selinux_native/jni/utils/pts.c
/*
* Copyright 2013, Tan Chee Eng (@tan-ce)
*
* 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.
*/
/*
* pts.c
*
* Manages the pseudo-terminal driver on Linux/Android and provides some
* helper functions to handle raw input mode and terminal window resizing
*/
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <termios.h>
#include <errno.h>
#include <pthread.h>
#include "deobfuscate.h"
#include "pts.h"
static unsigned char dev_ptmx[] = "\x4f\xa0\xe6\xa0\x6b\x6a\x79\xa0\x7f\x7b\x62\x77"; // "/dev/ptmx"
/*
* Helper functions
*/
// Ensures all the data is written out
static int write_blocking(int fd, char *buf, size_t bufsz) {
ssize_t ret, written;
written = 0;
do {
ret = write(fd, buf + written, bufsz - written);
if (ret == -1) return -1;
written += ret;
} while (written < bufsz);
return 0;
}
/*
* Pump data from input FD to output FD. If close_output is
* true, then close the output FD when we're done.
*/
static void pump_ex(int input, int output, int close_output) {
char buf[4096];
int len;
while ((len = read(input, buf, 4096)) > 0) {
if (write_blocking(output, buf, len) == -1) break;
}
close(input);
if (close_output) close(output);
}
/*
* Pump data from input FD to output FD. Will close the
* output FD when done.
*/
static void pump(int input, int output) {
pump_ex(input, output, 1);
}
static void* pump_thread(void* data) {
int* files = (int*)data;
int input = files[0];
int output = files[1];
pump(input, output);
free(data);
return NULL;
}
static void pump_async(int input, int output) {
pthread_t writer;
int* files = (int*)malloc(sizeof(int) * 2);
if (files == NULL) {
exit(-1);
}
files[0] = input;
files[1] = output;
pthread_create(&writer, NULL, pump_thread, files);
}
/*
* pts_open
*
* Opens a pts device and returns the name of the slave tty device.
*
* Arguments
* slave_name the name of the slave device
* slave_name_size the size of the buffer passed via slave_name
*
* Return Values
* on failure either -2 or -1 (errno set) is returned.
* on success, the file descriptor of the master device is returned.
*/
int pts_open(char *slave_name, size_t slave_name_size) {
int fdm;
char *sn_tmp;
// Open master ptmx device
fdm = open(deobfuscate(dev_ptmx), O_RDWR);
if (fdm == -1) return -1;
// Get the slave name
sn_tmp = ptsname(fdm);
if (!sn_tmp) {
close(fdm);
return -2;
}
strncpy(slave_name, sn_tmp, slave_name_size);
slave_name[slave_name_size - 1] = '\0';
// Grant, then unlock
if (grantpt(fdm) == -1) {
close(fdm);
return -1;
}
if (unlockpt(fdm) == -1) {
close(fdm);
return -1;
}
return fdm;
}
// Stores the previous termios of stdin
static struct termios old_stdin;
static int stdin_is_raw = 0;
/*
* set_stdin_raw
*
* Changes stdin to raw unbuffered mode, disables echo,
* auto carriage return, etc.
*
* Return Value
* on failure -1, and errno is set
* on success 0
*/
int set_stdin_raw(void) {
struct termios new_termios;
// Save the current stdin termios
if (tcgetattr(STDIN_FILENO, &old_stdin) < 0) {
return -1;
}
// Start from the current settings
new_termios = old_stdin;
// Make the terminal like an SSH or telnet client
new_termios.c_iflag |= IGNPAR;
new_termios.c_iflag &= ~(ISTRIP | INLCR | IGNCR | ICRNL | IXON | IXANY | IXOFF);
new_termios.c_lflag &= ~(ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHONL);
new_termios.c_oflag &= ~OPOST;
new_termios.c_cc[VMIN] = 1;
new_termios.c_cc[VTIME] = 0;
if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &new_termios) < 0) {
return -1;
}
stdin_is_raw = 1;
return 0;
}
/*
* restore_stdin
*
* Restore termios on stdin to the state it was before
* set_stdin_raw() was called. If set_stdin_raw() was
* never called, does nothing and doesn't return an error.
*
* This function is async-safe.
*
* Return Value
* on failure, -1 and errno is set
* on success, 0
*/
int restore_stdin(void) {
if (!stdin_is_raw) return 0;
if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &old_stdin) < 0) {
return -1;
}
stdin_is_raw = 0;
return 0;
}
// Flag indicating whether the sigwinch watcher should terminate.
volatile static int closing_time = 0;
/*
* Thread process. Wait for a SIGWINCH to be received, then update
* the terminal size.
*/
static void *watch_sigwinch(void *data) {
sigset_t winch;
int sig;
int master = ((int *)data)[0];
int slave = ((int *)data)[1];
sigemptyset(&winch);
sigaddset(&winch, SIGWINCH);
do {
// Wait for a SIGWINCH
sigwait(&winch, &sig);
if (closing_time) break;
// Get the new terminal size
struct winsize w;
if (ioctl(master, TIOCGWINSZ, &w) == -1) {
continue;
}
// Set the new terminal size
ioctl(slave, TIOCSWINSZ, &w);
} while (1);
free(data);
return NULL;
}
/*
* watch_sigwinch_async
*
* After calling this function, if the application receives
* SIGWINCH, the terminal window size will be read from
* "input" and set on "output".
*
* NOTE: This function blocks SIGWINCH and spawns a thread.
* NOTE 2: This function must be called before any of the
* pump functions.
*
* Arguments
* master A file descriptor of the TTY window size to follow
* slave A file descriptor of the TTY window size which is
* to be set on SIGWINCH
*
* Return Value
* on failure, -1 and errno will be set. In this case, no
* thread has been spawned and SIGWINCH will not be
* blocked.
* on success, 0
*/
int watch_sigwinch_async(int master, int slave) {
pthread_t watcher;
int *files = (int *) malloc(sizeof(int) * 2);
if (files == NULL) {
return -1;
}
// Block SIGWINCH so sigwait can later receive it
sigset_t winch;
sigemptyset(&winch);
sigaddset(&winch, SIGWINCH);
if (sigprocmask(SIG_BLOCK, &winch, NULL) == -1) {
free(files);
return -1;
}
// Initialize some variables, then start the thread
closing_time = 0;
files[0] = master;
files[1] = slave;
int ret = pthread_create(&watcher, NULL, &watch_sigwinch, files);
if (ret != 0) {
free(files);
errno = ret;
return -1;
}
// Set the initial terminal size
raise(SIGWINCH);
}
/*
* watch_sigwinch_cleanup
*
* Cause the SIGWINCH watcher thread to terminate
*/
void watch_sigwinch_cleanup(void) {
closing_time = 1;
raise(SIGWINCH);
}
/*
* pump_stdin_async
*
* Forward data from STDIN to the given FD
* in a seperate thread
*/
void pump_stdin_async(int outfd) {
// Put stdin into raw mode
set_stdin_raw();
// Pump data from stdin to the PTY
pump_async(STDIN_FILENO, outfd);
}
/*
* pump_stdout_blocking
*
* Forward data from the FD to STDOUT.
* Returns when the remote end of the FD closes.
*
* Before returning, restores stdin settings.
*/
void pump_stdout_blocking(int infd) {
// Pump data from stdout to PTY
pump_ex(infd, STDOUT_FILENO, 0 /* Don't close output when done */);
// Cleanup
restore_stdin();
watch_sigwinch_cleanup();
}