Magisk/native/jni/magiskhide/proc_monitor.cpp

180 lines
4.2 KiB
C++

/* proc_monitor.cpp - Monitor am_proc_start events and unmount
*
* We monitor the logcat am_proc_start events. When a target starts up,
* we pause it ASAP, and fork a new process to join its mount namespace
* and do all the unmounting/mocking
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/mount.h>
#include <vector>
#include <string>
#include <magisk.h>
#include <utils.h>
#include <logcat.h>
#include "magiskhide.h"
using namespace std;
extern char *system_block, *vendor_block, *magiskloop;
// Workaround for the lack of pthread_cancel
static void term_thread(int) {
LOGD("proc_monitor: running cleanup\n");
stop_logging(HIDE_EVENT);
hide_list.clear();
hide_enabled = false;
pthread_mutex_destroy(&list_lock);
LOGD("proc_monitor: terminating\n");
pthread_exit(nullptr);
}
static int read_ns(const int pid, struct stat *st) {
char path[32];
sprintf(path, "/proc/%d/ns/mnt", pid);
return stat(path, st);
}
static inline void lazy_unmount(const char* mountpoint) {
if (umount2(mountpoint, MNT_DETACH) != -1)
LOGD("hide_daemon: Unmounted (%s)\n", mountpoint);
}
static int parse_ppid(int pid) {
char path[32];
int ppid;
sprintf(path, "/proc/%d/stat", pid);
FILE *stat = fopen(path, "re");
if (stat == nullptr)
return -1;
/* PID COMM STATE PPID ..... */
fscanf(stat, "%*d %*s %*c %d", &ppid);
fclose(stat);
return ppid;
}
static void hide_daemon(int pid) {
LOGD("hide_daemon: handling pid=[%d]\n", pid);
char buffer[4096];
vector<string> mounts;
manage_selinux();
clean_magisk_props();
if (switch_mnt_ns(pid))
goto exit;
snprintf(buffer, sizeof(buffer), "/proc/%d", pid);
chdir(buffer);
mounts = file_to_vector("mounts");
// Unmount dummy skeletons and /sbin links
for (auto &s : mounts) {
if (str_contains(s, "tmpfs /system/") || str_contains(s, "tmpfs /vendor/") ||
str_contains(s, "tmpfs /sbin")) {
sscanf(s.c_str(), "%*s %4096s", buffer);
lazy_unmount(buffer);
}
}
// Re-read mount infos
mounts = file_to_vector("mounts");
// Unmount everything under /system, /vendor, and loop mounts
for (auto &s : mounts) {
if ((str_contains(s, " /system/") || str_contains(s, " /vendor/")) &&
(str_contains(s, system_block) || str_contains(s, vendor_block) || str_contains(s, magiskloop))) {
sscanf(s.c_str(), "%*s %4096s", buffer);
lazy_unmount(buffer);
}
}
exit:
// Send resume signal
kill(pid, SIGCONT);
_exit(0);
}
void proc_monitor() {
// Unblock user signals
sigset_t block_set;
sigemptyset(&block_set);
sigaddset(&block_set, TERM_THREAD);
pthread_sigmask(SIG_UNBLOCK, &block_set, nullptr);
// Register the cancel signal
struct sigaction act{};
act.sa_handler = term_thread;
sigaction(TERM_THREAD, &act, nullptr);
if (access("/proc/1/ns/mnt", F_OK) != 0) {
LOGE("proc_monitor: Your kernel doesn't support mount namespace :(\n");
term_thread(TERM_THREAD);
}
auto &queue = start_logging(HIDE_EVENT);
while (true) {
char *log;
int pid, ppid;
struct stat ns, pns;
string line = queue.take();
if ((log = strchr(&line[0], '[')) == nullptr)
continue;
// Extract pid
if (sscanf(log, "[%*d,%d", &pid) != 1)
continue;
// Extract last token (component name)
const char *tok, *cpnt = "";
while ((tok = strtok_r(nullptr, ",[]\n", &log)))
cpnt = tok;
if (cpnt[0] == '\0')
continue;
// Make sure our target is alive
if ((ppid = parse_ppid(pid)) < 0 || read_ns(ppid, &pns))
continue;
bool hide = false;
pthread_mutex_lock(&list_lock);
for (auto &s : hide_list) {
if (strncmp(cpnt, s.c_str(), s.size() - 1) == 0) {
hide = true;
break;
}
}
pthread_mutex_unlock(&list_lock);
if (!hide)
continue;
while (read_ns(pid, &ns) == 0 && ns.st_dev == pns.st_dev && ns.st_ino == pns.st_ino)
usleep(500);
// Send pause signal ASAP
if (kill(pid, SIGSTOP) == -1)
continue;
/*
* The setns system call do not support multithread processes
* We have to fork a new process, setns, then do the unmounts
*/
LOGI("proc_monitor: %s PID=[%d] ns=[%llu]\n", cpnt, pid, ns.st_ino);
if (fork_dont_care() == 0)
hide_daemon(pid);
}
}