bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[xenodasein--- via Bug reports for GNU Emacs, the Swiss army knife of text editors]

The command: ls -Z /etc/fstab
Outputs: unconfined_u:object_r:etc_t:s0 /etc/fstab
On an unmodified fstab file. If I modify the file using 'sudoedit'
command, which uses GNU Nano on this system, preserves the same extended
file attributes. However, after using emacs -Q:
C-x C-f /sudoedit::/etc/fstab
<any file modification>
C-x C-s
The command: ls -Z /etc/fstab
Outputs: unconfined_u:object_r:user_tmp_t:s0 /etc/fstab
Which will prevent system from booting.



In GNU Emacs 27.2 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.24.29, cairo version 1.17.4)
of 2021-06-14 built on buildvm-x86-32.iad2.fedoraproject.org
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Fedora 34 (Thirty Four)

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
current-kill: Kill ring is empty [2 times]
gui-get-primary-selection: No selection is available

Configured using:
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bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Eli Zaretskii]

> Date: Sat, 24 Jul 2021 19:47:20 +0200 (CEST)
> From: xenodasein--- via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> The command: ls -Z /etc/fstab
> Outputs: unconfined_u:object_r:etc_t:s0 /etc/fstab
> On an unmodified fstab file. If I modify the file using 'sudoedit'
> command, which uses GNU Nano on this system, preserves the same extended
> file attributes. However, after using emacs -Q:
> C-x C-f /sudoedit::/etc/fstab
> <any file modification>
> C-x C-s
> The command: ls -Z /etc/fstab
> Outputs: unconfined_u:object_r:user_tmp_t:s0 /etc/fstab
> Which will prevent system from booting.

Did you try to use backup-by-copying, with or without
backup-by-copying-when-privileged-mismatch?

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[xenodasein--- via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jul 24, 2021, 21:27 by eliz@gnu.org:

> Did you try to use backup-by-copying, with or without
> backup-by-copying-when-privileged-mismatch?
>

No, I can try again with an emacs -Q and some certain variables set if you require.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Eli Zaretskii]

> Date: Sat, 24 Jul 2021 20:46:30 +0200 (CEST)
> From: xenodasein@tutanota.de
> Cc: 49724@debbugs.gnu.org
> 
> Jul 24, 2021, 21:27 by eliz@gnu.org:
> 
> > Did you try to use backup-by-copying, with or without
> > backup-by-copying-when-privileged-mismatch?
> >
> 
> No, I can try again with an emacs -Q and some certain variables set if you require.

Michael, could that help?

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

>> > Did you try to use backup-by-copying, with or without
>> > backup-by-copying-when-privileged-mismatch?
>>
>> No, I can try again with an emacs -Q and some certain variables set if you require.
>
> Michael, could that help?

It's already on my todo, but rather for tomorrow.

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: xenodasein@tutanota.de,  49724@debbugs.gnu.org
> Date: Sat, 24 Jul 2021 21:06:15 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> > Did you try to use backup-by-copying, with or without
> >> > backup-by-copying-when-privileged-mismatch?
> >>
> >> No, I can try again with an emacs -Q and some certain variables set if you require.
> >
> > Michael, could that help?
> 
> It's already on my todo, but rather for tomorrow.

I'm asking whether using backup-by-copying could have helped the OP in
that use case.  If it could, I'd ask the OP to try that, but if you
say this is currently a deficiency for which we have no solution, then
the OP doesn't need to try backup-by-copying.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[xenodasein--- via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jul 24, 2021, 22:13 by eliz@gnu.org:

>> From: Michael Albinus <michael.albinus@gmx.de>
>> Cc: xenodasein@tutanota.de,  49724@debbugs.gnu.org
>> Date: Sat, 24 Jul 2021 21:06:15 +0200
>>
>> Eli Zaretskii <eliz@gnu.org> writes:
>>
>> >> > Did you try to use backup-by-copying, with or without
>> >> > backup-by-copying-when-privileged-mismatch?
>> >>
>> >> No, I can try again with an emacs -Q and some certain variables set if you require.
>> >
>> > Michael, could that help?
>>
>> It's already on my todo, but rather for tomorrow.
>>
>
> I'm asking whether using backup-by-copying could have helped the OP in
> that use case.  If it could, I'd ask the OP to try that, but if you
> say this is currently a deficiency for which we have no solution, then
> the OP doesn't need to try backup-by-copying.
>
Sorry to ask this here but now that I tried the same, tramp repeatedly asks for password, like an infinite loop?

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

> I'm asking whether using backup-by-copying could have helped the OP in
> that use case.  If it could, I'd ask the OP to try that, but if you
> say this is currently a deficiency for which we have no solution, then
> the OP doesn't need to try backup-by-copying.

Honestly, I don't know w/o code checking. I'll do tomorrow.

Since I run a Fedora-powered laptop, I hope also to reproduce the
problem myself.

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

Hi,

>> >> > Did you try to use backup-by-copying, with or without
>> >> > backup-by-copying-when-privileged-mismatch?
>> >>
>> >> No, I can try again with an emacs -Q and some certain variables set if you require.
>> >
>> > Michael, could that help?
>>
>> It's already on my todo, but rather for tomorrow.
>
> I'm asking whether using backup-by-copying could have helped the OP in
> that use case.  If it could, I'd ask the OP to try that, but if you
> say this is currently a deficiency for which we have no solution, then
> the OP doesn't need to try backup-by-copying.

There was indeed an error in tramp-sudoedit.el, which I could reproduce
locally. Shall be fixed now by last commit to master.

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

xenodasein@tutanota.de writes:

> Sorry to ask this here but now that I tried the same, tramp repeatedly asks for password, like an infinite loop?

This means that the password hasn't been cached. The sudoedit method
does not keep a running session in the background, so every operation
could require authentication.

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[xenodasein--- via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jul 25, 2021, 15:20 by michael.albinus@gmx.de:

> This means that the password hasn't been cached. The sudoedit method
> does not keep a running session in the background, so every operation
> could require authentication.
>

No matter how many times I retype the password, it doesn't work, keeps repeatedly asking for password. It works if I don't use emacs -Q, but use my own emacs configuration. How should I solve it for emacs -Q? 

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

xenodasein@tutanota.de writes:

>> This means that the password hasn't been cached. The sudoedit method
>> does not keep a running session in the background, so every operation
>> could require authentication.
>>
>
> No matter how many times I retype the password, it doesn't work, keeps repeatedly asking for password. It works if I don't use emacs -Q, but use my own emacs configuration. How should I solve it for emacs -Q?

I see. As said, caching is disabled when "emacs -Q" is called. This is a
problem for the sudoedit method. Could you try instead

emacs -Q --eval '(setq tramp-cache-read-persistent-data t)'

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[xenodasein--- via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jul 25, 2021, 17:05 by michael.albinus@gmx.de:

> xenodasein@tutanota.de writes:
>
>>> This means that the password hasn't been cached. The sudoedit method
>>> does not keep a running session in the background, so every operation
>>> could require authentication.
>>>
>>
>> No matter how many times I retype the password, it doesn't work, keeps repeatedly asking for password. It works if I don't use emacs -Q, but use my own emacs configuration. How should I solve it for emacs -Q?
>>
>
> I see. As said, caching is disabled when "emacs -Q" is called. This is a
> problem for the sudoedit method. Could you try instead
>
> emacs -Q --eval '(setq tramp-cache-read-persistent-data t)'
>
> Best regards, Michael.
>

That indeed worked. I also tried -q without the eval part and that works too, thanks for your help.

There isn't much hint to side effects like this on the 'Emacs Invocation' part of emacs manual, is this explained in elisp manual maybe? What I found is "-Q’ Equivalent to ‘-q --no-site-file --no-splash’." and that it doesn't load 'default.el'.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

xenodasein@tutanota.de writes:

Hi,

>> I see. As said, caching is disabled when "emacs -Q" is called. This is a
>> problem for the sudoedit method. Could you try instead
>>
>> emacs -Q --eval '(setq tramp-cache-read-persistent-data t)'
>
> That indeed worked. I also tried -q without the eval part and that works too, thanks for your help.
>
> There isn't much hint to side effects like this on the 'Emacs
> Invocation' part of emacs manual, is this explained in elisp manual
> maybe? What I found is "-Q’ Equivalent to ‘-q --no-site-file
> --no-splash’." and that it doesn't load 'default.el'.

The described emacs invocation is Tramp specific. I've added the hint
meanwhile to the Tramp manual, chapter "6 Reporting Bugs and
Problems". It reads now

--8<---------------cut here---------------start------------->8---
   To exclude cache-related problems, flush all caches before running
the test, *note Cleanup remote connections::.  Alternatively, and
often better for analysis, reproduce the problem in a clean Emacs
session started with ‘emacs -Q’.  Then, TRAMP does not load the
persistency file (*note Connection caching::), and it does not use
passwords from ‘auth-source.el’ (*note Password handling::).  If you
really need a password cache, for example for the ‘sudoedit’ method,
call

     emacs -Q -l tramp \
       --eval '(setq tramp-cache-read-persistent-data t)' \
       --eval '(tramp-cleanup-all-connections)'
--8<---------------cut here---------------end--------------->8---

Did you have a chance to test the patch, solving your sudoedit selinux
problem?

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

Michael Albinus <michael.albinus@gmx.de> writes:

Hi,

> The described emacs invocation is Tramp specific. I've added the hint
> meanwhile to the Tramp manual, chapter "6 Reporting Bugs and
> Problems". It reads now
>
>    To exclude cache-related problems, flush all caches before running
> the test, *note Cleanup remote connections::.  Alternatively, and
> often better for analysis, reproduce the problem in a clean Emacs
> session started with ‘emacs -Q’.  Then, TRAMP does not load the
> persistency file (*note Connection caching::), and it does not use
> passwords from ‘auth-source.el’ (*note Password handling::).  If you
> really need a password cache, for example for the ‘sudoedit’ method,
> call
>
>      emacs -Q -l tramp \
>        --eval '(setq tramp-cache-read-persistent-data t)' \
>        --eval '(tramp-cleanup-all-connections)'

FTR, I have adapted Tramp such a way that this hack isn't needed anymore.

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[xenodasein--- via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jul 25, 2021, 23:14 by michael.albinus@gmx.de:

> ...
> Did you have a chance to test the patch, solving your sudoedit selinux
> problem?
>
> Jul 26, 2021, 10:57 by > michael.albinus@gmx.de> :> ...
> FTR, I have adapted Tramp such a way that this hack isn't needed anymore.
>

I'm currently using 27.2 from the distribution, haven't tested it myself yet.
Thanks for such swift fixes, this is awesome.
I will compile the the latest branch to help testing.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

xenodasein@tutanota.de writes:

Hi,

> I'm currently using 27.2 from the distribution, haven't tested it myself yet.
> Thanks for such swift fixes, this is awesome.
> I will compile the the latest branch to help testing.

If you have problems in compiling Emacs, you might use Tramp 2.5.1.1
from GNU ELPA, which has been released meanwhile. It contains the patch.

Best regards, Michael.

bug#49724: 27.2; Tramp /sudoedit:: does not preserve file security context

[Michael Albinus]

Version: 28.1

Michael Albinus <michael.albinus@gmx.de> writes:

Hi,

>> I'm currently using 27.2 from the distribution, haven't tested it myself yet.
>> Thanks for such swift fixes, this is awesome.
>> I will compile the the latest branch to help testing.
>
> If you have problems in compiling Emacs, you might use Tramp 2.5.1.1
> from GNU ELPA, which has been released meanwhile. It contains the patch.

No further comment, so I'm closing the bug.

Best regards, Michael.