playing with linux namespaces
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ns_hacking/demo_userns.c

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1.5 KiB

/* demo_userns.c
Copyright 2013, Michael Kerrisk
Licensed under GNU General Public License v2 or later
Demonstrate the use of the clone() CLONE_NEWUSER flag.
Link with "-lcap" and make sure that the "libcap-devel" (or
similar) package is installed on the system.
*/
#define _GNU_SOURCE
#include <sys/capability.h>
#include <sys/wait.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \
} while (0)
static int /* Startup function for cloned child */
childFunc(void *arg)
{
cap_t caps;
for (;;) {
printf("eUID = %ld; eGID = %ld; ",
(long) geteuid(), (long) getegid());
caps = cap_get_proc();
printf("capabilities: %s\n", cap_to_text(caps, NULL));
if (arg == NULL)
break;
sleep(5);
}
return 0;
}
#define STACK_SIZE (1024 * 1024)
static char child_stack[STACK_SIZE]; /* Space for child's stack */
int
main(int argc, char *argv[])
{
pid_t pid;
/* Create child; child commences execution in childFunc() */
pid = clone(childFunc, child_stack + STACK_SIZE, /* Assume stack
grows downward */
CLONE_NEWUSER | SIGCHLD, argv[1]);
if (pid == -1)
errExit("clone");
/* Parent falls through to here. Wait for child. */
if (waitpid(pid, NULL, 0) == -1)
errExit("waitpid");
exit(EXIT_SUCCESS);
}