What is a SUID root file

[dcdcdc]

also how can i determine whether a file is suid root and why such file is important in developing secure systems

[sarumont]

A file with the SUID bit set allows the program to be run as root. You can tell if a file has SUID bit set with an ls -al

-rwsr-xr-x   1 root root  6.7K Jul 15 00:15 utempter

The s in the place of the x (execute) signifies that the suid bit is set for that file.

[imand]

SUID
The set user ID option is used in conjunction missions of whoeveer owns the file,and it tells Linux to run the program with the permissions of whoever wons the file ,rather than with the permissions of the user who runs the program.for instansce ,if a file is owned by root and has its SUID bit set,the program runs with root privileges and can therefore read any file on the computer.Some servers and other system programs run in this way ,which is often called SUID root.SUID programs are indicated by an s in the owners's execute bit positions of the permission string ,as in rwsr-xr-x

SUID root files
it's possible to set a file to execute as if run by root even when it's run by another user.This must be set on a program-by-program basis.but as you know its so dangerous.

[sreenadh]

Hi,

Please let me add some more points to that. SUID bit will be set for executables only. So an executable will of course be a command. If SUID bit is set for that command it will run with the permissions of the OWNER of the command and not with the permission of EXECUTOR of the command.

A good example will be the passwd command. It has got the SUID bit set. So when a user runs the passwd command he is running it with the same UserID as the owner of the file.