SSLObject.version returns incorrect value before handshake.

[Lukasa]

BPO	29781
Nosy	@tiran, @Lukasa
PRs	bpo-29781: Fix SSLObject.version before handshake #3364 [3.6] bpo-29781: Fix SSLObject.version before handshake (GH-3364) #3381
Files	test.c

^{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 2017-09-06.23:39:28.508>
created_at = <Date 2017-03-10.10:03:04.146>
labels = ['expert-SSL', 'type-bug']
title = 'SSLObject.version returns incorrect value before handshake.'
updated_at = <Date 2017-09-06.23:39:28.507>
user = 'https://github.com/Lukasa'

bugs.python.org fields:

activity = <Date 2017-09-06.23:39:28.507>
actor = 'christian.heimes'
assignee = 'christian.heimes'
closed = True
closed_date = <Date 2017-09-06.23:39:28.508>
closer = 'christian.heimes'
components = ['SSL']
creation = <Date 2017-03-10.10:03:04.146>
creator = 'Lukasa'
dependencies = []
files = ['46715']
hgrepos = []
issue_num = 29781
keywords = []
message_count = 7.0
messages = ['289346', '289348', '289350', '289352', '301384', '301439', '301468']
nosy_count = 2.0
nosy_names = ['christian.heimes', 'Lukasa']
pr_nums = ['3364', '3381']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29781'
versions = ['Python 3.5', 'Python 3.6']

[Lukasa]

The SSLObject object from the ssl module has a version() method that is undocumented. A reasonable assumption for the behaviour of that method is that it would follow the behaviour of the same method on SSLSocket(), which has the following documentation:

Return the actual SSL protocol version negotiated by the connection as
a string, or None is no secure connection is established. As of this
writing, possible return values include "SSLv2", "SSLv3", "TLSv1",
"TLSv1.1" and "TLSv1.2". Recent OpenSSL versions may define more return
values.

However, SSLObject does not follow that behaviour:

Python 3.6.0 (default, Jan 18 2017, 18:08:34) 
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import ssl
>>> ctx = ssl.create_default_context()
>>> in_bio = ssl.MemoryBIO()
>>> out_bio = ssl.MemoryBIO()
>>> buffers = ctx.wrap_bio(in_bio, out_bio)
>>> buffers.version()
'TLSv1.2'

That is, a SSLObject that does not have a TLS session established will incorrectly report that it is using a TLS version. This method should return None in this case.

[Lukasa]

A quick test reveals that Python 3.5 is also affected.

[Lukasa]

This actually appears to be an outcome of OpenSSL's logic. I've attached a smallish C file that, when run against OpenSSL 1.0.2 on my machine, prints "TLSv1.2".

This seems like a behaviour we'll have to work around in Python to get the outcome we want here.

[Lukasa]

I updated the test script to try with a file-descriptor set and OpenSSL returns TLSv1.2 for that one as well. This strongly suggests that OpenSSL's SSL_get_version documentation is somewhat misleading, and that an SSL object will return a version even when it's not connected.

If Python wants to consider this a bug, it will need to track connections state for the SSLObject like it does for the SSLSocket. Otherwise, Python can redocument version for SSLObject to say that it will always return a value.

[tiran]

It should be possible to solve the issue w/o tracking the connection state manually. It doesn't work correctly with transparent negotiation -- that is implicit handshake with SSL_write().

SSL_is_init_finished() (https://www.openssl.org/docs/manmaster/man3/SSL_get_state.html) might be the right function.

[tiran]

New changeset 6877111 by Christian Heimes in branch 'master':
bpo-29781: Fix SSLObject.version before handshake (bpo-3364)
6877111

[tiran]

New changeset 6da379b by Christian Heimes in branch '3.6':
[3.6] bpo-29781: Fix SSLObject.version before handshake (GH-3364) (bpo-3381)
6da379b