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sortix--sortix/utils/chroot.cpp
2015-12-12 16:53:42 +01:00

187 lines
4.8 KiB
C++

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2013, 2015.
This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
chroot.cpp
Runs a process with another root directory.
*******************************************************************************/
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <fsmarshall.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static void compact_arguments(int* argc, char*** argv)
{
for ( int i = 0; i < *argc; i++ )
{
while ( i < *argc && !(*argv)[i] )
{
for ( int n = i; n < *argc; n++ )
(*argv)[n] = (*argv)[n+1];
(*argc)--;
}
}
}
static void help(FILE* fp, const char* argv0)
{
fprintf(fp, "Usage: %s [OPTION]... ROOT [CMD] [ARGUMENT...]\n", argv0);
}
static void version(FILE* fp, const char* argv0)
{
fprintf(fp, "%s (Sortix) %s\n", argv0, VERSIONSTR);
fprintf(fp, "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.\n");
fprintf(fp, "This is free software: you are free to change and redistribute it.\n");
fprintf(fp, "There is NO WARRANTY, to the extent permitted by law.\n");
}
static char* mount_point_dev;
static void unmount_handler(int signum)
{
(void) signum;
if ( mount_point_dev )
{
unmount(mount_point_dev, 0);
mount_point_dev = NULL;
}
raise(signum);
}
int main(int argc, char* argv[])
{
bool devices = false;
const char* argv0 = argv[0];
for ( int i = 1; i < argc; i++ )
{
const char* arg = argv[i];
if ( arg[0] != '-' || !arg[1] )
break; // Intentionally not continue.
argv[i] = NULL;
if ( !strcmp(arg, "--") )
break;
if ( arg[1] != '-' )
{
while ( char c = *++arg ) switch ( c )
{
case 'd': devices = true; break;
default:
fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c);
help(stderr, argv0);
exit(1);
}
}
else if ( !strcmp(arg, "--help") )
help(stdout, argv0), exit(0);
else if ( !strcmp(arg, "--version") )
version(stdout, argv0), exit(0);
else
{
fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
help(stderr, argv0);
exit(1);
}
}
compact_arguments(&argc, &argv);
if ( argc < 2 )
error(1, 0, "missing operand, expected new root directory");
if ( devices )
{
if ( asprintf(&mount_point_dev, "%s/dev", argv[1]) < 0 )
error(1, errno, "asprintf: `%s/dev'", argv[1]);
// Create a device directory in the root filesystem.
mkdir(mount_point_dev, 0755);
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = unmount_handler;
sa.sa_flags = SA_RESETHAND;
sigaction(SIGHUP, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
sigaction(SIGQUIT, &sa, NULL);
// Mount the current device directory inside the new root filesystem.
int old_dev_fd = open("/dev", O_DIRECTORY | O_RDONLY);
int new_dev_fd = open(mount_point_dev, O_DIRECTORY | O_RDONLY);
fsm_fsbind(old_dev_fd, new_dev_fd, 0);
close(new_dev_fd);
close(old_dev_fd);
sigset_t oldset, sigs;
sigemptyset(&sigs);
sigaddset(&sigs, SIGHUP);
sigaddset(&sigs, SIGINT);
sigaddset(&sigs, SIGQUIT);
sigprocmask(SIG_BLOCK, &sigs, &oldset);
pid_t child_pid = fork();
if ( child_pid < 0 )
{
int errnum = errno;
unmount(mount_point_dev, 0);
mount_point_dev = NULL;
sigprocmask(SIG_SETMASK, &oldset, NULL);
error(1, errnum, "fork");
}
if ( child_pid != 0 )
{
sigprocmask(SIG_SETMASK, &oldset, NULL);
int code;
waitpid(child_pid, &code, 0);
sigprocmask(SIG_BLOCK, &sigs, &oldset);
unmount(mount_point_dev, 0);
sigprocmask(SIG_SETMASK, &oldset, NULL);
mount_point_dev = NULL;
if ( WIFEXITED(code) )
return WEXITSTATUS(code);
raise(WTERMSIG(code));
return 128 + WTERMSIG(code);
}
signal(SIGHUP, SIG_DFL);
signal(SIGINT, SIG_DFL);
signal(SIGQUIT, SIG_DFL);
sigprocmask(SIG_SETMASK, &oldset, NULL);
}
if ( chroot(argv[1]) != 0 )
error(1, errno, "`%s'", argv[1]);
if ( chdir("/.") != 0 )
error(1, errno, "chdir: `%s/.'", argv[1]);
char* default_argv[] = { (char*) "sh", (char*) NULL };
char** exec_argv = 3 <= argc ? argv + 2 : default_argv;
execvp(exec_argv[0], exec_argv);
error(0, errno, "`%s'", exec_argv[0]);
_exit(127);
}