Magisk/native/jni/su/pts.cpp

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/*
* Copyright 2013, Tan Chee Eng (@tan-ce)
*/
/*
* 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>
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#include <magisk.h>
#include "pts.h"
/**
* Helper functions
*/
// Ensures all the data is written out
static int write_blocking(int fd, char *buf, ssize_t bufsz) {
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ssize_t ret, written;
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written = 0;
do {
ret = write(fd, buf + written, bufsz - written);
if (ret == -1) return -1;
written += ret;
} while (written < bufsz);
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return 0;
}
/**
* Pump data from input FD to output FD. If close_output is
* true, then close the output FD when we're done.
*/
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static void pump(int input, int output, bool close_output = true) {
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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);
}
static void* pump_thread(void* data) {
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int *fds = (int*) data;
pump(fds[0], fds[1]);
delete[] fds;
return nullptr;
}
static void pump_async(int input, int output) {
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pthread_t writer;
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int *fds = new int[2];
fds[0] = input;
fds[1] = output;
pthread_create(&writer, nullptr, pump_thread, fds);
}
/**
* 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) {
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int fdm;
// Open master ptmx device
fdm = open("/dev/ptmx", O_RDWR);
if (fdm == -1)
goto error;
// Get the slave name
if (ptsname_r(fdm, slave_name, slave_name_size-1))
goto error;
slave_name[slave_name_size - 1] = '\0';
// Grant, then unlock
if (grantpt(fdm) == -1)
goto error;
if (unlockpt(fdm) == -1)
goto error;
return fdm;
error:
close(fdm);
PLOGE("pts_open");
return -1;
}
// 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) {
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struct termios new_termios;
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// Save the current stdin termios
if (tcgetattr(STDIN_FILENO, &old_stdin) < 0) {
return -1;
}
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// Start from the current settings
new_termios = old_stdin;
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// 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;
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if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &new_termios) < 0) {
return -1;
}
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stdin_is_raw = 1;
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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) {
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if (!stdin_is_raw) return 0;
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if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &old_stdin) < 0) {
return -1;
}
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stdin_is_raw = 0;
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return 0;
}
// Flag indicating whether the sigwinch watcher should terminate.
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static volatile bool close_sigwinch_watcher = false;
/**
* Thread process. Wait for a SIGWINCH to be received, then update
* the terminal size.
*/
static void *watch_sigwinch(void *data) {
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sigset_t winch;
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int *fds = (int *)data;
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int sig;
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sigemptyset(&winch);
sigaddset(&winch, SIGWINCH);
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pthread_sigmask(SIG_UNBLOCK, &winch, nullptr);
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do {
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if (close_sigwinch_watcher)
break;
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// Get the new terminal size
struct winsize w;
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if (ioctl(fds[0], TIOCGWINSZ, &w) == -1)
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continue;
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// Set the new terminal size
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ioctl(fds[1], TIOCSWINSZ, &w);
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} while (sigwait(&winch, &sig) == 0);
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delete[] fds;
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return nullptr;
}
/**
* 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) {
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pthread_t watcher;
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int *fds = new int[2];
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// Block SIGWINCH so sigwait can later receive it
sigset_t winch;
sigemptyset(&winch);
sigaddset(&winch, SIGWINCH);
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if (pthread_sigmask(SIG_BLOCK, &winch, nullptr) == -1) {
delete[] fds;
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return -1;
}
// Initialize some variables, then start the thread
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close_sigwinch_watcher = 0;
fds[0] = master;
fds[1] = slave;
int ret = pthread_create(&watcher, nullptr, &watch_sigwinch, fds);
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if (ret != 0) {
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delete[] fds;
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errno = ret;
return -1;
}
return 0;
}
/**
* pump_stdin_async
*
* Forward data from STDIN to the given FD
* in a seperate thread
*/
void pump_stdin_async(int outfd) {
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// Put stdin into raw mode
set_stdin_raw();
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// 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) {
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// Pump data from stdout to PTY
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pump(infd, STDOUT_FILENO, false /* Don't close output when done */);
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// Cleanup
restore_stdin();
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close_sigwinch_watcher = true;
raise(SIGWINCH);
}