1 /* $OpenBSD: sshpty.c,v 1.29 2014/09/03 18:55:07 djm 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
108 #ifdef _UNICOS
109 if (setsid() < 0)
110 error("setsid: %.100s", strerror(errno));
111
112 fd = open(tty, O_RDWR|O_NOCTTY);
113 if (fd != -1) {
114 signal(SIGHUP, SIG_IGN);
115 ioctl(fd, TCVHUP, (char *)NULL);
116 signal(SIGHUP, SIG_DFL);
117 setpgid(0, 0);
118 close(fd);
119 } else {
120 error("Failed to disconnect from controlling tty.");
121 }
122
123 debug("Setting controlling tty using TCSETCTTY.");
124 ioctl(*ttyfd, TCSETCTTY, NULL);
125 fd = open("/dev/tty", O_RDWR);
126 if (fd < 0)
127 error("%.100s: %.100s", tty, strerror(errno));
128 close(*ttyfd);
129 *ttyfd = fd;
130 #else /* _UNICOS */
131
132 /* First disconnect from the old controlling tty. */
133 #ifdef TIOCNOTTY
134 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
135 if (fd >= 0) {
136 (void) ioctl(fd, TIOCNOTTY, NULL);
137 close(fd);
138 }
139 #endif /* TIOCNOTTY */
140 if (setsid() < 0)
141 error("setsid: %.100s", strerror(errno));
142
143 /*
144 * Verify that we are successfully disconnected from the controlling
145 * tty.
146 */
147 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
148 if (fd >= 0) {
149 error("Failed to disconnect from controlling tty.");
150 close(fd);
151 }
152 /* Make it our controlling tty. */
153 #ifdef TIOCSCTTY
154 debug("Setting controlling tty using TIOCSCTTY.");
155 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
156 error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
157 #endif /* TIOCSCTTY */
158 #ifdef NEED_SETPGRP
159 if (setpgrp(0,0) < 0)
160 error("SETPGRP %s",strerror(errno));
161 #endif /* NEED_SETPGRP */
162 fd = open(tty, O_RDWR);
163 if (fd < 0) {
164 error("%.100s: %.100s", tty, strerror(errno));
165 } else {
166 close(fd);
167 }
168 /* Verify that we now have a controlling tty. */
169 fd = open(_PATH_TTY, O_WRONLY);
170 if (fd < 0)
171 error("open /dev/tty failed - could not set controlling tty: %.100s",
172 strerror(errno));
173 else
174 close(fd);
175 #endif /* _UNICOS */
176 }
177
178 /* Changes the window size associated with the pty. */
179
180 void
pty_change_window_size(int ptyfd,u_int row,u_int col,u_int xpixel,u_int ypixel)181 pty_change_window_size(int ptyfd, u_int row, u_int col,
182 u_int xpixel, u_int ypixel)
183 {
184 struct winsize w;
185
186 /* may truncate u_int -> u_short */
187 w.ws_row = row;
188 w.ws_col = col;
189 w.ws_xpixel = xpixel;
190 w.ws_ypixel = ypixel;
191 (void) ioctl(ptyfd, TIOCSWINSZ, &w);
192 }
193
194 void
pty_setowner(struct passwd * pw,const char * tty)195 pty_setowner(struct passwd *pw, const char *tty)
196 {
197 struct group *grp;
198 gid_t gid;
199 mode_t mode;
200 struct stat st;
201
202 /* Determine the group to make the owner of the tty. */
203 grp = getgrnam("tty");
204 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid;
205 mode = (grp != NULL) ? 0622 : 0600;
206
207 /*
208 * Change owner and mode of the tty as required.
209 * Warn but continue if filesystem is read-only and the uids match/
210 * tty is owned by root.
211 */
212 if (stat(tty, &st))
213 fatal("stat(%.100s) failed: %.100s", tty,
214 strerror(errno));
215
216 #ifdef WITH_SELINUX
217 ssh_selinux_setup_pty(pw->pw_name, tty);
218 #endif
219
220 if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
221 if (chown(tty, pw->pw_uid, gid) < 0) {
222 if (errno == EROFS &&
223 (st.st_uid == pw->pw_uid || st.st_uid == 0))
224 debug("chown(%.100s, %u, %u) failed: %.100s",
225 tty, (u_int)pw->pw_uid, (u_int)gid,
226 strerror(errno));
227 else
228 fatal("chown(%.100s, %u, %u) failed: %.100s",
229 tty, (u_int)pw->pw_uid, (u_int)gid,
230 strerror(errno));
231 }
232 }
233
234 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
235 if (chmod(tty, mode) < 0) {
236 if (errno == EROFS &&
237 (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
238 debug("chmod(%.100s, 0%o) failed: %.100s",
239 tty, (u_int)mode, strerror(errno));
240 else
241 fatal("chmod(%.100s, 0%o) failed: %.100s",
242 tty, (u_int)mode, strerror(errno));
243 }
244 }
245 }
246