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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
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105
native/jni/init/mount.cpp
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@@ -205,27 +205,89 @@ static void switch_root(const string &path) {
frm_rf(root);
}
static void mount_persist(const char *dev_base, const char *mnt_base) {
string mnt_point = mnt_base + "/persist"s;
strcpy(blk_info.partname, "persist");
void MagiskInit::mount_rules_dir(const char *dev_base, const char *mnt_base) {
char path[128];
xrealpath(dev_base, blk_info.block_dev);
char *s = blk_info.block_dev + strlen(blk_info.block_dev);
strcpy(s, "/persist");
xrealpath(mnt_base, path);
char *b = blk_info.block_dev + strlen(blk_info.block_dev);
char *p = path + strlen(path);
auto do_mount = [&](const char *type) -> bool {
xmkdir(path, 0755);
bool success = xmount(blk_info.block_dev, path, type, 0, nullptr) == 0;
if (success)
mount_list.emplace_back(path);
return success;
};
// First try userdata
strcpy(blk_info.partname, "userdata");
strcpy(b, "/data");
strcpy(p, "/data");
if (setup_block(false) < 0) {
// Fallback to cache
strcpy(blk_info.partname, "cache");
strcpy(s, "/cache");
if (setup_block(false) < 0) {
// Try NVIDIA's BS
strcpy(blk_info.partname, "CAC");
if (setup_block(false) < 0)
return;
}
xsymlink("./cache", mnt_point.data());
mnt_point = mnt_base + "/cache"s;
// Try NVIDIA naming scheme
strcpy(blk_info.partname, "UDA");
if (setup_block(false) < 0)
goto cache;
}
xmkdir(mnt_point.data(), 0755);
xmount(blk_info.block_dev, mnt_point.data(), "ext4", 0, nullptr);
// Try to mount with either ext4 or f2fs
// Failure means either FDE or metadata encryption
if (!do_mount("ext4") && !do_mount("f2fs"))
goto cache;
strcpy(p, "/data/unencrypted");
if (access(path, F_OK) == 0) {
// FBE, need to use an unencrypted path
custom_rules_dir = path + "/magisk"s;
} else {
// Skip if /data/adb does not exist
strcpy(p, "/data/adb");
if (access(path, F_OK) != 0)
return;
// Unencrypted, directly use module paths
custom_rules_dir = string(mnt_base) + MODULEROOT;
}
goto success;
cache:
// Fallback to cache
strcpy(blk_info.partname, "cache");
strcpy(b, "/cache");
strcpy(p, "/cache");
if (setup_block(false) < 0) {
// Try NVIDIA naming scheme
strcpy(blk_info.partname, "CAC");
if (setup_block(false) < 0)
goto metadata;
}
if (!do_mount("ext4"))
goto metadata;
custom_rules_dir = path + "/magisk"s;
goto success;
metadata:
// Fallback to metadata
strcpy(blk_info.partname, "metadata");
strcpy(b, "/metadata");
strcpy(p, "/metadata");
if (setup_block(false) < 0 || !do_mount("ext4"))
goto persist;
custom_rules_dir = path + "/magisk"s;
goto success;
persist:
// Fallback to persist
strcpy(blk_info.partname, "persist");
strcpy(b, "/persist");
strcpy(p, "/persist");
if (setup_block(false) < 0 || !do_mount("ext4"))
return;
custom_rules_dir = path + "/magisk"s;
success:
// Create symlinks so we don't need to go through this logic again
strcpy(p, "/sepolicy.rules");
xsymlink(custom_rules_dir.data(), path);
}
void RootFSInit::early_mount() {
@@ -235,11 +297,6 @@ void RootFSInit::early_mount() {
rename("/.backup/init", "/init");
mount_with_dt();
xmkdir("/dev/mnt", 0755);
mount_persist("/dev/block", "/dev/mnt");
mount_list.emplace_back("/dev/mnt/persist");
persist_dir = "/dev/mnt/persist/magisk";
}
void SARBase::backup_files() {
@@ -337,8 +394,6 @@ void MagiskInit::setup_tmp(const char *path) {
xmkdir(MIRRDIR, 0);
xmkdir(BLOCKDIR, 0);
mount_persist(BLOCKDIR, MIRRDIR);
int fd = xopen(INTLROOT "/config", O_WRONLY | O_CREAT, 0);
xwrite(fd, config.buf, config.sz);
close(fd);