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Remove requirement to use early-init daemon

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We used to construct /sbin tmpfs overlay in early-init stage after
SELinux is properly initialized. However the way it is implemented
(forking daemon from magiskinit with complicated file waiting triggers)
is extremely complicated and error prone.

This commit moves the construction of the sbin overlay to pre-init
stage. The catch is that since SELinux is not present at that point,
proper selabel has to be reconstructed afterwards. Some additional
SEPolicy rules are added to make sure init can access magisk binaries,
and the secontext relabeling task is assigned to the main Magisk daemon.
This commit is contained in:
topjohnwu 2019-04-24 00:13:48 -04:00
parent 515f346dcc
commit 003e44fb84
8 changed files with 110 additions and 117 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
native/jni/core/daemon.cpp
View File

@ -101,6 +101,8 @@ static void main_daemon() {
android_logging();
setsid();
setcon("u:r:" SEPOL_PROC_DOMAIN ":s0");
restore_rootcon();
int fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
xdup2(fd, STDOUT_FILENO);
xdup2(fd, STDERR_FILENO);

182
native/jni/core/init.cpp
View File

@ -46,7 +46,8 @@ static int vprintk(const char *fmt, va_list ap) {
static void setup_klog() {
mknod("/kmsg", S_IFCHR | 0666, makedev(1, 11));
kmsg = xfopen("/kmsg", "ae");
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;
@ -156,11 +157,10 @@ private:
bool read_dt_fstab(const char *name, char *partname, char *partfs);
bool patch_sepolicy();
void cleanup();
void re_exec_init();
public:
explicit MagiskInit(char *argv[]) : argv(argv) {}
void setup_overlay();
void re_exec_init();
void start();
void test();
};
@ -460,6 +460,27 @@ void MagiskInit::early_mount() {
mount_root(odm);
}
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);
}
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"
;
void MagiskInit::setup_rootfs() {
bool patch_init = patch_sepolicy();
@ -531,6 +552,7 @@ void MagiskInit::setup_rootfs() {
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);
fclose(rc);
clone_attr("/init.rc", "/init.p.rc");
@ -545,6 +567,56 @@ void MagiskInit::setup_rootfs() {
int rootdir = xopen("/root", O_RDONLY | O_CLOEXEC);
int sbin = xopen("/sbin", O_RDONLY | O_CLOEXEC);
link_dir(sbin, rootdir);
close(sbin);
LOGD("Mount /sbin tmpfs overlay\n");
xmount("tmpfs", "/sbin", "tmpfs", 0, "mode=755");
sbin = xopen("/sbin", O_RDONLY | O_CLOEXEC);
char path[64];
// Create symlinks pointing back to /root
DIR *dir = xfdopendir(rootdir);
struct dirent *entry;
while((entry = xreaddir(dir))) {
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
sprintf(path, "/root/%s", entry->d_name);
xsymlinkat(path, sbin, entry->d_name);
}
// Dump binaries
mkdir(MAGISKTMP, 0755);
fd = xopen(MAGISKTMP "/config", O_WRONLY | O_CREAT, 0000);
write(fd, config.buf, config.sz);
close(fd);
fd = xopen("/sbin/magiskinit", O_WRONLY | O_CREAT, 0755);
write(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);
write(fd, wrapper, sizeof(wrapper) - 1);
close(fd);
} else {
dump_magisk("/sbin/magisk", 0755);
patch_socket_name("/sbin/magisk");
}
// Create applet symlinks
for (int i = 0; applet_names[i]; ++i) {
sprintf(path, "/sbin/%s", applet_names[i]);
xsymlink("/sbin/magisk", path);
}
for (int i = 0; init_applet[i]; ++i) {
sprintf(path, "/sbin/%s", init_applet[i]);
xsymlink("/sbin/magiskinit", path);
}
close(rootdir);
close(sbin);
}
bool MagiskInit::patch_sepolicy() {
@ -603,99 +675,8 @@ void MagiskInit::cleanup() {
umount_root(odm);
}
static inline 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);
}
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";
void MagiskInit::setup_overlay() {
char path[128];
int fd;
// Wait for early-init start
while (access(EARLYINIT, F_OK) != 0)
usleep(10);
setcon("u:r:" SEPOL_PROC_DOMAIN ":s0");
unlink(EARLYINIT);
#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);
fd = xopen(MAGISKTMP "/config", O_WRONLY | O_CREAT, 0000);
write(fd, config.buf, config.sz);
close(fd);
fd = xopen("/sbin/magiskinit", O_WRONLY | O_CREAT, 0755);
write(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");
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) {
sprintf(path, "/sbin/%s", applet_names[i]);
xsymlink("/sbin/magisk", path);
}
for (int i = 0; init_applet[i]; ++i) {
sprintf(path, "/sbin/%s", init_applet[i]);
xsymlink("/sbin/magiskinit", path);
}
// Create symlinks pointing back to /root
DIR *dir = xopendir("/root");
struct dirent *entry;
fd = xopen("/sbin", O_RDONLY);
while((entry = xreaddir(dir))) {
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
sprintf(path, "/root/%s", entry->d_name);
xsymlinkat(path, fd, entry->d_name);
}
closedir(dir);
close(fd);
close(xopen(EARLYINITDONE, O_RDONLY | O_CREAT, 0));
exit(0);
}
void MagiskInit::re_exec_init() {
LOGD("Re-exec /init\n");
cleanup();
execv("/init", argv);
exit(1);
@ -722,6 +703,7 @@ void MagiskInit::start() {
preset();
early_mount();
setup_rootfs();
re_exec_init();
}
void MagiskInit::test() {
@ -767,14 +749,4 @@ int main(int argc, char *argv[]) {
// Run the main routine
init.start();
// Close all file descriptors
for (int i = 0; i < 30; ++i)
close(i);
// Launch daemon to setup overlay
if (fork_dont_care() == 0)
init.setup_overlay();
init.re_exec_init();
}

1
native/jni/core/magisk.cpp
View File

@ -71,6 +71,7 @@ int magisk_main(int argc, char *argv[]) {
unlock_blocks();
return 0;
} else if (strcmp(argv[1], "--restorecon") == 0) {
restore_rootcon();
restorecon();
return 0;
} else if (strcmp(argv[1], "--clone-attr") == 0) {

8
native/jni/core/magiskrc.h
View File

@ -1,15 +1,9 @@
#include <magisk.h>
#include <magiskpolicy.h>
static const char magiskrc[] =
constexpr const char magiskrc[] =
"\n\n"
"on early-init\n"
" write " EARLYINIT " 1\n"
" wait " EARLYINITDONE "\n"
" rm " EARLYINITDONE "\n"
"\n"
"on post-fs-data\n"
" start logd\n"
" load_persist_props\n"

2
native/jni/include/magisk.h
View File

@ -6,8 +6,6 @@
#define JAVA_PACKAGE_NAME "com.topjohnwu.magisk"
#define LOGFILE "/cache/magisk.log"
#define UNBLOCKFILE "/dev/.magisk_unblock"
#define EARLYINIT "/dev/.magisk_early_init"
#define EARLYINITDONE "/dev/.magisk_early_init_done"
#define DISABLEFILE "/cache/.disable_magisk"
#define MAGISKTMP "/sbin/.magisk"
#define MIRRDIR MAGISKTMP "/mirror"

2
native/jni/magiskpolicy/rules.cpp
View File

@ -54,6 +54,8 @@ void sepol_magisk_rules() {
// Let init run stuffs
sepol_allow("kernel", SEPOL_PROC_DOMAIN, "fd", "use");
sepol_allow("init", SEPOL_PROC_DOMAIN, "process", ALL);
sepol_allow("init", "tmpfs", "file", "getattr");
sepol_allow("init", "tmpfs", "file", "execute");
// Shell, properties, logs
if (sepol_exists("default_prop"))

1
native/jni/utils/include/selinux.h
View File

@ -36,6 +36,7 @@ void setfilecon_at(int dirfd, const char *name, const char *con);
void selinux_builtin_impl();
void dload_selinux();
void restorecon();
void restore_rootcon();
#ifdef __cplusplus
}

29
native/jni/utils/selinux.cpp
View File

@ -1,17 +1,21 @@
#include <sys/xattr.h>
#include <dlfcn.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <syscall.h>
#include <sys/xattr.h>
#include <string_view>
#include <magisk.h>
#include <utils.h>
#include <selinux.h>
using namespace std::literals;
#define UNLABEL_CON "u:object_r:unlabeled:s0"
#define SYSTEM_CON "u:object_r:system_file:s0"
#define ADB_CON "u:object_r:adb_data_file:s0"
#define ROOT_CON "u:object_r:rootfs:s0"
#define MAGISK_CON "u:object_r:" SEPOL_FILE_DOMAIN ":s0"
// Stub implementation
@ -164,7 +168,7 @@ static void restore_syscon(int dirfd) {
dir = xfdopendir(dirfd);
while ((entry = xreaddir(dir))) {
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
int fd = openat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
if (entry->d_type == DT_DIR) {
@ -193,7 +197,7 @@ static void restore_magiskcon(int dirfd) {
dir = xfdopendir(dirfd);
while ((entry = xreaddir(dir))) {
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
if (entry->d_type == DT_DIR) {
@ -220,3 +224,22 @@ void restorecon() {
restore_magiskcon(fd);
close(fd);
}
void restore_rootcon() {
setfilecon("/sbin", ROOT_CON);
struct dirent *entry;
DIR *dir = xopendir("/sbin");
int dfd = dirfd(dir);
while ((entry = xreaddir(dir))) {
if (entry->d_name == "."sv || entry->d_name == ".."sv)
continue;
setfilecon_at(dfd, entry->d_name, ROOT_CON);
}
setfilecon("/sbin/magisk.bin", MAGISK_CON);
setfilecon("/sbin/magisk", MAGISK_CON);
setfilecon("/sbin/magiskinit", MAGISK_CON);
closedir(dir);
}