Magisk/native/jni/init/rootdir.cpp

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#include <sys/types.h>
#include <sys/stat.h>
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#include <sys/mount.h>
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#include <fcntl.h>
#include <magisk.h>
#include <utils.h>
#include "init.h"
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#include "flags.h"
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#include "magiskrc.h"
#ifdef USE_64BIT
#define LIBNAME "lib64"
#else
#define LIBNAME "lib"
#endif
using namespace std;
static void patch_socket_name(const char *path) {
uint8_t *buf;
char name[sizeof(MAIN_SOCKET)];
size_t size;
mmap_rw(path, buf, size);
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);
}
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static void patch_init_rc(FILE *rc) {
file_readline("/init.rc", [&](string_view line) -> bool {
// Do not start vaultkeeper
if (str_contains(line, "start vaultkeeper")) {
LOGD("Remove vaultkeeper\n");
return true;
}
// Do not run flash_recovery
if (str_starts(line, "service flash_recovery")) {
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);
LOGD("Inject magisk services: [%s] [%s] [%s]\n", pfd_svc, ls_svc, bc_svc);
fprintf(rc, magiskrc, pfd_svc, pfd_svc, ls_svc, bc_svc, bc_svc);
}
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void RootFSInit::setup_rootfs() {
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if (patch_sepolicy()) {
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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
LOGD("Remove from init: " SPLIT_PLAT_CIL "\n");
memset(p, 'x', sizeof(SPLIT_PLAT_CIL) - 1);
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break;
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}
}
munmap(addr, size);
}
// Handle ramdisk overlays
int fd = open("/overlay", O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
LOGD("Merge overlay folder\n");
mv_dir(fd, root);
close(fd);
rmdir("/overlay");
}
// Patch init.rc
FILE *rc = xfopen("/init.p.rc", "we");
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patch_init_rc(rc);
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fclose(rc);
clone_attr("/init.rc", "/init.p.rc");
rename("/init.p.rc", "/init.rc");
// 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);
close(sbin);
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// Dump magiskinit as magisk
fd = xopen("/sbin/magisk", O_WRONLY | O_CREAT, 0755);
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write(fd, self.buf, self.sz);
close(fd);
}
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void SARCompatInit::setup_rootfs() {
// Clone rootfs
LOGD("Clone root dir from system to rootfs\n");
int system_root = xopen("/system_root", O_RDONLY | O_CLOEXEC);
clone_dir(system_root, root, false);
close(system_root);
RootFSInit::setup_rootfs();
}
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bool MagiskInit::patch_sepolicy(const char *file) {
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bool patch_init = false;
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;
}
// Mount selinuxfs to communicate with kernel
xmount("selinuxfs", SELINUX_MNT, "selinuxfs", 0, nullptr);
if (patch_init)
load_split_cil();
sepol_magisk_rules();
sepol_allow(SEPOL_PROC_DOMAIN, ALL, ALL, ALL);
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dump_policydb(file);
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// Remove OnePlus stupid debug sepolicy and use our own
if (access("/sepolicy_debug", F_OK) == 0) {
unlink("/sepolicy_debug");
link("/sepolicy", "/sepolicy_debug");
}
return patch_init;
}
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constexpr 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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static void sbin_overlay(const raw_data &self, const raw_data &config) {
LOGD("Mount /sbin tmpfs overlay\n");
xmount("tmpfs", "/sbin", "tmpfs", 0, "mode=755");
// Dump binaries
xmkdir(MAGISKTMP, 0755);
int fd = xopen(MAGISKTMP "/config", O_WRONLY | O_CREAT, 0000);
xwrite(fd, config.buf, config.sz);
close(fd);
fd = xopen("/sbin/magiskinit", O_WRONLY | O_CREAT, 0755);
xwrite(fd, self.buf, self.sz);
close(fd);
if (access("/system/apex", F_OK) == 0) {
LOGD("APEX detected, use wrapper\n");
dump_magisk("/sbin/magisk.bin", 0755);
patch_socket_name("/sbin/magisk.bin");
fd = xopen("/sbin/magisk", O_WRONLY | O_CREAT, 0755);
xwrite(fd, wrapper, sizeof(wrapper) - 1);
close(fd);
} else {
dump_magisk("/sbin/magisk", 0755);
patch_socket_name("/sbin/magisk");
}
// Create applet symlinks
char path[64];
for (int i = 0; applet_names[i]; ++i) {
sprintf(path, "/sbin/%s", applet_names[i]);
xsymlink("/sbin/magisk", path);
}
xsymlink("/sbin/magiskinit", "/sbin/magiskpolicy");
xsymlink("/sbin/magiskinit", "/sbin/supolicy");
}
#define ROOTMIR MIRRDIR "/system_root"
#define ROOTBLK BLOCKDIR "/system_root"
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#define MONOPOLICY "/sepolicy"
#define PATCHPOLICY "/sbin/.se"
#define LIBSELINUX "/system/" LIBNAME "/libselinux.so"
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void SARInit::patch_rootdir() {
sbin_overlay(self, config);
// Mount system_root mirror
xmkdir(MIRRDIR, 0777);
xmkdir(ROOTMIR, 0777);
xmkdir(BLOCKDIR, 0777);
mknod(ROOTBLK, S_IFBLK | 0600, system_dev);
if (xmount(ROOTBLK, ROOTMIR, "ext4", MS_RDONLY, nullptr))
xmount(ROOTBLK, ROOTMIR, "erofs", MS_RDONLY, nullptr);
// Recreate original sbin structure
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int src = xopen(ROOTMIR "/sbin", O_RDONLY | O_CLOEXEC);
int dest = xopen("/sbin", O_RDONLY | O_CLOEXEC);
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DIR *fp = fdopendir(src);
struct dirent *entry;
struct stat st;
char buf[256];
while ((entry = xreaddir(fp))) {
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
fstatat(src, entry->d_name, &st, AT_SYMLINK_NOFOLLOW);
if (S_ISLNK(st.st_mode)) {
xreadlinkat(src, entry->d_name, buf, sizeof(buf));
xsymlinkat(buf, dest, entry->d_name);
} else {
char tpath[256];
sprintf(buf, "/sbin/%s", entry->d_name);
sprintf(tpath, ROOTMIR "/sbin/%s", entry->d_name);
// Create dummy
if (S_ISDIR(st.st_mode))
xmkdir(tpath, st.st_mode & 0777);
else
close(xopen(tpath, O_CREAT | O_WRONLY | O_CLOEXEC, st.st_mode & 0777));
xmount(tpath, buf, nullptr, MS_BIND, nullptr);
}
}
close(src);
close(dest);
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/* ******************
* Customize rootdir
* ******************/
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char *addr;
size_t size;
file_attr attr;
bool redirect = false;
xmkdir(ROOTOVERLAY, 0);
src = xopen("/init", O_RDONLY | O_CLOEXEC);
fgetattr(src, &attr);
fd_full_read(src, (void**)&addr, &size);
close(src);
for (char *p = addr; p < addr + size; ++p) {
if (memcmp(p, SPLIT_PLAT_CIL, sizeof(SPLIT_PLAT_CIL)) == 0) {
// Force init to load monolithic policy
LOGD("Remove from init: " SPLIT_PLAT_CIL "\n");
memset(p, 'x', sizeof(SPLIT_PLAT_CIL) - 1);
p += sizeof(SPLIT_PLAT_CIL) - 1;
} else if (memcmp(p, MONOPOLICY, sizeof(MONOPOLICY)) == 0) {
// Redirect /sepolicy to tmpfs
LOGD("Patch init [" MONOPOLICY "] -> [" PATCHPOLICY "]\n");
memcpy(p, PATCHPOLICY, sizeof(PATCHPOLICY));
redirect = true;
p += sizeof(MONOPOLICY) - 1;
}
}
dest = xopen(ROOTOVERLAY "/init", O_CREAT | O_WRONLY | O_CLOEXEC);
xwrite(dest, addr, size);
free(addr);
fsetattr(dest, &attr);
close(dest);
xmount(ROOTOVERLAY "/init", "/init", nullptr, MS_BIND, nullptr);
if (!redirect) {
// init is dynamically linked, need to patch libselinux
full_read(LIBSELINUX, (void**)&addr, &size);
getattr(LIBSELINUX, &attr);
for (char *p = addr; p < addr + size; ++p) {
if (memcmp(p, MONOPOLICY, sizeof(MONOPOLICY)) == 0) {
// Redirect /sepolicy to tmpfs
LOGD("Patch libselinux.so [" MONOPOLICY "] -> [" PATCHPOLICY "]\n");
memcpy(p, PATCHPOLICY, sizeof(PATCHPOLICY));
break;
}
}
dest = xopen(ROOTOVERLAY "/libselinux.so", O_CREAT | O_WRONLY | O_CLOEXEC);
xwrite(dest, addr, size);
free(addr);
fsetattr(dest, &attr);
close(dest);
xmount(ROOTOVERLAY "/libselinux.so", LIBSELINUX, nullptr, MS_BIND, nullptr);
}
patch_sepolicy(PATCHPOLICY);
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FILE *rc = xfopen(ROOTOVERLAY "/init.rc", "we");
patch_init_rc(rc);
fclose(rc);
clone_attr("/init.rc", ROOTOVERLAY "/init.rc");
xmount(ROOTOVERLAY "/init.rc", "/init.rc", nullptr, MS_BIND, nullptr);
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}
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#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() {
int fd = xopen("/proc/kmsg", O_WRONLY | O_CLOEXEC);
kmsg = fdopen(fd, "w");
setbuf(kmsg, nullptr);
log_cb.d = log_cb.i = log_cb.w = log_cb.e = vprintk;
log_cb.ex = nop_ex;
}
#else
#define setup_klog(...)
#endif
int magisk_proxy_main(int argc, char *argv[]) {
setup_klog();
raw_data config;
raw_data self;
full_read("/sbin/magisk", &self.buf, &self.sz);
full_read("/.backup/.magisk", &config.buf, &config.sz);
xmount(nullptr, "/", nullptr, MS_REMOUNT, nullptr);
unlink("/sbin/magisk");
rm_rf("/.backup");
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sbin_overlay(self, config);
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// Create symlinks pointing back to /root
{
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char path[256];
int sbin = xopen("/sbin", O_RDONLY | O_CLOEXEC);
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unique_ptr<DIR, decltype(&closedir)> dir(xopendir("/root"), &closedir);
struct dirent *entry;
while((entry = xreaddir(dir.get()))) {
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
sprintf(path, "/root/%s", entry->d_name);
xsymlinkat(path, sbin, entry->d_name);
}
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close(sbin);
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}
setenv("REMOUNT_ROOT", "1", 1);
execv("/sbin/magisk", argv);
return 1;
}