SMB/CIFS mount: "only root can do that"

Ghodmode · 03-25-2008, 12:07 AM

Does anyone know how to mount SMB shares as a normal user?

I want to mount a SMB share from a Windows XP box on my Linux (Kubuntu) box with an unprivileged user and without adding the mount point to fstab.

Here are the two commands I've tried:

Code:

mount -t cifs -o username=king,password=kong //xp/C\$ /home/ghodmode/xp/C\$
mount -t smbfs -o username=king,password=kong //xp/C\$ /home/ghodmode/xp/C\$

When I try this, I get the message mount: only root can do that. It works if I run the command with sudo.

I can use Smb4K to accomplish this task without providing my root or sudo password. When I look at the mount points while a share is mounted using Smb4K, I can see that the share is mounted as cifs, but I can't tell how it did it.

All of the related commands have the setuid bit set:

Code:

ghodmode@home:~$ ls -l /bin/mount /sbin/mount.smb /usr/bin/smbmount /sbin/mount.cifs
-rwsr-xr-x 1 root root  80568 2007-10-03 17:48 /bin/mount
-rwsr-xr-x 1 root root  22628 2007-12-18 20:28 /sbin/mount.cifs
lrwxrwxrwx 1 root root     17 2008-02-04 11:08 /sbin/mount.smb -> /usr/bin/smbmount
-rwsr-xr-x 1 root root 906292 2007-12-18 20:28 /usr/bin/smbmount

Thank you,
Ghodmode

raskin · 03-25-2008, 01:32 AM

Well, all the 'mount' programs are setuid - and this sets effective ID, but they always check caller uid. Smb4K is probably installed setuid and it switches to root real UID before calling mount. 'sudo strace -s 1024 -f -o log -x smb4k ...' may help - look for execve calls in log, you will see how it calls mount; *uid calls will show you what happens with UID. If you want to be able to mount Samba with even less root actions involved, you can try fusesmb. It uses "File system in Userspace" interface, and the only thing requiring root (and it is done by a setuid program you already have , fusermount) is connecting the purely userspace, unprivileged program processing Samba (and possibly exposed to protocol implementation exploits) to file system interface.

pwalden · 03-27-2008, 05:23 PM

I use mount.cifs to mount ntfs drives whilst logged is as myself. I noticed you only have the suid bit set for user (root). Here is my ll:

Code:

[root@walden4 ~]# ll /sbin/mount*
-rwsr-sr-x 1 root root 23628 2007-12-10 08:19 /sbin/mount.cifs
-rwsr-xr-x 1 root root 55460 2007-09-17 12:15 /sbin/mount.nfs

Try chmod a+s /sbin/mount.cifs