Magisk/native/jni/magiskhide/proc_monitor.cpp

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/* proc_monitor.cpp - Monitor am_proc_start events and unmount
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*
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* 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
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*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
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#include <fcntl.h>
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#include <signal.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/wait.h>
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#include <sys/mount.h>
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#include "magisk.h"
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#include "daemon.h"
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#include "utils.h"
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#include "magiskhide.h"
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static int sockfd = -1;
extern char *system_block, *vendor_block, *magiskloop;
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// Workaround for the lack of pthread_cancel
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static void term_thread(int) {
LOGD("proc_monitor: running cleanup\n");
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hide_list.clear(true);
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hide_enabled = false;
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close(sockfd);
sockfd = -1;
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pthread_mutex_destroy(&list_lock);
LOGD("proc_monitor: terminating\n");
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pthread_exit(nullptr);
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}
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static int read_ns(const int pid, struct stat *st) {
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char path[32];
sprintf(path, "/proc/%d/ns/mnt", pid);
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return stat(path, st);
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}
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static inline void lazy_unmount(const char* mountpoint) {
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if (umount2(mountpoint, MNT_DETACH) != -1)
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LOGD("hide_daemon: Unmounted (%s)\n", mountpoint);
}
static int parse_ppid(int pid) {
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char path[32];
int ppid;
sprintf(path, "/proc/%d/stat", pid);
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FILE *stat = fopen(path, "re");
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if (stat == nullptr)
return -1;
/* PID COMM STATE PPID ..... */
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fscanf(stat, "%*d %*s %*c %d", &ppid);
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fclose(stat);
return ppid;
}
static void hide_daemon(int pid) {
LOGD("hide_daemon: handling pid=[%d]\n", pid);
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char buffer[4096];
Vector<CharArray> mounts;
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manage_selinux();
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clean_magisk_props();
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if (switch_mnt_ns(pid))
goto exit;
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snprintf(buffer, sizeof(buffer), "/proc/%d", pid);
chdir(buffer);
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file_to_vector("mounts", mounts);
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// Unmount dummy skeletons and /sbin links
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for (auto &s : mounts) {
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if (s.contains("tmpfs /system/") || s.contains("tmpfs /vendor/") || s.contains("tmpfs /sbin")) {
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sscanf(s, "%*s %4096s", buffer);
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lazy_unmount(buffer);
}
}
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mounts.clear();
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// Re-read mount infos
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file_to_vector("mounts", mounts);
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// Unmount everything under /system, /vendor, and loop mounts
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for (auto &s : mounts) {
if ((s.contains(" /system/") || s.contains(" /vendor/")) &&
(s.contains(system_block) || s.contains(vendor_block) || s.contains(magiskloop))) {
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sscanf(s, "%*s %4096s", buffer);
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lazy_unmount(buffer);
}
}
exit:
// Send resume signal
kill(pid, SIGCONT);
_exit(0);
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}
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void proc_monitor() {
// Unblock user signals
sigset_t block_set;
sigemptyset(&block_set);
sigaddset(&block_set, TERM_THREAD);
pthread_sigmask(SIG_UNBLOCK, &block_set, NULL);
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// Register the cancel signal
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struct sigaction act;
memset(&act, 0, sizeof(act));
act.sa_handler = term_thread;
sigaction(TERM_THREAD, &act, NULL);
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if (access("/proc/1/ns/mnt", F_OK) != 0) {
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LOGE("proc_monitor: Your kernel doesn't support mount namespace :(\n");
term_thread(TERM_THREAD);
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}
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// Connect to the log daemon
sockfd = connect_log_daemon();
if (sockfd < 0)
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pthread_exit(nullptr);
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write_int(sockfd, HIDE_CONNECT);
FILE *log_in = fdopen(sockfd, "r");
char buf[4096];
while (fgets(buf, sizeof(buf), log_in)) {
char *log;
int pid, ppid;
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struct stat ns, pns;
if ((log = strchr(buf, '[')) == 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')
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continue;
// Make sure our target is alive
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if ((ppid = parse_ppid(pid)) < 0 || read_ns(ppid, &pns))
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continue;
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bool hide = false;
pthread_mutex_lock(&list_lock);
for (auto &s : hide_list) {
if (strncmp(cpnt, s, s.size() - 1) == 0) {
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hide = true;
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break;
}
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}
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pthread_mutex_unlock(&list_lock);
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if (!hide)
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continue;
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while (read_ns(pid, &ns) == 0 && ns.st_dev == pns.st_dev && ns.st_ino == pns.st_ino)
usleep(500);
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// 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);
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if (fork_dont_care() == 0)
hide_daemon(pid);
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}
pthread_exit(nullptr);
}