Magisk/native/jni/magiskpolicy/policydb.cpp

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include <cil/cil.h>

#include <utils.h>
#include <logging.h>

#include "magiskpolicy.h"
#include "sepolicy.h"

policydb_t *policydb = nullptr;

int load_policydb(const char *file) {
	if (policydb)
		destroy_policydb();

	struct policy_file pf;
	policy_file_init(&pf);
	pf.fp = xfopen(file, "re");
	pf.type = PF_USE_STDIO;

	policydb = new policydb_t();
	if (policydb_init(policydb) || policydb_read(policydb, &pf, 0))
		return 1;

	fclose(pf.fp);

	return 0;
}

#define SHALEN 64
static bool cmp_sha256(const char *a, const char *b) {
	char id_a[SHALEN] = {0};
	char id_b[SHALEN] = {0};
	if (int fd = xopen(a, O_RDONLY | O_CLOEXEC); fd >= 0) {
		xread(fd, id_a, SHALEN);
		close(fd);
	} else {
		return false;
	}

	if (int fd = xopen(b, O_RDONLY | O_CLOEXEC); fd >= 0) {
		xread(fd, id_b, SHALEN);
		close(fd);
	} else {
		return false;
	}
	LOGD("%s=[%.*s]\n%s=[%.*s]\n", a, SHALEN, id_a, b, SHALEN, id_b);
	return memcmp(id_a, id_b, SHALEN) == 0;
}

static bool check_precompiled(const char *precompiled) {
	bool ok = false;
	const char *actual_sha;
	char compiled_sha[128];

	actual_sha = PLAT_POLICY_DIR "plat_and_mapping_sepolicy.cil.sha256";
	if (access(actual_sha, R_OK) == 0) {
		ok = true;
		sprintf(compiled_sha, "%s.plat_and_mapping.sha256", precompiled);
		if (!cmp_sha256(actual_sha, compiled_sha))
			return false;
	}

	actual_sha = PLAT_POLICY_DIR "plat_sepolicy_and_mapping.sha256";
	if (access(actual_sha, R_OK) == 0) {
		ok = true;
		sprintf(compiled_sha, "%s.plat_sepolicy_and_mapping.sha256", precompiled);
		if (!cmp_sha256(actual_sha, compiled_sha))
			return false;
	}

	actual_sha = PROD_POLICY_DIR "product_sepolicy_and_mapping.sha256";
	if (access(actual_sha, R_OK) == 0) {
		ok = true;
		sprintf(compiled_sha, "%s.product_sepolicy_and_mapping.sha256", precompiled);
		if (!cmp_sha256(actual_sha, compiled_sha) != 0)
			return false;
	}

	return ok;
}

int load_split_cil() {
	const char *odm_pre = ODM_POLICY_DIR "precompiled_sepolicy";
	const char *vend_pre = VEND_POLICY_DIR "precompiled_sepolicy";
	if (access(odm_pre, R_OK) == 0 && check_precompiled(odm_pre))
		return load_policydb(odm_pre);
	else if (access(vend_pre, R_OK) == 0 && check_precompiled(vend_pre))
		return load_policydb(vend_pre);
	else
		return compile_split_cil();
}

static void load_cil(struct cil_db *db, const char *file) {
	char *addr;
	size_t size;
	mmap_ro(file, addr, size);
	cil_add_file(db, (char *) file, addr, size);
	LOGD("cil_add[%s]\n", file);
	munmap(addr, size);
}

int compile_split_cil() {
	char path[128], plat_ver[10];
	struct cil_db *db = nullptr;
	sepol_policydb_t *pdb = nullptr;
	FILE *f;
	int policy_ver;
	const char *cil_file;

	cil_db_init(&db);
	cil_set_mls(db, 1);
	cil_set_multiple_decls(db, 1);
	cil_set_disable_neverallow(db, 1);
	cil_set_target_platform(db, SEPOL_TARGET_SELINUX);
	cil_set_attrs_expand_generated(db, 0);

	f = xfopen(SELINUX_VERSION, "re");
	fscanf(f, "%d", &policy_ver);
	fclose(f);
	cil_set_policy_version(db, policy_ver);

	// Get mapping version
	f = xfopen(VEND_POLICY_DIR "plat_sepolicy_vers.txt", "re");
	fscanf(f, "%s", plat_ver);
	fclose(f);

	// plat
	load_cil(db, SPLIT_PLAT_CIL);

	sprintf(path, PLAT_POLICY_DIR "mapping/%s.cil", plat_ver);
	load_cil(db, path);

	// product
	sprintf(path, PROD_POLICY_DIR "mapping/%s.cil", plat_ver);
	if (access(path, R_OK) == 0)
		load_cil(db, path);

	cil_file = PROD_POLICY_DIR "product_sepolicy.cil";
	if (access(cil_file, R_OK) == 0)
		load_cil(db, cil_file);

	// vendor
	cil_file = VEND_POLICY_DIR "nonplat_sepolicy.cil";
	if (access(cil_file, R_OK) == 0)
		load_cil(db, cil_file);

	cil_file = VEND_POLICY_DIR "plat_pub_versioned.cil";
	if (access(cil_file, R_OK) == 0)
		load_cil(db, cil_file);

	cil_file = VEND_POLICY_DIR "vendor_sepolicy.cil";
	if (access(cil_file, R_OK) == 0)
		load_cil(db, cil_file);

	// odm
	cil_file = ODM_POLICY_DIR "odm_sepolicy.cil";
	if (access(cil_file, R_OK) == 0)
		load_cil(db, cil_file);

	if (cil_compile(db))
		return 1;
	if (cil_build_policydb(db, &pdb))
		return 1;

	cil_db_destroy(&db);
	policydb = &pdb->p;
	return 0;
}

int dump_policydb(const char *file) {
	int fd, ret;
	void *data = nullptr;
	size_t len;
	policydb_to_image(nullptr, policydb, &data, &len);
	if (data == nullptr) {
		LOGE("Fail to dump policy image!\n");
		return 1;
	}

	fd = xopen(file, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
	if (fd < 0)
		return 1;
	ret = xwrite(fd, data, len);
	close(fd);
	if (ret < 0)
		return 1;
	return 0;
}

void destroy_policydb() {
	if (policydb) {
		policydb_destroy(policydb);
		delete policydb;
		policydb = nullptr;
	}
}