1 /* $OpenBSD: sshpty.c,v 1.28 2007/09/11 23:49:09 stevesk Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Allocating a pseudo-terminal, and making it the controlling tty.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 */
14
15 #include "includes.h"
16
17 #include <sys/types.h>
18 #include <sys/ioctl.h>
19 #include <sys/stat.h>
20 #include <signal.h>
21
22 #include <errno.h>
23 #include <fcntl.h>
24 #include <grp.h>
25 #ifdef HAVE_PATHS_H
26 # include <paths.h>
27 #endif
28 #include <pwd.h>
29 #include <stdarg.h>
30 #include <string.h>
31 #include <termios.h>
32 #ifdef HAVE_UTIL_H
33 # include <util.h>
34 #endif
35 #include <unistd.h>
36
37 #include "sshpty.h"
38 #include "log.h"
39 #include "misc.h"
40
41 #ifdef HAVE_PTY_H
42 # include <pty.h>
43 #endif
44
45 #ifndef O_NOCTTY
46 #define O_NOCTTY 0
47 #endif
48
49 #ifdef __APPLE__
50 # include <AvailabilityMacros.h>
51 # if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5)
52 # define __APPLE_PRIVPTY__
53 # endif
54 #endif
55
56 /*
57 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or
58 * nonzero if a pty was successfully allocated. On success, open file
59 * descriptors for the pty and tty sides and the name of the tty side are
60 * returned (the buffer must be able to hold at least 64 characters).
61 */
62
63 int
pty_allocate(int * ptyfd,int * ttyfd,char * namebuf,size_t namebuflen)64 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
65 {
66 /* openpty(3) exists in OSF/1 and some other os'es */
67 char *name;
68 int i;
69
70 i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
71 if (i < 0) {
72 error("openpty: %.100s", strerror(errno));
73 return 0;
74 }
75 #ifdef ANDROID
76 /* Android does not have a working ttyname() */
77 name = "/dev/ptmx";
78 #else
79 name = ttyname(*ttyfd);
80 if (!name)
81 fatal("openpty returns device for which ttyname fails.");
82 #endif
83
84 strlcpy(namebuf, name, namebuflen); /* possible truncation */
85 return 1;
86 }
87
88 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */
89
90 void
pty_release(const char * tty)91 pty_release(const char *tty)
92 {
93 #ifndef __APPLE_PRIVPTY__
94 if (chown(tty, (uid_t) 0, (gid_t) 0) < 0)
95 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno));
96 if (chmod(tty, (mode_t) 0666) < 0)
97 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno));
98 #endif /* __APPLE_PRIVPTY__ */
99 }
100
101 /* Makes the tty the process's controlling tty and sets it to sane modes. */
102
103 void
pty_make_controlling_tty(int * ttyfd,const char * tty)104 pty_make_controlling_tty(int *ttyfd, const char *tty)
105 {
106 int fd;
107 #ifdef USE_VHANGUP
108 void *old;
109 #endif /* USE_VHANGUP */
110
111 #ifdef _UNICOS
112 if (setsid() < 0)
113 error("setsid: %.100s", strerror(errno));
114
115 fd = open(tty, O_RDWR|O_NOCTTY);
116 if (fd != -1) {
117 signal(SIGHUP, SIG_IGN);
118 ioctl(fd, TCVHUP, (char *)NULL);
119 signal(SIGHUP, SIG_DFL);
120 setpgid(0, 0);
121 close(fd);
122 } else {
123 error("Failed to disconnect from controlling tty.");
124 }
125
126 debug("Setting controlling tty using TCSETCTTY.");
127 ioctl(*ttyfd, TCSETCTTY, NULL);
128 fd = open("/dev/tty", O_RDWR);
129 if (fd < 0)
130 error("%.100s: %.100s", tty, strerror(errno));
131 close(*ttyfd);
132 *ttyfd = fd;
133 #else /* _UNICOS */
134
135 /* First disconnect from the old controlling tty. */
136 #ifdef TIOCNOTTY
137 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
138 if (fd >= 0) {
139 (void) ioctl(fd, TIOCNOTTY, NULL);
140 close(fd);
141 }
142 #endif /* TIOCNOTTY */
143 if (setsid() < 0)
144 error("setsid: %.100s", strerror(errno));
145
146 /*
147 * Verify that we are successfully disconnected from the controlling
148 * tty.
149 */
150 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
151 if (fd >= 0) {
152 error("Failed to disconnect from controlling tty.");
153 close(fd);
154 }
155 /* Make it our controlling tty. */
156 #ifdef TIOCSCTTY
157 debug("Setting controlling tty using TIOCSCTTY.");
158 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
159 error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
160 #endif /* TIOCSCTTY */
161 #ifdef NEED_SETPGRP
162 if (setpgrp(0,0) < 0)
163 error("SETPGRP %s",strerror(errno));
164 #endif /* NEED_SETPGRP */
165 #ifdef USE_VHANGUP
166 old = signal(SIGHUP, SIG_IGN);
167 vhangup();
168 signal(SIGHUP, old);
169 #endif /* USE_VHANGUP */
170 fd = open(tty, O_RDWR);
171 if (fd < 0) {
172 error("%.100s: %.100s", tty, strerror(errno));
173 } else {
174 #ifdef USE_VHANGUP
175 close(*ttyfd);
176 *ttyfd = fd;
177 #else /* USE_VHANGUP */
178 close(fd);
179 #endif /* USE_VHANGUP */
180 }
181 /* Verify that we now have a controlling tty. */
182 fd = open(_PATH_TTY, O_WRONLY);
183 if (fd < 0)
184 error("open /dev/tty failed - could not set controlling tty: %.100s",
185 strerror(errno));
186 else
187 close(fd);
188 #endif /* _UNICOS */
189 }
190
191 /* Changes the window size associated with the pty. */
192
193 void
pty_change_window_size(int ptyfd,u_int row,u_int col,u_int xpixel,u_int ypixel)194 pty_change_window_size(int ptyfd, u_int row, u_int col,
195 u_int xpixel, u_int ypixel)
196 {
197 struct winsize w;
198
199 /* may truncate u_int -> u_short */
200 w.ws_row = row;
201 w.ws_col = col;
202 w.ws_xpixel = xpixel;
203 w.ws_ypixel = ypixel;
204 (void) ioctl(ptyfd, TIOCSWINSZ, &w);
205 }
206
207 void
pty_setowner(struct passwd * pw,const char * tty)208 pty_setowner(struct passwd *pw, const char *tty)
209 {
210 struct group *grp;
211 gid_t gid;
212 mode_t mode;
213 struct stat st;
214
215 /* Determine the group to make the owner of the tty. */
216 grp = getgrnam("tty");
217 if (grp) {
218 gid = grp->gr_gid;
219 mode = S_IRUSR | S_IWUSR | S_IWGRP;
220 } else {
221 gid = pw->pw_gid;
222 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
223 }
224
225 /*
226 * Change owner and mode of the tty as required.
227 * Warn but continue if filesystem is read-only and the uids match/
228 * tty is owned by root.
229 */
230 if (stat(tty, &st))
231 fatal("stat(%.100s) failed: %.100s", tty,
232 strerror(errno));
233
234 #ifdef WITH_SELINUX
235 ssh_selinux_setup_pty(pw->pw_name, tty);
236 #endif
237
238 if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
239 if (chown(tty, pw->pw_uid, gid) < 0) {
240 if (errno == EROFS &&
241 (st.st_uid == pw->pw_uid || st.st_uid == 0))
242 debug("chown(%.100s, %u, %u) failed: %.100s",
243 tty, (u_int)pw->pw_uid, (u_int)gid,
244 strerror(errno));
245 else
246 fatal("chown(%.100s, %u, %u) failed: %.100s",
247 tty, (u_int)pw->pw_uid, (u_int)gid,
248 strerror(errno));
249 }
250 }
251
252 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
253 if (chmod(tty, mode) < 0) {
254 if (errno == EROFS &&
255 (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
256 debug("chmod(%.100s, 0%o) failed: %.100s",
257 tty, (u_int)mode, strerror(errno));
258 else
259 fatal("chmod(%.100s, 0%o) failed: %.100s",
260 tty, (u_int)mode, strerror(errno));
261 }
262 }
263 }
264