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//
// $Id$
//
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/types.h>
/// Run by the child process
static int child(int argc, char* argv[]);
static int max_child_time = 300;
const char *child_name = 0;
static int parse_args(int& argc, char* argv[]);
int
main(int argc, char* argv[])
{
if (parse_args(argc, argv) != 0)
return 1;
pid_t pid = fork();
if (pid == -1) {
fprintf(stderr, "Error in fork\n");
return 1;
}
if (pid == 0) {
// In the child...
return child(argc, argv);
}
int status;
pid_t child = waitpid(pid, &status, 0);
if (child == -1) {
fprintf(stderr, "sandbox: error waiting for child\n");
return 1;
}
// Return whatever status the child has...
return status;
}
sig_atomic_t child_died = 0;
extern "C" void
sigchld_handler(int signal)
{
child_died = 1;
}
static int
child (int /* argc */, char* argv[])
{
// The child becomes its own session, implicitly this turns the
// child process into its own process group leader, allowing us to
// terminate a hierarchy of children easily.
pid_t sid = setsid();
if (sid == -1)
{
fprintf(stderr, "sandbox: error in setid\n");
return 1;
}
// Setup the signal handler to receive SIGCHLD signals:
(void) signal(SIGCHLD, sigchld_handler);
// Now we must fork again to wait for the grandchild process...
pid_t grandchild = fork();
if (grandchild == 0) {
// Exec the arguments...
int r = execvp(child_name, argv);
if (r == -1) {
fprintf(stderr, "sandbox: error in execvp()\n");
return 1;
}
}
// As the process leader we wait until the child returns or there is
// a timeout...
int status;
int remaining_time = max_child_time;
while (remaining_time != 0)
{
// We use the signal handler to return from sleep before all the
// time expires
remaining_time = sleep(remaining_time);
// We could exit
if (child_died)
{
pid_t child = waitpid(grandchild, &status, WNOHANG);
if (child == -1)
{
fprintf(stderr,
"sandbox: no grandchild process (%d), panic\n",
grandchild);
return 1;
}
if (child != 0)
{
//printf("sandbox: grandchild %d exits with status %d\n",
// child, status);
return status;
}
}
}
printf("sandbox: timeout for grandchild %d\n", grandchild);
// timeout, try to kill the child
(void) kill(grandchild, SIGTERM);
// Second chance, if the child does not die, then really kill it:
pid_t killed = waitpid(grandchild, &status, WNOHANG);
if (killed == 0)
{
// TERM did not work, use the heavy duty signal
(void) kill(grandchild, SIGQUIT); sleep(1);
killed = waitpid(grandchild, &status, WNOHANG);
}
if (killed == -1)
{
fprintf(stderr, "No such child (%d), panic\n",
grandchild);
return 1;
}
sleep(1);
printf("sandbox: killing session %d\n", sid);
// OK, now commit suicide, kill the session ID and all their friends
(void) killpg(sid, SIGQUIT);
fprintf(stderr, "sandbox: ooops! I should be dead!\n");
return 1;
}
static int
parse_args(int &argc, char* argv[])
{
if (argc < 3) {
fprintf(stderr, "Usage: sandbox max_time program arguments\n");
return 1;
}
max_child_time = atoi(argv[1]);
child_name = argv[2];
argc -= 2;
for (int i = 0; i != argc; ++i)
{
argv[i] = argv[i + 2];
}
argv[argc] = 0;
if (child_name == 0)
return 1;
return 0;
}
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