes_gcm test_socket
Run tests sequentially
0:00:00 [1/1] test_socket
test test_socket failed -- Traceback (most recent call last):
  File "/home/heimes/dev/python/cpython/Lib/test/support/__init__.py", line 556, in wrapper
    return func(*args, **kw)
  File "/home/heimes/dev/python/cpython/Lib/test/test_socket.py", line 5515, in test_aead_aes_gcm
    res = op.recv(assoclen + len(plain) + taglen)
OSError: [Errno 22] Invalid argument

The tests were written and passed under Linux Kernel 4.7. I was under the assumption that the API is stable. But the most recent version 4.9 has changed the API for AEAD mode slightly. libkcapi project maintain a well written documentation of the Kernel crypto API,
smuellerDD/libkcapi@be242c3

Fedora 24 and 25 are affected. I'm going to update the tests. Downstream distributors: Feel free to disable the test in the mean time. The feature is not critical.

[tiran]

recv(64) works. I need to figure out why 64 and what's in the extra bytes.

[matejcik]

The "'0' * taglen" part is now considered part of plaintext. Which makes a lot of sense :)
Removing the "empty taglen" fixes the encryption part of the tests for me. Similarly, for the decryption test, we must only read and check the message without the tag.

[matejcik]

the attached patch fixes the test for me

[vstinner]

I confirm that test_socket pass with test_socket_aead_kernel49.patch on my Fedora 25 (kernel 4.9.5-200.fc25.x86_64).

I would be nice to fix test_socket which is currently broken ;-)

[warsaw]

Confirmed that test_socket_aead_kernel49.patch fixes the problem for Ubuntu 17.04. It'll probably fix it for Debian Stretch too give its kernel version number, but I haven't tested that yet.

[tiran]

Thx Barry,

I'll try to find some time to verify the new Kernel API and commit the patch early next week.

[vstinner]

@matejcik: would you mind to create a pull request for your patch?

[vstinner]

Even when the fix will be backported to Python 3.6, please keep the issue open until Christian Heimes has time to review the kernel changes. Copy/paste of his message on the PR#133:

"I still haven't had time to study the changes in the Linux kernel. Let's merge the PR to silence the test error. Please leave the ticket open as reminder for me."

[nascheme]

This patch works for me as well. Debian testing, kernel:
Linux version 4.9.0-3-amd64 (debian-kernel@lists.debian.org) (gcc version 6.3.0 20170425 (Debian 6.3.0-16) ) #1 SMP Debian 4.9.25-1 (2017-05-02)

In the 3.6.1 Python release, test_socket fails with:

test test_socket failed -- Traceback (most recent call last):
  File "/home/nas/src/cpython/Lib/test/support/__init__.py", line 556, in wrapper
    return func(*args, **kw)
  File "/home/nas/src/cpython/Lib/test/test_socket.py", line 5497, in test_aead_aes_gcm
    res = op.recv(assoclen + len(plain) + taglen)
OSError: [Errno 22] Invalid argument

[vstinner]

The fix was also merged to master. It should be backported to 3.6. Neil, do
you want to try to backport it?