[issue44762] getpass.getpass on Windows fallback detection is bad

[jan matejek]

New submission from jan matejek <ja+python at matejcik.cz>:

The fallback detection for `win_getpass` checks that `sys.stdin` is different from `sys.__stdin__`. If yes, it assumes that it's incapable of disabling echo, and calls `default_getpass` which reads from stdin.

If they are the same object, it assumes it's in a terminal and uses `msvcrt` to read characters.

I was not able to find any rationale for this check, it seems to have been introduced, oh wow, in 2001, to fix something IDLE-related.

Anyway, the check is trivially incorrect. It fails when such script is launched from `subprocess.Popen(stdin=PIPE)`, where both `sys.stdin` and `sys.__stdin__` are the same instance of `TextIOWrapper`. Same actually happens in MinTTY (Git Bash etc.) which is not a true terminal as far as I was able to find out?

It seems that a better check would be, e.g., `sys.stdin.isatty()`, which correctly returns `False` both in subprocesses and in MinTTY.

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components: Library (Lib)
messages: 398370
nosy: matejcik
priority: normal
severity: normal
status: open
title: getpass.getpass on Windows fallback detection is bad
type: behavior
versions: Python 3.10, Python 3.11, Python 3.6, Python 3.7, Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue44762>
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