sshpty.c revision 99063 
1/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 *                    All rights reserved
5 * Allocating a pseudo-terminal, and making it the controlling tty.
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose.  Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 */
13
14#include "includes.h"
15RCSID("$OpenBSD: sshpty.c,v 1.7 2002/06/24 17:57:20 deraadt Exp $");
16RCSID("$FreeBSD: head/crypto/openssh/sshpty.c 99063 2002-06-29 11:48:59Z des $");
17
18#ifdef HAVE_UTIL_H
19# include <util.h>
20#endif /* HAVE_UTIL_H */
21
22#include "sshpty.h"
23#include "log.h"
24#include "misc.h"
25
26/* Pty allocated with _getpty gets broken if we do I_PUSH:es to it. */
27#if defined(HAVE__GETPTY) || defined(HAVE_OPENPTY)
28#undef HAVE_DEV_PTMX
29#endif
30
31#ifdef HAVE_PTY_H
32# include <pty.h>
33#endif
34#if defined(HAVE_DEV_PTMX) && defined(HAVE_SYS_STROPTS_H)
35# include <sys/stropts.h>
36#endif
37
38#ifndef O_NOCTTY
39#define O_NOCTTY 0
40#endif
41
42/*
43 * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
44 * nonzero if a pty was successfully allocated.  On success, open file
45 * descriptors for the pty and tty sides and the name of the tty side are
46 * returned (the buffer must be able to hold at least 64 characters).
47 */
48
49int
50pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
51{
52#if defined(HAVE_OPENPTY) || defined(BSD4_4)
53	/* openpty(3) exists in OSF/1 and some other os'es */
54	char *name;
55	int i;
56
57	i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
58	if (i < 0) {
59		error("openpty: %.100s", strerror(errno));
60		return 0;
61	}
62	name = ttyname(*ttyfd);
63	if (!name)
64		fatal("openpty returns device for which ttyname fails.");
65
66	strlcpy(namebuf, name, namebuflen);	/* possible truncation */
67	return 1;
68#else /* HAVE_OPENPTY */
69#ifdef HAVE__GETPTY
70	/*
71	 * _getpty(3) exists in SGI Irix 4.x, 5.x & 6.x -- it generates more
72	 * pty's automagically when needed
73	 */
74	char *slave;
75
76	slave = _getpty(ptyfd, O_RDWR, 0622, 0);
77	if (slave == NULL) {
78		error("_getpty: %.100s", strerror(errno));
79		return 0;
80	}
81	strlcpy(namebuf, slave, namebuflen);
82	/* Open the slave side. */
83	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
84	if (*ttyfd < 0) {
85		error("%.200s: %.100s", namebuf, strerror(errno));
86		close(*ptyfd);
87		return 0;
88	}
89	return 1;
90#else /* HAVE__GETPTY */
91#if defined(HAVE_DEV_PTMX)
92	/*
93	 * This code is used e.g. on Solaris 2.x.  (Note that Solaris 2.3
94	 * also has bsd-style ptys, but they simply do not work.)
95	 */
96	int ptm;
97	char *pts;
98	mysig_t old_signal;
99
100	ptm = open("/dev/ptmx", O_RDWR | O_NOCTTY);
101	if (ptm < 0) {
102		error("/dev/ptmx: %.100s", strerror(errno));
103		return 0;
104	}
105	old_signal = mysignal(SIGCHLD, SIG_DFL);
106	if (grantpt(ptm) < 0) {
107		error("grantpt: %.100s", strerror(errno));
108		return 0;
109	}
110	mysignal(SIGCHLD, old_signal);
111	if (unlockpt(ptm) < 0) {
112		error("unlockpt: %.100s", strerror(errno));
113		return 0;
114	}
115	pts = ptsname(ptm);
116	if (pts == NULL)
117		error("Slave pty side name could not be obtained.");
118	strlcpy(namebuf, pts, namebuflen);
119	*ptyfd = ptm;
120
121	/* Open the slave side. */
122	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
123	if (*ttyfd < 0) {
124		error("%.100s: %.100s", namebuf, strerror(errno));
125		close(*ptyfd);
126		return 0;
127	}
128#ifndef HAVE_CYGWIN
129	/*
130	 * Push the appropriate streams modules, as described in Solaris pts(7).
131	 * HP-UX pts(7) doesn't have ttcompat module.
132	 */
133	if (ioctl(*ttyfd, I_PUSH, "ptem") < 0)
134		error("ioctl I_PUSH ptem: %.100s", strerror(errno));
135	if (ioctl(*ttyfd, I_PUSH, "ldterm") < 0)
136		error("ioctl I_PUSH ldterm: %.100s", strerror(errno));
137#ifndef __hpux
138	if (ioctl(*ttyfd, I_PUSH, "ttcompat") < 0)
139		error("ioctl I_PUSH ttcompat: %.100s", strerror(errno));
140#endif
141#endif
142	return 1;
143#else /* HAVE_DEV_PTMX */
144#ifdef HAVE_DEV_PTS_AND_PTC
145	/* AIX-style pty code. */
146	const char *name;
147
148	*ptyfd = open("/dev/ptc", O_RDWR | O_NOCTTY);
149	if (*ptyfd < 0) {
150		error("Could not open /dev/ptc: %.100s", strerror(errno));
151		return 0;
152	}
153	name = ttyname(*ptyfd);
154	if (!name)
155		fatal("Open of /dev/ptc returns device for which ttyname fails.");
156	strlcpy(namebuf, name, namebuflen);
157	*ttyfd = open(name, O_RDWR | O_NOCTTY);
158	if (*ttyfd < 0) {
159		error("Could not open pty slave side %.100s: %.100s",
160		    name, strerror(errno));
161		close(*ptyfd);
162		return 0;
163	}
164	return 1;
165#else /* HAVE_DEV_PTS_AND_PTC */
166#ifdef _CRAY
167	char buf[64];
168	int i;
169	int highpty;
170
171#ifdef _SC_CRAY_NPTY
172	highpty = sysconf(_SC_CRAY_NPTY);
173	if (highpty == -1)
174		highpty = 128;
175#else
176	highpty = 128;
177#endif
178
179	for (i = 0; i < highpty; i++) {
180		snprintf(buf, sizeof(buf), "/dev/pty/%03d", i);
181		*ptyfd = open(buf, O_RDWR|O_NOCTTY);
182		if (*ptyfd < 0)
183			continue;
184		snprintf(namebuf, namebuflen, "/dev/ttyp%03d", i);
185		/* Open the slave side. */
186		*ttyfd = open(namebuf, O_RDWR|O_NOCTTY);
187		if (*ttyfd < 0) {
188			error("%.100s: %.100s", namebuf, strerror(errno));
189			close(*ptyfd);
190			return 0;
191		}
192		return 1;
193	}
194	return 0;
195#else
196	/* BSD-style pty code. */
197	char buf[64];
198	int i;
199	const char *ptymajors = "pqrstuvwxyzabcdefghijklmnoABCDEFGHIJKLMNOPQRSTUVWXYZ";
200	const char *ptyminors = "0123456789abcdef";
201	int num_minors = strlen(ptyminors);
202	int num_ptys = strlen(ptymajors) * num_minors;
203	struct termios tio;
204
205	for (i = 0; i < num_ptys; i++) {
206		snprintf(buf, sizeof buf, "/dev/pty%c%c", ptymajors[i / num_minors],
207			 ptyminors[i % num_minors]);
208		snprintf(namebuf, namebuflen, "/dev/tty%c%c",
209		    ptymajors[i / num_minors], ptyminors[i % num_minors]);
210
211		*ptyfd = open(buf, O_RDWR | O_NOCTTY);
212		if (*ptyfd < 0) {
213			/* Try SCO style naming */
214			snprintf(buf, sizeof buf, "/dev/ptyp%d", i);
215			snprintf(namebuf, namebuflen, "/dev/ttyp%d", i);
216			*ptyfd = open(buf, O_RDWR | O_NOCTTY);
217			if (*ptyfd < 0)
218				continue;
219		}
220
221		/* Open the slave side. */
222		*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
223		if (*ttyfd < 0) {
224			error("%.100s: %.100s", namebuf, strerror(errno));
225			close(*ptyfd);
226			return 0;
227		}
228		/* set tty modes to a sane state for broken clients */
229		if (tcgetattr(*ptyfd, &tio) < 0)
230			log("Getting tty modes for pty failed: %.100s", strerror(errno));
231		else {
232			tio.c_lflag |= (ECHO | ISIG | ICANON);
233			tio.c_oflag |= (OPOST | ONLCR);
234			tio.c_iflag |= ICRNL;
235
236			/* Set the new modes for the terminal. */
237			if (tcsetattr(*ptyfd, TCSANOW, &tio) < 0)
238				log("Setting tty modes for pty failed: %.100s", strerror(errno));
239		}
240
241		return 1;
242	}
243	return 0;
244#endif /* CRAY */
245#endif /* HAVE_DEV_PTS_AND_PTC */
246#endif /* HAVE_DEV_PTMX */
247#endif /* HAVE__GETPTY */
248#endif /* HAVE_OPENPTY */
249}
250
251/* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */
252
253void
254pty_release(const char *ttyname)
255{
256	if (chown(ttyname, (uid_t) 0, (gid_t) 0) < 0)
257		error("chown %.100s 0 0 failed: %.100s", ttyname, strerror(errno));
258	if (chmod(ttyname, (mode_t) 0666) < 0)
259		error("chmod %.100s 0666 failed: %.100s", ttyname, strerror(errno));
260}
261
262/* Makes the tty the processes controlling tty and sets it to sane modes. */
263
264void
265pty_make_controlling_tty(int *ttyfd, const char *ttyname)
266{
267	int fd;
268#ifdef USE_VHANGUP
269	void *old;
270#endif /* USE_VHANGUP */
271
272#ifdef _CRAY
273	if (setsid() < 0)
274		error("setsid: %.100s", strerror(errno));
275
276	fd = open(ttyname, O_RDWR|O_NOCTTY);
277	if (fd != -1) {
278		mysignal(SIGHUP, SIG_IGN);
279		ioctl(fd, TCVHUP, (char *)NULL);
280		mysignal(SIGHUP, SIG_DFL);
281		setpgid(0, 0);
282		close(fd);
283	} else {
284		error("Failed to disconnect from controlling tty.");
285	}
286
287	debug("Setting controlling tty using TCSETCTTY.");
288	ioctl(*ttyfd, TCSETCTTY, NULL);
289	fd = open("/dev/tty", O_RDWR);
290	if (fd < 0)
291		error("%.100s: %.100s", ttyname, strerror(errno));
292	close(*ttyfd);
293	*ttyfd = fd;
294#else /* _CRAY */
295
296	/* First disconnect from the old controlling tty. */
297#ifdef TIOCNOTTY
298	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
299	if (fd >= 0) {
300		(void) ioctl(fd, TIOCNOTTY, NULL);
301		close(fd);
302	}
303#endif /* TIOCNOTTY */
304	if (setsid() < 0)
305		error("setsid: %.100s", strerror(errno));
306
307	/*
308	 * Verify that we are successfully disconnected from the controlling
309	 * tty.
310	 */
311	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
312	if (fd >= 0) {
313		error("Failed to disconnect from controlling tty.");
314		close(fd);
315	}
316	/* Make it our controlling tty. */
317#ifdef TIOCSCTTY
318	debug("Setting controlling tty using TIOCSCTTY.");
319	if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
320		error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
321#endif /* TIOCSCTTY */
322#ifdef HAVE_NEWS4
323	if (setpgrp(0,0) < 0)
324		error("SETPGRP %s",strerror(errno));
325#endif /* HAVE_NEWS4 */
326#ifdef USE_VHANGUP
327	old = mysignal(SIGHUP, SIG_IGN);
328	vhangup();
329	mysignal(SIGHUP, old);
330#endif /* USE_VHANGUP */
331	fd = open(ttyname, O_RDWR);
332	if (fd < 0) {
333		error("%.100s: %.100s", ttyname, strerror(errno));
334	} else {
335#ifdef USE_VHANGUP
336		close(*ttyfd);
337		*ttyfd = fd;
338#else /* USE_VHANGUP */
339		close(fd);
340#endif /* USE_VHANGUP */
341	}
342	/* Verify that we now have a controlling tty. */
343	fd = open(_PATH_TTY, O_WRONLY);
344	if (fd < 0)
345		error("open /dev/tty failed - could not set controlling tty: %.100s",
346		    strerror(errno));
347	else
348		close(fd);
349#endif /* _CRAY */
350}
351
352/* Changes the window size associated with the pty. */
353
354void
355pty_change_window_size(int ptyfd, int row, int col,
356	int xpixel, int ypixel)
357{
358	struct winsize w;
359
360	w.ws_row = row;
361	w.ws_col = col;
362	w.ws_xpixel = xpixel;
363	w.ws_ypixel = ypixel;
364	(void) ioctl(ptyfd, TIOCSWINSZ, &w);
365}
366
367void
368pty_setowner(struct passwd *pw, const char *ttyname)
369{
370	struct group *grp;
371	gid_t gid;
372	mode_t mode;
373	struct stat st;
374
375	/* Determine the group to make the owner of the tty. */
376	grp = getgrnam("tty");
377	if (grp) {
378		gid = grp->gr_gid;
379		mode = S_IRUSR | S_IWUSR | S_IWGRP;
380	} else {
381		gid = pw->pw_gid;
382		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
383	}
384
385	/*
386	 * Change owner and mode of the tty as required.
387	 * Warn but continue if filesystem is read-only and the uids match/
388	 * tty is owned by root.
389	 */
390	if (stat(ttyname, &st))
391		fatal("stat(%.100s) failed: %.100s", ttyname,
392		    strerror(errno));
393
394	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
395		if (chown(ttyname, pw->pw_uid, gid) < 0) {
396			if (errno == EROFS &&
397			    (st.st_uid == pw->pw_uid || st.st_uid == 0))
398				error("chown(%.100s, %u, %u) failed: %.100s",
399				    ttyname, (u_int)pw->pw_uid, (u_int)gid,
400				    strerror(errno));
401			else
402				fatal("chown(%.100s, %u, %u) failed: %.100s",
403				    ttyname, (u_int)pw->pw_uid, (u_int)gid,
404				    strerror(errno));
405		}
406	}
407
408	if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
409		if (chmod(ttyname, mode) < 0) {
410			if (errno == EROFS &&
411			    (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
412				error("chmod(%.100s, 0%o) failed: %.100s",
413				    ttyname, mode, strerror(errno));
414			else
415				fatal("chmod(%.100s, 0%o) failed: %.100s",
416				    ttyname, mode, strerror(errno));
417		}
418	}
419}
420