Unexpected enforced file permissions when the archive is created from STDIN

[schors]

I create the archive from STDIN:
borg create --umask 0022 --compression lz4 --stdin-name dbname.sql '::mysql-dbname-{now:%Y-%m-%dT%H:%M:%S}' -
File in the archive has 660 permissions:

borg list ::mysql-dbname-2020-09-11T06:25:38
-rw-rw---- root   root    8667267 Fri, 2020-09-11 06:25:41 dbname.sql

I tried to set different umask, nothing changed. I created the archive without umask, nothing changed. I did new clean init every time

borg -V
borg 1.1.13

[knutov]

Full steps to reproduce:

borg init stdin-test-repo --umask 0022 -e none

echo '123' | borg create --umask 0022 stdin-test-repo::test-001 -

borg list stdin-test-repo::test-001
-rw-rw---- root   root          4 Sat, 2020-09-12 03:46:34 stdin

[ThomasWaldmann]

If you create from stdin, there is no real file metadata, just (content) data.

But because borg usually stores metadata for each file, it just makes them up in case of stdin.

umask only affects file creation and the borg --umask option only affects files created by borg in the filesystem (e.g. new segment files in the repo, index files, caches, etc.) - for extracted files, borg always sets the permissions from what it finds in the archive.

So, this is not a bug, but expected behaviour.

If you want to have more control, you can also extract to stdout and then do whatever you like with the stream.

[knutov]

@ThomasWaldmann the real problem is reading this file under some non root user in case of borg mount with allow_other option made under root.

May be it is beter to add option to set file rights with backup from stdin?

[schors]

"umask" is not a point. We use "umask" just in case. Permissions is the point. 0660 isn't expected behavior. Why is 0660? It's a weather on the Mars for any cases

The problem is sharing repo to users. By borg mount for example

[ThomasWaldmann]

0o660 was chosen because it does not include permissions "for everybody" (which can always be seen as a security issue).

And root/root (uid/gid 0/0) was chosen because that is the only / most simple user that is present on all UNIX-like systems (and also to not cause security issues).

Options you have:

• borg extract to stdout and then redirect to whereever you want
• borg mount with --uid / --gid option?

[ThomasWaldmann]

One metadata related option --stdin-name already exists.

--stdin-mode, --stdin-user and --stdin-group [--stdin-uid and --stdin-gid?] could be added (PRs welcome).

Not sure if it is worth the overhead in the code, help and docs though, considering that a workaround (see previous comment) exists.

[schors]

Adding --stdin-mode is easy. The main problem is how and where to handle --stdin-user and --stdin-group. What if --stdin-user or --stdin-group are not matching certain records in the password database? Where is the best place to handle errors?

[ThomasWaldmann]

In that case I guess it is easiest to terminate with an error.

Try e.g. raise Error("no such user: %s" % username).