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Significantly broaden sepolicy.rule compatibility

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Previously, Magisk uses persist or cache for storing modules' custom
sepolicy rules. In this commit, we significantly broaden its
compatibility and also prevent mounting errors.

The persist partition is non-standard and also critical for Snapdragon
devices, so we prefer not to use it by default.

We will go through the following logic to find the best suitable
non-volatile, writable location to store and load sepolicy.rule files:

Unencrypted data -> FBE data unencrypted dir -> cache -> metadata -> persist

This should cover almost all possible cases: very old devices have
cache partitions; newer devices will use FBE; latest devices will use
metadata FBE (which guarantees a metadata parition); and finally,
all Snapdragon devices have the persist partition (as a last resort).

Fix #3179
This commit is contained in:
topjohnwu
2020-11-02 23:20:38 -08:00
parent cf47214ee4
commit 16e4c67992
9 changed files with 237 additions and 105 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
native/jni/init/rootdir.cpp
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@ -81,33 +81,6 @@ static void load_overlay_rc(const char *overlay) {
}
}
void RootFSInit::setup_rootfs() {
if (patch_sepolicy("/sepolicy")) {
auto init = raw_data::mmap_rw("/init");
init.patch({ make_pair(SPLIT_PLAT_CIL, "xxx") });
}
// Handle overlays
if (access("/overlay.d", F_OK) == 0) {
LOGD("Merge overlay.d\n");
load_overlay_rc("/overlay.d");
mv_path("/overlay.d", "/");
}
patch_init_rc("/init.rc", "/init.p.rc", "/sbin");
rename("/init.p.rc", "/init.rc");
// Create hardlink mirror of /sbin to /root
mkdir("/root", 0750);
clone_attr("/sbin", "/root");
link_path("/sbin", "/root");
// Dump magiskinit as magisk
int fd = xopen("/sbin/magisk", O_WRONLY | O_CREAT, 0755);
write(fd, self.buf, self.sz);
close(fd);
}
bool MagiskInit::patch_sepolicy(const char *file) {
bool patch_init = false;
sepolicy *sepol = nullptr;
@ -135,12 +108,14 @@ bool MagiskInit::patch_sepolicy(const char *file) {
sepol->magisk_rules();
// Custom rules
if (auto dir = open_dir(persist_dir.data()); dir) {
for (dirent *entry; (entry = xreaddir(dir.get()));) {
auto rule = persist_dir + "/" + entry->d_name + "/sepolicy.rule";
if (access(rule.data(), R_OK) == 0) {
LOGD("Loading custom sepolicy patch: %s\n", rule.data());
sepol->load_rule_file(rule.data());
if (!custom_rules_dir.empty()) {
if (auto dir = open_dir(custom_rules_dir.data())) {
for (dirent *entry; (entry = xreaddir(dir.get()));) {
auto rule = custom_rules_dir + "/" + entry->d_name + "/sepolicy.rule";
if (access(rule.data(), R_OK) == 0) {
LOGD("Loading custom sepolicy patch: %s\n", rule.data());
sepol->load_rule_file(rule.data());
}
}
}
}
@ -229,9 +204,8 @@ void SARBase::patch_rootdir() {
}
setup_tmp(tmp_dir);
persist_dir = MIRRDIR "/persist/magisk";
chdir(tmp_dir);
mount_rules_dir(BLOCKDIR, MIRRDIR);
// Mount system_root mirror
struct stat st;
@ -317,11 +291,55 @@ void SARBase::patch_rootdir() {
chdir("/");
}
#define TMP_MNTDIR "/dev/mnt"
#define TMP_RULESDIR "/.backup/.sepolicy.rules"
void RootFSInit::setup_rootfs() {
// Handle custom sepolicy rules
xmkdir(TMP_MNTDIR, 0755);
mount_rules_dir("/dev/block", TMP_MNTDIR);
// Preserve custom rule path
if (!custom_rules_dir.empty()) {
string rules_dir = "./" + custom_rules_dir.substr(sizeof(TMP_MNTDIR));
xsymlink(rules_dir.data(), TMP_RULESDIR);
}
if (patch_sepolicy("/sepolicy")) {
auto init = raw_data::mmap_rw("/init");
init.patch({ make_pair(SPLIT_PLAT_CIL, "xxx") });
}
// Handle overlays
if (access("/overlay.d", F_OK) == 0) {
LOGD("Merge overlay.d\n");
load_overlay_rc("/overlay.d");
mv_path("/overlay.d", "/");
}
patch_init_rc("/init.rc", "/init.p.rc", "/sbin");
rename("/init.p.rc", "/init.rc");
// Create hardlink mirror of /sbin to /root
mkdir("/root", 0750);
clone_attr("/sbin", "/root");
link_path("/sbin", "/root");
// Dump magiskinit as magisk
int fd = xopen("/sbin/magisk", O_WRONLY | O_CREAT, 0755);
write(fd, self.buf, self.sz);
close(fd);
}
void MagiskProxy::start() {
// Mount rootfs as rw to do post-init rootfs patches
xmount(nullptr, "/", nullptr, MS_REMOUNT, nullptr);
// Backup stuffs before removing them
self = raw_data::read("/sbin/magisk");
config = raw_data::read("/.backup/.magisk");
xmount(nullptr, "/", nullptr, MS_REMOUNT, nullptr);
char custom_rules_dir[64];
custom_rules_dir[0] = '\0';
xreadlink(TMP_RULESDIR, custom_rules_dir, sizeof(custom_rules_dir));
unlink("/sbin/magisk");
rm_rf("/.backup");
@ -331,6 +349,10 @@ void MagiskProxy::start() {
// Create symlinks pointing back to /root
recreate_sbin("/root", false);
if (custom_rules_dir[0])
xsymlink(custom_rules_dir, "/sbin/" RULESDIR);
// Tell magiskd to remount rootfs
setenv("REMOUNT_ROOT", "1", 1);
execv("/sbin/magisk", argv);
}