Shell Programming and Scripting

Hi All,

Thanks for your help in advanced.

Could you please kindly help on why my SETUID does not work?

create a file, only root can read write it

Code:

/tmp>ls -l a.log
-rw------- 1 root root 3 Nov 12 18:57 a.log

create a script under root with SETUID

Code:

/tmp>ls -l a.sh
-rwsr-sr-x 1 root root 23 Nov 16 00:18 a.sh

the script will read above created file

Code:

/tmp>cat a.sh
#! /bin/bash
cat a.log

run under non-root account, but still failed? why?

Code:

/tmp>a.sh
cat: a.log: Permission denied

Is it due to 'cat' is not setuid? If so, how can I modify my script to let SETUID take effect?

I vaguely remember having read that certain systems' shells can't be run setuid. Try printing the effective UID from within the script.

Is this script in a non-SUID filesystem perhaps? Have a look at the mount options for the filesystem that the script is in. You can probably get it by:-

Code:

df /path/to/your/script

You can then review /etc/fstab, /etc/vfstab or /etc/filesystems as applicable to your operating system (you don't say which, so these are the most common)

You might also get the same information from the mount command by itself, but this may be OS specific, so I'd be less sure about that.


Does that help?
Robin

Linux and most other Unix-like OSes by design ignore the setuid bit on an executable script.