sshpty.c revision 98941 
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 1.4 2001/12/19 07:18:56 deraadt Exp $");
16
17#ifdef HAVE_UTIL_H
18# include <util.h>
19#endif /* HAVE_UTIL_H */
20
21#include "sshpty.h"
22#include "log.h"
23#include "misc.h"
24
25/* Pty allocated with _getpty gets broken if we do I_PUSH:es to it. */
26#if defined(HAVE__GETPTY) || defined(HAVE_OPENPTY)
27#undef HAVE_DEV_PTMX
28#endif
29
30#ifdef HAVE_PTY_H
31# include <pty.h>
32#endif
33#if defined(HAVE_DEV_PTMX) && defined(HAVE_SYS_STROPTS_H)
34# include <sys/stropts.h>
35#endif
36
37#ifndef O_NOCTTY
38#define O_NOCTTY 0
39#endif
40
41/*
42 * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
43 * nonzero if a pty was successfully allocated.  On success, open file
44 * descriptors for the pty and tty sides and the name of the tty side are
45 * returned (the buffer must be able to hold at least 64 characters).
46 */
47
48int
49pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
50{
51#if defined(HAVE_OPENPTY) || defined(BSD4_4)
52	/* openpty(3) exists in OSF/1 and some other os'es */
53	char *name;
54	int i;
55
56	i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
57	if (i < 0) {
58		error("openpty: %.100s", strerror(errno));
59		return 0;
60	}
61	name = ttyname(*ttyfd);
62	if (!name)
63		fatal("openpty returns device for which ttyname fails.");
64
65	strlcpy(namebuf, name, namebuflen);	/* possible truncation */
66	return 1;
67#else /* HAVE_OPENPTY */
68#ifdef HAVE__GETPTY
69	/*
70	 * _getpty(3) exists in SGI Irix 4.x, 5.x & 6.x -- it generates more
71	 * pty's automagically when needed
72	 */
73	char *slave;
74
75	slave = _getpty(ptyfd, O_RDWR, 0622, 0);
76	if (slave == NULL) {
77		error("_getpty: %.100s", strerror(errno));
78		return 0;
79	}
80	strlcpy(namebuf, slave, namebuflen);
81	/* Open the slave side. */
82	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
83	if (*ttyfd < 0) {
84		error("%.200s: %.100s", namebuf, strerror(errno));
85		close(*ptyfd);
86		return 0;
87	}
88	return 1;
89#else /* HAVE__GETPTY */
90#if defined(HAVE_DEV_PTMX)
91	/*
92	 * This code is used e.g. on Solaris 2.x.  (Note that Solaris 2.3
93	 * also has bsd-style ptys, but they simply do not work.)
94	 */
95	int ptm;
96	char *pts;
97	mysig_t old_signal;
98
99	ptm = open("/dev/ptmx", O_RDWR | O_NOCTTY);
100	if (ptm < 0) {
101		error("/dev/ptmx: %.100s", strerror(errno));
102		return 0;
103	}
104	old_signal = mysignal(SIGCHLD, SIG_DFL);
105	if (grantpt(ptm) < 0) {
106		error("grantpt: %.100s", strerror(errno));
107		return 0;
108	}
109	mysignal(SIGCHLD, old_signal);
110	if (unlockpt(ptm) < 0) {
111		error("unlockpt: %.100s", strerror(errno));
112		return 0;
113	}
114	pts = ptsname(ptm);
115	if (pts == NULL)
116		error("Slave pty side name could not be obtained.");
117	strlcpy(namebuf, pts, namebuflen);
118	*ptyfd = ptm;
119
120	/* Open the slave side. */
121	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
122	if (*ttyfd < 0) {
123		error("%.100s: %.100s", namebuf, strerror(errno));
124		close(*ptyfd);
125		return 0;
126	}
127#ifndef HAVE_CYGWIN
128	/*
129	 * Push the appropriate streams modules, as described in Solaris pts(7).
130	 * HP-UX pts(7) doesn't have ttcompat module.
131	 */
132	if (ioctl(*ttyfd, I_PUSH, "ptem") < 0)
133		error("ioctl I_PUSH ptem: %.100s", strerror(errno));
134	if (ioctl(*ttyfd, I_PUSH, "ldterm") < 0)
135		error("ioctl I_PUSH ldterm: %.100s", strerror(errno));
136#ifndef __hpux
137	if (ioctl(*ttyfd, I_PUSH, "ttcompat") < 0)
138		error("ioctl I_PUSH ttcompat: %.100s", strerror(errno));
139#endif
140#endif
141	return 1;
142#else /* HAVE_DEV_PTMX */
143#ifdef HAVE_DEV_PTS_AND_PTC
144	/* AIX-style pty code. */
145	const char *name;
146
147	*ptyfd = open("/dev/ptc", O_RDWR | O_NOCTTY);
148	if (*ptyfd < 0) {
149		error("Could not open /dev/ptc: %.100s", strerror(errno));
150		return 0;
151	}
152	name = ttyname(*ptyfd);
153	if (!name)
154		fatal("Open of /dev/ptc returns device for which ttyname fails.");
155	strlcpy(namebuf, name, namebuflen);
156	*ttyfd = open(name, O_RDWR | O_NOCTTY);
157	if (*ttyfd < 0) {
158		error("Could not open pty slave side %.100s: %.100s",
159		    name, strerror(errno));
160		close(*ptyfd);
161		return 0;
162	}
163	return 1;
164#else /* HAVE_DEV_PTS_AND_PTC */
165#ifdef _CRAY
166	char buf[64];
167	int i;
168	int highpty;
169
170#ifdef _SC_CRAY_NPTY
171	highpty = sysconf(_SC_CRAY_NPTY);
172	if (highpty == -1)
173		highpty = 128;
174#else
175	highpty = 128;
176#endif
177
178	for (i = 0; i < highpty; i++) {
179		snprintf(buf, sizeof(buf), "/dev/pty/%03d", i);
180		*ptyfd = open(buf, O_RDWR|O_NOCTTY);
181		if (*ptyfd < 0)
182			continue;
183		snprintf(namebuf, namebuflen, "/dev/ttyp%03d", i);
184		/* Open the slave side. */
185		*ttyfd = open(namebuf, O_RDWR|O_NOCTTY);
186		if (*ttyfd < 0) {
187			error("%.100s: %.100s", namebuf, strerror(errno));
188			close(*ptyfd);
189			return 0;
190		}
191		return 1;
192	}
193	return 0;
194#else
195	/* BSD-style pty code. */
196	char buf[64];
197	int i;
198	const char *ptymajors = "pqrstuvwxyzabcdefghijklmnoABCDEFGHIJKLMNOPQRSTUVWXYZ";
199	const char *ptyminors = "0123456789abcdef";
200	int num_minors = strlen(ptyminors);
201	int num_ptys = strlen(ptymajors) * num_minors;
202	struct termios tio;
203
204	for (i = 0; i < num_ptys; i++) {
205		snprintf(buf, sizeof buf, "/dev/pty%c%c", ptymajors[i / num_minors],
206			 ptyminors[i % num_minors]);
207		snprintf(namebuf, namebuflen, "/dev/tty%c%c",
208		    ptymajors[i / num_minors], ptyminors[i % num_minors]);
209
210		*ptyfd = open(buf, O_RDWR | O_NOCTTY);
211		if (*ptyfd < 0) {
212			/* Try SCO style naming */
213			snprintf(buf, sizeof buf, "/dev/ptyp%d", i);
214			snprintf(namebuf, namebuflen, "/dev/ttyp%d", i);
215			*ptyfd = open(buf, O_RDWR | O_NOCTTY);
216			if (*ptyfd < 0)
217				continue;
218		}
219
220		/* Open the slave side. */
221		*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
222		if (*ttyfd < 0) {
223			error("%.100s: %.100s", namebuf, strerror(errno));
224			close(*ptyfd);
225			return 0;
226		}
227		/* set tty modes to a sane state for broken clients */
228		if (tcgetattr(*ptyfd, &tio) < 0)
229			log("Getting tty modes for pty failed: %.100s", strerror(errno));
230		else {
231			tio.c_lflag |= (ECHO | ISIG | ICANON);
232			tio.c_oflag |= (OPOST | ONLCR);
233			tio.c_iflag |= ICRNL;
234
235			/* Set the new modes for the terminal. */
236			if (tcsetattr(*ptyfd, TCSANOW, &tio) < 0)
237				log("Setting tty modes for pty failed: %.100s", strerror(errno));
238		}
239
240		return 1;
241	}
242	return 0;
243#endif /* CRAY */
244#endif /* HAVE_DEV_PTS_AND_PTC */
245#endif /* HAVE_DEV_PTMX */
246#endif /* HAVE__GETPTY */
247#endif /* HAVE_OPENPTY */
248}
249
250/* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */
251
252void
253pty_release(const char *ttyname)
254{
255	if (chown(ttyname, (uid_t) 0, (gid_t) 0) < 0)
256		error("chown %.100s 0 0 failed: %.100s", ttyname, strerror(errno));
257	if (chmod(ttyname, (mode_t) 0666) < 0)
258		error("chmod %.100s 0666 failed: %.100s", ttyname, strerror(errno));
259}
260
261/* Makes the tty the processes controlling tty and sets it to sane modes. */
262
263void
264pty_make_controlling_tty(int *ttyfd, const char *ttyname)
265{
266	int fd;
267#ifdef USE_VHANGUP
268	void *old;
269#endif /* USE_VHANGUP */
270
271#ifdef _CRAY
272	if (setsid() < 0)
273		error("setsid: %.100s", strerror(errno));
274
275	fd = open(ttyname, O_RDWR|O_NOCTTY);
276	if (fd != -1) {
277		mysignal(SIGHUP, SIG_IGN);
278		ioctl(fd, TCVHUP, (char *)NULL);
279		mysignal(SIGHUP, SIG_DFL);
280		setpgid(0, 0);
281		close(fd);
282	} else {
283		error("Failed to disconnect from controlling tty.");
284	}
285
286	debug("Setting controlling tty using TCSETCTTY.");
287	ioctl(*ttyfd, TCSETCTTY, NULL);
288	fd = open("/dev/tty", O_RDWR);
289	if (fd < 0)
290		error("%.100s: %.100s", ttyname, strerror(errno));
291	close(*ttyfd);
292	*ttyfd = fd;
293#else /* _CRAY */
294
295	/* First disconnect from the old controlling tty. */
296#ifdef TIOCNOTTY
297	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
298	if (fd >= 0) {
299		(void) ioctl(fd, TIOCNOTTY, NULL);
300		close(fd);
301	}
302#endif /* TIOCNOTTY */
303	if (setsid() < 0)
304		error("setsid: %.100s", strerror(errno));
305
306	/*
307	 * Verify that we are successfully disconnected from the controlling
308	 * tty.
309	 */
310	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
311	if (fd >= 0) {
312		error("Failed to disconnect from controlling tty.");
313		close(fd);
314	}
315	/* Make it our controlling tty. */
316#ifdef TIOCSCTTY
317	debug("Setting controlling tty using TIOCSCTTY.");
318	if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
319		error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
320#endif /* TIOCSCTTY */
321#ifdef HAVE_NEWS4
322	if (setpgrp(0,0) < 0)
323		error("SETPGRP %s",strerror(errno));
324#endif /* HAVE_NEWS4 */
325#ifdef USE_VHANGUP
326	old = mysignal(SIGHUP, SIG_IGN);
327	vhangup();
328	mysignal(SIGHUP, old);
329#endif /* USE_VHANGUP */
330	fd = open(ttyname, O_RDWR);
331	if (fd < 0) {
332		error("%.100s: %.100s", ttyname, strerror(errno));
333	} else {
334#ifdef USE_VHANGUP
335		close(*ttyfd);
336		*ttyfd = fd;
337#else /* USE_VHANGUP */
338		close(fd);
339#endif /* USE_VHANGUP */
340	}
341	/* Verify that we now have a controlling tty. */
342	fd = open(_PATH_TTY, O_WRONLY);
343	if (fd < 0)
344		error("open /dev/tty failed - could not set controlling tty: %.100s",
345		    strerror(errno));
346	else {
347		close(fd);
348	}
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	w.ws_row = row;
360	w.ws_col = col;
361	w.ws_xpixel = xpixel;
362	w.ws_ypixel = ypixel;
363	(void) ioctl(ptyfd, TIOCSWINSZ, &w);
364}
365
366void
367pty_setowner(struct passwd *pw, const char *ttyname)
368{
369	struct group *grp;
370	gid_t gid;
371	mode_t mode;
372	struct stat st;
373
374	/* Determine the group to make the owner of the tty. */
375	grp = getgrnam("tty");
376	if (grp) {
377		gid = grp->gr_gid;
378		mode = S_IRUSR | S_IWUSR | S_IWGRP;
379	} else {
380		gid = pw->pw_gid;
381		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
382	}
383
384	/*
385	 * Change owner and mode of the tty as required.
386	 * Warn but continue if filesystem is read-only and the uids match/
387	 * tty is owned by root.
388	 */
389	if (stat(ttyname, &st))
390		fatal("stat(%.100s) failed: %.100s", ttyname,
391		    strerror(errno));
392
393	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
394		if (chown(ttyname, pw->pw_uid, gid) < 0) {
395			if (errno == EROFS &&
396			   (st.st_uid == pw->pw_uid || st.st_uid == 0))
397				error("chown(%.100s, %d, %d) failed: %.100s",
398				    ttyname, pw->pw_uid, gid,
399				    strerror(errno));
400			else
401				fatal("chown(%.100s, %d, %d) failed: %.100s",
402				    ttyname, pw->pw_uid, gid,
403				    strerror(errno));
404		}
405	}
406
407	if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
408		if (chmod(ttyname, mode) < 0) {
409			if (errno == EROFS &&
410			    (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
411				error("chmod(%.100s, 0%o) failed: %.100s",
412				    ttyname, mode, strerror(errno));
413			else
414				fatal("chmod(%.100s, 0%o) failed: %.100s",
415				    ttyname, mode, strerror(errno));
416		}
417	}
418}
419