Magisk/native/jni/core/init.cpp

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#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/sendfile.h>
#include <sys/sysmacros.h>
#include <linux/input.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <fcntl.h>
#include <libgen.h>
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#include <functional>
#include <string_view>
#include <xz.h>
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#include <magisk.h>
#include <magiskpolicy.h>
#include <selinux.h>
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#include <cpio.h>
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#include <utils.h>
#include <flags.h>
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#include "binaries.h"
#ifdef USE_64BIT
#include "binaries_arch64.h"
#define LIBNAME "lib64"
#else
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#include "binaries_arch.h"
#define LIBNAME "lib"
#endif
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#include "magiskrc.h"
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using namespace std;
#define DEFAULT_DT_DIR "/proc/device-tree/firmware/android"
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#ifdef MAGISK_DEBUG
static FILE *kmsg;
static char kbuf[4096];
static int vprintk(const char *fmt, va_list ap) {
vsprintf(kbuf, fmt, ap);
return fprintf(kmsg, "magiskinit: %s", kbuf);
}
static void setup_klog() {
mknod("/kmsg", S_IFCHR | 0666, makedev(1, 11));
kmsg = xfopen("/kmsg", "ae");
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 };
struct cmdline {
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bool system_as_root;
char slot[3];
char dt_dir[128];
};
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struct raw_data {
void *buf;
size_t sz;
};
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;
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LOGD("Decompressing ramdisk from %s\n", ramdisk_xz);
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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);
}
static 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;
}
class MagiskInit {
private:
cmdline cmd{};
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raw_data self{};
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raw_data config{};
int root = -1;
char **argv;
bool load_sepol = false;
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bool mnt_system = false;
bool mnt_vendor = false;
bool mnt_product = false;
bool mnt_odm = false;
void load_kernel_info();
void preset();
void early_mount();
void setup_rootfs();
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bool read_dt_fstab(const char *name, char *partname, char *partfs);
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bool patch_sepolicy();
void cleanup();
public:
explicit MagiskInit(char *argv[]) : argv(argv) {}
void setup_overlay();
void re_exec_init();
void start();
void test();
};
static inline void parse_cmdline(const std::function<void (std::string_view, const char *)> &fn) {
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char cmdline[4096];
int fd = open("/proc/cmdline", O_RDONLY | O_CLOEXEC);
cmdline[read(fd, cmdline, sizeof(cmdline))] = '\0';
close(fd);
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char *tok, *eql, *tmp, *saveptr;
saveptr = cmdline;
while ((tok = strtok_r(nullptr, " \n", &saveptr)) != nullptr) {
eql = strchr(tok, '=');
if (eql) {
*eql = '\0';
if (eql[1] == '"') {
tmp = strchr(saveptr, '"');
if (tmp != nullptr) {
*tmp = '\0';
saveptr[-1] = ' ';
saveptr = tmp + 1;
eql++;
}
}
fn(tok, eql + 1);
} else {
fn(tok, "");
}
}
}
#define test_bit(bit, array) (array[bit / 8] & (1 << (bit % 8)))
static bool check_key_combo() {
uint8_t bitmask[(KEY_MAX + 1) / 8];
int eventfd = -1;
for (int minor = 64; minor < 96; ++minor) {
if (mknod("/event", S_IFCHR | 0444, makedev(13, minor))) {
PLOGE("mknod");
continue;
}
eventfd = xopen("/event", O_RDWR | O_CLOEXEC);
unlink("/event");
if (eventfd < 0)
continue;
memset(bitmask, 0, sizeof(bitmask));
ioctl(eventfd, EVIOCGBIT(EV_KEY, sizeof(bitmask)), bitmask);
if (test_bit(KEY_POWER, bitmask) && test_bit(KEY_VOLUMEUP, bitmask)) {
// Check KEY_POWER because KEY_VOLUMEUP could be headphone input
break;
}
}
if (eventfd < 0)
return false;
// Return true if volume key up is hold for more than 3 seconds
int count = 0;
for (int i = 0; i < 500; ++i) {
memset(bitmask, 0, sizeof(bitmask));
ioctl(eventfd, EVIOCGKEY(sizeof(bitmask)), bitmask);
count = test_bit(KEY_VOLUMEUP, bitmask) ? count + 1 : 0;
if (count >= 300) {
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LOGD("KEY_VOLUMEUP detected: disable system-as-root\n");
close(eventfd);
return true;
}
// Check every 10ms
usleep(10000);
}
close(eventfd);
return false;
}
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void MagiskInit::load_kernel_info() {
// Communicate with kernel using procfs and sysfs
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xmkdir("/proc", 0755);
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xmount("proc", "/proc", "proc", 0, nullptr);
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xmkdir("/sys", 0755);
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xmount("sysfs", "/sys", "sysfs", 0, nullptr);
bool enter_recovery = false;
bool kirin = false;
bool recovery_mode = false;
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parse_cmdline([&](auto key, auto value) -> void {
LOGD("cmdline: [%s]=[%s]\n", key.data(), value);
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if (key == "androidboot.slot_suffix") {
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strcpy(cmd.slot, value);
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} else if (key == "androidboot.slot") {
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cmd.slot[0] = '_';
strcpy(cmd.slot + 1, value);
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} else if (key == "skip_initramfs") {
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cmd.system_as_root = true;
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} else if (key == "androidboot.android_dt_dir") {
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strcpy(cmd.dt_dir, value);
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} else if (key == "enter_recovery") {
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enter_recovery = value[0] == '1';
} else if (key == "androidboot.hardware") {
kirin = strstr(value, "kirin") || strstr(value, "hi3660");
}
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});
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parse_prop_file("/.backup/.magisk", [&](auto key, auto value) -> bool {
if (key == "RECOVERYMODE" && value == "true")
recovery_mode = true;
return true;
});
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if (kirin && enter_recovery) {
// Inform that we are actually booting as recovery
if (!recovery_mode) {
if (FILE *f = fopen("/.backup/.magisk", "ae"); f) {
fprintf(f, "RECOVERYMODE=true\n");
fclose(f);
}
recovery_mode = true;
}
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}
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if (recovery_mode) {
LOGD("Running in recovery mode, waiting for key...\n");
cmd.system_as_root = !check_key_combo();
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}
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if (cmd.dt_dir[0] == '\0')
strcpy(cmd.dt_dir, DEFAULT_DT_DIR);
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LOGD("system_as_root=[%d]\n", cmd.system_as_root);
LOGD("slot=[%s]\n", cmd.slot);
LOGD("dt_dir=[%s]\n", cmd.dt_dir);
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}
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void MagiskInit::preset() {
root = open("/", O_RDONLY | O_CLOEXEC);
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if (cmd.system_as_root) {
// Clear rootfs
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LOGD("Cleaning rootfs\n");
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frm_rf(root, { "overlay", "proc", "sys" });
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} else {
decompress_ramdisk();
// Revert original init binary
rename("/.backup/init", "/init");
rm_rf("/.backup");
// Do not go further if device is booting into recovery
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if (access("/sbin/recovery", F_OK) == 0) {
LOGD("Ramdisk is recovery, abort\n");
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re_exec_init();
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}
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}
}
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struct device {
int major;
int minor;
char devname[32];
char partname[32];
};
static inline void parse_device(device *dev, const char *uevent) {
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dev->partname[0] = '\0';
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FILE *fp = xfopen(uevent, "re");
char buf[64];
while (fgets(buf, sizeof(buf), fp)) {
if (strncmp(buf, "MAJOR", 5) == 0) {
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sscanf(buf, "MAJOR=%d", &dev->major);
} else if (strncmp(buf, "MINOR", 5) == 0) {
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sscanf(buf, "MINOR=%d", &dev->minor);
} else if (strncmp(buf, "DEVNAME", 7) == 0) {
sscanf(buf, "DEVNAME=%s", dev->devname);
} else if (strncmp(buf, "PARTNAME", 8) == 0) {
sscanf(buf, "PARTNAME=%s", dev->partname);
}
}
fclose(fp);
}
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static vector<device> dev_list;
static void collect_devices() {
char path[128];
struct dirent *entry;
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device dev;
DIR *dir = xopendir("/sys/dev/block");
if (dir == nullptr)
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return;
while ((entry = readdir(dir))) {
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if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
sprintf(path, "/sys/dev/block/%s/uevent", entry->d_name);
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parse_device(&dev, path);
dev_list.push_back(dev);
}
closedir(dir);
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}
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static bool setup_block(const char *partname, char *block_dev) {
if (dev_list.empty())
collect_devices();
for (auto &dev : dev_list) {
if (strcasecmp(dev.partname, partname) == 0) {
sprintf(block_dev, "/dev/block/%s", dev.devname);
LOGD("Found %s: [%s] (%d, %d)\n", dev.partname, dev.devname, dev.major, dev.minor);
xmkdir("/dev", 0755);
xmkdir("/dev/block", 0755);
mknod(block_dev, S_IFBLK | 0600, makedev(dev.major, dev.minor));
return true;
}
}
return false;
}
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bool MagiskInit::read_dt_fstab(const char *name, char *partname, char *partfs) {
char path[128];
int fd;
sprintf(path, "%s/fstab/%s/dev", cmd.dt_dir, name);
if ((fd = xopen(path, O_RDONLY | O_CLOEXEC)) >= 0) {
read(fd, path, sizeof(path));
close(fd);
// Some custom treble use different names, so use what we read
name = rtrim(strrchr(path, '/') + 1);
sprintf(partname, "%s%s", name, strend(name, cmd.slot) ? cmd.slot : "");
sprintf(path, "%s/fstab/%s/type", cmd.dt_dir, name);
if ((fd = xopen(path, O_RDONLY | O_CLOEXEC)) >= 0) {
read(fd, partfs, 32);
close(fd);
return true;
}
}
return false;
}
static inline bool is_lnk(const char *name) {
struct stat st;
if (lstat(name, &st))
return false;
return S_ISLNK(st.st_mode);
}
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#define link_root(name) \
if (is_lnk("/system_root" name)) \
cp_afc("/system_root" name, name)
#define mount_root(name) \
if (!is_lnk("/" #name) && read_dt_fstab(#name, partname, fstype)) { \
LOGD("Early mount " #name "\n"); \
setup_block(partname, block_dev); \
xmkdir("/" #name, 0755); \
xmount(block_dev, "/" #name, fstype, MS_RDONLY, nullptr); \
mnt_##name = true; \
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}
void MagiskInit::early_mount() {
char partname[32];
char fstype[32];
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char block_dev[64];
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if (cmd.system_as_root) {
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LOGD("Early mount system_root\n");
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sprintf(partname, "system%s", cmd.slot);
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setup_block(partname, block_dev);
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xmkdir("/system_root", 0755);
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xmount(block_dev, "/system_root", "ext4", MS_RDONLY, nullptr);
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xmkdir("/system", 0755);
xmount("/system_root/system", "/system", nullptr, MS_BIND, nullptr);
// Android Q
if (is_lnk("/system_root/init"))
load_sepol = true;
// System-as-root with monolithic sepolicy
if (access("/system_root/sepolicy", F_OK) == 0)
cp_afc("/system_root/sepolicy", "/sepolicy");
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// Copy if these partitions are symlinks
link_root("/vendor");
link_root("/product");
link_root("/odm");
} else {
mount_root(system);
}
mount_root(vendor);
mount_root(product);
mount_root(odm);
}
void MagiskInit::setup_rootfs() {
bool patch_init = patch_sepolicy();
if (cmd.system_as_root) {
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// Clone rootfs
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LOGD("Clone root dir from system to rootfs\n");
int system_root = xopen("/system_root", O_RDONLY | O_CLOEXEC);
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clone_dir(system_root, root, false);
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close(system_root);
}
if (patch_init) {
constexpr char SYSTEM_INIT[] = "/system/bin/init";
// If init is symlink, copy it to rootfs so we can patch
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if (is_lnk("/init"))
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cp_afc(SYSTEM_INIT, "/init");
char *addr;
size_t size;
mmap_rw("/init", addr, size);
for (char *p = addr; p < addr + size; ++p) {
if (memcmp(p, SPLIT_PLAT_CIL, sizeof(SPLIT_PLAT_CIL)) == 0) {
// Force init to load /sepolicy
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LOGD("Remove from init: " SPLIT_PLAT_CIL "\n");
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memset(p, 'x', sizeof(SPLIT_PLAT_CIL) - 1);
p += sizeof(SPLIT_PLAT_CIL) - 1;
} else if (memcmp(p, SYSTEM_INIT, sizeof(SYSTEM_INIT)) == 0) {
// Force execute /init instead of /system/bin/init
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LOGD("Patch init: [/system/bin/init] -> [/init]\n");
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strcpy(p, "/init");
p += sizeof(SYSTEM_INIT) - 1;
}
}
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munmap(addr, size);
}
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// Handle ramdisk overlays
int fd = open("/overlay", O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
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LOGD("Merge overlay folder\n");
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mv_dir(fd, root);
close(fd);
rmdir("/overlay");
}
// Patch init.rc
FILE *rc = xfopen("/init.p.rc", "we");
file_readline("/init.rc", [&](auto line) -> bool {
// Do not start vaultkeeper
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if (str_contains(line, "start vaultkeeper")) {
LOGD("Remove vaultkeeper\n");
return true;
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}
// Do not run flash_recovery
if (str_starts(line, "service flash_recovery")) {
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LOGD("Remove flash_recovery\n");
fprintf(rc, "service flash_recovery /system/bin/xxxxx\n");
return true;
}
// Else just write the line
fprintf(rc, "%s", line.data());
return true;
});
char pfd_svc[8], ls_svc[8], bc_svc[8];
// Make sure to be unique
pfd_svc[0] = 'a';
ls_svc[0] = '0';
bc_svc[0] = 'A';
gen_rand_str(pfd_svc + 1, sizeof(pfd_svc) - 1);
gen_rand_str(ls_svc + 1, sizeof(ls_svc) - 1);
gen_rand_str(bc_svc + 1, sizeof(bc_svc) - 1);
fprintf(rc, magiskrc, pfd_svc, pfd_svc, ls_svc, bc_svc, bc_svc);
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fclose(rc);
clone_attr("/init.rc", "/init.p.rc");
rename("/init.p.rc", "/init.rc");
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// Don't let init run in init yet
lsetfilecon("/init", "u:object_r:rootfs:s0");
// Create hardlink mirror of /sbin to /root
mkdir("/root", 0750);
clone_attr("/sbin", "/root");
int rootdir = xopen("/root", O_RDONLY | O_CLOEXEC);
int sbin = xopen("/sbin", O_RDONLY | O_CLOEXEC);
link_dir(sbin, rootdir);
}
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bool MagiskInit::patch_sepolicy() {
bool patch_init = false;
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if (access(SPLIT_PLAT_CIL, R_OK) == 0) {
LOGD("sepol: split policy\n");
patch_init = true;
} else if (access("/sepolicy", R_OK) == 0) {
LOGD("sepol: monolithic policy\n");
load_policydb("/sepolicy");
} else {
LOGD("sepol: no selinux\n");
return false;
}
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// Mount selinuxfs to communicate with kernel
xmount("selinuxfs", SELINUX_MNT, "selinuxfs", 0, nullptr);
if (patch_init)
load_split_cil();
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sepol_magisk_rules();
sepol_allow(SEPOL_PROC_DOMAIN, ALL, ALL, ALL);
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dump_policydb("/sepolicy");
// Load policy to kernel so we can label rootfs
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if (load_sepol) {
LOGD("sepol: preload sepolicy\n");
dump_policydb(SELINUX_LOAD);
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}
// Remove OnePlus stupid debug sepolicy and use our own
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if (access("/sepolicy_debug", F_OK) == 0) {
unlink("/sepolicy_debug");
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link("/sepolicy", "/sepolicy_debug");
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}
// Enable selinux functions
selinux_builtin_impl();
return patch_init;
}
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#define umount_root(name) \
if (mnt_##name) \
umount("/" #name);
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void MagiskInit::cleanup() {
umount(SELINUX_MNT);
umount("/sys");
umount("/proc");
umount_root(system);
umount_root(vendor);
umount_root(product);
umount_root(odm);
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}
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static inline void patch_socket_name(const char *path) {
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uint8_t *buf;
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char name[sizeof(MAIN_SOCKET)];
size_t size;
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mmap_rw(path, buf, size);
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for (int i = 0; i < size; ++i) {
if (memcmp(buf + i, MAIN_SOCKET, sizeof(MAIN_SOCKET)) == 0) {
gen_rand_str(name, sizeof(name));
memcpy(buf + i, name, sizeof(name));
i += sizeof(name);
}
}
munmap(buf, size);
}
static const char wrapper[] =
"#!/system/bin/sh\n"
"export LD_LIBRARY_PATH=\"$LD_LIBRARY_PATH:/apex/com.android.runtime/" LIBNAME "\"\n"
"exec /sbin/magisk.bin \"$0\" \"$@\"\n";
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void MagiskInit::setup_overlay() {
char path[128];
int fd;
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// Wait for early-init start
while (access(EARLYINIT, F_OK) != 0)
usleep(10);
setcon("u:r:" SEPOL_PROC_DOMAIN ":s0");
unlink(EARLYINIT);
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#ifdef MAGISK_DEBUG
kmsg = xfopen("/dev/kmsg", "ae");
setbuf(kmsg, nullptr);
#endif
LOGD("Setting up overlay\n");
// Mount the /sbin tmpfs overlay
xmount("tmpfs", "/sbin", "tmpfs", 0, nullptr);
chmod("/sbin", 0755);
setfilecon("/sbin", "u:object_r:rootfs:s0");
// Dump binaries
mkdir(MAGISKTMP, 0755);
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fd = xopen(MAGISKTMP "/config", O_WRONLY | O_CREAT, 0000);
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write(fd, config.buf, config.sz);
close(fd);
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fd = xopen("/sbin/magiskinit", O_WRONLY | O_CREAT, 0755);
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write(fd, self.buf, self.sz);
close(fd);
if (access("/system/apex", F_OK) == 0) {
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LOGD("APEX detected, use wrapper\n");
dump_magisk("/sbin/magisk.bin", 0755);
patch_socket_name("/sbin/magisk.bin");
setfilecon("/sbin/magisk.bin", "u:object_r:" SEPOL_FILE_DOMAIN ":s0");
fd = xopen("/sbin/magisk", O_WRONLY | O_CREAT, 0755);
write(fd, wrapper, sizeof(wrapper) - 1);
close(fd);
} else {
dump_magisk("/sbin/magisk", 0755);
patch_socket_name("/sbin/magisk");
}
setfilecon("/sbin/magisk", "u:object_r:" SEPOL_FILE_DOMAIN ":s0");
setfilecon("/sbin/magiskinit", "u:object_r:" SEPOL_FILE_DOMAIN ":s0");
// Create applet symlinks
for (int i = 0; applet_names[i]; ++i) {
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sprintf(path, "/sbin/%s", applet_names[i]);
xsymlink("/sbin/magisk", path);
}
for (int i = 0; init_applet[i]; ++i) {
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sprintf(path, "/sbin/%s", init_applet[i]);
xsymlink("/sbin/magiskinit", path);
}
// Create symlinks pointing back to /root
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DIR *dir = xopendir("/root");
struct dirent *entry;
fd = xopen("/sbin", O_RDONLY);
while((entry = xreaddir(dir))) {
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if (entry->d_name == "."sv || entry->d_name == ".."sv)
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continue;
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sprintf(path, "/root/%s", entry->d_name);
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xsymlinkat(path, fd, entry->d_name);
}
closedir(dir);
close(fd);
close(xopen(EARLYINITDONE, O_RDONLY | O_CREAT, 0));
exit(0);
}
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void MagiskInit::re_exec_init() {
cleanup();
execv("/init", argv);
exit(1);
}
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void MagiskInit::start() {
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// 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);
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if (null > STDERR_FILENO)
close(null);
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setup_klog();
load_kernel_info();
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full_read("/init", &self.buf, &self.sz);
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full_read("/.backup/.magisk", &config.buf, &config.sz);
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preset();
early_mount();
setup_rootfs();
}
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void MagiskInit::test() {
cmdline_logging();
log_cb.ex = nop_ex;
chdir(dirname(argv[0]));
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chroot(".");
chdir("/");
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load_kernel_info();
preset();
early_mount();
setup_rootfs();
cleanup();
}
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static int test_main(int, char *argv[]) {
MagiskInit init(argv);
init.test();
return 0;
}
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int main(int argc, char *argv[]) {
umask(0);
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for (int i = 0; init_applet[i]; ++i) {
if (strcmp(basename(argv[0]), init_applet[i]) == 0)
return (*init_applet_main[i])(argc, argv);
}
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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;
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MagiskInit init(argv);
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// Run the main routine
init.start();
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// Close all file descriptors
for (int i = 0; i < 30; ++i)
close(i);
// Launch daemon to setup overlay
if (fork_dont_care() == 0)
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init.setup_overlay();
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init.re_exec_init();
}