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Bug #509 ยป at.c

qhwt+dfly, 01/07/2007 08:34 AM

 
/*
* usage:
* $ gcc -W -Wall at.c
* $ su
* # chown root a.out; chmod u+s a.out
* # exit
* $ ./a.out
*/
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#define CHECK(expr) \
if ((expr) != 0) \
err(1, #expr)

int
main()
{
uid_t real_uid, effective_uid;
int fd;

real_uid = getuid();
effective_uid = geteuid();
CHECK(setreuid(effective_uid, real_uid));

CHECK(setreuid(real_uid, effective_uid));
fd = open("/etc/hosts", O_RDONLY);
CHECK(setreuid(effective_uid, real_uid));
close(fd), fd = -1; /* move this above the previous line */

CHECK(setreuid(real_uid, effective_uid));
printf("uid %d, euid %d\n", getuid(), geteuid());
CHECK(setreuid(effective_uid, real_uid));
return 0;
}

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