1/*	$OpenBSD: posix_pty.c,v 1.3 2019/01/25 00:19:25 millert Exp $	*/
2
3/*
4 * Copyright (c) 2012 Todd C. Miller <millert@openbsd.org>
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
31int
32posix_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_ACCMODE) != O_RDWR ||
39	    (oflag & ~(O_ACCMODE | O_NOCTTY)) != 0) {
40		errno = EINVAL;
41		return -1;
42	}
43
44	/* Get pty master and slave (this API only uses the master). */
45	fd = open(PATH_PTMDEV, O_RDWR);
46	if (fd != -1) {
47		if (ioctl(fd, PTMGET, &ptm) != -1) {
48			close(ptm.sfd);
49			mfd = ptm.cfd;
50		}
51		close(fd);
52	}
53
54	return mfd;
55}
56
57/*
58 * Look up the name of the specified pty master fd.
59 * Note that the name returned does *not* include the /dev/ prefix.
60 * Returns the name on success and NULL on error, setting errno.
61 */
62static const char *
63ptmname(int mfd)
64{
65	struct stat sb;
66	const char *name;
67
68	/* Make sure it is a pty master. */
69	if (fstat(mfd, &sb) != 0)
70		return NULL;
71	if (!S_ISCHR(sb.st_mode)) {
72		errno = EINVAL;
73		return NULL;
74	}
75	name = devname(sb.st_rdev, S_IFCHR);
76	if (strncmp(name, "pty", 3) != 0) {
77		errno = EINVAL;
78		return NULL;
79	}
80	return name;
81}
82
83/*
84 * The PTMGET ioctl handles the mode and owner for us.
85 */
86int
87grantpt(int mfd)
88{
89	return ptmname(mfd) ? 0 : -1;
90}
91
92/*
93 * The PTMGET ioctl unlocks the pty master and slave for us.
94 */
95int
96unlockpt(int mfd)
97{
98	return ptmname(mfd) ? 0 : -1;
99}
100
101/*
102 * Look up the path of the slave pty that corresponds to the master fd.
103 * Returns the path if successful or NULL on error.
104 */
105char *
106ptsname(int mfd)
107{
108	const char *master;
109	static char slave[sizeof(((struct ptmget *)NULL)->sn)];
110
111	if ((master = ptmname(mfd)) == NULL)
112		return NULL;
113
114	/* Add /dev/ prefix and convert "pty" to "tty". */
115	strlcpy(slave, _PATH_DEV, sizeof(slave));
116	strlcat(slave, master, sizeof(slave));
117	slave[sizeof(_PATH_DEV) - 1] = 't';
118
119	return slave;
120}
121