sshpty.c revision 137019 
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 1.12 2004/06/21 17:36:31 avsm 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#ifdef HAVE_PTY_H
26# include <pty.h>
27#endif
28
29#ifndef O_NOCTTY
30#define O_NOCTTY 0
31#endif
32
33/*
34 * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
35 * nonzero if a pty was successfully allocated.  On success, open file
36 * descriptors for the pty and tty sides and the name of the tty side are
37 * returned (the buffer must be able to hold at least 64 characters).
38 */
39
40int
41pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
42{
43	/* openpty(3) exists in OSF/1 and some other os'es */
44	char *name;
45	int i;
46
47	i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
48	if (i < 0) {
49		error("openpty: %.100s", strerror(errno));
50		return 0;
51	}
52	name = ttyname(*ttyfd);
53	if (!name)
54		fatal("openpty returns device for which ttyname fails.");
55
56	strlcpy(namebuf, name, namebuflen);	/* possible truncation */
57	return 1;
58}
59
60/* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */
61
62void
63pty_release(const char *tty)
64{
65	if (chown(tty, (uid_t) 0, (gid_t) 0) < 0)
66		error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno));
67	if (chmod(tty, (mode_t) 0666) < 0)
68		error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno));
69}
70
71/* Makes the tty the process's controlling tty and sets it to sane modes. */
72
73void
74pty_make_controlling_tty(int *ttyfd, const char *tty)
75{
76	int fd;
77#ifdef USE_VHANGUP
78	void *old;
79#endif /* USE_VHANGUP */
80
81#ifdef _UNICOS
82	if (setsid() < 0)
83		error("setsid: %.100s", strerror(errno));
84
85	fd = open(tty, O_RDWR|O_NOCTTY);
86	if (fd != -1) {
87		signal(SIGHUP, SIG_IGN);
88		ioctl(fd, TCVHUP, (char *)NULL);
89		signal(SIGHUP, SIG_DFL);
90		setpgid(0, 0);
91		close(fd);
92	} else {
93		error("Failed to disconnect from controlling tty.");
94	}
95
96	debug("Setting controlling tty using TCSETCTTY.");
97	ioctl(*ttyfd, TCSETCTTY, NULL);
98	fd = open("/dev/tty", O_RDWR);
99	if (fd < 0)
100		error("%.100s: %.100s", tty, strerror(errno));
101	close(*ttyfd);
102	*ttyfd = fd;
103#else /* _UNICOS */
104
105	/* First disconnect from the old controlling tty. */
106#ifdef TIOCNOTTY
107	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
108	if (fd >= 0) {
109		(void) ioctl(fd, TIOCNOTTY, NULL);
110		close(fd);
111	}
112#endif /* TIOCNOTTY */
113	if (setsid() < 0)
114		error("setsid: %.100s", strerror(errno));
115
116	/*
117	 * Verify that we are successfully disconnected from the controlling
118	 * tty.
119	 */
120	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
121	if (fd >= 0) {
122		error("Failed to disconnect from controlling tty.");
123		close(fd);
124	}
125	/* Make it our controlling tty. */
126#ifdef TIOCSCTTY
127	debug("Setting controlling tty using TIOCSCTTY.");
128	if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
129		error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
130#endif /* TIOCSCTTY */
131#ifdef HAVE_NEWS4
132	if (setpgrp(0,0) < 0)
133		error("SETPGRP %s",strerror(errno));
134#endif /* HAVE_NEWS4 */
135#ifdef USE_VHANGUP
136	old = signal(SIGHUP, SIG_IGN);
137	vhangup();
138	signal(SIGHUP, old);
139#endif /* USE_VHANGUP */
140	fd = open(tty, O_RDWR);
141	if (fd < 0) {
142		error("%.100s: %.100s", tty, strerror(errno));
143	} else {
144#ifdef USE_VHANGUP
145		close(*ttyfd);
146		*ttyfd = fd;
147#else /* USE_VHANGUP */
148		close(fd);
149#endif /* USE_VHANGUP */
150	}
151	/* Verify that we now have a controlling tty. */
152	fd = open(_PATH_TTY, O_WRONLY);
153	if (fd < 0)
154		error("open /dev/tty failed - could not set controlling tty: %.100s",
155		    strerror(errno));
156	else
157		close(fd);
158#endif /* _UNICOS */
159}
160
161/* Changes the window size associated with the pty. */
162
163void
164pty_change_window_size(int ptyfd, int row, int col,
165	int xpixel, int ypixel)
166{
167	struct winsize w;
168
169	w.ws_row = row;
170	w.ws_col = col;
171	w.ws_xpixel = xpixel;
172	w.ws_ypixel = ypixel;
173	(void) ioctl(ptyfd, TIOCSWINSZ, &w);
174}
175
176void
177pty_setowner(struct passwd *pw, const char *tty)
178{
179	struct group *grp;
180	gid_t gid;
181	mode_t mode;
182	struct stat st;
183
184	/* Determine the group to make the owner of the tty. */
185	grp = getgrnam("tty");
186	if (grp) {
187		gid = grp->gr_gid;
188		mode = S_IRUSR | S_IWUSR | S_IWGRP;
189	} else {
190		gid = pw->pw_gid;
191		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
192	}
193
194	/*
195	 * Change owner and mode of the tty as required.
196	 * Warn but continue if filesystem is read-only and the uids match/
197	 * tty is owned by root.
198	 */
199	if (stat(tty, &st))
200		fatal("stat(%.100s) failed: %.100s", tty,
201		    strerror(errno));
202
203	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
204		if (chown(tty, pw->pw_uid, gid) < 0) {
205			if (errno == EROFS &&
206			    (st.st_uid == pw->pw_uid || st.st_uid == 0))
207				debug("chown(%.100s, %u, %u) failed: %.100s",
208				    tty, (u_int)pw->pw_uid, (u_int)gid,
209				    strerror(errno));
210			else
211				fatal("chown(%.100s, %u, %u) failed: %.100s",
212				    tty, (u_int)pw->pw_uid, (u_int)gid,
213				    strerror(errno));
214		}
215	}
216
217	if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
218		if (chmod(tty, mode) < 0) {
219			if (errno == EROFS &&
220			    (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
221				debug("chmod(%.100s, 0%o) failed: %.100s",
222				    tty, (u_int)mode, strerror(errno));
223			else
224				fatal("chmod(%.100s, 0%o) failed: %.100s",
225				    tty, (u_int)mode, strerror(errno));
226		}
227	}
228}
229