sshpty.c revision 92559 
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 $");
16RCSID("$FreeBSD: head/crypto/openssh/sshpty.c 92559 2002-03-18 10:09:43Z des $");
17
18#include <libutil.h>
19#include "sshpty.h"
20#include "log.h"
21
22/* Pty allocated with _getpty gets broken if we do I_PUSH:es to it. */
23#if defined(HAVE__GETPTY) || defined(HAVE_OPENPTY)
24#undef HAVE_DEV_PTMX
25#endif
26
27#ifndef O_NOCTTY
28#define O_NOCTTY 0
29#endif
30
31/*
32 * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
33 * nonzero if a pty was successfully allocated.  On success, open file
34 * descriptors for the pty and tty sides and the name of the tty side are
35 * returned (the buffer must be able to hold at least 64 characters).
36 */
37
38int
39pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
40{
41#if defined(HAVE_OPENPTY) || defined(BSD4_4)
42	/* openpty(3) exists in OSF/1 and some other os'es */
43	char buf[64];
44	int i;
45
46	i = openpty(ptyfd, ttyfd, buf, NULL, NULL);
47	if (i < 0) {
48		error("openpty: %.100s", strerror(errno));
49		return 0;
50	}
51	strlcpy(namebuf, buf, namebuflen);	/* possible truncation */
52	return 1;
53#else /* HAVE_OPENPTY */
54#ifdef HAVE__GETPTY
55	/*
56	 * _getpty(3) exists in SGI Irix 4.x, 5.x & 6.x -- it generates more
57	 * pty's automagically when needed
58	 */
59	char *slave;
60
61	slave = _getpty(ptyfd, O_RDWR, 0622, 0);
62	if (slave == NULL) {
63		error("_getpty: %.100s", strerror(errno));
64		return 0;
65	}
66	strlcpy(namebuf, slave, namebuflen);
67	/* Open the slave side. */
68	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
69	if (*ttyfd < 0) {
70		error("%.200s: %.100s", namebuf, strerror(errno));
71		close(*ptyfd);
72		return 0;
73	}
74	return 1;
75#else /* HAVE__GETPTY */
76#ifdef HAVE_DEV_PTMX
77	/*
78	 * This code is used e.g. on Solaris 2.x.  (Note that Solaris 2.3
79	 * also has bsd-style ptys, but they simply do not work.)
80	 */
81	int ptm;
82	char *pts;
83
84	ptm = open("/dev/ptmx", O_RDWR | O_NOCTTY);
85	if (ptm < 0) {
86		error("/dev/ptmx: %.100s", strerror(errno));
87		return 0;
88	}
89	if (grantpt(ptm) < 0) {
90		error("grantpt: %.100s", strerror(errno));
91		return 0;
92	}
93	if (unlockpt(ptm) < 0) {
94		error("unlockpt: %.100s", strerror(errno));
95		return 0;
96	}
97	pts = ptsname(ptm);
98	if (pts == NULL)
99		error("Slave pty side name could not be obtained.");
100	strlcpy(namebuf, pts, namebuflen);
101	*ptyfd = ptm;
102
103	/* Open the slave side. */
104	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
105	if (*ttyfd < 0) {
106		error("%.100s: %.100s", namebuf, strerror(errno));
107		close(*ptyfd);
108		return 0;
109	}
110	/* Push the appropriate streams modules, as described in Solaris pts(7). */
111	if (ioctl(*ttyfd, I_PUSH, "ptem") < 0)
112		error("ioctl I_PUSH ptem: %.100s", strerror(errno));
113	if (ioctl(*ttyfd, I_PUSH, "ldterm") < 0)
114		error("ioctl I_PUSH ldterm: %.100s", strerror(errno));
115	if (ioctl(*ttyfd, I_PUSH, "ttcompat") < 0)
116		error("ioctl I_PUSH ttcompat: %.100s", strerror(errno));
117	return 1;
118#else /* HAVE_DEV_PTMX */
119#ifdef HAVE_DEV_PTS_AND_PTC
120	/* AIX-style pty code. */
121	const char *name;
122
123	*ptyfd = open("/dev/ptc", O_RDWR | O_NOCTTY);
124	if (*ptyfd < 0) {
125		error("Could not open /dev/ptc: %.100s", strerror(errno));
126		return 0;
127	}
128	name = ttyname(*ptyfd);
129	if (!name)
130		fatal("Open of /dev/ptc returns device for which ttyname fails.");
131	strlcpy(namebuf, name, namebuflen);
132	*ttyfd = open(name, O_RDWR | O_NOCTTY);
133	if (*ttyfd < 0) {
134		error("Could not open pty slave side %.100s: %.100s",
135		    name, strerror(errno));
136		close(*ptyfd);
137		return 0;
138	}
139	return 1;
140#else /* HAVE_DEV_PTS_AND_PTC */
141	/* BSD-style pty code. */
142	char buf[64];
143	int i;
144	const char *ptymajors = "pqrstuvwxyzabcdefghijklmnoABCDEFGHIJKLMNOPQRSTUVWXYZ";
145	const char *ptyminors = "0123456789abcdef";
146	int num_minors = strlen(ptyminors);
147	int num_ptys = strlen(ptymajors) * num_minors;
148
149	for (i = 0; i < num_ptys; i++) {
150		snprintf(buf, sizeof buf, "/dev/pty%c%c", ptymajors[i / num_minors],
151			 ptyminors[i % num_minors]);
152		*ptyfd = open(buf, O_RDWR | O_NOCTTY);
153		if (*ptyfd < 0)
154			continue;
155		snprintf(namebuf, namebuflen, "/dev/tty%c%c",
156		    ptymajors[i / num_minors], ptyminors[i % num_minors]);
157
158		/* Open the slave side. */
159		*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
160		if (*ttyfd < 0) {
161			error("%.100s: %.100s", namebuf, strerror(errno));
162			close(*ptyfd);
163			return 0;
164		}
165		return 1;
166	}
167	return 0;
168#endif /* HAVE_DEV_PTS_AND_PTC */
169#endif /* HAVE_DEV_PTMX */
170#endif /* HAVE__GETPTY */
171#endif /* HAVE_OPENPTY */
172}
173
174/* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */
175
176void
177pty_release(const char *ttyname)
178{
179	if (chown(ttyname, (uid_t) 0, (gid_t) 0) < 0)
180		error("chown %.100s 0 0 failed: %.100s", ttyname, strerror(errno));
181	if (chmod(ttyname, (mode_t) 0666) < 0)
182		error("chmod %.100s 0666 failed: %.100s", ttyname, strerror(errno));
183}
184
185/* Makes the tty the processes controlling tty and sets it to sane modes. */
186
187void
188pty_make_controlling_tty(int *ttyfd, const char *ttyname)
189{
190	int fd;
191
192	/* First disconnect from the old controlling tty. */
193#ifdef TIOCNOTTY
194	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
195	if (fd >= 0) {
196		(void) ioctl(fd, TIOCNOTTY, NULL);
197		close(fd);
198	}
199#endif /* TIOCNOTTY */
200	if (setsid() < 0)
201		error("setsid: %.100s", strerror(errno));
202
203	/*
204	 * Verify that we are successfully disconnected from the controlling
205	 * tty.
206	 */
207	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
208	if (fd >= 0) {
209		error("Failed to disconnect from controlling tty.");
210		close(fd);
211	}
212	/* Make it our controlling tty. */
213#ifdef TIOCSCTTY
214	debug("Setting controlling tty using TIOCSCTTY.");
215	if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
216		error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
217#endif /* TIOCSCTTY */
218	fd = open(ttyname, O_RDWR);
219	if (fd < 0)
220		error("%.100s: %.100s", ttyname, strerror(errno));
221	else
222		close(fd);
223
224	/* Verify that we now have a controlling tty. */
225	fd = open(_PATH_TTY, O_WRONLY);
226	if (fd < 0)
227		error("open /dev/tty failed - could not set controlling tty: %.100s",
228		    strerror(errno));
229	else {
230		close(fd);
231	}
232}
233
234/* Changes the window size associated with the pty. */
235
236void
237pty_change_window_size(int ptyfd, int row, int col,
238	int xpixel, int ypixel)
239{
240	struct winsize w;
241	w.ws_row = row;
242	w.ws_col = col;
243	w.ws_xpixel = xpixel;
244	w.ws_ypixel = ypixel;
245	(void) ioctl(ptyfd, TIOCSWINSZ, &w);
246}
247
248void
249pty_setowner(struct passwd *pw, const char *ttyname)
250{
251	struct group *grp;
252	gid_t gid;
253	mode_t mode;
254	struct stat st;
255
256	/* Determine the group to make the owner of the tty. */
257	grp = getgrnam("tty");
258	if (grp) {
259		gid = grp->gr_gid;
260		mode = S_IRUSR | S_IWUSR | S_IWGRP;
261	} else {
262		gid = pw->pw_gid;
263		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
264	}
265
266	/*
267	 * Change owner and mode of the tty as required.
268	 * Warn but continue if filesystem is read-only and the uids match/
269	 * tty is owned by root.
270	 */
271	if (stat(ttyname, &st))
272		fatal("stat(%.100s) failed: %.100s", ttyname,
273		    strerror(errno));
274
275	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
276		if (chown(ttyname, pw->pw_uid, gid) < 0) {
277			if (errno == EROFS &&
278			   (st.st_uid == pw->pw_uid || st.st_uid == 0))
279				error("chown(%.100s, %d, %d) failed: %.100s",
280				    ttyname, pw->pw_uid, gid,
281				    strerror(errno));
282			else
283				fatal("chown(%.100s, %d, %d) failed: %.100s",
284				    ttyname, pw->pw_uid, gid,
285				    strerror(errno));
286		}
287	}
288
289	if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
290		if (chmod(ttyname, mode) < 0) {
291			if (errno == EROFS &&
292			    (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
293				error("chmod(%.100s, 0%o) failed: %.100s",
294				    ttyname, mode, strerror(errno));
295			else
296				fatal("chmod(%.100s, 0%o) failed: %.100s",
297				    ttyname, mode, strerror(errno));
298		}
299	}
300}
301