Magisk/native/jni/init/rootfs.cpp

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#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <magisk.h>
#include <utils.h>
#include "init.h"
#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);
}
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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void BaseInit::setup_rootfs() {
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bool patch_init = patch_sepolicy();
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if (cmd->system_as_root) {
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// 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);
}
if (patch_init) {
constexpr char SYSTEM_INIT[] = "/system/bin/init";
// If init is symlink, copy it to rootfs so we can patch
if (is_lnk("/init"))
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
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, SYSTEM_INIT, sizeof(SYSTEM_INIT)) == 0) {
// Force execute /init instead of /system/bin/init
LOGD("Patch init: [/system/bin/init] -> [/init]\n");
strcpy(p, "/init");
p += sizeof(SYSTEM_INIT) - 1;
}
}
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");
file_readline("/init.rc", [&](auto 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);
fclose(rc);
clone_attr("/init.rc", "/init.p.rc");
rename("/init.p.rc", "/init.rc");
// 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);
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);
}
xsymlink("/sbin/magiskinit", "/sbin/magiskpolicy");
xsymlink("/sbin/magiskinit", "/sbin/supolicy");
close(rootdir);
close(sbin);
}
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bool BaseInit::patch_sepolicy() {
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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);
dump_policydb("/sepolicy");
// Load policy to kernel so we can label rootfs
if (load_sepol) {
LOGD("sepol: preload sepolicy\n");
dump_policydb(SELINUX_LOAD);
}
// Remove OnePlus stupid debug sepolicy and use our own
if (access("/sepolicy_debug", F_OK) == 0) {
unlink("/sepolicy_debug");
link("/sepolicy", "/sepolicy_debug");
}
// Enable selinux functions
selinux_builtin_impl();
return patch_init;
}