mirror of
https://github.com/topjohnwu/Magisk.git
synced 2024-11-24 10:35:26 +00:00
398 lines
8.8 KiB
C++
398 lines
8.8 KiB
C++
#include <unistd.h>
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#include <pthread.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <string.h>
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#include <signal.h>
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#include <pwd.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/wait.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 "su.h"
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#include "pts.h"
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#include "selinux.h"
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#define TIMEOUT 3
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#define LOCK_CACHE() pthread_mutex_lock(&cache_lock)
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#define UNLOCK_CACHE() pthread_mutex_unlock(&cache_lock)
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static pthread_mutex_t cache_lock = PTHREAD_MUTEX_INITIALIZER;
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static su_info *cache;
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su_info::su_info(unsigned uid) :
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uid(uid), access(DEFAULT_SU_ACCESS), _lock(PTHREAD_MUTEX_INITIALIZER),
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count(0), ref(0), life(0), mgr_st({}) {}
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su_info::~su_info() {
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pthread_mutex_destroy(&_lock);
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}
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void su_info::lock() {
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pthread_mutex_lock(&_lock);
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}
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void su_info::unlock() {
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pthread_mutex_unlock(&_lock);
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}
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static void *info_collector(void *node) {
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su_info *info = (su_info *) node;
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while (1) {
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sleep(1);
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if (info->life) {
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LOCK_CACHE();
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if (--info->life == 0 && cache && info->uid == cache->uid)
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cache = nullptr;
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UNLOCK_CACHE();
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}
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if (!info->life && !info->ref) {
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delete info;
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return nullptr;
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}
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}
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}
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static void database_check(su_info *info) {
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int uid = info->uid;
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sqlite3 *db = get_magiskdb();
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if (db) {
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get_db_settings(db, &info->cfg);
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get_db_strings(db, &info->str);
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// Check multiuser settings
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switch (info->cfg[SU_MULTIUSER_MODE]) {
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case MULTIUSER_MODE_OWNER_ONLY:
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if (info->uid / 100000) {
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uid = -1;
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info->access = NO_SU_ACCESS;
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}
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break;
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case MULTIUSER_MODE_OWNER_MANAGED:
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uid = info->uid % 100000;
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break;
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case MULTIUSER_MODE_USER:
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default:
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break;
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}
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if (uid > 0)
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get_uid_policy(db, uid, &info->access);
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sqlite3_close_v2(db);
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}
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// We need to check our manager
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if (info->access.log || info->access.notify)
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validate_manager(info->str[SU_MANAGER], uid / 100000, &info->mgr_st);
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}
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static struct su_info *get_su_info(unsigned uid) {
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su_info *info;
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bool cache_miss = false;
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LOCK_CACHE();
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if (cache && cache->uid == uid) {
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info = cache;
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} else {
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cache_miss = true;
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info = new su_info(uid);
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cache = info;
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}
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// Update the cache status
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info->life = TIMEOUT;
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++info->ref;
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// Start a thread to maintain the cache
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if (cache_miss) {
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pthread_t thread;
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xpthread_create(&thread, nullptr, info_collector, info);
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pthread_detach(thread);
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}
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UNLOCK_CACHE();
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LOGD("su: request from uid=[%d] (#%d)\n", info->uid, ++info->count);
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// Lock before the policy is determined
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info->lock();
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if (info->access.policy == QUERY) {
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// Not cached, get data from database
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database_check(info);
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// Check su access settings
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switch (info->cfg[ROOT_ACCESS]) {
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case ROOT_ACCESS_DISABLED:
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LOGW("Root access is disabled!\n");
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info->access = NO_SU_ACCESS;
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break;
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case ROOT_ACCESS_ADB_ONLY:
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if (info->uid != UID_SHELL) {
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LOGW("Root access limited to ADB only!\n");
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info->access = NO_SU_ACCESS;
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}
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break;
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case ROOT_ACCESS_APPS_ONLY:
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if (info->uid == UID_SHELL) {
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LOGW("Root access is disabled for ADB!\n");
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info->access = NO_SU_ACCESS;
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}
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break;
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case ROOT_ACCESS_APPS_AND_ADB:
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default:
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break;
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}
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// If it's the manager, allow it silently
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if ((info->uid % 100000) == (info->mgr_st.st_uid % 100000))
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info->access = SILENT_SU_ACCESS;
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// Allow if it's root
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if (info->uid == UID_ROOT)
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info->access = SILENT_SU_ACCESS;
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// If still not determined, check if manager exists
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if (info->access.policy == QUERY && info->str[SU_MANAGER][0] == '\0')
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info->access = NO_SU_ACCESS;
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}
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// If still not determined, ask manager
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if (info->access.policy == QUERY) {
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// Create random socket
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struct sockaddr_un addr;
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int sockfd = create_rand_socket(&addr);
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// Connect manager
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app_connect(addr.sun_path + 1, info);
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int fd = socket_accept(sockfd, 60);
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if (fd < 0) {
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info->access.policy = DENY;
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} else {
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socket_send_request(fd, info);
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int ret = read_int_be(fd);
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info->access.policy = ret < 0 ? DENY : static_cast<policy_t>(ret);
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close(fd);
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}
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close(sockfd);
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}
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// Unlock
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info->unlock();
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return info;
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}
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static void populate_environment(struct su_request *req) {
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struct passwd *pw;
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if (req->keepenv)
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return;
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pw = getpwuid(req->uid);
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if (pw) {
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setenv("HOME", pw->pw_dir, 1);
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if (req->shell)
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setenv("SHELL", req->shell, 1);
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else
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setenv("SHELL", DEFAULT_SHELL, 1);
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if (req->login || req->uid) {
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setenv("USER", pw->pw_name, 1);
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setenv("LOGNAME", pw->pw_name, 1);
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}
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}
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}
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static void set_identity(unsigned uid) {
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/*
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* Set effective uid back to root, otherwise setres[ug]id will fail
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* if uid isn't root.
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*/
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if (seteuid(0)) {
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PLOGE("seteuid (root)");
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}
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if (setresgid(uid, uid, uid)) {
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PLOGE("setresgid (%u)", uid);
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}
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if (setresuid(uid, uid, uid)) {
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PLOGE("setresuid (%u)", uid);
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}
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}
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void su_daemon_handler(int client, struct ucred *credential) {
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LOGD("su: request from client: %d\n", client);
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su_info *info = get_su_info(credential->uid);
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// Fail fast
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if (info->access.policy == DENY && info->str[SU_MANAGER][0] == '\0') {
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LOGD("su: fast deny\n");
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write_int(client, DENY);
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close(client);
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return;
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}
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/* Fork a new process, the child process will need to setsid,
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* open a pseudo-terminal if needed, and will eventually run exec
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* The parent process will wait for the result and
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* send the return code back to our client
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*/
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int child = xfork();
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if (child) {
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// Decrement reference count
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--info->ref;
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// Wait result
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LOGD("su: waiting child: [%d]\n", child);
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int status, code;
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if (waitpid(child, &status, 0) > 0)
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code = WEXITSTATUS(status);
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else
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code = -1;
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LOGD("su: return code: [%d]\n", code);
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write(client, &code, sizeof(code));
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close(client);
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return;
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}
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LOGD("su: fork handler\n");
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struct su_context ctx = {
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.info = info,
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.pid = credential->pid
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};
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// ack
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write_int(client, 0);
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// Become session leader
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xsetsid();
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// Migrate environment from client
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char path[32], buf[4096];
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snprintf(path, sizeof(path), "/proc/%d/cwd", ctx.pid);
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xreadlink(path, buf, sizeof(buf));
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chdir(buf);
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snprintf(path, sizeof(path), "/proc/%d/environ", ctx.pid);
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memset(buf, 0, sizeof(buf));
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int fd = open(path, O_RDONLY);
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read(fd, buf, sizeof(buf));
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close(fd);
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clearenv();
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for (size_t pos = 0; buf[pos];) {
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putenv(buf + pos);
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pos += strlen(buf + pos) + 1;
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}
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// Read su_request
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xxread(client, &ctx.req, sizeof(su_req_base));
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ctx.req.shell = read_string(client);
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ctx.req.command = read_string(client);
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// Get pts_slave
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char *pts_slave = read_string(client);
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// The FDs for each of the streams
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int infd = recv_fd(client);
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int outfd = recv_fd(client);
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int errfd = recv_fd(client);
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int ptsfd = -1;
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if (pts_slave[0]) {
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LOGD("su: pts_slave=[%s]\n", pts_slave);
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// Check pts_slave file is owned by daemon_from_uid
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struct stat st;
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xstat(pts_slave, &st);
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// If caller is not root, ensure the owner of pts_slave is the caller
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if(st.st_uid != info->uid && info->uid != 0) {
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LOGE("su: Wrong permission of pts_slave");
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info->access.policy = DENY;
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exit(1);
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}
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// Set our pts_slave to devpts, same restriction as adb shell
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lsetfilecon(pts_slave, "u:object_r:devpts:s0");
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// Opening the TTY has to occur after the
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// fork() and setsid() so that it becomes
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// our controlling TTY and not the daemon's
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ptsfd = xopen(pts_slave, O_RDWR);
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if (infd < 0)
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infd = ptsfd;
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if (outfd < 0)
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outfd = ptsfd;
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if (errfd < 0)
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errfd = ptsfd;
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}
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free(pts_slave);
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// Swap out stdin, stdout, stderr
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xdup2(infd, STDIN_FILENO);
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xdup2(outfd, STDOUT_FILENO);
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xdup2(errfd, STDERR_FILENO);
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close(ptsfd);
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close(client);
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// Handle namespaces
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if (ctx.req.mount_master)
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info->cfg[SU_MNT_NS] = NAMESPACE_MODE_GLOBAL;
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switch (info->cfg[SU_MNT_NS]) {
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case NAMESPACE_MODE_GLOBAL:
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LOGD("su: use global namespace\n");
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break;
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case NAMESPACE_MODE_REQUESTER:
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LOGD("su: use namespace of pid=[%d]\n", ctx.pid);
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if (switch_mnt_ns(ctx.pid)) {
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LOGD("su: setns failed, fallback to isolated\n");
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xunshare(CLONE_NEWNS);
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}
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break;
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case NAMESPACE_MODE_ISOLATE:
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LOGD("su: use new isolated namespace\n");
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xunshare(CLONE_NEWNS);
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break;
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}
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if (info->access.log)
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app_log(&ctx);
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else if (info->access.notify)
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app_notify(&ctx);
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if (info->access.policy == ALLOW) {
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const char *argv[] = { nullptr, nullptr, nullptr, nullptr };
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argv[0] = ctx.req.login ? "-" : ctx.req.shell;
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if (ctx.req.command[0]) {
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argv[1] = "-c";
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argv[2] = ctx.req.command;
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}
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// Setup shell
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umask(022);
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populate_environment(&ctx.req);
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set_identity(ctx.req.uid);
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execvp(ctx.req.shell, (char **) argv);
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fprintf(stderr, "Cannot execute %s: %s\n", ctx.req.shell, strerror(errno));
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PLOGE("exec");
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exit(EXIT_FAILURE);
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} else {
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LOGW("su: request rejected (%u->%u)", info->uid, ctx.req.uid);
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fprintf(stderr, "%s\n", strerror(EACCES));
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exit(EXIT_FAILURE);
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}
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}
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