CODEWITHSUNDEEP
linuxvirtual-machinesshfslinux-capabilities
Abhishek Bansal
Abhishek Bansal

Reputation: 31

Setcap over SSHFS

I am running a VM on my machine and have mounted a host folder inside VM using sshfs (auto-mounted via fstab).

abc@xyz:/home/machine/test on /home/vm/test type fuse.sshfs (rw,relatime,user_id=0,group_id=0,allow_other)

That folder has an executable which I want to run inside the VM. But I also need some capabilities before running that executable. So my script looks like:

#!/bin/bash
# Some preprocessing.
sudo setcap CAP_DAC_OVERRIDE+ep /home/vm/test/my_exec
/home/vm/test/my_exec

But I am getting below error : 

Failed to set capabilities on file `/home/vm/test/my_exec' (Operation not supported)
The value of the capability argument is not permitted for a file. Or the file is not a regular (non-symlink) file

But if I copy executable inside the VM (say in /tmp/), then it works perfectly fine. Is this a known limitation of sshfs or am I missing something here ?

Upvotes: 1

Views: 423

Answers (2)

user10678532
user10678532

Reputation:

File capabilities are implemented on Linux with extended attributes (specifically the security.capability attribute), and not all filesystems implement extended attributes.

sshfs in particular does not.

Upvotes: 1

user149341
user149341

Reputation:

sshfs can only perform operations which the remote user is authorized to perform. You're logged into the remote host as abc, so you can only perform actions over sshfs which abc can perform -- which doesn't include setcap, since that operation can only be performed by root. Using sudo on your local machine doesn't change that.

Upvotes: 0

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