137 lines
3.2 KiB
C
137 lines
3.2 KiB
C
#include <sys/mount.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#include <sys/reboot.h>
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#include <sys/syscall.h>
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char *splash[] = {
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"",
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" ------------------------------||-------------------------------",
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" [##]",
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" /~~~~~~\\",
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" |~~\\ /~~|",
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" ==][===|___||___|===][==",
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" [::] ( () ) [::]",
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" ~/~~~~\\~",
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" O' `o", "",NULL
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};
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static int run_shell()
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{
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char *new_argv[] = { "/bin/bash", NULL };
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char *new_env[] = { "TERM=xterm-256color", "HOME=/home/user", NULL };
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char **p;
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for(p = splash; *p; p++) {
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printf("%s\n", *p);
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}
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return execve("/bin/bash", new_argv, new_env);
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}
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static void do_mkdir(const char* path) {
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if(mkdir(path, 0755) < 0) {
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printf("mkdir %s failed: %s\n", path, strerror(errno));
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}
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}
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static void mount_tmpfs(const char *path) {
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if(mount("tmpfs", path, "tmpfs", 0, "mode=755") < 0) {
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printf("mount tmpfs to %s failed: %s\n", path, strerror(errno));
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}
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}
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static void pivot_root(const char *new_root, const char *put_old) {
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if(syscall(SYS_pivot_root, new_root, put_old) < 0) {
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printf("pivot_root failed (%s : %s) : %s\n", new_root, put_old, strerror(errno));
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}
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}
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static void move_mount(const char *source, const char *target) {
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if(mount(source, target, "", MS_MOVE, NULL) < 0) {
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printf("move mount of %s to %s failed: %s\n", source, target, strerror(errno));
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}
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}
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static void setup_overlay(void) {
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mount_tmpfs("/tmp");
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do_mkdir("/tmp/ro");
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do_mkdir("/tmp/rw");
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mount_tmpfs("/tmp/rw");
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do_mkdir("/tmp/rw/upper");
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do_mkdir("/tmp/rw/work");
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do_mkdir("/tmp/overlay");
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pivot_root("/tmp", "/tmp/ro");
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/*
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* /ro real root mounted here
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* /rw tmpfs mounted here
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* /rw/upper empty directory
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* /rw/work empty directory
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* /overlay empty directory
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*
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*/
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if(mount("overlay", "/overlay", "overlay", 0, "lowerdir=/ro,upperdir=/rw/upper,workdir=/rw/work") < 0) {
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printf("mount overlay failed: %s\n", strerror(errno));
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}
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do_mkdir("/overlay/ro");
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do_mkdir("/overlay/rw");
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do_mkdir("/overlay/old-root");
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move_mount("/ro", "/overlay/ro");
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move_mount("/rw", "/overlay/rw");
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pivot_root("/overlay", "/overlay/old-root");
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umount("/old-root");
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umount("/ro/tmp");
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}
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static void do_mounts(void)
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{
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mount("sysfs", "/sys", "sysfs", 0, NULL);
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mount("proc", "/proc", "proc", 0, NULL);
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mount("devtmpfs", "/dev", "devtmpfs", 0, NULL);
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mkdir("/dev/pts", 0755);
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mount("devpts", "/dev/pts", "devpts", 0, NULL);
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}
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int main(int argc, char *argv[])
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{
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pid_t child;
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int status;
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setup_overlay();
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do_mounts();
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sethostname("airwolf", 7);
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/* get session leader */
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setsid();
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/* set controlling terminal */
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ioctl(0, TIOCSCTTY, 1);
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child = fork();
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if (child < 0) {
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printf("Fatal: fork() failed with %d\n", child);
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return 0;
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} else if (child == 0) {
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run_shell();
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} else {
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pid_t corpse;
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do {
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corpse = waitpid(-1, &status, 0);
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} while (corpse != child);
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}
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reboot(RB_AUTOBOOT);
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printf("Init failed: %s\n", strerror(errno));
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return 0;
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}
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