File: getty.c

package info (click to toggle)
busybox 1%3A1.20.0-7
  • links: PTS, VCS
  • area: main
  • in suites: wheezy
  • size: 16,060 kB
  • sloc: ansic: 185,325; sh: 6,510; cpp: 1,428; makefile: 1,047; yacc: 570; lex: 355; perl: 312; python: 250; awk: 29
file content (693 lines) | stat: -rw-r--r-- 20,815 bytes parent folder | download
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
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
/* vi: set sw=4 ts=4: */
/*
 * Based on agetty - another getty program for Linux. By W. Z. Venema 1989
 * Ported to Linux by Peter Orbaek <poe@daimi.aau.dk>
 * This program is freely distributable.
 *
 * option added by Eric Rasmussen <ear@usfirst.org> - 12/28/95
 *
 * 1999-02-22 Arkadiusz Mickiewicz <misiek@misiek.eu.org>
 * - Added Native Language Support
 *
 * 1999-05-05 Thorsten Kranzkowski <dl8bcu@gmx.net>
 * - Enabled hardware flow control before displaying /etc/issue
 *
 * 2011-01 Venys Vlasenko
 * - Removed parity detection code. It can't work reliably:
 * if all chars received have bit 7 cleared and odd (or even) parity,
 * it is impossible to determine whether other side is 8-bit,no-parity
 * or 7-bit,odd(even)-parity. It also interferes with non-ASCII usernames.
 * - From now on, we assume that parity is correctly set.
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"
#include <syslog.h>
#ifndef IUCLC
# define IUCLC 0
#endif

#ifndef LOGIN_PROCESS
# undef ENABLE_FEATURE_UTMP
# undef ENABLE_FEATURE_WTMP
# define ENABLE_FEATURE_UTMP 0
# define ENABLE_FEATURE_WTMP 0
#endif


/* The following is used for understandable diagnostics */
#ifdef DEBUGGING
static FILE *dbf;
# define DEBUGTERM "/dev/ttyp0"
# define debug(...) do { fprintf(dbf, __VA_ARGS__); fflush(dbf); } while (0)
#else
# define debug(...) ((void)0)
#endif


/*
 * Things you may want to modify.
 *
 * You may disagree with the default line-editing etc. characters defined
 * below. Note, however, that DEL cannot be used for interrupt generation
 * and for line editing at the same time.
 */
#undef  _PATH_LOGIN
#define _PATH_LOGIN "/bin/login"

/* Displayed before the login prompt.
 * If ISSUE is not defined, getty will never display the contents of the
 * /etc/issue file. You will not want to spit out large "issue" files at the
 * wrong baud rate.
 */
#define ISSUE "/etc/issue"

/* Macro to build Ctrl-LETTER. Assumes ASCII dialect */
#define CTL(x)          ((x) ^ 0100)

/*
 * When multiple baud rates are specified on the command line,
 * the first one we will try is the first one specified.
 */
#define MAX_SPEED       10              /* max. nr. of baud rates */

struct globals {
	unsigned timeout;
	const char *login;              /* login program */
	const char *fakehost;
	const char *tty_name;
	char *initstring;               /* modem init string */
	const char *issue;              /* alternative issue file */
	int numspeed;                   /* number of baud rates to try */
	int speeds[MAX_SPEED];          /* baud rates to be tried */
	unsigned char eol;              /* end-of-line char seen (CR or NL) */
	struct termios tty_attrs;
	char line_buf[128];
};

#define G (*ptr_to_globals)
#define INIT_G() do { \
	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
} while (0)

//usage:#define getty_trivial_usage
//usage:       "[OPTIONS] BAUD_RATE[,BAUD_RATE]... TTY [TERMTYPE]"
//usage:#define getty_full_usage "\n\n"
//usage:       "Open TTY, prompt for login name, then invoke /bin/login\n"
//usage:     "\n	-h		Enable hardware RTS/CTS flow control"
//usage:     "\n	-L		Set CLOCAL (ignore Carrier Detect state)"
//usage:     "\n	-m		Get baud rate from modem's CONNECT status message"
//usage:     "\n	-n		Don't prompt for login name"
//usage:     "\n	-w		Wait for CR or LF before sending /etc/issue"
//usage:     "\n	-i		Don't display /etc/issue"
//usage:     "\n	-f ISSUE_FILE	Display ISSUE_FILE instead of /etc/issue"
//usage:     "\n	-l LOGIN	Invoke LOGIN instead of /bin/login"
//usage:     "\n	-t SEC		Terminate after SEC if no login name is read"
//usage:     "\n	-I INITSTR	Send INITSTR before anything else"
//usage:     "\n	-H HOST		Log HOST into the utmp file as the hostname"
//usage:     "\n"
//usage:     "\nBAUD_RATE of 0 leaves it unchanged"

static const char opt_string[] ALIGN1 = "I:LH:f:hil:mt:wn";
#define F_INITSTRING    (1 << 0)   /* -I */
#define F_LOCAL         (1 << 1)   /* -L */
#define F_FAKEHOST      (1 << 2)   /* -H */
#define F_CUSTISSUE     (1 << 3)   /* -f */
#define F_RTSCTS        (1 << 4)   /* -h */
#define F_NOISSUE       (1 << 5)   /* -i */
#define F_LOGIN         (1 << 6)   /* -l */
#define F_PARSE         (1 << 7)   /* -m */
#define F_TIMEOUT       (1 << 8)   /* -t */
#define F_WAITCRLF      (1 << 9)   /* -w */
#define F_NOPROMPT      (1 << 10)  /* -n */


/* convert speed string to speed code; return <= 0 on failure */
static int bcode(const char *s)
{
	int value = bb_strtou(s, NULL, 10); /* yes, int is intended! */
	if (value < 0) /* bad terminating char, overflow, etc */
		return value;
	return tty_value_to_baud(value);
}

/* parse alternate baud rates */
static void parse_speeds(char *arg)
{
	char *cp;

	/* NB: at least one iteration is always done */
	debug("entered parse_speeds\n");
	while ((cp = strsep(&arg, ",")) != NULL) {
		G.speeds[G.numspeed] = bcode(cp);
		if (G.speeds[G.numspeed] < 0)
			bb_error_msg_and_die("bad speed: %s", cp);
		/* note: arg "0" turns into speed B0 */
		G.numspeed++;
		if (G.numspeed > MAX_SPEED)
			bb_error_msg_and_die("too many alternate speeds");
	}
	debug("exiting parse_speeds\n");
}

/* parse command-line arguments */
static void parse_args(char **argv)
{
	char *ts;
	int flags;

	opt_complementary = "-2:t+"; /* at least 2 args; -t N */
	flags = getopt32(argv, opt_string,
		&G.initstring, &G.fakehost, &G.issue,
		&G.login, &G.timeout
	);
	if (flags & F_INITSTRING) {
		G.initstring = xstrdup(G.initstring);
		/* decode \ddd octal codes into chars */
		strcpy_and_process_escape_sequences(G.initstring, G.initstring);
	}
	argv += optind;
	debug("after getopt\n");

	/* We loosen up a bit and accept both "baudrate tty" and "tty baudrate" */
	G.tty_name = argv[0];
	ts = argv[1];            /* baud rate(s) */
	if (isdigit(argv[0][0])) {
		/* A number first, assume it's a speed (BSD style) */
		G.tty_name = ts; /* tty name is in argv[1] */
		ts = argv[0];    /* baud rate(s) */
	}
	parse_speeds(ts);

	if (argv[2])
		xsetenv("TERM", argv[2]);

	debug("exiting parse_args\n");
}

/* set up tty as standard input, output, error */
static void open_tty(void)
{
	/* Set up new standard input, unless we are given an already opened port */
	if (NOT_LONE_DASH(G.tty_name)) {
		if (G.tty_name[0] != '/')
			G.tty_name = xasprintf("/dev/%s", G.tty_name); /* will leak it */

		/* Open the tty as standard input */
		debug("open(2)\n");
		close(0);
		xopen(G.tty_name, O_RDWR | O_NONBLOCK); /* uses fd 0 */

		/* Set proper protections and ownership */
		fchown(0, 0, 0);        /* 0:0 */
		fchmod(0, 0620);        /* crw--w---- */
	} else {
		char *n;
		/*
		 * Standard input should already be connected to an open port.
		 * Make sure it is open for read/write.
		 */
		if ((fcntl(0, F_GETFL) & (O_RDWR|O_RDONLY|O_WRONLY)) != O_RDWR)
			bb_error_msg_and_die("stdin is not open for read/write");

		/* Try to get real tty name instead of "-" */
		n = xmalloc_ttyname(0);
		if (n)
			G.tty_name = n;
	}
	applet_name = xasprintf("getty: %s", skip_dev_pfx(G.tty_name));
}

static void set_tty_attrs(void)
{
	if (tcsetattr_stdin_TCSANOW(&G.tty_attrs) < 0)
		bb_perror_msg_and_die("tcsetattr");
}

/* We manipulate tty_attrs this way:
 * - first, we read existing tty_attrs
 * - init_tty_attrs modifies some parts and sets it
 * - auto_baud and/or BREAK processing can set different speed and set tty attrs
 * - finalize_tty_attrs again modifies some parts and sets tty attrs before
 *   execing login
 */
static void init_tty_attrs(int speed)
{
	/* Try to drain output buffer, with 5 sec timeout.
	 * Added on request from users of ~600 baud serial interface
	 * with biggish buffer on a 90MHz CPU.
	 * They were losing hundreds of bytes of buffered output
	 * on tcflush.
	 */
	signal_no_SA_RESTART_empty_mask(SIGALRM, record_signo);
	alarm(5);
	tcdrain(STDIN_FILENO);
	alarm(0);

	/* Flush input and output queues, important for modems! */
	tcflush(STDIN_FILENO, TCIOFLUSH);

	/* Set speed if it wasn't specified as "0" on command line */
	if (speed != B0)
		cfsetspeed(&G.tty_attrs, speed);

	/* Initial settings: 8-bit characters, raw mode, blocking i/o.
	 * Special characters are set after we have read the login name; all
	 * reads will be done in raw mode anyway.
	 */
	/* Clear all bits except: */
	G.tty_attrs.c_cflag &= (0
		/* 2 stop bits (1 otherwise)
		 * Enable parity bit (both on input and output)
		 * Odd parity (else even)
		 */
		| CSTOPB | PARENB | PARODD
#ifdef CMSPAR
		| CMSPAR  /* mark or space parity */
#endif
#ifdef CBAUD
		| CBAUD   /* (output) baud rate */
#endif
#ifdef CBAUDEX
		| CBAUDEX /* (output) baud rate */
#endif
#ifdef CIBAUD
		| CIBAUD   /* input baud rate */
#endif
	);
	/* Set: 8 bits; hang up (drop DTR) on last close; enable receive */
	G.tty_attrs.c_cflag |= CS8 | HUPCL | CREAD;
	if (option_mask32 & F_LOCAL) {
		/* ignore Carrier Detect pin:
		 * opens don't block when CD is low,
		 * losing CD doesn't hang up processes whose ctty is this tty
		 */
		G.tty_attrs.c_cflag |= CLOCAL;
	}
#ifdef CRTSCTS
	if (option_mask32 & F_RTSCTS)
		G.tty_attrs.c_cflag |= CRTSCTS; /* flow control using RTS/CTS pins */
#endif
	G.tty_attrs.c_iflag = 0;
	G.tty_attrs.c_lflag = 0;
	/* non-raw output; add CR to each NL */
	G.tty_attrs.c_oflag = OPOST | ONLCR;

	/* reads would block only if < 1 char is available */
	G.tty_attrs.c_cc[VMIN] = 1;
	/* no timeout (reads block forever) */
	G.tty_attrs.c_cc[VTIME] = 0;
#ifdef __linux__
	G.tty_attrs.c_line = 0;
#endif

	set_tty_attrs();

	debug("term_io 2\n");
}

static void finalize_tty_attrs(void)
{
	/* software flow control on output (stop sending if XOFF is recvd);
	 * and on input (send XOFF when buffer is full)
	 */
	G.tty_attrs.c_iflag |= IXON | IXOFF;
	if (G.eol == '\r') {
		G.tty_attrs.c_iflag |= ICRNL; /* map CR on input to NL */
	}
	/* Other bits in c_iflag:
	 * IXANY   Any recvd char enables output (any char is also a XON)
	 * INPCK   Enable parity check
	 * IGNPAR  Ignore parity errors (drop bad bytes)
	 * PARMRK  Mark parity errors with 0xff, 0x00 prefix
	 *         (else bad byte is received as 0x00)
	 * ISTRIP  Strip parity bit
	 * IGNBRK  Ignore break condition
	 * BRKINT  Send SIGINT on break - maybe set this?
	 * INLCR   Map NL to CR
	 * IGNCR   Ignore CR
	 * ICRNL   Map CR to NL
	 * IUCLC   Map uppercase to lowercase
	 * IMAXBEL Echo BEL on input line too long
	 * IUTF8   Appears to affect tty's idea of char widths,
	 *         observed to improve backspacing through Unicode chars
	 */

	/* line buffered input (NL or EOL or EOF chars end a line);
	 * recognize INT/QUIT/SUSP chars;
	 * echo input chars;
	 * echo BS-SP-BS on erase character;
	 * echo kill char specially, not as ^c (ECHOKE controls how exactly);
	 * erase all input via BS-SP-BS on kill char (else go to next line)
	 */
	G.tty_attrs.c_lflag |= ICANON | ISIG | ECHO | ECHOE | ECHOK | ECHOKE;
	/* Other bits in c_lflag:
	 * XCASE   Map uppercase to \lowercase [tried, doesn't work]
	 * ECHONL  Echo NL even if ECHO is not set
	 * ECHOCTL Echo ctrl chars as ^c (else don't echo) - maybe set this?
	 * ECHOPRT On erase, echo erased chars
	 *         [qwe<BS><BS><BS> input looks like "qwe\ewq/" on screen]
	 * NOFLSH  Don't flush input buffer after interrupt or quit chars
	 * IEXTEN  Enable extended functions (??)
	 *         [glibc says it enables c_cc[LNEXT] "enter literal char"
	 *         and c_cc[VDISCARD] "toggle discard buffered output" chars]
	 * FLUSHO  Output being flushed (c_cc[VDISCARD] is in effect)
	 * PENDIN  Retype pending input at next read or input char
	 *         (c_cc[VREPRINT] is being processed)
	 * TOSTOP  Send SIGTTOU for background output
	 *         (why "stty sane" unsets this bit?)
	 */

	G.tty_attrs.c_cc[VINTR] = CTL('C');
	G.tty_attrs.c_cc[VQUIT] = CTL('\\');
	G.tty_attrs.c_cc[VEOF] = CTL('D');
	G.tty_attrs.c_cc[VEOL] = '\n';
#ifdef VSWTC
	G.tty_attrs.c_cc[VSWTC] = 0;
#endif
#ifdef VSWTCH
	G.tty_attrs.c_cc[VSWTCH] = 0;
#endif
	G.tty_attrs.c_cc[VKILL] = CTL('U');
	/* Other control chars:
	 * VEOL2
	 * VERASE, VWERASE - (word) erase. we may set VERASE in get_logname
	 * VREPRINT - reprint current input buffer
	 * VLNEXT, VDISCARD, VSTATUS
	 * VSUSP, VDSUSP - send (delayed) SIGTSTP
	 * VSTART, VSTOP - chars used for IXON/IXOFF
	 */

	set_tty_attrs();

	/* Now the newline character should be properly written */
	full_write(STDOUT_FILENO, "\n", 1);
}

/* extract baud rate from modem status message */
static void auto_baud(void)
{
	int nread;

	/*
	 * This works only if the modem produces its status code AFTER raising
	 * the DCD line, and if the computer is fast enough to set the proper
	 * baud rate before the message has gone by. We expect a message of the
	 * following format:
	 *
	 * <junk><number><junk>
	 *
	 * The number is interpreted as the baud rate of the incoming call. If the
	 * modem does not tell us the baud rate within one second, we will keep
	 * using the current baud rate. It is advisable to enable BREAK
	 * processing (comma-separated list of baud rates) if the processing of
	 * modem status messages is enabled.
	 */

	G.tty_attrs.c_cc[VMIN] = 0; /* don't block reads (min read is 0 chars) */
	set_tty_attrs();

	/*
	 * Wait for a while, then read everything the modem has said so far and
	 * try to extract the speed of the dial-in call.
	 */
	sleep(1);
	nread = safe_read(STDIN_FILENO, G.line_buf, sizeof(G.line_buf) - 1);
	if (nread > 0) {
		int speed;
		char *bp;
		G.line_buf[nread] = '\0';
		for (bp = G.line_buf; bp < G.line_buf + nread; bp++) {
			if (isdigit(*bp)) {
				speed = bcode(bp);
				if (speed > 0)
					cfsetspeed(&G.tty_attrs, speed);
				break;
			}
		}
	}

	/* Restore terminal settings */
	G.tty_attrs.c_cc[VMIN] = 1; /* restore to value set by init_tty_attrs */
	set_tty_attrs();
}

/* get user name, establish parity, speed, erase, kill, eol;
 * return NULL on BREAK, logname on success
 */
static char *get_logname(void)
{
	char *bp;
	char c;

	/* Flush pending input (esp. after parsing or switching the baud rate) */
	usleep(100*1000); /* 0.1 sec */
	tcflush(STDIN_FILENO, TCIFLUSH);

	/* Prompt for and read a login name */
	do {
		/* Write issue file and prompt */
#ifdef ISSUE
		if (!(option_mask32 & F_NOISSUE))
			print_login_issue(G.issue, G.tty_name);
#endif
		print_login_prompt();

		/* Read name, watch for break, erase, kill, end-of-line */
		bp = G.line_buf;
		while (1) {
			/* Do not report trivial EINTR/EIO errors */
			errno = EINTR; /* make read of 0 bytes be silent too */
			if (read(STDIN_FILENO, &c, 1) < 1) {
				finalize_tty_attrs();
				if (errno == EINTR || errno == EIO)
					exit(EXIT_SUCCESS);
				bb_perror_msg_and_die(bb_msg_read_error);
			}

			switch (c) {
			case '\r':
			case '\n':
				*bp = '\0';
				G.eol = c;
				goto got_logname;
			case CTL('H'):
			case 0x7f:
				G.tty_attrs.c_cc[VERASE] = c;
				if (bp > G.line_buf) {
					full_write(STDOUT_FILENO, "\010 \010", 3);
					bp--;
				}
				break;
			case CTL('U'):
				while (bp > G.line_buf) {
					full_write(STDOUT_FILENO, "\010 \010", 3);
					bp--;
				}
				break;
			case CTL('C'):
			case CTL('D'):
				finalize_tty_attrs();
				exit(EXIT_SUCCESS);
			case '\0':
				/* BREAK. If we have speeds to try,
				 * return NULL (will switch speeds and return here) */
				if (G.numspeed > 1)
					return NULL;
				/* fall through and ignore it */
			default:
				if ((unsigned char)c < ' ') {
					/* ignore garbage characters */
				} else if ((int)(bp - G.line_buf) < sizeof(G.line_buf) - 1) {
					/* echo and store the character */
					full_write(STDOUT_FILENO, &c, 1);
					*bp++ = c;
				}
				break;
			}
		} /* end of get char loop */
 got_logname: ;
	} while (G.line_buf[0] == '\0');  /* while logname is empty */

	return G.line_buf;
}

static void alarm_handler(int sig UNUSED_PARAM)
{
	finalize_tty_attrs();
	_exit(EXIT_SUCCESS);
}

int getty_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int getty_main(int argc UNUSED_PARAM, char **argv)
{
	int n;
	pid_t pid, tsid;
	char *logname;

	INIT_G();
	G.login = _PATH_LOGIN;    /* default login program */
#ifdef ISSUE
	G.issue = ISSUE;          /* default issue file */
#endif
	G.eol = '\r';

	/* Parse command-line arguments */
	parse_args(argv);

	/* Create new session and pgrp, lose controlling tty */
	pid = setsid();  /* this also gives us our pid :) */
	if (pid < 0) {
		int fd;
		/* :(
		 * docs/ctty.htm says:
		 * "This is allowed only when the current process
		 *  is not a process group leader".
		 * Thus, setsid() will fail if we _already_ are
		 * a session leader - which is quite possible for getty!
		 */
		pid = getpid();
		if (getsid(0) != pid)
			bb_perror_msg_and_die("setsid");
		/* Looks like we are already a session leader.
		 * In this case (setsid failed) we may still have ctty,
		 * and it may be different from tty we need to control!
		 * If we still have ctty, on Linux ioctl(TIOCSCTTY)
		 * (which we are going to use a bit later) always fails -
		 * even if we try to take ctty which is already ours!
		 * Try to drop old ctty now to prevent that.
		 * Use O_NONBLOCK: old ctty may be a serial line.
		 */
		fd = open("/dev/tty", O_RDWR | O_NONBLOCK);
		if (fd >= 0) {
			/* TIOCNOTTY sends SIGHUP to the foreground
			 * process group - which may include us!
			 * Make sure to not die on it:
			 */
			sighandler_t old = signal(SIGHUP, SIG_IGN);
			ioctl(fd, TIOCNOTTY);
			close(fd);
			signal(SIGHUP, old);
		}
	}

	/* Close stdio, and stray descriptors, just in case */
	n = xopen(bb_dev_null, O_RDWR);
	/* dup2(n, 0); - no, we need to handle "getty - 9600" too */
	xdup2(n, 1);
	xdup2(n, 2);
	while (n > 2)
		close(n--);

	/* Logging. We want special flavor of error_msg_and_die */
	die_sleep = 10;
	msg_eol = "\r\n";
	/* most likely will internally use fd #3 in CLOEXEC mode: */
	openlog(applet_name, LOG_PID, LOG_AUTH);
	logmode = LOGMODE_BOTH;

#ifdef DEBUGGING
	dbf = xfopen_for_write(DEBUGTERM);
	for (n = 1; argv[n]; n++) {
		debug(argv[n]);
		debug("\n");
	}
#endif

	/* Open the tty as standard input, if it is not "-" */
	debug("calling open_tty\n");
	open_tty();
	ndelay_off(STDIN_FILENO);
	debug("duping\n");
	xdup2(STDIN_FILENO, 1);
	xdup2(STDIN_FILENO, 2);

	/* Steal ctty if we don't have it yet */
	tsid = tcgetsid(STDIN_FILENO);
	if (tsid < 0 || pid != tsid) {
		if (ioctl(STDIN_FILENO, TIOCSCTTY, /*force:*/ (long)1) < 0)
			bb_perror_msg_and_die("TIOCSCTTY");
	}

#ifdef __linux__
	/* Make ourself a foreground process group within our session */
	if (tcsetpgrp(STDIN_FILENO, pid) < 0)
		bb_perror_msg_and_die("tcsetpgrp");
#endif

	/*
	 * The following ioctl will fail if stdin is not a tty, but also when
	 * there is noise on the modem control lines. In the latter case, the
	 * common course of action is (1) fix your cables (2) give the modem more
	 * time to properly reset after hanging up. SunOS users can achieve (2)
	 * by patching the SunOS kernel variable "zsadtrlow" to a larger value;
	 * 5 seconds seems to be a good value.
	 */
	if (tcgetattr(STDIN_FILENO, &G.tty_attrs) < 0)
		bb_perror_msg_and_die("tcgetattr");

	/* Update the utmp file. This tty is ours now! */
	update_utmp(pid, LOGIN_PROCESS, G.tty_name, "LOGIN", G.fakehost);

	/* Initialize tty attrs (raw mode, eight-bit, blocking i/o) */
	debug("calling init_tty_attrs\n");
	init_tty_attrs(G.speeds[0]);

	/* Write the modem init string and DON'T flush the buffers */
	if (option_mask32 & F_INITSTRING) {
		debug("writing init string\n");
		full_write1_str(G.initstring);
	}

	/* Optionally detect the baud rate from the modem status message */
	debug("before autobaud\n");
	if (option_mask32 & F_PARSE)
		auto_baud();

	/* Set the optional timer */
	signal(SIGALRM, alarm_handler);
	alarm(G.timeout); /* if 0, alarm is not set */

	/* Optionally wait for CR or LF before writing /etc/issue */
	if (option_mask32 & F_WAITCRLF) {
		char ch;
		debug("waiting for cr-lf\n");
		while (safe_read(STDIN_FILENO, &ch, 1) == 1) {
			debug("read %x\n", (unsigned char)ch);
			if (ch == '\n' || ch == '\r')
				break;
		}
	}

	logname = NULL;
	if (!(option_mask32 & F_NOPROMPT)) {
		/* NB: init_tty_attrs already set line speed
		 * to G.speeds[0] */
		int baud_index = 0;

		while (1) {
			/* Read the login name */
			debug("reading login name\n");
			logname = get_logname();
			if (logname)
				break;
			/* We are here only if G.numspeed > 1 */
			baud_index = (baud_index + 1) % G.numspeed;
			cfsetspeed(&G.tty_attrs, G.speeds[baud_index]);
			set_tty_attrs();
		}
	}

	/* Disable timer */
	alarm(0);

	finalize_tty_attrs();

	/* Let the login program take care of password validation */
	/* We use PATH because we trust that root doesn't set "bad" PATH,
	 * and getty is not suid-root applet */
	/* With -n, logname == NULL, and login will ask for username instead */
	BB_EXECLP(G.login, G.login, "--", logname, NULL);
	bb_error_msg_and_die("can't execute '%s'", G.login);
}