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Official Transmission BitTorrent client repository
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setting for permission of files in .config/transmission-daemon/ (not download-dir) #7006

Open ilf opened 1 month ago

ilf commented 1 month ago

What is the issue?

settings.json has a setting umask, but apparently that's only for files in download-dir.

In /var/lib/transmission-daemon/.config/transmission-daemon, all files (dht.dat, stats.json, resume/*.resume and torrents/*.torrent are created -rw------- (umask 077). I would like to change that to -rw-r----- (umask 027), so I can back them up as a different user in the transmission group.

I've asked where to set this, but I believe it's not possible yet.

Which application of Transmission?

transmission-daemon

Which version of Transmission?

3.00

killemov commented 1 month ago

Correct, this is not possible. But you can install a (*)cron job to change the flags or user:group every couple of minutes.

ilf commented 1 month ago

@killemov: Thanks for confirming. I believe these facts (it's currently not possible, it can be implemented, people want this) fill the definition of a feature request.

Thank you for the suggested workaround. But that's rather hacky and might cause unintented side-effects.

killemov commented 1 month ago

But that's rather hacky and might cause unintented side-effects.

Not really, I can't even fathom the amount of services around the world and beyond that depend on cron. Also, if you don't remove rights you should be okay.

ilf commented 1 month ago

Can anyone explain to me why transmission-daemon makes config-files unreadable for its own group? Is there a good reason? Or could we change the default value from group unreadable to group readable?

killemov commented 1 month ago

unreadable for its own group

This is actually a very astute observation. Why indeed?

tearfur commented 1 month ago

Can anyone explain to me why transmission-daemon makes config-files unreadable for its own group? Is there a good reason?

After reading the code, my guess is that it's just an unintended side effect.

When saving each of these files, Transmission first uses mkstemp() to save the contents to a temp file, then after the temp file is written successfully, the temp file is moved to the final destination. mkstemp() is hard coded to create the temp file with permission 0600.

The reason for first saving the contents to a temp file instead of creating the file directly is explained in the source code in this function:

https://github.com/transmission/transmission/blob/3e9f5f614a875aae987235d3836d0ca555a80d80/libtransmission/utils.cc#L179

ilf commented 1 month ago

@tearfur: Great find, thanks!

If it is indeed "just an unintended side effect", can we adjust it and fix the permissions?

There's already a post-save step to "move it from '.tmp' to the correct filename":

https://github.com/transmission/transmission/blob/3e9f5f614a875aae987235d3836d0ca555a80d80/libtransmission/utils.cc#L210