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108
votes
7answers
71k views

Allow setuid on shell scripts

The setuid permission bit tells Linux to run a program with the effective user id of the owner instead of the executor: > cat setuid-test.c #include <stdio.h> #include <unistd.h> int ...
24
votes
2answers
14k views

Using the setuid bit properly

I have a process that needs root privileges when run by a normal user. Apparently I can use the "setuid bit" to accomplish this. What is the proper way of doing this on a POSIX system? Also, how ...
8
votes
5answers
8k views

how does real and effective user ID works?

When a normal user wants to make change to the passwd file, the user will by setuid be given the effective user access. User becomes root temporarily and can edit passwd. However you can only edit ...
10
votes
2answers
7k views

Can gdb debug suid root programs?

I wrote a program that calls setuid(0) and execve("/bin/bash",NULL,NULL). Then I did chown root:root a.out && chmod +s a.out When I execute ./a.out I get a root shell. However when I do gdb ...
0
votes
2answers
106 views

Why is the suid bit having no effect on a shell or perl script? [duplicate]

As an experiment in playing with the suid bit, I tried writing a script to run apt-get update from a bash script, and then set the suid bit on it, so I could just run ~/update or something. apt-get ...
35
votes
6answers
2k views

What is the safest way for programmatically writing to a file with root privileges?

A huge application needs, at one specific time, to perform a small number of writes to a file which requires root permissions. It is not really a file but a hardware interface which is exposed to ...
8
votes
1answer
4k views

Difference between owner/root and RUID/EUID

I am relatively new to the concepts mentioned in the question and reading about them from different sources only makes them more confusing. So this is what I understood so far: When we are given ...
4
votes
2answers
2k views

setuid and setgid confusion

I'm trying to fully grasp the concept of setuid and setgid, and I'm not quite sure in what way permissions are actually elevated. Let me provide an example: Users userA (groups: userA groupA) userB (...
6
votes
1answer
423 views

How does having /dev/fd make running shell scripts under sudo safe?

At the end of the man page for sudo, there's the following remark: Running shell scripts via sudo can expose the same kernel bugs that make setuid shell scripts unsafe on some operating systems ...
6
votes
2answers
6k views

Setuid bit seems to have no effect on bash

I was experimenting a bit and noticed something strange: setting the setuid bit on a copy of bash located at /usr/bin/bash-test seemed to have no effect. When I ran an instance of bash-test, my home ...
2
votes
1answer
1k views

How to suid iwconfig on Debian wheezy?

I have a script running under my own user account that takes care of all sorts of wireless interfaces. It (more or less) intelligently switches wireless LAN off and on and so forth. However, it does ...
2
votes
3answers
136 views

Why does FreeBSD require terminal programs to be started as root?

On FreeBSD all graphical terminal programs (e.g. xterm, rxvt) seem to be installed setuid root, or with setuid root wrappers. On Linux, this is not the case on any distribution I have ever used. Why ...
1
vote
1answer
238 views

Using find -perm to find setuid files

I want to find list of all suid binaries. I use the command find / -perm 4000 However this does not give me any output. I understand that the SUID file may be in 4xxx permission mode. But if I ...