File: sshpty.c

package info (click to toggle)
dropbear 2012.55-1.3
  • links: PTS
  • area: main
  • in suites: wheezy
  • size: 7,556 kB
  • sloc: ansic: 67,976; sh: 3,159; makefile: 645; perl: 409; asm: 30
file content (412 lines) | stat: -rw-r--r-- 10,632 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
/*
 * Dropbear - a SSH2 server
 *
 * Copied from OpenSSH-3.5p1 source, modified by Matt Johnston 2003
 * 
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Allocating a pseudo-terminal, and making it the controlling tty.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

/*RCSID("OpenBSD: sshpty.c,v 1.7 2002/06/24 17:57:20 deraadt Exp ");*/

#include "includes.h"
#include "dbutil.h"
#include "errno.h"
#include "sshpty.h"

/* Pty allocated with _getpty gets broken if we do I_PUSH:es to it. */
#if defined(HAVE__GETPTY) || defined(HAVE_OPENPTY)
#undef HAVE_DEV_PTMX
#endif

#ifdef HAVE_PTY_H
# include <pty.h>
#endif
#if defined(USE_DEV_PTMX) && defined(HAVE_STROPTS_H)
# include <stropts.h>
#endif

#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif

/*
 * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
 * nonzero if a pty was successfully allocated.  On success, open file
 * descriptors for the pty and tty sides and the name of the tty side are
 * returned (the buffer must be able to hold at least 64 characters).
 */

int
pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
{
#if defined(HAVE_OPENPTY)
	/* exists in recent (4.4) BSDs and OSF/1 */
	char *name;
	int i;

	i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
	if (i < 0) {
		dropbear_log(LOG_WARNING, 
				"pty_allocate: openpty: %.100s", strerror(errno));
		return 0;
	}
	name = ttyname(*ttyfd);
	if (!name) {
		dropbear_exit("ttyname fails for openpty device");
	}

	strlcpy(namebuf, name, namebuflen);	/* possible truncation */
	return 1;
#else /* HAVE_OPENPTY */
#ifdef HAVE__GETPTY
	/*
	 * _getpty(3) exists in SGI Irix 4.x, 5.x & 6.x -- it generates more
	 * pty's automagically when needed
	 */
	char *slave;

	slave = _getpty(ptyfd, O_RDWR, 0622, 0);
	if (slave == NULL) {
		dropbear_log(LOG_WARNING,
				"pty_allocate: _getpty: %.100s", strerror(errno));
		return 0;
	}
	strlcpy(namebuf, slave, namebuflen);
	/* Open the slave side. */
	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
	if (*ttyfd < 0) {
		dropbear_log(LOG_WARNING,
				"pty_allocate error: ttyftd open error");
		close(*ptyfd);
		return 0;
	}
	return 1;
#else /* HAVE__GETPTY */
#if defined(USE_DEV_PTMX)
	/*
	 * This code is used e.g. on Solaris 2.x.  (Note that Solaris 2.3
	 * also has bsd-style ptys, but they simply do not work.)
	 *
	 * Linux systems may have the /dev/ptmx device, but this code won't work.
	 */
	int ptm;
	char *pts;

	ptm = open("/dev/ptmx", O_RDWR | O_NOCTTY);
	if (ptm < 0) {
		dropbear_log(LOG_WARNING,
				"pty_allocate: /dev/ptmx: %.100s", strerror(errno));
		return 0;
	}
	if (grantpt(ptm) < 0) {
		dropbear_log(LOG_WARNING,
				"grantpt: %.100s", strerror(errno));
		return 0;
	}
	if (unlockpt(ptm) < 0) {
		dropbear_log(LOG_WARNING,
				"unlockpt: %.100s", strerror(errno));
		return 0;
	}
	pts = ptsname(ptm);
	if (pts == NULL) {
		dropbear_log(LOG_WARNING,
				"Slave pty side name could not be obtained.");
	}
	strlcpy(namebuf, pts, namebuflen);
	*ptyfd = ptm;

	/* Open the slave side. */
	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
	if (*ttyfd < 0) {
		dropbear_log(LOG_ERR,
			"error opening pts %.100s: %.100s", namebuf, strerror(errno));
		close(*ptyfd);
		return 0;
	}
#ifndef HAVE_CYGWIN
	/*
	 * Push the appropriate streams modules, as described in Solaris pts(7).
	 * HP-UX pts(7) doesn't have ttcompat module.
	 */
	if (ioctl(*ttyfd, I_PUSH, "ptem") < 0) {
		dropbear_log(LOG_WARNING,
				"ioctl I_PUSH ptem: %.100s", strerror(errno));
	}
	if (ioctl(*ttyfd, I_PUSH, "ldterm") < 0) {
		dropbear_log(LOG_WARNING,
			"ioctl I_PUSH ldterm: %.100s", strerror(errno));
	}
#ifndef __hpux
	if (ioctl(*ttyfd, I_PUSH, "ttcompat") < 0) {
		dropbear_log(LOG_WARNING,
			"ioctl I_PUSH ttcompat: %.100s", strerror(errno));
	}
#endif
#endif
	return 1;
#else /* USE_DEV_PTMX */
#ifdef HAVE_DEV_PTS_AND_PTC
	/* AIX-style pty code. */
	const char *name;

	*ptyfd = open("/dev/ptc", O_RDWR | O_NOCTTY);
	if (*ptyfd < 0) {
		dropbear_log(LOG_ERR,
			"Could not open /dev/ptc: %.100s", strerror(errno));
		return 0;
	}
	name = ttyname(*ptyfd);
	if (!name) {
		dropbear_exit("ttyname fails for /dev/ptc device");
	}
	strlcpy(namebuf, name, namebuflen);
	*ttyfd = open(name, O_RDWR | O_NOCTTY);
	if (*ttyfd < 0) {
		dropbear_log(LOG_ERR,
			"Could not open pty slave side %.100s: %.100s",
		    name, strerror(errno));
		close(*ptyfd);
		return 0;
	}
	return 1;
#else /* HAVE_DEV_PTS_AND_PTC */

	/* BSD-style pty code. */
	char buf[64];
	int i;
	const char *ptymajors = "pqrstuvwxyzabcdefghijklmnoABCDEFGHIJKLMNOPQRSTUVWXYZ";
	const char *ptyminors = "0123456789abcdef";
	int num_minors = strlen(ptyminors);
	int num_ptys = strlen(ptymajors) * num_minors;
	struct termios tio;

	for (i = 0; i < num_ptys; i++) {
		snprintf(buf, sizeof buf, "/dev/pty%c%c", ptymajors[i / num_minors],
			 ptyminors[i % num_minors]);
		snprintf(namebuf, namebuflen, "/dev/tty%c%c",
		    ptymajors[i / num_minors], ptyminors[i % num_minors]);

		*ptyfd = open(buf, O_RDWR | O_NOCTTY);
		if (*ptyfd < 0) {
			/* Try SCO style naming */
			snprintf(buf, sizeof buf, "/dev/ptyp%d", i);
			snprintf(namebuf, namebuflen, "/dev/ttyp%d", i);
			*ptyfd = open(buf, O_RDWR | O_NOCTTY);
			if (*ptyfd < 0) {
				continue;
			}
		}

		/* Open the slave side. */
		*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
		if (*ttyfd < 0) {
			dropbear_log(LOG_ERR,
				"pty_allocate: %.100s: %.100s", namebuf, strerror(errno));
			close(*ptyfd);
			return 0;
		}
		/* set tty modes to a sane state for broken clients */
		if (tcgetattr(*ptyfd, &tio) < 0) {
			dropbear_log(LOG_WARNING,
				"ptyallocate: tty modes failed: %.100s", strerror(errno));
		} else {
			tio.c_lflag |= (ECHO | ISIG | ICANON);
			tio.c_oflag |= (OPOST | ONLCR);
			tio.c_iflag |= ICRNL;

			/* Set the new modes for the terminal. */
			if (tcsetattr(*ptyfd, TCSANOW, &tio) < 0) {
				dropbear_log(LOG_WARNING,
					"Setting tty modes for pty failed: %.100s",
					strerror(errno));
			}
		}

		return 1;
	}
	dropbear_log(LOG_WARNING, "Failed to open any /dev/pty?? devices");
	return 0;
#endif /* HAVE_DEV_PTS_AND_PTC */
#endif /* USE_DEV_PTMX */
#endif /* HAVE__GETPTY */
#endif /* HAVE_OPENPTY */
}

/* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */

void
pty_release(const char *tty_name)
{
	if (chown(tty_name, (uid_t) 0, (gid_t) 0) < 0
			&& (errno != ENOENT)) {
		dropbear_log(LOG_ERR,
				"chown %.100s 0 0 failed: %.100s", tty_name, strerror(errno));
	}
	if (chmod(tty_name, (mode_t) 0666) < 0
			&& (errno != ENOENT)) {
		dropbear_log(LOG_ERR,
			"chmod %.100s 0666 failed: %.100s", tty_name, strerror(errno));
	}
}

/* Makes the tty the processes controlling tty and sets it to sane modes. */

void
pty_make_controlling_tty(int *ttyfd, const char *tty_name)
{
	int fd;
#ifdef USE_VHANGUP
	void *old;
#endif /* USE_VHANGUP */

	/* Solaris has a problem with TIOCNOTTY for a bg process, so
	 * we disable the signal which would STOP the process - matt */
	signal(SIGTTOU, SIG_IGN);

	/* First disconnect from the old controlling tty. */
#ifdef TIOCNOTTY
	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
	if (fd >= 0) {
		(void) ioctl(fd, TIOCNOTTY, NULL);
		close(fd);
	}
#endif /* TIOCNOTTY */
	if (setsid() < 0) {
		dropbear_log(LOG_ERR,
			"setsid: %.100s", strerror(errno));
	}

	/*
	 * Verify that we are successfully disconnected from the controlling
	 * tty.
	 */
	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
	if (fd >= 0) {
		dropbear_log(LOG_ERR,
				"Failed to disconnect from controlling tty.\n");
		close(fd);
	}
	/* Make it our controlling tty. */
#ifdef TIOCSCTTY
	if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) {
		dropbear_log(LOG_ERR,
			"ioctl(TIOCSCTTY): %.100s", strerror(errno));
	}
#endif /* TIOCSCTTY */
#ifdef HAVE_NEWS4
	if (setpgrp(0,0) < 0) {
		dropbear_log(LOG_ERR,
			error("SETPGRP %s",strerror(errno)));
	}
#endif /* HAVE_NEWS4 */
#ifdef USE_VHANGUP
	old = mysignal(SIGHUP, SIG_IGN);
	vhangup();
	mysignal(SIGHUP, old);
#endif /* USE_VHANGUP */
	fd = open(tty_name, O_RDWR);
	if (fd < 0) {
		dropbear_log(LOG_ERR,
			"%.100s: %.100s", tty_name, strerror(errno));
	} else {
#ifdef USE_VHANGUP
		close(*ttyfd);
		*ttyfd = fd;
#else /* USE_VHANGUP */
		close(fd);
#endif /* USE_VHANGUP */
	}
	/* Verify that we now have a controlling tty. */
	fd = open(_PATH_TTY, O_WRONLY);
	if (fd < 0) {
		dropbear_log(LOG_ERR,
			"open /dev/tty failed - could not set controlling tty: %.100s",
		    strerror(errno));
	} else {
		close(fd);
	}
}

/* Changes the window size associated with the pty. */

void
pty_change_window_size(int ptyfd, int row, int col,
	int xpixel, int ypixel)
{
	struct winsize w;

	w.ws_row = row;
	w.ws_col = col;
	w.ws_xpixel = xpixel;
	w.ws_ypixel = ypixel;
	(void) ioctl(ptyfd, TIOCSWINSZ, &w);
}

void
pty_setowner(struct passwd *pw, const char *tty_name)
{
	struct group *grp;
	gid_t gid;
	mode_t mode;
	struct stat st;

	/* Determine the group to make the owner of the tty. */
	grp = getgrnam("tty");
	if (grp) {
		gid = grp->gr_gid;
		mode = S_IRUSR | S_IWUSR | S_IWGRP;
	} else {
		gid = pw->pw_gid;
		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
	}

	/*
	 * Change owner and mode of the tty as required.
	 * Warn but continue if filesystem is read-only and the uids match/
	 * tty is owned by root.
	 */
	if (stat(tty_name, &st)) {
		dropbear_exit("pty_setowner: stat(%.101s) failed: %.100s",
				tty_name, strerror(errno));
	}

	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
		if (chown(tty_name, pw->pw_uid, gid) < 0) {
			if (errno == EROFS &&
			    (st.st_uid == pw->pw_uid || st.st_uid == 0)) {
				dropbear_log(LOG_ERR,
					"chown(%.100s, %u, %u) failed: %.100s",
						tty_name, (unsigned int)pw->pw_uid, (unsigned int)gid,
						strerror(errno));
			} else {
				dropbear_exit("chown(%.100s, %u, %u) failed: %.100s",
				    tty_name, (unsigned int)pw->pw_uid, (unsigned int)gid,
				    strerror(errno));
			}
		}
	}

	if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
		if (chmod(tty_name, mode) < 0) {
			if (errno == EROFS &&
			    (st.st_mode & (S_IRGRP | S_IROTH)) == 0) {
				dropbear_log(LOG_ERR,
					"chmod(%.100s, 0%o) failed: %.100s",
					tty_name, mode, strerror(errno));
			} else {
				dropbear_exit("chmod(%.100s, 0%o) failed: %.100s",
				    tty_name, mode, strerror(errno));
			}
		}
	}
}