[New-bugs-announce] [issue42458] Pathlib resolve() on Mac Catalina prepends secret path

[John Engelke]

New submission from John Engelke <john.engelke at gmail.com>:

On Mac OS X Catalina+, Pathlib's resolve() method prepends the System Integrity Protection (SIP) path to the front of the resolved Path, whether you like it or not. 

>>> from pathlib import Path
>>> host_path_str = "/home/somewhere/there/../nowhere"
>>> host_path = Path(host_path_str)
>>> host_path
PosixPath('/home/somewhere/there/../nowhere')
>>> host_path.resolve()
PosixPath('/System/Volumes/Data/home/somewhere/nowhere')
>>> import platform
>>> platform.platform()
'Darwin-19.6.0-x86_64-i386-64bit'
>>> import sys
>>> print (sys.version)
3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 16:52:21) 
[Clang 6.0 (clang-600.0.57)]
>>> 

In my particular case, I'm just using this feature to resolve paths for an FTP host, so the path is contrived and doesn't actually exist locally. As one may guess, this breaks my FTP transfers by foisting a path on me that isn't on the server. 

I know there are other tix for Pathlib's erratic behavior across platforms which don't talk about this specific issue. I don't think it a behavior across platforms thing, anyway. Pathlib obviously isn't behaving nicely with SIP and Apple's Firmlink wormhole like directory traversal stuffs. Oy vey!

----------
components: macOS
messages: 381792
nosy: john.engelke, ned.deily, ronaldoussoren
priority: normal
severity: normal
status: open
title: Pathlib resolve() on Mac Catalina prepends secret path
type: behavior
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42458>
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