Magisk/jni/daemon/daemon.c

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/* daemon.c - Magisk Daemon
*
* Start the daemon and wait for requests
* Connect the daemon and send requests through sockets
*/
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
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#include <sys/un.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
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#include <sys/mount.h>
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#include <selinux/selinux.h>
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#include "magisk.h"
#include "utils.h"
#include "daemon.h"
#include "magiskpolicy.h"
pthread_t sepol_patch;
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int null_fd;
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static void *request_handler(void *args) {
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// Setup the default error handler for threads
err_handler = exit_thread;
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int client = *((int *) args);
free(args);
client_request req = read_int(client);
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struct ucred credentials;
get_client_cred(client, &credentials);
switch (req) {
case LAUNCH_MAGISKHIDE:
case STOP_MAGISKHIDE:
case ADD_HIDELIST:
case RM_HIDELIST:
case POST_FS:
case POST_FS_DATA:
case LATE_START:
if (credentials.uid != 0) {
write_int(client, ROOT_REQUIRED);
close(client);
return NULL;
}
default:
break;
}
switch (req) {
case LAUNCH_MAGISKHIDE:
launch_magiskhide(client);
break;
case STOP_MAGISKHIDE:
stop_magiskhide(client);
break;
case ADD_HIDELIST:
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add_hide_list(client);
break;
case RM_HIDELIST:
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rm_hide_list(client);
break;
case SUPERUSER:
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su_daemon_receiver(client);
break;
case CHECK_VERSION:
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write_string(client, MAGISK_VER_STR);
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close(client);
break;
case CHECK_VERSION_CODE:
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write_int(client, MAGISK_VER_CODE);
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close(client);
break;
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case POST_FS:
post_fs(client);
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break;
case POST_FS_DATA:
post_fs_data(client);
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break;
case LATE_START:
late_start(client);
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break;
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default:
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break;
}
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// Just in case
close(client);
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return NULL;
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}
/* Setup the address and return socket fd */
static int setup_socket(struct sockaddr_un *sun) {
int fd = xsocket(AF_LOCAL, SOCK_STREAM, 0);
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if (fcntl(fd, F_SETFD, FD_CLOEXEC))
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PLOGE("fcntl FD_CLOEXEC");
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memset(sun, 0, sizeof(*sun));
sun->sun_family = AF_LOCAL;
memcpy(sun->sun_path, REQUESTOR_DAEMON_PATH, REQUESTOR_DAEMON_PATH_LEN);
return fd;
}
static void *large_sepol_patch(void *args) {
LOGD("sepol: Starting large patch thread\n");
// Patch su to everything
sepol_allow("su", ALL, ALL, ALL);
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dump_policydb(SELINUX_LOAD);
LOGD("sepol: Large patch done\n");
destroy_policydb();
return NULL;
}
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void start_daemon(int client) {
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// Launch the daemon, create new session, set proper context
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if (getuid() != UID_ROOT || getgid() != UID_ROOT) {
fprintf(stderr, "Starting daemon requires root: %s\n", strerror(errno));
PLOGE("start daemon");
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}
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switch (fork()) {
case -1:
PLOGE("fork");
case 0:
break;
default:
return;
}
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// First close the client, it's useless for us
close(client);
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xsetsid();
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setcon("u:r:su:s0");
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umask(022);
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null_fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
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xdup2(null_fd, STDIN_FILENO);
xdup2(null_fd, STDOUT_FILENO);
xdup2(null_fd, STDERR_FILENO);
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// Patch selinux with medium patch before we do anything
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load_policydb(SELINUX_POLICY);
sepol_med_rules();
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dump_policydb(SELINUX_LOAD);
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// Continue the larger patch in another thread, we will join later
pthread_create(&sepol_patch, NULL, large_sepol_patch, NULL);
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struct sockaddr_un sun;
int fd = setup_socket(&sun);
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xbind(fd, (struct sockaddr*) &sun, sizeof(sun));
xlisten(fd, 10);
// Change process name
strcpy(argv0, "magisk_daemon");
// The root daemon should not do anything if an error occurs
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// It should stay intact under any circumstances
err_handler = do_nothing;
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LOGI("Magisk v" xstr(MAGISK_VERSION) " daemon started\n");
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// Unlock all blocks for rw
unlock_blocks();
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// Setup links under /sbin
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xmount(NULL, "/", NULL, MS_REMOUNT, NULL);
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create_links(NULL, "/sbin");
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xchmod("/sbin", 0755);
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xmkdir("/magisk", 0755);
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xchmod("/magisk", 0755);
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xmount(NULL, "/", NULL, MS_REMOUNT | MS_RDONLY, NULL);
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// Loop forever to listen for requests
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while(1) {
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int *client = xmalloc(sizeof(int));
*client = xaccept(fd, NULL, NULL);
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// Just in case, set to close on exec
fcntl(*client, F_SETFD, FD_CLOEXEC);
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pthread_t thread;
xpthread_create(&thread, NULL, request_handler, client);
// Detach the thread, we will never join it
pthread_detach(thread);
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}
}
/* Connect the daemon, and return a socketfd */
int connect_daemon() {
struct sockaddr_un sun;
int fd = setup_socket(&sun);
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// LOGD("client: trying to connect socket\n");
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if (connect(fd, (struct sockaddr*) &sun, sizeof(sun))) {
/* If we cannot access the daemon, we start the daemon
* since there is no clear entry point when the daemon should be started
*/
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LOGD("client: connect fail, try launching new daemon process\n");
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start_daemon(fd);
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do {
// Wait for 10ms
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usleep(10);
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} while (connect(fd, (struct sockaddr*) &sun, sizeof(sun)));
}
return fd;
}