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Magisk/daemon.c
topjohnwu 3dfcc6b0be Checkout from seSuperuser/Superuser, leaving only native parts 
- Checkout from https://github.com/seSuperuser/Superuser (commit: 69f84dd7a035b4a9f18dea69d9e0452bf0f73103)
- Move Superuser/Superuser/jni/su/* to root
- Move Superuser/jni/sqlite3/* to sqlite3
2018-07-18 18:12:47 +08:00

827 lines
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/*
** Copyright 2010, Adam Shanks (@ChainsDD)
** Copyright 2008, Zinx Verituse (@zinxv)
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
#define _GNU_SOURCE /* for unshare() */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <sys/select.h>
#include <sys/time.h>
#include <unistd.h>
#include <limits.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <stdint.h>
#include <pwd.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#include <stdarg.h>
#include <sys/types.h>
#include <pthread.h>
#include <sched.h>
#include <termios.h>
#include <signal.h>
#include <string.h>
#include <selinux/selinux.h>
#ifdef SUPERUSER_EMBEDDED
#include <cutils/multiuser.h>
#endif
#include "binds.h"
#include "su.h"
#include "utils.h"
#include "pts.h"
int is_daemon = 0;
int daemon_from_uid = 0;
int daemon_from_pid = 0;
// Constants for the atty bitfield
#define ATTY_IN 1
#define ATTY_OUT 2
#define ATTY_ERR 4
/*
* Receive a file descriptor from a Unix socket.
* Contributed by @mkasick
*
* Returns the file descriptor on success, or -1 if a file
* descriptor was not actually included in the message
*
* On error the function terminates by calling exit(-1)
*/
static int recv_fd(int sockfd) {
// Need to receive data from the message, otherwise don't care about it.
char iovbuf;
struct iovec iov = {
.iov_base = &iovbuf,
.iov_len = 1,
};
char cmsgbuf[CMSG_SPACE(sizeof(int))];
struct msghdr msg = {
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cmsgbuf,
.msg_controllen = sizeof(cmsgbuf),
};
if (recvmsg(sockfd, &msg, MSG_WAITALL) != 1) {
goto error;
}
// Was a control message actually sent?
switch (msg.msg_controllen) {
case 0:
// No, so the file descriptor was closed and won't be used.
return -1;
case sizeof(cmsgbuf):
// Yes, grab the file descriptor from it.
break;
default:
goto error;
}
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg == NULL ||
cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
cmsg->cmsg_level != SOL_SOCKET ||
cmsg->cmsg_type != SCM_RIGHTS) {
error:
LOGE("unable to read fd");
exit(-1);
}
return *(int *)CMSG_DATA(cmsg);
}
/*
* Send a file descriptor through a Unix socket.
* Contributed by @mkasick
*
* On error the function terminates by calling exit(-1)
*
* fd may be -1, in which case the dummy data is sent,
* but no control message with the FD is sent.
*/
static void send_fd(int sockfd, int fd) {
// Need to send some data in the message, this will do.
struct iovec iov = {
.iov_base = "",
.iov_len = 1,
};
struct msghdr msg = {
.msg_iov = &iov,
.msg_iovlen = 1,
};
char cmsgbuf[CMSG_SPACE(sizeof(int))];
if (fd != -1) {
// Is the file descriptor actually open?
if (fcntl(fd, F_GETFD) == -1) {
if (errno != EBADF) {
goto error;
}
// It's closed, don't send a control message or sendmsg will EBADF.
} else {
// It's open, send the file descriptor in a control message.
msg.msg_control = cmsgbuf;
msg.msg_controllen = sizeof(cmsgbuf);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
*(int *)CMSG_DATA(cmsg) = fd;
}
}
if (sendmsg(sockfd, &msg, 0) != 1) {
error:
PLOGE("unable to send fd");
exit(-1);
}
}
static int read_int(int fd) {
int val;
int len = read(fd, &val, sizeof(int));
if (len != sizeof(int)) {
LOGE("unable to read int: %d", len);
exit(-1);
}
return val;
}
static void write_int(int fd, int val) {
int written = write(fd, &val, sizeof(int));
if (written != sizeof(int)) {
PLOGE("unable to write int");
exit(-1);
}
}
static char* read_string(int fd) {
int len = read_int(fd);
if (len > PATH_MAX || len < 0) {
LOGE("invalid string length %d", len);
exit(-1);
}
char* val = malloc(sizeof(char) * (len + 1));
if (val == NULL) {
LOGE("unable to malloc string");
exit(-1);
}
val[len] = '\0';
int amount = read(fd, val, len);
if (amount != len) {
LOGE("unable to read string");
exit(-1);
}
return val;
}
static void write_string(int fd, char* val) {
int len = strlen(val);
write_int(fd, len);
int written = write(fd, val, len);
if (written != len) {
PLOGE("unable to write string");
exit(-1);
}
}
#ifdef SUPERUSER_EMBEDDED
static void mount_emulated_storage(int user_id) {
const char *emulated_source = getenv("EMULATED_STORAGE_SOURCE");
const char *emulated_target = getenv("EMULATED_STORAGE_TARGET");
const char* legacy = getenv("EXTERNAL_STORAGE");
if (!emulated_source || !emulated_target) {
// No emulated storage is present
return;
}
// Create a second private mount namespace for our process
if (unshare(CLONE_NEWNS) < 0) {
PLOGE("unshare");
return;
}
if (mount("rootfs", "/", NULL, MS_SLAVE | MS_REC, NULL) < 0) {
PLOGE("mount rootfs as slave");
return;
}
// /mnt/shell/emulated -> /storage/emulated
if (mount(emulated_source, emulated_target, NULL, MS_BIND, NULL) < 0) {
PLOGE("mount emulated storage");
}
char target_user[PATH_MAX];
snprintf(target_user, PATH_MAX, "%s/%d", emulated_target, user_id);
// /mnt/shell/emulated/<user> -> /storage/emulated/legacy
if (mount(target_user, legacy, NULL, MS_BIND | MS_REC, NULL) < 0) {
PLOGE("mount legacy path");
}
}
#endif
static int run_daemon_child(int infd, int outfd, int errfd, int argc, char** argv) {
if (-1 == dup2(outfd, STDOUT_FILENO)) {
PLOGE("dup2 child outfd");
exit(-1);
}
if (-1 == dup2(errfd, STDERR_FILENO)) {
PLOGE("dup2 child errfd");
exit(-1);
}
if (-1 == dup2(infd, STDIN_FILENO)) {
PLOGE("dup2 child infd");
exit(-1);
}
close(infd);
close(outfd);
close(errfd);
return su_main_nodaemon(argc, argv);
}
static int daemon_accept(int fd) {
is_daemon = 1;
int pid = read_int(fd);
LOGD("remote pid: %d", pid);
char *pts_slave = read_string(fd);
LOGD("remote pts_slave: %s", pts_slave);
daemon_from_uid = read_int(fd);
LOGD("remote uid: %d", daemon_from_uid);
daemon_from_pid = read_int(fd);
LOGD("remote req pid: %d", daemon_from_pid);
struct ucred credentials;
int ucred_length = sizeof(struct ucred);
/* fill in the user data structure */
if(getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &credentials, &ucred_length)) {
LOGE("could obtain credentials from unix domain socket");
exit(-1);
}
// if the credentials on the other side of the wire are NOT root,
// we can't trust anything being sent.
if (credentials.uid != 0) {
daemon_from_uid = credentials.uid;
pid = credentials.pid;
daemon_from_pid = credentials.pid;
}
int mount_storage = read_int(fd);
// The the FDs for each of the streams
int infd = recv_fd(fd);
int outfd = recv_fd(fd);
int errfd = recv_fd(fd);
int argc = read_int(fd);
if (argc < 0 || argc > 512) {
LOGE("unable to allocate args: %d", argc);
exit(-1);
}
LOGD("remote args: %d", argc);
char** argv = (char**)malloc(sizeof(char*) * (argc + 1));
argv[argc] = NULL;
int i;
for (i = 0; i < argc; i++) {
argv[i] = read_string(fd);
}
// ack
write_int(fd, 1);
// Fork the child process. The fork has to happen before calling
// setsid() and opening the pseudo-terminal so that the parent
// is not affected
int child = fork();
if (child < 0) {
// fork failed, send a return code and bail out
PLOGE("unable to fork");
write(fd, &child, sizeof(int));
close(fd);
return child;
}
if (child != 0) {
// In parent, wait for the child to exit, and send the exit code
// across the wire.
int status, code;
free(pts_slave);
LOGD("waiting for child exit");
if (waitpid(child, &status, 0) > 0) {
code = WEXITSTATUS(status);
}
else {
code = -1;
}
// Pass the return code back to the client
LOGD("sending code");
if (write(fd, &code, sizeof(int)) != sizeof(int)) {
PLOGE("unable to write exit code");
}
close(fd);
LOGD("child exited");
return code;
}
// We are in the child now
// Close the unix socket file descriptor
close (fd);
// Become session leader
if (setsid() == (pid_t) -1) {
PLOGE("setsid");
}
int ptsfd;
if (pts_slave[0]) {
//Check pts_slave file is owned by daemon_from_uid
{
struct stat stbuf;
int res = stat(pts_slave, &stbuf);
if(res) {
PLOGE("stat(pts_slave) daemon");
exit(-1);
}
//If caller is not root, ensure the owner of pts_slave is the caller
if(stbuf.st_uid != credentials.uid &&
credentials.uid != 0) {
PLOGE("Wrong permission of pts_slave");
exit(-1);
}
}
// Opening the TTY has to occur after the
// fork() and setsid() so that it becomes
// our controlling TTY and not the daemon's
ptsfd = open(pts_slave, O_RDWR);
if (ptsfd == -1) {
PLOGE("open(pts_slave) daemon");
exit(-1);
}
//Check we haven't been fooled
{
struct stat stbuf;
int res = fstat(ptsfd, &stbuf);
if(res) {
//If we have been fooled DO NOT WRITE ANYTHING
_exit(2);
}
if(stbuf.st_uid != credentials.uid &&
credentials.uid != 0) {
_exit(2);
}
}
if (infd < 0) {
LOGD("daemon: stdin using PTY");
infd = ptsfd;
}
if (outfd < 0) {
LOGD("daemon: stdout using PTY");
outfd = ptsfd;
}
if (errfd < 0) {
LOGD("daemon: stderr using PTY");
errfd = ptsfd;
}
} else {
// If a TTY was sent directly, make it the CTTY.
if (isatty(infd)) {
ioctl(infd, TIOCSCTTY, 1);
}
}
free(pts_slave);
#ifdef SUPERUSER_EMBEDDED
if (mount_storage) {
mount_emulated_storage(multiuser_get_user_id(daemon_from_uid));
}
#endif
return run_daemon_child(infd, outfd, errfd, argc, argv);
}
static int copy_file(const char* src, const char* dst, int mode) {
int ifd = open(src, O_RDONLY);
if(ifd<0)
return 1;
if(mode == 0) {
struct stat stbuf;
if(fstat(ifd, &stbuf))
return 1;
mode = stbuf.st_mode & 0777;
LOGE("File %s found mode %o", src, mode);
}
int ofd = open(dst, O_WRONLY|O_CREAT, mode);
if(ofd<0)
return 1;
size_t s = lseek(ifd, 0, SEEK_END);
if(s<0)
return 1;
lseek(ifd, 0, SEEK_SET);
int ret = sendfile(ofd, ifd, NULL, s);
if(ret<0)
return 1;
close(ofd);
close(ifd);
return 0;
}
static void prepare_su_bind() {
int ret = 0;
//Check if there is a use to mount bind
if(access("/system/xbin/su", R_OK) != 0)
return;
ret = copy_file("/sbin/su", "/dev/su/su", 0755);
if(ret) {
PLOGE("Failed to copy su");
return;
}
chmod("/dev/su/su", 0755);
ret = setfilecon("/dev/su/su", "u:object_r:system_file:s0");
if(ret) {
LOGE("Failed to set file context");
return;
}
ret = mount("/dev/su/su", "/system/xbin/su", "", MS_BIND, NULL);
if(ret) {
LOGE("Failed to mount bind");
return;
}
}
static void prepare_binds() {
mkdir("/data/su", 0700);
static int i = 0;
auto void cb(void *arg, int uid, const char *src, const char *dst) {
int ret = 0;
char *tmpfile = NULL;
asprintf(&tmpfile, "/dev/su/bind%d", i++);
struct stat stbuf;
ret = stat(src, &stbuf);
if(ret) {
free(tmpfile);
LOGE("Failed to stat src %s file", src);
return;
}
//Only shell uid is allowed to bind files not his own
if(uid != 2000 && uid != stbuf.st_uid) {
LOGE("File %s has wrong owner: %d vs %d", src, uid, stbuf.st_uid);
return;
}
ret = copy_file(src, tmpfile, 0);
if(ret) {
free(tmpfile);
PLOGE("Failed to copy su");
return;
}
chmod(tmpfile, stbuf.st_mode);
ret = setfilecon(tmpfile, "u:object_r:system_file:s0");
if(ret) {
LOGE("Failed to set file context");
return;
}
ret = mount(tmpfile, dst, "", MS_BIND, NULL);
if(ret) {
LOGE("Failed to mount bind");
return;
}
}
bind_foreach(cb, NULL);
}
static void do_init() {
auto void cb(void *arg, int uid, const char *path) {
int ret = 0;
int p = fork();
if(p)
return;
while(access("/system/bin/sh", R_OK)) sleep(1);
ret = setexeccon("u:r:su:s0");
execl(path, path, NULL);
LOGE("Failed to execute %s. Trying as shell script, ret = %d", path, ret);
ret = setexeccon("u:r:su:s0");
execl("/system/bin/sh", "/system/bin/sh", path, NULL);
LOGE("Failed to execute %s as shell script", path);
_exit(1);
}
init_foreach(cb, NULL);
}
static void prepare() {
setfscreatecon("u:object_r:su_daemon:s0");
mkdir("/dev/su", 0700);
prepare_su_bind();
prepare_binds();
do_init();
setfscreatecon(NULL);
}
int run_daemon() {
if (getuid() != 0 || getgid() != 0) {
PLOGE("daemon requires root. uid/gid not root");
return -1;
}
prepare();
int fd;
struct sockaddr_un sun;
fd = socket(AF_LOCAL, SOCK_STREAM, 0);
if (fd < 0) {
PLOGE("socket");
return -1;
}
if (fcntl(fd, F_SETFD, FD_CLOEXEC)) {
PLOGE("fcntl FD_CLOEXEC");
goto err;
}
memset(&sun, 0, sizeof(sun));
sun.sun_family = AF_LOCAL;
sprintf(sun.sun_path, "%s/server", REQUESTOR_DAEMON_PATH);
/*
* Delete the socket to protect from situations when
* something bad occured previously and the kernel reused pid from that process.
* Small probability, isn't it.
*/
unlink(sun.sun_path);
unlink(REQUESTOR_DAEMON_PATH);
int previous_umask = umask(027);
mkdir(REQUESTOR_DAEMON_PATH, 0777);
memset(sun.sun_path, 0, sizeof(sun.sun_path));
memcpy(sun.sun_path, "\0" "SUPERUSER", strlen("SUPERUSER") + 1);
if (bind(fd, (struct sockaddr*)&sun, sizeof(sun)) < 0) {
PLOGE("daemon bind");
goto err;
}
chmod(REQUESTOR_DAEMON_PATH, 0755);
chmod(sun.sun_path, 0777);
umask(previous_umask);
if (listen(fd, 10) < 0) {
PLOGE("daemon listen");
goto err;
}
int client;
while ((client = accept(fd, NULL, NULL)) > 0) {
if (fork_zero_fucks() == 0) {
close(fd);
return daemon_accept(client);
}
else {
close(client);
}
}
LOGE("daemon exiting");
err:
close(fd);
return -1;
}
// List of signals which cause process termination
static int quit_signals[] = { SIGALRM, SIGHUP, SIGPIPE, SIGQUIT, SIGTERM, SIGINT, 0 };
static void sighandler(int sig) {
(void)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;
int i;
memset(&act, '\0', sizeof(act));
act.sa_handler = SIG_DFL;
for (i = 0; quit_signals[i]; i++) {
if (sigaction(quit_signals[i], &act, NULL) < 0) {
PLOGE("Error removing signal handler");
continue;
}
}
}
/**
* Setup signal handlers trap signals which should result in program termination
* so that we can restore the terminal to its normal state and retrieve the
* return code.
*/
static void setup_sighandlers(void) {
struct sigaction act;
int i;
// Install the termination handlers
// Note: we're assuming that none of these signal handlers are already trapped.
// If they are, we'll need to modify this code to save the previous handler and
// call it after we restore stdin to its previous state.
memset(&act, '\0', sizeof(act));
act.sa_handler = &sighandler;
for (i = 0; quit_signals[i]; i++) {
if (sigaction(quit_signals[i], &act, NULL) < 0) {
PLOGE("Error installing signal handler");
continue;
}
}
}
int connect_daemon(int argc, char *argv[], int ppid) {
int uid = getuid();
int ptmx = -1;
char pts_slave[PATH_MAX];
struct sockaddr_un sun;
// Open a socket to the daemon
int socketfd = socket(AF_LOCAL, SOCK_STREAM, 0);
if (socketfd < 0) {
PLOGE("socket");
exit(-1);
}
if (fcntl(socketfd, F_SETFD, FD_CLOEXEC)) {
PLOGE("fcntl FD_CLOEXEC");
exit(-1);
}
memset(&sun, 0, sizeof(sun));
sun.sun_family = AF_LOCAL;
sprintf(sun.sun_path, "%s/server", REQUESTOR_DAEMON_PATH);
memset(sun.sun_path, 0, sizeof(sun.sun_path));
memcpy(sun.sun_path, "\0" "SUPERUSER", strlen("SUPERUSER") + 1);
if (0 != connect(socketfd, (struct sockaddr*)&sun, sizeof(sun))) {
PLOGE("connect");
exit(-1);
}
LOGD("connecting client %d", getpid());
int mount_storage = getenv("MOUNT_EMULATED_STORAGE") != NULL;
// Determine which one of our streams are attached to a TTY
int atty = 0;
// Send TTYs directly (instead of proxying with a PTY) if
// the SUPERUSER_SEND_TTY environment variable is set.
if (getenv("SUPERUSER_SEND_TTY") == NULL) {
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));
if (ptmx < 0) {
PLOGE("pts_open");
exit(-1);
}
} else {
pts_slave[0] = '\0';
}
// Send some info to the daemon, starting with our PID
write_int(socketfd, getpid());
// Send the slave path to the daemon
// (This is "" if we're not using PTYs)
write_string(socketfd, pts_slave);
// User ID
write_int(socketfd, uid);
// Parent PID
write_int(socketfd, ppid);
write_int(socketfd, mount_storage);
// Send stdin
if (atty & ATTY_IN) {
// Using PTY
send_fd(socketfd, -1);
} else {
send_fd(socketfd, STDIN_FILENO);
}
// Send stdout
if (atty & ATTY_OUT) {
// Forward SIGWINCH
watch_sigwinch_async(STDOUT_FILENO, ptmx);
// Using PTY
send_fd(socketfd, -1);
} else {
send_fd(socketfd, STDOUT_FILENO);
}
// Send stderr
if (atty & ATTY_ERR) {
// Using PTY
send_fd(socketfd, -1);
} else {
send_fd(socketfd, STDERR_FILENO);
}
// Number of command line arguments
write_int(socketfd, mount_storage ? argc - 1 : argc);
// Command line arguments
int i;
for (i = 0; i < argc; i++) {
if (i == 1 && mount_storage) {
continue;
}
write_string(socketfd, argv[i]);
}
// Wait for acknowledgement from daemon
read_int(socketfd);
if (atty & ATTY_IN) {
setup_sighandlers();
pump_stdin_async(ptmx);
}
if (atty & ATTY_OUT) {
pump_stdout_blocking(ptmx);
}
// Get the exit code
int code = read_int(socketfd);
close(socketfd);
LOGD("client exited %d", code);
return code;
}
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