Magisk/native/jni/init/init.cpp
2019-05-27 00:29:43 -07:00

231 lines
4.7 KiB
C++

#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/sysmacros.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <fcntl.h>
#include <libgen.h>
#include <xz.h>
#include <magisk.h>
#include <selinux.h>
#include <cpio.h>
#include <utils.h>
#include <flags.h>
#include "binaries.h"
#ifdef USE_64BIT
#include "binaries_arch64.h"
#else
#include "binaries_arch.h"
#endif
#include "init.h"
using namespace std;
#ifdef MAGISK_DEBUG
static FILE *kmsg;
static int vprintk(const char *fmt, va_list ap) {
fprintf(kmsg, "magiskinit: ");
return vfprintf(kmsg, fmt, ap);
}
static void setup_klog() {
mknod("/kmsg", S_IFCHR | 0666, makedev(1, 11));
int fd = xopen("/kmsg", O_WRONLY | O_CLOEXEC);
kmsg = fdopen(fd, "w");
setbuf(kmsg, nullptr);
unlink("/kmsg");
log_cb.d = log_cb.i = log_cb.w = log_cb.e = vprintk;
log_cb.ex = nop_ex;
}
#else
#define setup_klog(...)
#endif
static int test_main(int argc, char *argv[]);
constexpr const char *init_applet[] =
{ "magiskpolicy", "supolicy", "init_test", nullptr };
constexpr int (*init_applet_main[])(int, char *[]) =
{ magiskpolicy_main, magiskpolicy_main, test_main, nullptr };
static bool unxz(int fd, const uint8_t *buf, size_t size) {
uint8_t out[8192];
xz_crc32_init();
struct xz_dec *dec = xz_dec_init(XZ_DYNALLOC, 1 << 26);
struct xz_buf b = {
.in = buf,
.in_pos = 0,
.in_size = size,
.out = out,
.out_pos = 0,
.out_size = sizeof(out)
};
enum xz_ret ret;
do {
ret = xz_dec_run(dec, &b);
if (ret != XZ_OK && ret != XZ_STREAM_END)
return false;
write(fd, out, b.out_pos);
b.out_pos = 0;
} while (b.in_pos != size);
return true;
}
static void decompress_ramdisk() {
constexpr char tmp[] = "tmp.cpio";
constexpr char ramdisk_xz[] = "ramdisk.cpio.xz";
if (access(ramdisk_xz, F_OK))
return;
LOGD("Decompressing ramdisk from %s\n", ramdisk_xz);
uint8_t *buf;
size_t sz;
mmap_ro(ramdisk_xz, buf, sz);
int fd = open(tmp, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC);
unxz(fd, buf, sz);
munmap(buf, sz);
close(fd);
cpio_mmap cpio(tmp);
cpio.extract();
unlink(tmp);
unlink(ramdisk_xz);
}
int dump_magisk(const char *path, mode_t mode) {
int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, mode);
if (fd < 0)
return 1;
if (!unxz(fd, magisk_xz, sizeof(magisk_xz)))
return 1;
close(fd);
return 0;
}
static int dump_manager(const char *path, mode_t mode) {
int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, mode);
if (fd < 0)
return 1;
if (!unxz(fd, manager_xz, sizeof(manager_xz)))
return 1;
close(fd);
return 0;
}
void MagiskInit::preset() {
root = open("/", O_RDONLY | O_CLOEXEC);
if (cmd.system_as_root) {
// Clear rootfs
LOGD("Cleaning rootfs\n");
frm_rf(root, { "overlay", "proc", "sys" });
} else {
decompress_ramdisk();
// Revert original init binary
rename("/.backup/init", "/init");
rm_rf("/.backup");
// Do not go further if device is booting into recovery
if (access("/sbin/recovery", F_OK) == 0) {
LOGD("Ramdisk is recovery, abort\n");
re_exec_init();
}
}
}
#define umount_root(name) \
if (mnt_##name) \
umount("/" #name);
void MagiskInit::cleanup() {
umount(SELINUX_MNT);
umount("/sys");
umount("/proc");
umount_root(system);
umount_root(vendor);
umount_root(product);
umount_root(odm);
}
void MagiskInit::re_exec_init() {
LOGD("Re-exec /init\n");
cleanup();
execv("/init", argv);
exit(1);
}
void MagiskInit::start() {
// Prevent file descriptor confusion
mknod("/null", S_IFCHR | 0666, makedev(1, 3));
int null = open("/null", O_RDWR | O_CLOEXEC);
unlink("/null");
xdup3(null, STDIN_FILENO, O_CLOEXEC);
xdup3(null, STDOUT_FILENO, O_CLOEXEC);
xdup3(null, STDERR_FILENO, O_CLOEXEC);
if (null > STDERR_FILENO)
close(null);
setup_klog();
load_kernel_info();
full_read("/init", &self.buf, &self.sz);
full_read("/.backup/.magisk", &config.buf, &config.sz);
preset();
early_mount();
setup_rootfs();
re_exec_init();
}
void MagiskInit::test() {
cmdline_logging();
log_cb.ex = nop_ex;
chdir(dirname(argv[0]));
chroot(".");
chdir("/");
load_kernel_info();
preset();
early_mount();
setup_rootfs();
cleanup();
}
static int test_main(int, char *argv[]) {
MagiskInit init(argv);
init.test();
return 0;
}
int main(int argc, char *argv[]) {
umask(0);
for (int i = 0; init_applet[i]; ++i) {
if (strcmp(basename(argv[0]), init_applet[i]) == 0)
return (*init_applet_main[i])(argc, argv);
}
if (argc > 1 && strcmp(argv[1], "-x") == 0) {
if (strcmp(argv[2], "magisk") == 0)
return dump_magisk(argv[3], 0755);
else if (strcmp(argv[2], "manager") == 0)
return dump_manager(argv[3], 0644);
}
if (getpid() != 1)
return 1;
MagiskInit init(argv);
// Run the main routine
init.start();
}