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4
votes
2answers
1k views

Purpose of using setuid() in SUID programs

I wonder that an SUID program like passwd is using the setuid() function call. Why does it drop root privileges? Against what types of attack does this help? Buffer-overflow?
4
votes
1answer
759 views

Clear setuid permission using numeric mode

On an Ubuntu Linux I have a directory with the setuid bit set (drwsr-xr-x) which I want to unset. Neither chmod 755 nor chmod 0755 nor chmod 00755 (I though maybe the first 0 is interpreted as just ...
2
votes
3answers
5k views

How does the set-user-ID mechanism work in Unix?

Can someone please explain the set-user-ID mechanism in Unix ? What was the rationale behind this design decision? How is it different from effective user id mechanism ?
3
votes
1answer
1k views

How to replace setuid with file-system capabilities

Inspired by this question here is the follow-up: As some of you may know setuid-binaries are dangerous, since some exploits use these to escalate their rights up to root. Now it seems that there has ...
3
votes
2answers
1k 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 ...
5
votes
1answer
879 views

root owned program with setuid bit on

Ping is a a program owned by root with the user id bit set. $ ls -l `which ping` -rwsr-xr-x 1 root root 35752 Nov 4 2011 /bin/ping As I understand it, if a user runs the ping process, then the ...
4
votes
1answer
668 views

Environment settings on setuid executables

I am observing a curious behavior when running a program with setuid bit enabled. Program foo is owned by user bar with setuid bit set. User execbar runs foo foo reports that one of the dynamic ...
5
votes
2answers
214 views

Running setuid binary temporarily without setuid?

Currently setting up xpra, which wants to run an X instance as non-root using the dummy driver, but the system Xorg binary is SUID. Since the system auto-updates, I would prefer not making and ...
5
votes
3answers
12k views

What does GID mean?

What does GID actually mean? I have Googled it and this is what linux.about.com said: Group identification number for the process. Valid group numbers are given in /etc/group, and in the ...
5
votes
2answers
2k views

Why is mount.cifs not installed suid by default?

I am using Gentoo, and on my machine at least mount.cifs is not installed suid root by default. In particular, this means that I can't use the user mount option with CIFS shares. I noticed that ...
2
votes
1answer
805 views

using Set uid to run a root command from non-root user

Consider the following two files. summarize's executable UID bit has been set, so that another user belonging to another group can execute the summarize executable that uses the customers.dat file. ...
-1
votes
1answer
311 views

Are there any setuid/setguid bits in OpenBSD?

https://en.wikipedia.org/wiki/Setuid Are there anything like this under OpenBSD?
5
votes
3answers
2k views

Changing the UID of files in /proc

In a follow up to this question about changing the UID of a user, it is recommended to change the ownership of all files on the system (this answer) find / -uid 1000 -exec chown 5000 '{}' \+ where ...
2
votes
3answers
424 views

How does setting the Setuid bit affect shell scripts that run on boot of the system, before any login has occurred?

Would enabling the setuid bit on a shell script make a difference at all when that script is run on boot? Who would the effective user be?
5
votes
4answers
5k 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 ...
6
votes
2answers
4k 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 ...
2
votes
2answers
468 views

Unix executable file permission vs runtime user's permissions

I have heard that it is good practice to run an executable as a user with a completely different privilege set than the owner of the task. In fact I heard that it is best to run it as a different user ...
79
votes
6answers
50k 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 ...