File: open_init_pty.c

package info (click to toggle)
android-platform-external-libselinux 10.0.0%2Br36-2
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid, trixie
  • size: 34,176 kB
  • sloc: ansic: 147,112; python: 25,790; makefile: 1,930; yacc: 1,389; sh: 1,206; lex: 452; xml: 180
file content (445 lines) | stat: -rw-r--r-- 10,242 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
/*                               -*- Mode: C -*- 
 * open_init_pty.c --- 
 * Author           : Manoj Srivastava ( srivasta@glaurung.internal.golden-gryphon.com ) 
 * Created On       : Fri Jan 14 10:48:28 2005
 * Created On Node  : glaurung.internal.golden-gryphon.com
 * Last Modified By : Manoj Srivastava
 * Last Modified On : Thu Sep 15 00:57:00 2005
 * Last Machine Used: glaurung.internal.golden-gryphon.com
 * Update Count     : 92
 * Status           : Unknown, Use with caution!
 * HISTORY          : 
 * Description      : 
 *
 * Distributed under the terms of the GNU General Public License v2
 *
 * open_init_pty
 *
 * SYNOPSIS:
 *
 * This program allows a systems administrator to execute daemons
 * which need to work in the initrc domain, and which need to have
 * pty's as system_u:system_r:initrc_t
 *
 * USAGE:
 *
 * * arch-tag: a5583d39-72b9-4cdf-ba1b-5678ea4cbe20
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>

#include <sysexits.h>

#include <pty.h>		/* for forkpty */
#include <termios.h>
#include <fcntl.h>

#include <sys/select.h>
#include <sys/wait.h>


#define MAXRETR 3		/* The max number of IO retries on a fd */
#define BUFSIZE 2048		/* The ring buffer size */

static struct termios saved_termios;
static int saved_fd = -1;
static enum { RESET, RAW, CBREAK } tty_state = RESET;

static int tty_semi_raw(int fd)
{
	struct termios buf;

	if (tty_state == RESET) {
		if (tcgetattr(fd, &saved_termios) < 0) {
			return -1;
		}
	}

	buf = saved_termios;
	/*
	 * echo off, canonical mode off, extended input processing off,
	 * signal chars off 
	 */
	buf.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
	/*
	 * no SIGINT on break, CR-to-NL off, input parity check off, do not
	 * strip 8th bit on input,output flow control off
	 */
	buf.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
	/* Clear size bits, parity checking off */
	buf.c_cflag &= ~(CSIZE | PARENB);
	/* set 8 bits/char */
	buf.c_cflag |= CS8;
	/* Output processing off 
	   buf.c_oflag    &= ~(OPOST); */

	buf.c_cc[VMIN] = 1;	/* one byte at a time, no timer */
	buf.c_cc[VTIME] = 0;
	if (tcsetattr(fd, TCSANOW, &buf) < 0) {
		return -1;
	}			/* end of if(tcsetattr(fileno(stdin), TCSANOW, &buf) < 0) */
	tty_state = RAW;
	saved_fd = fd;
	return 0;
}

static void tty_atexit(void)
{
	if (tty_state != CBREAK && tty_state != RAW) {
		return;
	}

	if (tcsetattr(saved_fd, TCSANOW, &saved_termios) < 0) {
		return;
	}
	tty_state = RESET;
	return;
}


/* The simple ring buffer */
struct ring_buffer {
	char *buf; /* pointer to buffer memory */
	char *wptr;
	char *rptr;
	size_t size; /* the number of bytes allocated for buf */
	size_t count;
};

static void rb_init(struct ring_buffer *b, char *buf, size_t size)
{
	b->buf = b->wptr = b->rptr = buf;
	b->size = size;
	b->count = 0;
}

static int rb_isempty(struct ring_buffer *b)
{
	return b->count == 0;
}

/* return the unused space size in the buffer */
static size_t rb_space(struct ring_buffer *b)
{
	if (b->rptr > b->wptr)
		return b->rptr - b->wptr;

	if (b->rptr < b->wptr || b->count == 0)
		return b->buf + b->size - b->wptr;

	return 0; /* should not hit this */
}

/* return the used space in the buffer */
static size_t rb_chunk_size(struct ring_buffer *b)
{
	if (b->rptr < b->wptr)
		return b->wptr - b->rptr;

	if (b->rptr > b->wptr || b->count > 0)
		return b->buf + b->size - b->rptr;

	return 0; /* should not hit this */
}

/* read from fd and write to buffer memory */
static ssize_t rb_read(struct ring_buffer *b, int fd)
{
	ssize_t n = read(fd, b->wptr, rb_space(b));
	if (n <= 0)
		return n;

	b->wptr += n;
	b->count += n;
	if (b->buf + b->size <= b->wptr)
		b->wptr = b->buf;

	return n;
}

static ssize_t rb_write(struct ring_buffer *b, int fd)
{
	ssize_t n = write(fd, b->rptr, rb_chunk_size(b));
	if (n <= 0)
		return n;

	b->rptr += n;
	b->count -= n;
	if (b->buf + b->size <= b->rptr)
		b->rptr = b->buf;

	return n;
}

static void setfd_nonblock(int fd)
{
	int fsflags = fcntl(fd, F_GETFL);

	if (fsflags < 0) {
		fprintf(stderr, "fcntl(%d, F_GETFL): %s\n", fd, strerror(errno));
		exit(EX_IOERR);
	}

	if (fcntl(fd, F_SETFL, fsflags | O_NONBLOCK) < 0) {
		fprintf(stderr, "fcntl(%d, F_SETFL, ... | O_NONBLOCK): %s\n", fd, strerror(errno));
		exit(EX_IOERR);
	}
}

static void setfd_block(int fd)
{
	int fsflags = fcntl(fd, F_GETFL);

	if (fsflags < 0) {
		fprintf(stderr, "fcntl(%d, F_GETFL): %s\n", fd, strerror(errno));
		exit(EX_IOERR);
	}

	if (fcntl(fd, F_SETFL, fsflags & ~O_NONBLOCK) < 0) {
		fprintf(stderr, "fcntl(%d, F_SETFL, ... & ~O_NONBLOCK): %s\n", fd, strerror(errno));
		exit(EX_IOERR);
	}
}

static void setfd_atexit(void)
{
	setfd_block(STDIN_FILENO);
	setfd_block(STDOUT_FILENO);
	return;
}

static void sigchld_handler(int asig __attribute__ ((unused)))
{
}

int main(int argc, char *argv[])
{
	pid_t child_pid;
	int child_exit_status;
	struct termios tty_attr;
	struct winsize window_size;
	int pty_master;

	/* for select */
	fd_set readfds;
	fd_set writefds;

	unsigned err_n_rpty = 0;
	unsigned err_n_wpty = 0;
	unsigned err_n_stdin = 0;
	unsigned err_n_stdout = 0;

	int done = 0;

	/* the ring buffers */
	char inbuf_mem[BUFSIZE];
	char outbuf_mem[BUFSIZE];
	struct ring_buffer inbuf;
	struct ring_buffer outbuf;
	rb_init(&inbuf, inbuf_mem, sizeof(inbuf_mem));
	rb_init(&outbuf, outbuf_mem, sizeof(outbuf_mem));

	if (argc == 1) {
		printf("usage: %s PROGRAM [ARGS]...\n", argv[0]);
		exit(1);
	}

	/* We need I/O calls to fail with EINTR on SIGCHLD... */
	if (signal(SIGCHLD, sigchld_handler) == SIG_ERR) {
		perror("signal(SIGCHLD,...)");
		exit(EX_OSERR);
	}

	if (isatty(STDIN_FILENO)) {
		/* get terminal parameters associated with stdout */
		if (tcgetattr(STDOUT_FILENO, &tty_attr) < 0) {
			perror("tcgetattr(stdout,...)");
			exit(EX_OSERR);
		}

		/* get window size */
		if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &window_size) < 0) {
			perror("ioctl(stdout,...)");
			exit(1);
		}

		child_pid = forkpty(&pty_master, NULL, &tty_attr, &window_size);
	} else { /* not interactive */
		child_pid = forkpty(&pty_master, NULL, NULL, NULL);
	}

	if (child_pid < 0) {
		perror("forkpty()");
		exit(EX_OSERR);
	}
	if (child_pid == 0) { /* in the child */
		struct termios s_tty_attr;
		if (tcgetattr(STDIN_FILENO, &s_tty_attr)) {
			perror("tcgetattr(stdin,...)");
			exit(EXIT_FAILURE);
		}
		/* Turn off echo */
		s_tty_attr.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
		/* Also turn of NL to CR?LF on output */
		s_tty_attr.c_oflag &= ~(ONLCR);
		if (tcsetattr(STDIN_FILENO, TCSANOW, &s_tty_attr)) {
			perror("tcsetattr(stdin,...)");
			exit(EXIT_FAILURE);
		}

		if (execvp(argv[1], argv + 1)) {
			perror("execvp()");
			exit(EXIT_FAILURE);
		}
	}

	/* Non blocking mode for all file descriptors. */
	setfd_nonblock(pty_master);
	setfd_nonblock(STDIN_FILENO);
	setfd_nonblock(STDOUT_FILENO);
	if (atexit(setfd_atexit) < 0) {
		perror("atexit()");
		exit(EXIT_FAILURE);
	}

	if (isatty(STDIN_FILENO)) {
		if (tty_semi_raw(STDIN_FILENO) < 0) {
			perror("tty_semi_raw(stdin)");
		}
		if (atexit(tty_atexit) < 0) {
			perror("atexit()");
		}
	}

	do {
		/* Accept events only on fds, that we can handle now. */
		int do_select = 0;
		FD_ZERO(&readfds);
		FD_ZERO(&writefds);

		if (rb_space(&outbuf) > 0 && err_n_rpty < MAXRETR) {
			FD_SET(pty_master, &readfds);
			do_select = 1;
		}

		if (!rb_isempty(&inbuf) && err_n_wpty < MAXRETR) {
			FD_SET(pty_master, &writefds);
			do_select = 1;
		}

		if (rb_space(&inbuf) > 0 && err_n_stdin < MAXRETR) {
			FD_SET(STDIN_FILENO, &readfds);
			do_select = 1;
		}

		if (!rb_isempty(&outbuf) && err_n_stdout < MAXRETR) {
			FD_SET(STDOUT_FILENO, &writefds);
			do_select = 1;
		}

		if (!do_select) {
#ifdef DEBUG
			fprintf(stderr, "No I/O job for us, calling waitpid()...\n");
#endif
			while (waitpid(child_pid, &child_exit_status, 0) < 0)
			{
				/* nothing */
			}
			break;
		}

		errno = 0;
		int select_rc = select(pty_master + 1, &readfds, &writefds, NULL, NULL);
		if (select_rc < 0 && errno != EINTR) {
			perror("select()");
			exit(EX_IOERR);
		}
#ifdef DEBUG
		fprintf(stderr, "select() returned %d\n", select_rc);
#endif

		if (FD_ISSET(STDOUT_FILENO, &writefds)) {
#ifdef DEBUG
			fprintf(stderr, "stdout can be written\n");
#endif
			ssize_t n = rb_write(&outbuf, STDOUT_FILENO);
			if (n <= 0 && n != EINTR && n != EAGAIN)
				err_n_stdout++;
#ifdef DEBUG
			if (n >= 0)
				fprintf(stderr, "%d bytes written into stdout\n", n);
			else
				perror("write(stdout,...)");
#endif
		}

		if (FD_ISSET(pty_master, &writefds)) {
#ifdef DEBUG
			fprintf(stderr, "pty_master can be written\n");
#endif
			ssize_t n = rb_write(&inbuf, pty_master);
			if (n <= 0 && n != EINTR && n != EAGAIN)
				err_n_wpty++;
#ifdef DEBUG
			if (n >= 0)
				fprintf(stderr, "%d bytes written into pty_master\n", n);
			else
				perror("write(pty_master,...)");
#endif
		}

		if (FD_ISSET(STDIN_FILENO, &readfds)) {
#ifdef DEBUG
			fprintf(stderr, "stdin can be read\n");
#endif
			ssize_t n = rb_read(&inbuf, STDIN_FILENO);
			if (n <= 0 && n != EINTR && n != EAGAIN)
				err_n_stdin++;
#ifdef DEBUG
			if (n >= 0)
				fprintf(stderr, "%d bytes read from stdin\n", n);
			else
				perror("read(stdin,...)");
#endif
		}

		if (FD_ISSET(pty_master, &readfds)) {
#ifdef DEBUG
			fprintf(stderr, "pty_master can be read\n");
#endif
			ssize_t n = rb_read(&outbuf, pty_master);
			if (n <= 0 && n != EINTR && n != EAGAIN)
				err_n_rpty++;
#ifdef DEBUG
			if (n >= 0)
				fprintf(stderr, "%d bytes read from pty_master\n", n);
			else
				perror("read(pty_master,...)");
#endif
		}

		if (!done && waitpid(child_pid, &child_exit_status, WNOHANG) > 0)
			done = 1;

	} while (!done
		|| !(rb_isempty(&inbuf) || err_n_wpty >= MAXRETR)
		|| !(rb_isempty(&outbuf) || err_n_stdout >= MAXRETR));

#ifdef DEBUG
	fprintf(stderr, "inbuf: %u bytes left, outbuf: %u bytes left\n", inbuf.count, outbuf.count);
	fprintf(stderr, "err_n_rpty=%u, err_n_wpty=%u, err_n_stdin=%u, err_n_stdout=%u\n",
		err_n_rpty, err_n_wpty, err_n_stdin, err_n_stdout);
#endif

	if (WIFEXITED(child_exit_status))
		exit(WEXITSTATUS(child_exit_status));
	else if (WIFSIGNALED(child_exit_status))
		exit(128 + WTERMSIG(child_exit_status));

	exit(EXIT_FAILURE);
}