How do I set default permissions for SFTP for an Ubuntu Server?

Question

We have an Ubuntu 10.04 server. How can I set it so that new files created (or copied) over SFTP or SSH have g+rw and g+rwx permissions (where appropriate)?

I'm also using setgid (chmod g+s) so that they inherit the proper group owner.

Solution 1

In /etc/ssh/sshd_config, change the following:

Subsystem sftp /usr/lib/openssh/sftp-server

to:

Subsystem sftp /bin/sh -c 'umask 0002; exec /usr/libexec/openssh/sftp-server'

Soure: http://jeff.robbins.ws/articles/setting-the-umask-for-sftp-transactions

Solution 2

In /etc/ssh/sshd_config, you can pass a flag and value in (-u 0002) like the following to set the umask value:

Subsystem sftp /usr/lib/openssh/sftp-server -u 0002

Append the -u 0002 to the existing Subsystem sftp line of the configuration file.

Afterwards, you will need to restart ssh for the changes to take effect:

service ssh restart

Comments

[user1686]

It's better to put an exec before the final /usr/.../sftp-server, so that you won't have useless sh processes lying around.

[user1686]

Also, an umask is just a number; 0002 can be written shorter as 02.

[user1686]

Yes, umasks are octal. That doesn't mean you need three leading zeroes - one is enough. (In fact, the umask command doesn't need any leading zeroes, it always reads the argument as an octal number.) ... But on the second thought, maybe 0002 is clearer to understand.

[Andrew B]

This only applies to newer versions of OpenSSH, but should be the preferred solution where possible.

[Joost]

This only works if you need more restrictive permissions than what is set by the client, not more loose.

[flight]

As Joost said, this doesn't help to force group-write permissions. I would help to forbid group-write.

[underscore_d]

According to recent documentation, the same options can be used with Subsystem sftp internal-sftp.

[Cano64]

This answer doesn't work with new openssh anymore. Received unexpected end-of-file from SFTP server. See the other answer.