SSL recv_into requires the object to implement __len__ unlike socket one

[tzickel]

BPO	40262
Nosy	@tiran, @serhiy-storchaka, @tzickel, @ZackerySpytz
PRs	gh-84443: SSLSocket.recv_into() shouldn't require __len__ #20310

^{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 = None
created_at = <Date 2020-04-12.17:28:17.837>
labels = ['expert-SSL', '3.8', 'type-bug', '3.7', '3.9']
title = 'SSL recv_into requires the object to implement __len__ unlike socket one'
updated_at = <Date 2020-05-22.05:35:19.503>
user = 'https://github.com/tzickel'

bugs.python.org fields:

activity = <Date 2020-05-22.05:35:19.503>
actor = 'ZackerySpytz'
assignee = 'christian.heimes'
closed = False
closed_date = None
closer = None
components = ['SSL']
creation = <Date 2020-04-12.17:28:17.837>
creator = 'tzickel'
dependencies = []
files = []
hgrepos = []
issue_num = 40262
keywords = ['patch']
message_count = 2.0
messages = ['366257', '367742']
nosy_count = 4.0
nosy_names = ['christian.heimes', 'serhiy.storchaka', 'tzickel', 'ZackerySpytz']
pr_nums = ['20310']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40262'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

Linked PRs

• [3.12] gh-84443: SSLSocket.recv_into() now support buffer protocol with itemsize != 1 (GH-20310) #112458
• [3.11] gh-84443: SSLSocket.recv_into() now support buffer protocol with itemsize != 1 (GH-20310) #112459

[tzickel]

I am writing this as a bug, as I have an object which implements the buffer protocol but not the __len__.

SSL's recv_into seems to require the buffer object to implement __len__, but this is unlike the socket recv_into which uses the buffer protocol length.

Here is the socket.recv_into implementation:

cpython/Modules/socketmodule.c

Line 3556 in 402e1cd

/* If nbytes was not specified, use the buffer's length */

as you can see, the length is optional, and it not given, it takes it from the buffer protocol length.

But here is SSL recv_into implementation:
https://github.com/python/cpython/blob/master/Lib/ssl.py#L1233

if length is not given, it tries to call the __len__ of the object itself (not it's buffer protocol).

[serhiy-storchaka]

Yes, it is a bug. __len__ can return a value different from the amount of bytes (in array.array, memoryview).

len(buffer) can be replaced with memoryview(buffer).nbytes, but maybe we could keep None and let the lower level to handle it.