1 /* $OpenBSD: pty.c,v 1.13 2004/05/28 07:03:47 deraadt Exp $ */
2
3 /*-
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #if defined(LIBC_SCCS) && !defined(lint)
33 /* from: static char sccsid[] = "@(#)pty.c 8.1 (Berkeley) 6/4/93"; */
34 static const char rcsid[] = "$Id: pty.c,v 1.13 2004/05/28 07:03:47 deraadt Exp $";
35 #endif /* LIBC_SCCS and not lint */
36
37 #include <sys/cdefs.h>
38 #include <sys/types.h>
39 #include <sys/stat.h>
40 #include <sys/ioctl.h>
41 #include <fcntl.h>
42 #include <termios.h>
43 #include <errno.h>
44 #include <unistd.h>
45 #include <stdio.h>
46 #include <string.h>
47 #include <grp.h>
48 #include <sys/tty.h>
49
50 #include "util.h"
51
52 #define TTY_LETTERS "pqrstuvwxyzPQRST"
53 #define TTY_SUFFIX "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
54
55 int
openpty(int * amaster,int * aslave,char * name,struct termios * termp,struct winsize * winp)56 openpty(int *amaster, int *aslave, char *name, struct termios *termp,
57 struct winsize *winp)
58 {
59 char line[] = "/dev/ptyXX";
60 const char *cp1, *cp2;
61 int master, slave, fd;
62 struct ptmget ptm;
63 struct group *gr;
64 gid_t ttygid;
65
66 /*
67 * Try to use /dev/ptm and the PTMGET ioctl to get a properly set up
68 * and owned pty/tty pair. If this fails, (because we might not have
69 * the ptm device, etc.) fall back to using the traditional method
70 * of walking through the pty entries in /dev for the moment, until
71 * there is less chance of people being seriously boned by running
72 * kernels without /dev/ptm in them.
73 */
74 fd = open(PATH_PTMDEV, O_RDWR, 0);
75 if (fd == -1)
76 goto walkit;
77 if ((ioctl(fd, PTMGET, &ptm) == -1)) {
78 close(fd);
79 goto walkit;
80 }
81 close(fd);
82 master = ptm.cfd;
83 slave = ptm.sfd;
84 if (name) {
85 /*
86 * Manual page says "at least 16 characters".
87 */
88 strlcpy(name, ptm.sn, 16);
89 }
90 *amaster = master;
91 *aslave = slave;
92 if (termp)
93 (void) tcsetattr(slave, TCSAFLUSH, termp);
94 if (winp)
95 (void) ioctl(slave, TIOCSWINSZ, (char *)winp);
96 return (0);
97 walkit:
98 if ((gr = getgrnam("tty")) != NULL)
99 ttygid = gr->gr_gid;
100 else
101 ttygid = -1;
102
103 for (cp1 = TTY_LETTERS; *cp1; cp1++) {
104 line[8] = *cp1;
105 for (cp2 = TTY_SUFFIX; *cp2; cp2++) {
106 line[9] = *cp2;
107 line[5] = 'p';
108 if ((master = open(line, O_RDWR, 0)) == -1) {
109 if (errno == ENOENT)
110 return (-1); /* out of ptys */
111 } else {
112 line[5] = 't';
113 (void) chown(line, getuid(), ttygid);
114 (void) chmod(line, S_IRUSR|S_IWUSR|S_IWGRP);
115 (void) revoke(line);
116 if ((slave = open(line, O_RDWR, 0)) != -1) {
117 *amaster = master;
118 *aslave = slave;
119 if (name) {
120 /*
121 * Manual page says "at least
122 * 16 characters".
123 */
124 strlcpy(name, line, 16);
125 }
126 if (termp)
127 (void) tcsetattr(slave,
128 TCSAFLUSH, termp);
129 if (winp)
130 (void) ioctl(slave, TIOCSWINSZ,
131 (char *)winp);
132 return (0);
133 }
134 (void) close(master);
135 }
136 }
137 }
138 errno = ENOENT; /* out of ptys */
139 return (-1);
140 }
141
142 pid_t
forkpty(amaster,name,termp,winp)143 forkpty(amaster, name, termp, winp)
144 int *amaster;
145 char *name;
146 struct termios *termp;
147 struct winsize *winp;
148 {
149 int master, slave;
150 pid_t pid;
151
152 if (openpty(&master, &slave, name, termp, winp) == -1)
153 return (-1);
154 switch (pid = fork()) {
155 case -1:
156 return (-1);
157 case 0:
158 /*
159 * child
160 */
161 (void) close(master);
162 login_tty(slave);
163 return (0);
164 }
165 /*
166 * parent
167 */
168 *amaster = master;
169 (void) close(slave);
170 return (pid);
171 }
172