462 lines
11 KiB
C
462 lines
11 KiB
C
/* su_daemon.c - The entrypoint for su, connect to daemon and send correct info
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*/
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#define _GNU_SOURCE
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#include <limits.h>
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#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 <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 "list.h"
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// Constants for the atty bitfield
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#define ATTY_IN 1
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#define ATTY_OUT 2
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#define ATTY_ERR 4
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#define TIMEOUT 3
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#define LOCK_LIST() pthread_mutex_lock(&list_lock)
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#define LOCK_UID() pthread_mutex_lock(&info->lock)
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#define UNLOCK_LIST() pthread_mutex_unlock(&list_lock)
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#define UNLOCK_UID() pthread_mutex_unlock(&ctx.info->lock)
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static struct list_head info_cache = { .prev = &info_cache, .next = &info_cache };
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static pthread_mutex_t list_lock = PTHREAD_MUTEX_INITIALIZER;
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static void sighandler(int sig) {
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restore_stdin();
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// Assume we'll only be called before death
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// See note before sigaction() in set_stdin_raw()
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//
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// Now, close all standard I/O to cause the pumps
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// to exit so we can continue and retrieve the exit
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// code
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close(STDIN_FILENO);
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close(STDOUT_FILENO);
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close(STDERR_FILENO);
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// Put back all the default handlers
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struct sigaction act;
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memset(&act, 0, sizeof(act));
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act.sa_handler = SIG_DFL;
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for (int i = 0; quit_signals[i]; ++i) {
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sigaction(quit_signals[i], &act, NULL);
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}
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}
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static void *info_collector(void *node) {
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struct su_info *info = node;
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while (1) {
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sleep(1);
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if (info->clock && --info->clock == 0) {
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LOCK_LIST();
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list_pop(&info->pos);
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UNLOCK_LIST();
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}
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if (!info->clock && !info->ref) {
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pthread_mutex_destroy(&info->lock);
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free(info);
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return NULL;
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}
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}
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}
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static void database_check(struct 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, -1, &info->dbs);
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get_db_strings(db, -1, &info->str);
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// Check multiuser settings
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switch (info->dbs.v[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(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.s[SU_MANAGER], uid / 100000, &info->manager_stat);
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}
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static struct su_info *get_su_info(unsigned uid) {
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struct su_info *info = NULL, *node;
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LOCK_LIST();
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// Search for existing info in cache
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list_for_each(node, &info_cache, struct su_info, pos) {
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if (node->uid == uid) {
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info = node;
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break;
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}
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}
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int cache_miss = info == NULL;
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if (cache_miss) {
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// If cache miss, create a new one and push to cache
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info = malloc(sizeof(*info));
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info->uid = uid;
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info->dbs = DEFAULT_DB_SETTINGS;
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info->access = DEFAULT_SU_ACCESS;
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INIT_DB_STRINGS(&info->str);
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info->ref = 0;
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info->count = 0;
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pthread_mutex_init(&info->lock, NULL);
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list_insert_end(&info_cache, &info->pos);
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}
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// Update the cache status
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info->clock = TIMEOUT;
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++info->ref;
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// Start a thread to maintain the info cache
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if (cache_miss) {
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pthread_t thread;
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xpthread_create(&thread, NULL, info_collector, info);
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pthread_detach(thread);
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}
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UNLOCK_LIST();
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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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LOCK_UID();
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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->dbs.v[ROOT_ACCESS]) {
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case ROOT_ACCESS_DISABLED:
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LOGE("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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LOGE("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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LOGE("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->manager_stat.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.s[SU_MANAGER][0] == '\0')
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info->access = NO_SU_ACCESS;
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}
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return info;
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}
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void su_daemon_receiver(int client, struct ucred *credential) {
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LOGD("su: request from client: %d\n", client);
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// Default values
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struct su_context ctx = {
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.info = get_su_info(credential->uid),
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.to = {
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.uid = UID_ROOT,
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.login = 0,
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.keepenv = 0,
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.shell = DEFAULT_SHELL,
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.command = NULL,
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},
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.pid = credential->pid,
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.pipefd = { -1, -1 }
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};
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// Fail fast
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if (ctx.info->access.policy == DENY && !ctx.info->access.log && !ctx.info->access.notify) {
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UNLOCK_UID();
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write_int(client, DENY);
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return;
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}
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// If still not determined, open a pipe and wait for results
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if (ctx.info->access.policy == QUERY)
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xpipe2(ctx.pipefd, O_CLOEXEC);
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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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// Wait for results
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if (ctx.pipefd[0] >= 0) {
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xxread(ctx.pipefd[0], &ctx.info->access.policy, sizeof(policy_t));
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close(ctx.pipefd[0]);
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close(ctx.pipefd[1]);
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}
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// The policy is determined, unlock
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UNLOCK_UID();
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// Info is now useless to us, decrement reference count
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--ctx.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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/* Passing the return code back to the client:
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* The client might be closed unexpectedly (e.g. swipe a root app out of recents)
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* In that case, writing to the client (which doesn't exist) will result in SIGPIPE
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* Here we simply just ignore the situation.
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*/
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struct sigaction act;
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memset(&act, 0, sizeof(act));
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act.sa_handler = SIG_IGN;
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sigaction(SIGPIPE, &act, NULL);
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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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// Restore default handler for SIGPIPE
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act.sa_handler = SIG_DFL;
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sigaction(SIGPIPE, &act, NULL);
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return;
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}
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LOGD("su: child process started\n");
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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, ctx.cwd, sizeof(ctx.cwd));
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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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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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// Let's read some info from the socket
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int argc = read_int(client);
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if (argc < 0 || argc > 512) {
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LOGE("unable to allocate args: %d", argc);
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exit2(1);
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}
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LOGD("su: argc=[%d]\n", argc);
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char **argv = (char**) xmalloc(sizeof(char*) * (argc + 1));
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argv[argc] = NULL;
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for (int i = 0; i < argc; i++) {
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argv[i] = read_string(client);
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LOGD("su: argv[%d]=[%s]\n", i, argv[i]);
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// Replace -cn with -z, -mm with -M for supporting getopt_long
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if (strcmp(argv[i], "-cn") == 0)
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strcpy(argv[i], "-z");
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else if (strcmp(argv[i], "-mm") == 0)
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strcpy(argv[i], "-M");
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}
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// Get pts_slave
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char *pts_slave = read_string(client);
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LOGD("su: pts_slave=[%s]\n", pts_slave);
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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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// We no longer need the access to socket in the child, close it
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close(client);
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if (pts_slave[0]) {
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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 != credential->uid && credential->uid != 0) {
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LOGE("su: Wrong permission of pts_slave");
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exit2(1);
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}
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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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LOGD("su: stdin using PTY");
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infd = ptsfd;
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}
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if (outfd < 0) {
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LOGD("su: stdout using PTY");
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outfd = ptsfd;
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}
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if (errfd < 0) {
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LOGD("su: stderr using PTY");
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errfd = ptsfd;
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}
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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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// Give main the reference
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su_ctx = &ctx;
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su_daemon_main(argc, argv);
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}
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/*
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* Connect daemon, send argc, argv, cwd, pts slave
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*/
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int su_client_main(int argc, char *argv[]) {
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char buffer[PATH_MAX];
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int ptmx, socketfd;
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// Connect to client
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socketfd = connect_daemon();
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// Tell the daemon we are su
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write_int(socketfd, SUPERUSER);
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// Number of command line arguments
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write_int(socketfd, argc);
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// Command line arguments
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for (int i = 0; i < argc; i++) {
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write_string(socketfd, argv[i]);
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}
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// Determine which one of our streams are attached to a TTY
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int atty = 0;
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if (isatty(STDIN_FILENO)) atty |= ATTY_IN;
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if (isatty(STDOUT_FILENO)) atty |= ATTY_OUT;
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if (isatty(STDERR_FILENO)) atty |= ATTY_ERR;
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if (atty) {
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// We need a PTY. Get one.
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ptmx = pts_open(buffer, sizeof(buffer));
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} else {
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buffer[0] = '\0';
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}
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// Send the pts_slave path to the daemon
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write_string(socketfd, buffer);
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// Send stdin
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if (atty & ATTY_IN) {
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// Using PTY
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send_fd(socketfd, -1);
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} else {
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send_fd(socketfd, STDIN_FILENO);
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}
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// Send stdout
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if (atty & ATTY_OUT) {
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// Forward SIGWINCH
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watch_sigwinch_async(STDOUT_FILENO, ptmx);
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// Using PTY
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send_fd(socketfd, -1);
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} else {
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send_fd(socketfd, STDOUT_FILENO);
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}
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// Send stderr
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if (atty & ATTY_ERR) {
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// Using PTY
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send_fd(socketfd, -1);
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} else {
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send_fd(socketfd, STDERR_FILENO);
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}
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// Wait for acknowledgement from daemon
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if (read_int(socketfd)) {
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// Fast fail
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fprintf(stderr, "%s\n", strerror(EACCES));
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return DENY;
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}
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if (atty & ATTY_IN) {
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setup_sighandlers(sighandler);
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pump_stdin_async(ptmx);
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}
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if (atty & ATTY_OUT) {
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pump_stdout_blocking(ptmx);
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}
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// Get the exit code
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int code = read_int(socketfd);
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close(socketfd);
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return code;
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}
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