Bug 471972

Summary:	chmod after file upload breaks sftp-server's Fedora-specific file permission enforcement
Product:	[Applications] dolphin	Reporter:	regime_unsold498
Component:	general	Assignee:	Dolphin Bug Assignee <dolphin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	kfm-devel, sitter
Priority:	NOR
Version First Reported In:	22.12.3
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description regime_unsold498 2023-07-05 11:58:06 UTC

SUMMARY

kio sftp does an additional chmod on uploaded files, which overrides server-side enforced permissions. The issue does not occur with the standard sftp command-line client.


STEPS TO REPRODUCE
I have a server running RHEL 9 where sftp-server enforces file permissions with the -m switch, using the following configuration in /etc/openssh/sshd_config:

`Subsystem sftp /usr/libexec/openssh/sftp-server -m 0660 -u 0006`

This is a Fedora/RHEL-specific feature, as can be seen [here](https://src.fedoraproject.org/rpms/openssh/blob/f34/f/openssh-6.7p1-sftp-force-permission.patch).

To reproduce, upload a file with permission bits 600 via Dolphin.


OBSERVED RESULT
If I upload a file with permission bits 600 with Dolphin, it ends up with 600.

sftp-server debug log:
```
Jul 05 12:18:02 rlvm sftp-server[13792]: open "/srv/test/upload.txt.part" flags WRITE,CREATE,TRUNCATE mode 0660
Jul 05 12:18:02 rlvm sftp-server[13792]: debug1: request 10: sent handle handle 0
Jul 05 12:18:02 rlvm sftp-server[13792]: debug1: request 11: write "/srv/test/upload.txt.part" (handle 0) off 0 len 2
Jul 05 12:18:02 rlvm sftp-server[13792]: sent status Success
Jul 05 12:18:02 rlvm sftp-server[13792]: close "/srv/test/upload.txt.part" bytes read 0 written 2
Jul 05 12:18:02 rlvm sftp-server[13792]: sent status Success
Jul 05 12:18:02 rlvm sftp-server[13792]: rename old "/srv/test/upload.txt.part" new "/srv/test/upload.txt"
Jul 05 12:18:02 rlvm sftp-server[13792]: sent status Success
Jul 05 12:18:02 rlvm sftp-server[13792]: debug1: request 14: setstat name "/srv/test/upload.txt"
Jul 05 12:18:02 rlvm sftp-server[13792]: set "/srv/test/upload.txt" mode 0600
Jul 05 12:18:02 rlvm sftp-server[13792]: sent status Success
```

EXPECTED RESULT
If I upload a file with permission bits 600 by using the sftp command, it ends up with 660 on the server, as expected.

sftp-server debug log:
```
Jul 05 12:48:50 rlvm sftp-server[14962]: sent status Success
Jul 05 12:48:56 rlvm sftp-server[14962]: open "/srv/test/upload.txt" flags WRITE,CREATE,TRUNCATE mode 0660
Jul 05 12:48:56 rlvm sftp-server[14962]: debug1: request 13: sent handle handle 0
Jul 05 12:48:56 rlvm sftp-server[14962]: debug1: request 15: write "/srv/test/upload.txt" (handle 0) off 0 len 2
Jul 05 12:48:56 rlvm sftp-server[14962]: sent status Success
Jul 05 12:48:56 rlvm sftp-server[14962]: close "/srv/test/upload.txt" bytes read 0 written 2
Jul 05 12:48:56 rlvm sftp-server[14962]: sent status Success
```


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 37
KDE Plasma Version:  5.27.4
KDE Frameworks Version: 5.105.0
Qt Version: 5.15.9


ADDITIONAL INFORMATION

As you can see, the culprit is the additional mode change. I assume this line of code causes this:
https://github.com/KDE/kio-extras/blob/master/sftp/kio_sftp.cpp#L1545

Why is this explicit chmod being done here? Would it be possible to remove this? Thank you!

Comment 1 Harald Sitter 2023-07-05 13:02:34 UTC

When the client asks for a given permissions set we need to try to apply that set in kio-sftp. Moving bug to dolphin, though I'm almost sure it tries to forward the permissions the local file has, so that too may be working as intended.

Comment 2 regime_unsold498 2023-07-05 13:19:46 UTC

(In reply to Harald Sitter from comment #1)
> When the client asks for a given permissions set we need to try to apply
> that set in kio-sftp. Moving bug to dolphin, though I'm almost sure it tries
> to forward the permissions the local file has, so that too may be working as
> intended.

Isn't that already done by this line?
https://github.com/KDE/kio-extras/blob/master/sftp/kio_sftp.cpp#L1458

To my best knowledge, sftp-server preserves the mode requested by the client (unless the -m switch is present, which is why it was implemented) without the need of an additional chmod.

From what I can tell, Dolphin passes the local permissions to kio core, which passes them to kio sftp, all of which assume that file permissions should be preserved.

Comment 3 Harald Sitter 2023-07-06 11:05:25 UTC

Now this rings a bell. There was already a report about this!

*** This bug has been marked as a duplicate of bug 345687 ***