Execute shell command from other user

I want to execute shell command by user with uid 501. I run this application by root. I wrote:

Code:

---

#include <iostream>
using namespace std;
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>


int main() {
       
//cout<<"started as uid="<<getuid()<<", pid="<<getpid()<<endl;
       
        pid_t result = fork();

        if (result==-1) {cout<<"error fork()"<<endl;
        return 1;} else cout<<"fork()="<<result<<endl;

        if(result==0){
        int status=setuid(501);
       
//cout<<"child print setuid()="<<status<<endl;

        if(status>0)
        {

//cout<<"child uid="<<getuid()<<endl;
//cout<<"child pid="<<getpid()<<endl;

sleep(20);


system("date >/media/disk/log");
system("whoami >/media/disk/log");


        }} else if(result!=0){
               
//cout<<"parent uid="<<getuid()<<endl;
//cout<<"parent pid="<<getpid()<<endl;}

        return 0;
}

---

but /media/disk/log is empty.

move to C++

While we wait for the move to C++, I will ask: do you get any error messages on the console? Does the user have privileges to write to /media/disk/log? Are you aware that using > as redirect will delete any previous contents of the file, meaning you'll never see the date?

Such a short program, yet somehow unreadable.

Quote:

---

Originally Posted by Salem

Such a short program, yet somehow unreadable.

---

I guess that's an achievement in itself.

Excuse for unreadable.

Quote:

---

While we wait for the move to C++, I will ask: do you get any error messages on the console? Does the user have privileges to write to /media/disk/log? Are you aware that using > as redirect will delete any previous contents of the file, meaning you'll never see the date?

---

Code:

---

[andrew@COR disk]$ ls -l
-rwxrwxrwx.  1 root  root          6 Авг 23 18:37 log

---

I know that > will delete any previous contents of the file.
Before:

Code:

---

[andrew@COR disk]$ cat log
empty file

---

After:

Code:

---

[root@COR Release]# ./ssetu
started as uid=0, pid=8859
fork()=0
child print setuid()=0
fork()=8860
parent uid=0
parent pid=8859
[root@COR Release]# cat /media/disk/log
empty file

---

My attempt to make a code more readable:

Code:

---

#include <iostream>
using namespace std;
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>


int main() {
       
        pid_t result = fork();

        if (result==-1)  {
            cout<<"error fork()"<<endl;
            return 1;
       
        } else
            cout<<"fork()="<<result<<endl;

        if (result==0){
              int status=setuid(501);
       
                if (status>0){
                          sleep(20);
                          system("date >/media/disk/log");
                }

        }
        return 0;
}

---

If you take away the redirect, do you get any output?

Quote:

---

Originally Posted by tabstop

If you take away the redirect, do you get any output?

---

no, if i run by root or by user with uid=501 i get nothing.
by root:

Code:

---

[root@COR Release]# ./ssetu
started as uid=0, pid=9571
fork()=9572
parent uid=0
parent pid=9571
fork()=0
child print setuid()=0

---

by uid=501:

Code:

---

[andrew@COR disk]$ ./ssetu
started as uid=501, pid=9601
fork()=9602
parent uid=501
parent pid=9601
fork()=0
child print setuid()=0

---

by other user:

Code:

---

[up@COR disk]$ ./ssetu
started as uid=500, pid=9537
fork()=9538
parent uid=500
parent pid=9537
fork()=0
child print setuid()=-1

---

So ... that would be why your file is empty. Can you type "date" or "whoami" at the terminal? Does uid 501 not have a name that whoami doesn't print?

Here's my implementation:

Code:

---

sudo -u \#501 command

---

Quote:

---

Originally Posted by tabstop

So ... that would be why your file is empty. Can you type "date" or "whoami" at the terminal? Does uid 501 not have a name that whoami doesn't print?

---

Code:

---

[andrew@COR up]$ id
uid=501(andrew) gid=501(andrew) группы=500(up),501(andrew),502(vboxusers) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
[andrew@COR up]$ whoami
andrew
[andrew@COR up]$ date
Пнд Авг 24 16:44:30 EEST 2009
[andrew@COR up]$

---

What if you execute
date >/media/disk/log
as user andrew?

Or try to use the full path to date, as the $PATH environment variable might be not set.

Thank's all, but my mistake was that i check wrong value: if setuid() finished successfully it return 0.

Code:

---

#include <iostream>
using namespace std;
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>


int main() {
       
        pid_t result = fork();

        if (result==-1)  {
            cout<<"error fork()"<<endl;
            return 1;
       
        } else
            cout<<"fork()="<<result<<endl;

        if (result==0){
              int status=setuid(501);
       
                if (status==0){
                          sleep(20);
                          system("date >/media/disk/log");
                }

        }
        return 0;
}

---