Magisk/native/jni/su/su_daemon.c
2018-08-02 20:29:18 +08:00

437 lines
10 KiB
C

/* su_daemon.c - The entrypoint for su, connect to daemon and send correct info
*/
#define _GNU_SOURCE
#include <limits.h>
#include <unistd.h>
#include <pthread.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <selinux/selinux.h>
#include "magisk.h"
#include "daemon.h"
#include "utils.h"
#include "su.h"
#include "pts.h"
#include "list.h"
// Constants for the atty bitfield
#define ATTY_IN 1
#define ATTY_OUT 2
#define ATTY_ERR 4
#define TIMEOUT 3
#define LOCK_LIST() pthread_mutex_lock(&list_lock)
#define LOCK_UID() pthread_mutex_lock(&info->lock)
#define UNLOCK_LIST() pthread_mutex_unlock(&list_lock)
#define UNLOCK_UID() pthread_mutex_unlock(&ctx.info->lock)
static struct list_head info_cache = { .prev = &info_cache, .next = &info_cache };
static pthread_mutex_t list_lock = PTHREAD_MUTEX_INITIALIZER;
static void sighandler(int sig) {
restore_stdin();
// Assume we'll only be called before death
// See note before sigaction() in set_stdin_raw()
//
// Now, close all standard I/O to cause the pumps
// to exit so we can continue and retrieve the exit
// code
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
// Put back all the default handlers
struct sigaction act;
memset(&act, 0, sizeof(act));
act.sa_handler = SIG_DFL;
for (int i = 0; quit_signals[i]; ++i) {
sigaction(quit_signals[i], &act, NULL);
}
}
static void *info_collector(void *node) {
struct su_info *info = node;
while (1) {
sleep(1);
if (info->clock && --info->clock == 0) {
LOCK_LIST();
list_pop(&info->pos);
UNLOCK_LIST();
}
if (!info->clock && !info->ref) {
pthread_mutex_destroy(&info->lock);
free(info);
return NULL;
}
}
}
static void database_check(struct su_info *info) {
int uid = info->uid;
sqlite3 *db = get_magiskdb();
if (db) {
get_db_settings(db, -1, &info->dbs);
get_db_strings(db, -1, &info->str);
// Check multiuser settings
switch (info->dbs.v[SU_MULTIUSER_MODE]) {
case MULTIUSER_MODE_OWNER_ONLY:
if (info->uid / 100000) {
uid = -1;
info->access = NO_SU_ACCESS;
}
break;
case MULTIUSER_MODE_OWNER_MANAGED:
uid = info->uid % 100000;
break;
case MULTIUSER_MODE_USER:
default:
break;
}
if (uid > 0)
get_uid_policy(db, uid, &info->access);
sqlite3_close(db);
}
// We need to check our manager
if (info->access.log || info->access.notify)
validate_manager(info->str.s[SU_MANAGER], uid / 100000, &info->manager_stat);
}
static struct su_info *get_su_info(unsigned uid) {
struct su_info *info = NULL, *node;
LOCK_LIST();
// Search for existing info in cache
list_for_each(node, &info_cache, struct su_info, pos) {
if (node->uid == uid) {
info = node;
break;
}
}
int cache_miss = info == NULL;
if (cache_miss) {
// If cache miss, create a new one and push to cache
info = malloc(sizeof(*info));
info->uid = uid;
info->dbs = DEFAULT_DB_SETTINGS;
info->access = DEFAULT_SU_ACCESS;
INIT_DB_STRINGS(&info->str);
info->ref = 0;
info->count = 0;
pthread_mutex_init(&info->lock, NULL);
list_insert_end(&info_cache, &info->pos);
}
// Update the cache status
info->clock = TIMEOUT;
++info->ref;
// Start a thread to maintain the info cache
if (cache_miss) {
pthread_t thread;
xpthread_create(&thread, NULL, info_collector, info);
pthread_detach(thread);
}
UNLOCK_LIST();
LOGD("su: request from uid=[%d] (#%d)\n", info->uid, ++info->count);
// Lock before the policy is determined
LOCK_UID();
if (info->access.policy == QUERY) {
// Not cached, get data from database
database_check(info);
// Check su access settings
switch (info->dbs.v[ROOT_ACCESS]) {
case ROOT_ACCESS_DISABLED:
LOGE("Root access is disabled!\n");
info->access = NO_SU_ACCESS;
break;
case ROOT_ACCESS_ADB_ONLY:
if (info->uid != UID_SHELL) {
LOGE("Root access limited to ADB only!\n");
info->access = NO_SU_ACCESS;
}
break;
case ROOT_ACCESS_APPS_ONLY:
if (info->uid == UID_SHELL) {
LOGE("Root access is disabled for ADB!\n");
info->access = NO_SU_ACCESS;
}
break;
case ROOT_ACCESS_APPS_AND_ADB:
default:
break;
}
// If it's the manager, allow it silently
if ((info->uid % 100000) == (info->manager_stat.st_uid % 100000))
info->access = SILENT_SU_ACCESS;
// Allow if it's root
if (info->uid == UID_ROOT)
info->access = SILENT_SU_ACCESS;
// If still not determined, check if manager exists
if (info->access.policy == QUERY && info->str.s[SU_MANAGER][0] == '\0')
info->access = NO_SU_ACCESS;
}
return info;
}
static void su_executor(int client) {
LOGD("su: executor started\n");
// Become session leader
xsetsid();
// Migrate environment from client
char path[32], buf[4096];
snprintf(path, sizeof(path), "/proc/%d/cwd", su_ctx->pid);
xreadlink(path, su_ctx->cwd, sizeof(su_ctx->cwd));
snprintf(path, sizeof(path), "/proc/%d/environ", su_ctx->pid);
memset(buf, 0, sizeof(buf));
int fd = open(path, O_RDONLY);
read(fd, buf, sizeof(buf));
clearenv();
for (size_t pos = 0; buf[pos];) {
putenv(buf + pos);
pos += strlen(buf + pos) + 1;
}
// Let's read some info from the socket
int argc = read_int(client);
if (argc < 0 || argc > 512) {
LOGE("unable to allocate args: %d", argc);
exit2(1);
}
LOGD("su: argc=[%d]\n", argc);
char **argv = (char**) xmalloc(sizeof(char*) * (argc + 1));
argv[argc] = NULL;
for (int i = 0; i < argc; i++) {
argv[i] = read_string(client);
LOGD("su: argv[%d]=[%s]\n", i, argv[i]);
// Replace -cn with -z, -mm with -M for supporting getopt_long
if (strcmp(argv[i], "-cn") == 0)
strcpy(argv[i], "-z");
else if (strcmp(argv[i], "-mm") == 0)
strcpy(argv[i], "-M");
}
// Get pts_slave
char *pts_slave = read_string(client);
// The FDs for each of the streams
int infd = recv_fd(client);
int outfd = recv_fd(client);
int errfd = recv_fd(client);
int ptsfd = -1;
if (pts_slave[0]) {
LOGD("su: pts_slave=[%s]\n", pts_slave);
// Check pts_slave file is owned by daemon_from_uid
struct stat st;
xstat(pts_slave, &st);
// If caller is not root, ensure the owner of pts_slave is the caller
if(st.st_uid != su_ctx->info->uid && su_ctx->info->uid != 0) {
LOGE("su: Wrong permission of pts_slave");
su_ctx->info->access.policy = DENY;
exit2(1);
}
// Set our pts_slave to devpts, same restriction as adb shell
lsetfilecon(pts_slave, "u:object_r:devpts:s0");
// Opening the TTY has to occur after the
// fork() and setsid() so that it becomes
// our controlling TTY and not the daemon's
ptsfd = xopen(pts_slave, O_RDWR);
if (infd < 0) {
LOGD("su: stdin using PTY");
infd = ptsfd;
}
if (outfd < 0) {
LOGD("su: stdout using PTY");
outfd = ptsfd;
}
if (errfd < 0) {
LOGD("su: stderr using PTY");
errfd = ptsfd;
}
}
free(pts_slave);
// Swap out stdin, stdout, stderr
xdup2(infd, STDIN_FILENO);
xdup2(outfd, STDOUT_FILENO);
xdup2(errfd, STDERR_FILENO);
close(ptsfd);
// ack and close
write_int(client, 0);
close(client);
// Run the actual main
su_daemon_main(argc, argv);
}
void su_daemon_receiver(int client, struct ucred *credential) {
LOGD("su: request from client: %d\n", client);
// Default values
struct su_context ctx = {
.info = get_su_info(credential->uid),
.to = {
.uid = UID_ROOT,
.login = 0,
.keepenv = 0,
.shell = DEFAULT_SHELL,
.command = NULL,
},
.pid = credential->pid,
.pipefd = { -1, -1 }
};
// Fail fast
if (ctx.info->access.policy == DENY && !ctx.info->access.log && !ctx.info->access.notify) {
UNLOCK_UID();
write_int(client, DENY);
return;
}
// If still not determined, open a pipe and wait for results
if (ctx.info->access.policy == QUERY)
xpipe2(ctx.pipefd, O_CLOEXEC);
/* Fork a new process, the child process will need to setsid,
* open a pseudo-terminal if needed, and will eventually run exec
* The parent process will wait for the result and
* send the return code back to our client
*/
int child = xfork();
if (child == 0) {
su_ctx = &ctx;
su_executor(client);
}
// Wait for results
if (ctx.pipefd[0] >= 0) {
xxread(ctx.pipefd[0], &ctx.info->access.policy, sizeof(policy_t));
close(ctx.pipefd[0]);
close(ctx.pipefd[1]);
}
// The policy is determined, unlock
UNLOCK_UID();
// Info is now useless to us, decrement reference count
--ctx.info->ref;
// Wait result
LOGD("su: waiting child: [%d]\n", child);
int status, code;
if (waitpid(child, &status, 0) > 0)
code = WEXITSTATUS(status);
else
code = -1;
LOGD("su: return code: [%d]\n", code);
write(client, &code, sizeof(code));
close(client);
return;
}
/*
* Connect daemon, send argc, argv, cwd, pts slave
*/
int su_client_main(int argc, char *argv[]) {
char pts_slave[PATH_MAX];
int ptmx, socketfd;
// Connect to client
socketfd = connect_daemon();
// Tell the daemon we are su
write_int(socketfd, SUPERUSER);
// Number of command line arguments
write_int(socketfd, argc);
// Command line arguments
for (int i = 0; i < argc; i++) {
write_string(socketfd, argv[i]);
}
// Determine which one of our streams are attached to a TTY
int atty = 0;
if (isatty(STDIN_FILENO)) atty |= ATTY_IN;
if (isatty(STDOUT_FILENO)) atty |= ATTY_OUT;
if (isatty(STDERR_FILENO)) atty |= ATTY_ERR;
if (atty) {
// We need a PTY. Get one.
ptmx = pts_open(pts_slave, sizeof(pts_slave));
} else {
pts_slave[0] = '\0';
}
// Send the pts_slave path to the daemon
write_string(socketfd, pts_slave);
// Send stdin
send_fd(socketfd, (atty & ATTY_IN) ? -1 : STDIN_FILENO);
// Send stdout
send_fd(socketfd, (atty & ATTY_OUT) ? -1 : STDOUT_FILENO);
// Send stderr
send_fd(socketfd, (atty & ATTY_ERR) ? -1 : STDERR_FILENO);
// Wait for acknowledgement from daemon
if (read_int(socketfd)) {
// Fast fail
fprintf(stderr, "%s\n", strerror(EACCES));
return DENY;
}
if (atty & ATTY_IN) {
setup_sighandlers(sighandler);
pump_stdin_async(ptmx);
}
if (atty & ATTY_OUT) {
// Forward SIGWINCH
watch_sigwinch_async(STDOUT_FILENO, ptmx);
pump_stdout_blocking(ptmx);
}
// Get the exit code
int code = read_int(socketfd);
close(socketfd);
return code;
}