xref: /openbsd-src/lib/libc/stdlib/posix_pty.c (revision 91f110e064cd7c194e59e019b83bb7496c1c84d4)
1 /*	$OpenBSD: posix_pty.c,v 1.1 2012/12/03 20:08:33 millert Exp $	*/
2 
3 /*
4  * Copyright (c) 2012 Todd C. Miller <Todd.Miller@courtesan.com>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  */
18 
19 #include <sys/types.h>
20 #include <sys/ioctl.h>
21 #include <sys/stat.h>
22 #include <sys/tty.h>
23 #include <errno.h>
24 #include <fcntl.h>
25 #include <paths.h>
26 #include <stddef.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <unistd.h>
30 
31 int
32 posix_openpt(int oflag)
33 {
34 	struct ptmget ptm;
35 	int fd, mfd = -1;
36 
37 	/* User must specify O_RDWR in oflag. */
38 	if (!(oflag & O_RDWR)) {
39 		errno = EINVAL;
40 		return -1;
41 	}
42 
43 	/* Get pty master and slave (this API only uses the master). */
44 	fd = open(PATH_PTMDEV, O_RDWR);
45 	if (fd != -1) {
46 		if (ioctl(fd, PTMGET, &ptm) != -1) {
47 			close(ptm.sfd);
48 			mfd = ptm.cfd;
49 		}
50 		close(fd);
51 	}
52 
53 	return mfd;
54 }
55 
56 /*
57  * Look up the name of the specified pty master fd.
58  * Note that the name returned does *not* include the /dev/ prefix.
59  * Returns the name on success and NULL on error, setting errno.
60  */
61 static const char *
62 ptmname(int mfd)
63 {
64 	struct stat sb;
65 	const char *name;
66 
67 	/* Make sure it is a pty master. */
68 	if (fstat(mfd, &sb) != 0)
69 		return NULL;
70 	if (!S_ISCHR(sb.st_mode)) {
71 		errno = EINVAL;
72 		return NULL;
73 	}
74 	name = devname(sb.st_rdev, S_IFCHR);
75 	if (strncmp(name, "pty", 3) != 0) {
76 		errno = EINVAL;
77 		return NULL;
78 	}
79 	return name;
80 }
81 
82 /*
83  * The PTMGET ioctl handles the mode and owner for us.
84  */
85 int
86 grantpt(int mfd)
87 {
88 	return ptmname(mfd) ? 0 : -1;
89 }
90 
91 /*
92  * The PTMGET ioctl unlocks the pty master and slave for us.
93  */
94 int
95 unlockpt(int mfd)
96 {
97 	return ptmname(mfd) ? 0 : -1;
98 }
99 
100 /*
101  * Look up the path of the slave pty that corresponds to the master fd.
102  * Returns the path if successful or NULL on error.
103  */
104 char *
105 ptsname(int mfd)
106 {
107 	const char *master;
108 	static char slave[sizeof(((struct ptmget *)NULL)->sn)];
109 
110 	if ((master = ptmname(mfd)) == NULL)
111 		return NULL;
112 
113 	/* Add /dev/ prefix and convert "pty" to "tty". */
114 	strlcpy(slave, _PATH_DEV, sizeof(slave));
115 	strlcat(slave, master, sizeof(slave));
116 	slave[sizeof(_PATH_DEV) - 1] = 't';
117 
118 	return slave;
119 }
120