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
31 int
posix_openpt(int oflag)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_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 */
62 static const char *
ptmname(int mfd)63 ptmname(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 */
86 int
grantpt(int mfd)87 grantpt(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 */
95 int
unlockpt(int mfd)96 unlockpt(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 */
105 char *
ptsname(int mfd)106 ptsname(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