321 lines
7.6 KiB
C++
321 lines
7.6 KiB
C++
/* proc_monitor.cpp - Monitor am_proc_start events and unmount
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*
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* We monitor the listed APK files from /data/app until they get opened
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* via inotify to detect a new app launch.
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*
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* If it's a target we pause it ASAP, and fork a new process to join
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* its mount namespace and do all the unmounting/mocking.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <pthread.h>
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#include <sys/inotify.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/mount.h>
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#include <vector>
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#include <string>
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#include <map>
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#include <magisk.h>
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#include <utils.h>
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#include "magiskhide.h"
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using namespace std;
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extern char *system_block, *vendor_block, *data_block;
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static int inotify_fd = -1;
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#define EVENT_SIZE sizeof(struct inotify_event)
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#define EVENT_BUF_LEN (1024 * (EVENT_SIZE + 16))
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#define __ALIGN_EVENT __attribute__ ((aligned(__alignof__(struct inotify_event))))
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// Workaround for the lack of pthread_cancel
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static void term_thread(int) {
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LOGD("proc_monitor: running cleanup\n");
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hide_list.clear();
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hide_uid.clear();
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hide_enabled = false;
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pthread_mutex_destroy(&list_lock);
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close(inotify_fd);
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inotify_fd = -1;
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LOGD("proc_monitor: terminating\n");
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pthread_exit(nullptr);
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}
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static inline int read_ns(const int pid, struct stat *st) {
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char path[32];
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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);
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}
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/* APK monitoring doesn't seem to require checking namespace
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* separation from PPID. Preserve this function just in case */
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#if 0
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static inline int parse_ppid(const int pid) {
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char path[32];
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int ppid;
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sprintf(path, "/proc/%d/stat", pid);
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FILE *stat = fopen(path, "re");
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if (stat == nullptr)
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return -1;
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/* PID COMM STATE PPID ..... */
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fscanf(stat, "%*d %*s %*c %d", &ppid);
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fclose(stat);
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return ppid;
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}
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#endif
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static bool is_pid_safetynet_process(const int pid) {
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char path[32];
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char buf[64];
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int fd;
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ssize_t len;
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sprintf(path, "/proc/%d/cmdline", pid);
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fd = open(path, O_RDONLY);
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if (fd == -1)
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return false;
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len = read(fd, buf, sizeof(buf));
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close(fd);
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if (len == -1)
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return false;
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return !strcmp(buf, SAFETYNET_PROCESS);
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}
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static void hide_daemon(int pid) {
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LOGD("hide_daemon: handling PID=[%d]\n", pid);
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char buffer[4096];
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vector<string> mounts;
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manage_selinux();
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clean_magisk_props();
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if (switch_mnt_ns(pid))
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goto exit;
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snprintf(buffer, sizeof(buffer), "/proc/%d", pid);
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chdir(buffer);
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mounts = file_to_vector("mounts");
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// Unmount dummy skeletons and /sbin links
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for (auto &s : mounts) {
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if (str_contains(s, "tmpfs /system/") || str_contains(s, "tmpfs /vendor/") ||
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str_contains(s, "tmpfs /sbin")) {
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sscanf(s.c_str(), "%*s %4096s", buffer);
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lazy_unmount(buffer);
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}
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}
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// Re-read mount infos
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mounts = file_to_vector("mounts");
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// Unmount everything under /system, /vendor, and data mounts
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for (auto &s : mounts) {
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if ((str_contains(s, " /system/") || str_contains(s, " /vendor/")) &&
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(str_contains(s, system_block) || str_contains(s, vendor_block) || str_contains(s, data_block))) {
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sscanf(s.c_str(), "%*s %4096s", buffer);
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lazy_unmount(buffer);
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}
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}
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exit:
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// Send resume signal
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kill(pid, SIGCONT);
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_exit(0);
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}
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// A mapping from pid to namespace inode to avoid time-consuming GC
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static map<int, uint64_t> pid_ns_map;
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static bool process_pid(int pid) {
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// We're only interested in PIDs > 1000
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if (pid <= 1000)
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return true;
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struct stat ns;
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int uid = get_uid(pid);
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if (hide_uid.count(uid)) {
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// Make sure we can read mount namespace
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if (read_ns(pid, &ns))
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return true;
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// Check if it's a process we haven't already hijacked
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auto pos = pid_ns_map.find(pid);
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if (pos != pid_ns_map.end() && pos->second == ns.st_ino)
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return true;
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if (uid == gms_uid) {
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// Check /proc/uid/cmdline to see if it's SAFETYNET_PROCESS
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if (!is_pid_safetynet_process(pid))
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return true;
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LOGD("proc_monitor: " SAFETYNET_PROCESS "\n");
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}
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// Send pause signal ASAP
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if (kill(pid, SIGSTOP) == -1)
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return true;
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pid_ns_map[pid] = ns.st_ino;
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LOGI("proc_monitor: UID=[%d] PID=[%d] ns=[%llu]\n", uid, pid, ns.st_ino);
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/*
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* The setns system call do not support multithread processes
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* We have to fork a new process, setns, then do the unmounts
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*/
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if (fork_dont_care() == 0)
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hide_daemon(pid);
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}
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return true;
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}
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static int xinotify_add_watch(int fd, const char* path, uint32_t mask) {
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int ret = inotify_add_watch(fd, path, mask);
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if (ret >= 0) {
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LOGI("proc_monitor: Monitoring %s\n", path);
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} else {
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PLOGE("proc_monitor: Monitor %s", path);
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}
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return ret;
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}
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static char *append_path(char *eof, const char *name) {
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*(eof++) = '/';
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char c;
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while ((c = *(name++)))
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*(eof++) = c;
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*eof = '\0';
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return eof;
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}
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#define DATA_APP "/data/app"
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static void find_apks(char *path, char *eof) {
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DIR *dir = opendir(path);
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if (dir == nullptr)
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return;
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// assert(*eof == '\0');
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struct dirent *entry;
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while ((entry = xreaddir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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if (entry->d_type == DT_DIR) {
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find_apks(path, append_path(eof, entry->d_name));
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*eof = '\0';
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} else if (strend(entry->d_name, ".apk") == 0) {
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// Path will be in this format: /data/app/[pkg]-[hash or 1 or 2]
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char *dash = strchr(path, '-');
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*dash = '\0';
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for (auto &s : hide_list) {
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if (s == path + sizeof(DATA_APP)) {
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*dash = '-';
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append_path(eof, entry->d_name);
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xinotify_add_watch(inotify_fd, path, IN_OPEN | IN_DELETE);
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*eof = '\0';
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break;
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}
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}
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*dash = '-';
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break;
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}
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}
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closedir(dir);
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}
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// Iterate through /data/app and search all .apk files
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void update_inotify_mask() {
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char buf[4096];
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if (inotify_fd >= 0)
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close(inotify_fd);
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inotify_fd = inotify_init();
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if (inotify_fd < 0) {
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LOGE("proc_monitor: Cannot initialize inotify: %s\n", strerror(errno));
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term_thread(TERM_THREAD);
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}
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LOGI("proc_monitor: Updating APK list\n");
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strcpy(buf, DATA_APP);
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pthread_mutex_lock(&list_lock);
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find_apks(buf, buf + sizeof(DATA_APP) - 1);
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pthread_mutex_unlock(&list_lock);
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// Add /data/app itself to the watch list to detect app (un)installations/updates
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xinotify_add_watch(inotify_fd, DATA_APP, IN_CLOSE_WRITE | IN_MOVED_TO | IN_DELETE);
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}
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void proc_monitor() {
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// Unblock user signals
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sigset_t block_set;
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sigemptyset(&block_set);
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sigaddset(&block_set, TERM_THREAD);
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pthread_sigmask(SIG_UNBLOCK, &block_set, nullptr);
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// Register the cancel signal
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struct sigaction act{};
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act.sa_handler = term_thread;
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sigaction(TERM_THREAD, &act, nullptr);
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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");
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term_thread(TERM_THREAD);
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}
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// Read inotify events
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struct inotify_event *event;
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ssize_t len;
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char *p;
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char buffer[EVENT_BUF_LEN] __ALIGN_EVENT;
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for (;;) {
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len = read(inotify_fd, buffer, EVENT_BUF_LEN);
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if (len == -1) {
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PLOGE("proc_monitor: read inotify");
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sleep(1);
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continue;
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}
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for (p = buffer; p < buffer + len; ) {
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event = (struct inotify_event *)p;
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if (event->mask & IN_OPEN) {
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// Since we're just watching files,
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// extracting file name is not possible from querying event
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pthread_mutex_lock(&list_lock);
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crawl_procfs(process_pid);
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pthread_mutex_unlock(&list_lock);
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} else {
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LOGI("proc_monitor: inotify: /data/app change detected\n");
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pthread_mutex_lock(&list_lock);
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refresh_uid();
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pthread_mutex_unlock(&list_lock);
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update_inotify_mask();
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break;
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}
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p += EVENT_SIZE + event->len;
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}
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}
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}
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