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Magisk
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Add sbin overlay to system-as-root

This commit is contained in:
topjohnwu 2019-06-24 01:21:33 -07:00
parent 9ec8bc2166
commit a1a1ac0bbb
6 changed files with 100 additions and 40 deletions
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10
native/jni/init/early_mount.cpp
View File

@ -53,7 +53,7 @@ static void collect_devices() {
closedir(dir);
}
static void setup_block(const char *partname, char *block_dev = nullptr) {
static dev_t setup_block(const char *partname, char *block_dev = nullptr) {
if (dev_list.empty())
collect_devices();
for (;;) {
@ -65,9 +65,9 @@ static void setup_block(const char *partname, char *block_dev = nullptr) {
xmkdir("/dev/block", 0755);
}
LOGD("Found %s: [%s] (%d, %d)\n", dev.partname, dev.devname, dev.major, dev.minor);
mknod(block_dev ? block_dev : "/dev/root", S_IFBLK | 0600,
makedev(dev.major, dev.minor));
return;
dev_t rdev = makedev(dev.major, dev.minor);
mknod(block_dev ? block_dev : "/dev/root", S_IFBLK | 0600, rdev);
return rdev;
}
}
// Wait 10ms and try again
@ -174,7 +174,7 @@ void SARInit::early_mount() {
LOGD("Early mount system_root\n");
sprintf(partname, "system%s", cmd->slot);
setup_block(partname);
system_dev = setup_block(partname);
xmkdir("/system_root", 0755);
if (xmount("/dev/root", "/system_root", "ext4", MS_RDONLY, nullptr))
xmount("/dev/root", "/system_root", "erofs", MS_RDONLY, nullptr);

4
native/jni/init/init.cpp
View File

@ -134,6 +134,7 @@ void LegacyInit::preset() {
void SARInit::preset() {
full_read("/init", &self.buf, &self.sz);
full_read("/.backup/.magisk", &config.buf, &config.sz);
LOGD("Cleaning rootfs\n");
root = open("/", O_RDONLY | O_CLOEXEC);
@ -145,7 +146,7 @@ void SARCompatInit::preset() {
LOGD("Cleaning rootfs\n");
root = open("/", O_RDONLY | O_CLOEXEC);
frm_rf(root, { "overlay", "proc", "sys" });
frm_rf(root, { ".backup", "overlay", "proc", "sys" });
}
void RootFSInit::start() {
@ -158,6 +159,7 @@ void RootFSInit::start() {
void SARInit::start() {
preset();
early_mount();
patch_rootdir();
re_exec_init();
}

4
native/jni/init/init.h
View File

@ -44,8 +44,12 @@ public:
class SARInit : public MagiskInit {
protected:
raw_data config{};
dev_t system_dev;
void preset() override;
void early_mount() override;
void patch_rootdir();
public:
SARInit(char *argv[], cmdline *cmd) : MagiskInit(argv, cmd) {};
void start() override;

115
native/jni/init/rootdir.cpp
View File

@ -175,6 +175,84 @@ bool MagiskInit::patch_sepolicy() {
return patch_init;
}
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"
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
int src = xopen(ROOTMIR, O_RDONLY | O_CLOEXEC);
int dest = xopen(ROOTMIR, O_RDONLY | O_CLOEXEC);
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);
}
#ifdef MAGISK_DEBUG
static FILE *kmsg;
static int vprintk(const char *fmt, va_list ap) {
@ -206,14 +284,12 @@ int magisk_proxy_main(int argc, char *argv[]) {
unlink("/sbin/magisk");
rm_rf("/.backup");
LOGD("Mount /sbin tmpfs overlay\n");
xmount("tmpfs", "/sbin", "tmpfs", 0, "mode=755");
int sbin = xopen("/sbin", O_RDONLY | O_CLOEXEC);
char path[64];
sbin_overlay(self, config);
// Create symlinks pointing back to /root
{
char path[256];
int sbin = xopen("/sbin", O_RDONLY | O_CLOEXEC);
unique_ptr<DIR, decltype(&closedir)> dir(xopendir("/root"), &closedir);
struct dirent *entry;
while((entry = xreaddir(dir.get()))) {
@ -222,36 +298,9 @@ int magisk_proxy_main(int argc, char *argv[]) {
sprintf(path, "/root/%s", entry->d_name);
xsymlinkat(path, sbin, entry->d_name);
}
close(sbin);
}
// Dump binaries
mkdir(MAGISKTMP, 0755);
int 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);
}
xsymlink("/sbin/magiskinit", "/sbin/magiskpolicy");
xsymlink("/sbin/magiskinit", "/sbin/supolicy");
setenv("REMOUNT_ROOT", "1", 1);
execv("/sbin/magisk", argv);

5
native/jni/utils/include/missing.h
View File

@ -9,6 +9,7 @@
#define setns __setns
#define unshare __unshare
#define accept4 __accept4
#define dup3 __dup3
#define readlinkat __readlinkat
#define symlinkat __symlinkat
#define linkat __linkat
@ -39,6 +40,10 @@ static inline int __accept4(int sockfd, struct sockaddr *addr, socklen_t *addrle
return syscall(__NR_accept4, sockfd, addr, addrlen, flags);
}
static inline int __dup3(int oldfd, int newfd, int flags) {
return syscall(__NR_dup3, oldfd, newfd, flags);
}
static inline ssize_t __readlinkat(int dirfd, const char *pathname, char *buf, size_t bufsiz) {
return syscall(__NR_readlinkat, dirfd, pathname, buf, bufsiz);
}

2
native/jni/utils/xwrap.cpp
View File

@ -278,7 +278,7 @@ int xdup2(int oldfd, int newfd) {
}
int xdup3(int oldfd, int newfd, int flags) {
int ret = (int) syscall(__NR_dup3, oldfd, newfd, flags);
int ret = dup3(oldfd, newfd, flags);
if (ret == -1) {
PLOGE("dup3");
}