Magisk/su_client.c
2017-05-08 03:08:34 +08:00

267 lines
5.6 KiB
C

/* su_client.c - The entrypoint for su, connect to daemon and send correct info
*/
#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 "magisk.h"
#include "daemon.h"
#include "utils.h"
#include "su.h"
#include "pts.h"
// Constants for the atty bitfield
#define ATTY_IN 1
#define ATTY_OUT 2
#define ATTY_ERR 4
struct ucred su_credentials;
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 sigpipe_handler(int sig) {
LOGD("su: Client killed unexpectedly\n");
}
void su_daemon_receiver(int client) {
LOGD("su: get request from client: %d\n", client);
// 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 = fork();
if (child < 0) {
write(client, &child, sizeof(child));
close(client);
PLOGE("fork");
return;
} else if (child != 0) {
// Wait result
LOGD("su: wait_result waiting for %d\n", child);
int status, code;
// Handle SIGPIPE, since we don't want to crash our daemon
struct sigaction act;
memset(&act, 0, sizeof(act));
act.sa_handler = sigpipe_handler;
sigaction(SIGPIPE, &act, NULL);
if (waitpid(child, &status, 0) > 0)
code = WEXITSTATUS(status);
else
code = -1;
// Pass the return code back to the client
write_int(client, code);
LOGD("su: return code to client: %d\n", code);
close(client);
return;
}
LOGD("su: child process started\n");
// ack
write_int(client, 1);
// Become session leader
xsetsid();
// Get the credentials
get_client_cred(client, &su_credentials);
// 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);
exit(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]);
}
// Change directory to cwd
char *cwd = read_string(client);
LOGD("su: cwd=[%s]\n", cwd);
chdir(cwd);
free(cwd);
// Get pts_slave
char *pts_slave = read_string(client);
LOGD("su: pts_slave=[%s]\n", pts_slave);
// The 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;
// We no longer need the access to socket in the child, close it
close(client);
if (pts_slave[0]) {
//Check pts_slave file is owned by daemon_from_uid
struct stat stbuf;
xstat(pts_slave, &stbuf);
//If caller is not root, ensure the owner of pts_slave is the caller
if(stbuf.st_uid != su_credentials.uid && su_credentials.uid != 0) {
LOGE("su: 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 = 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);
su_daemon_main(argc, argv);
}
/*
* Connect daemon, send argc, argv, cwd, pts slave
*/
int su_client_main(int argc, char *argv[]) {
char buffer[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]);
}
// CWD
getcwd(buffer, sizeof(buffer));
write_string(socketfd, buffer);
// 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(buffer, sizeof(buffer));
} else {
buffer[0] = '\0';
}
// Send the pts_slave path to the daemon
write_string(socketfd, buffer);
// 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);
}
// Wait for acknowledgement from daemon
read_int(socketfd);
if (atty & ATTY_IN) {
setup_sighandlers(sighandler);
pump_stdin_async(ptmx);
}
if (atty & ATTY_OUT) {
pump_stdout_blocking(ptmx);
}
// Get the exit code
int code = read_int(socketfd);
close(socketfd);
return code;
}