*** This bug is a security vulnerability ***
You have been subscribed to a public security bug by Eduardo Barretto
(ebarretto):
When I use the python constructor for apt.Cache with a rootdir=/mnt/host
(which is mounted read-only) and memonly=True, it isn't behaving as if
it's memonly. It's trying to create directories on the mounted system.
Here's my stack: (note, python click module takes up a bit of the top of
the stack)
```
Collecting apt-based metrics...
Traceback (most recent call last):
File "./restart_check.py", line 165, in <module>
_main()
File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 1157, in
__call__
return self.main(*args, **kwargs)
File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 1078, in
main
rv = self.invoke(ctx)
File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 1434, in
invoke
return ctx.invoke(self.callback, **ctx.params)
File "/usr/local/lib/python3.8/dist-packages/click/core.py", line 783, in
invoke
return __callback(*args, **kwargs)
File "./restart_check.py", line 139, in _main
cache = apt.cache.Cache(rootdir=root_dir, memonly=True)
File "/usr/lib/python3/dist-packages/apt/cache.py", line 161, in __init__
self._check_and_create_required_dirs(rootdir)
File "/usr/lib/python3/dist-packages/apt/cache.py", line 201, in
_check_and_create_required_dirs
os.makedirs(rootdir + d)
File "/usr/lib/python3.8/os.py", line 213, in makedirs
makedirs(head, exist_ok=exist_ok)
File "/usr/lib/python3.8/os.py", line 213, in makedirs
makedirs(head, exist_ok=exist_ok)
File "/usr/lib/python3.8/os.py", line 223, in makedirs
mkdir(name, mode)
OSError: [Errno 30] Read-only file system: '/mnt/host/var'
```
Why are those create-dir calls not protected from the memonly flag? Are
they truly needed to be able to set up the cache?
Ya know what, this could be a security vulnerability, making writes to a
system that was supposed to be treated as read-only, particularly for
those that mounted to a disk in a non-read-only way. memonly is not as
advertised.
** Affects: python-apt (Ubuntu)
Importance: Undecided
Status: New
--
python apt Cache(memonly=True) does not behave as if memonly.
https://bugs.launchpad.net/bugs/2039217
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