Magisk/native/jni/utils/selinux.cpp
2019-02-24 17:45:08 -05:00

171 lines
4.2 KiB
C++

#include <dlfcn.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <syscall.h>
#include <sys/xattr.h>
#include <magisk.h>
#include <utils.h>
#include <selinux.h>
#define UNLABEL_CON "u:object_r:unlabeled:s0"
#define SYSTEM_CON "u:object_r:system_file:s0"
#define ADB_CON "u:object_r:adb_data_file:s0"
#define MAGISK_CON "u:object_r:" SEPOL_FILE_DOMAIN ":s0"
// Stub implementation
static int stub(const char *) { return 0; }
static int stub(const char *, const char *) { return 0; }
static int stub(const char *, char **ctx) {
*ctx = strdup("");
return 0;
}
// Builtin implementation
static void __freecon(char *s) {
free(s);
}
static int __setcon(const char *ctx) {
int fd = open("/proc/self/attr/current", O_WRONLY | O_CLOEXEC);
if (fd < 0)
return fd;
size_t len = strlen(ctx) + 1;
int rc = write(fd, ctx, len);
close(fd);
return rc != len;
}
static int __getfilecon(const char *path, char **ctx) {
char buf[1024];
int rc = syscall(__NR_getxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
if (rc > 0)
*ctx = strdup(buf);
return rc;
}
static int __lgetfilecon(const char *path, char **ctx) {
char buf[1024];
int rc = syscall(__NR_lgetxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
if (rc > 0)
*ctx = strdup(buf);
return rc;
}
static int __setfilecon(const char *path, const char *ctx) {
return syscall(__NR_setxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
}
static int __lsetfilecon(const char *path, const char *ctx) {
return syscall(__NR_lsetxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
}
// Function pointers
void (*freecon)(char *) = __freecon;
int (*setcon)(const char *) = stub;
int (*getfilecon)(const char *, char **) = stub;
int (*lgetfilecon)(const char *, char **) = stub;
int (*setfilecon)(const char *, const char *) = stub;
int (*lsetfilecon)(const char *, const char *) = stub;
void selinux_builtin_impl() {
setcon = __setcon;
getfilecon = __getfilecon;
lgetfilecon = __lgetfilecon;
setfilecon = __setfilecon;
lsetfilecon = __lsetfilecon;
}
void dload_selinux() {
if (access("/system/lib/libselinux.so", F_OK))
return;
/* We only check whether libselinux.so exists but don't dlopen.
* For some reason calling symbols returned from dlsym
* will result to SEGV_ACCERR on some devices.
* Always use builtin implementations for SELinux stuffs. */
selinux_builtin_impl();
}
static void restore_syscon(int dirfd) {
struct dirent *entry;
DIR *dir;
char path[PATH_MAX], *con;
fd_getpath(dirfd, path, sizeof(path));
size_t len = strlen(path);
getfilecon(path, &con);
if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
lsetfilecon(path, SYSTEM_CON);
freecon(con);
dir = xfdopendir(dirfd);
while ((entry = xreaddir(dir))) {
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
continue;
if (entry->d_type == DT_DIR) {
int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
restore_syscon(fd);
close(fd);
} else {
path[len] = '/';
strcpy(path + len + 1, entry->d_name);
lgetfilecon(path, &con);
if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
lsetfilecon(path, SYSTEM_CON);
freecon(con);
path[len] = '\0';
}
}
}
static void restore_magiskcon(int dirfd) {
struct dirent *entry;
DIR *dir;
char path[PATH_MAX];
fd_getpath(dirfd, path, sizeof(path));
size_t len = strlen(path);
lsetfilecon(path, MAGISK_CON);
lchown(path, 0, 0);
dir = xfdopendir(dirfd);
while ((entry = xreaddir(dir))) {
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
continue;
if (entry->d_type == DT_DIR) {
int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
restore_magiskcon(fd);
close(fd);
} else {
path[len] = '/';
strcpy(path + len + 1, entry->d_name);
lsetfilecon(path, MAGISK_CON);
lchown(path, 0, 0);
path[len] = '\0';
}
}
}
void restorecon() {
int fd;
fd = xopen(SELINUX_CONTEXT, O_WRONLY | O_CLOEXEC);
if (write(fd, ADB_CON, sizeof(ADB_CON)) >= 0)
lsetfilecon(SECURE_DIR, ADB_CON);
close(fd);
lsetfilecon(MODULEROOT, MAGISK_CON);
fd = xopen(MODULEROOT, O_RDONLY | O_CLOEXEC);
restore_syscon(fd);
close(fd);
fd = xopen(DATABIN, O_RDONLY | O_CLOEXEC);
restore_magiskcon(fd);
close(fd);
}