1/* Copyright (C) 1991-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <limits.h>
20#include <stddef.h>
21#include <dirent.h>
22#include <sys/types.h>
23#include <sys/stat.h>
24#include <termios.h>
25#include <unistd.h>
26#include <string.h>
27#include <stdlib.h>
28
29#include <fd_to_filename.h>
30
31#include "ttyname.h"
32
33static int getttyname_r (char *buf, size_t buflen,
34 const struct __stat64_t64 *mytty, int save,
35 int *dostat);
36
37static int
38attribute_compat_text_section
39getttyname_r (char *buf, size_t buflen, const struct __stat64_t64 *mytty,
40 int save, int *dostat)
41{
42 struct __stat64_t64 st;
43 DIR *dirstream;
44 struct dirent64 *d;
45 size_t devlen = strlen (buf);
46
47 dirstream = __opendir (buf);
48 if (dirstream == NULL)
49 {
50 *dostat = -1;
51 return errno;
52 }
53
54 while ((d = __readdir64 (dirstream)) != NULL)
55 if ((d->d_fileno == mytty->st_ino || *dostat)
56 && strcmp (d->d_name, "stdin")
57 && strcmp (d->d_name, "stdout")
58 && strcmp (d->d_name, "stderr"))
59 {
60 char *cp;
61 size_t needed = _D_EXACT_NAMLEN (d) + 1;
62
63 if (needed > buflen)
64 {
65 *dostat = -1;
66 (void) __closedir (dirstream);
67 __set_errno (ERANGE);
68 return ERANGE;
69 }
70
71 cp = __stpncpy (buf + devlen, d->d_name, needed);
72 cp[0] = '\0';
73
74 if (__stat64_time64 (buf, &st) == 0
75 && is_mytty (mytty, &st))
76 {
77 (void) __closedir (dirstream);
78 __set_errno (save);
79 return 0;
80 }
81 }
82
83 (void) __closedir (dirstream);
84 __set_errno (save);
85 /* It is not clear what to return in this case. `isatty' says FD
86 refers to a TTY but no entry in /dev has this inode. */
87 return ENOTTY;
88}
89
90/* Store at most BUFLEN character of the pathname of the terminal FD is
91 open on in BUF. Return 0 on success, otherwise an error number. */
92int
93__ttyname_r (int fd, char *buf, size_t buflen)
94{
95 struct fd_to_filename filename;
96 struct __stat64_t64 st, st1;
97 int dostat = 0;
98 int doispty = 0;
99 int save = errno;
100
101 /* Test for the absolute minimal size. This makes life easier inside
102 the loop. */
103 if (!buf)
104 {
105 __set_errno (EINVAL);
106 return EINVAL;
107 }
108
109 if (buflen < sizeof ("/dev/pts/"))
110 {
111 __set_errno (ERANGE);
112 return ERANGE;
113 }
114
115 /* isatty check, tcgetattr is used because it sets the correct
116 errno (EBADF resp. ENOTTY) on error. */
117 struct termios term;
118 if (__glibc_unlikely (__tcgetattr (fd, &term) < 0))
119 return errno;
120
121 if (__fstat64_time64 (fd, &st) < 0)
122 return errno;
123
124 /* We try using the /proc filesystem. */
125 ssize_t ret = __readlink (__fd_to_filename (fd, &filename), buf, buflen - 1);
126 if (__glibc_unlikely (ret == -1 && errno == ENAMETOOLONG))
127 {
128 __set_errno (ERANGE);
129 return ERANGE;
130 }
131
132 if (__glibc_likely (ret != -1))
133 {
134#define UNREACHABLE_LEN strlen ("(unreachable)")
135 if (ret > UNREACHABLE_LEN
136 && memcmp (buf, "(unreachable)", UNREACHABLE_LEN) == 0)
137 {
138 memmove (buf, buf + UNREACHABLE_LEN, ret - UNREACHABLE_LEN);
139 ret -= UNREACHABLE_LEN;
140 }
141
142 /* readlink need not terminate the string. */
143 buf[ret] = '\0';
144
145 /* Verify readlink result, fall back on iterating through devices. */
146 if (buf[0] == '/'
147 && __stat64_time64 (buf, &st1) == 0
148 && is_mytty (&st, &st1))
149 return 0;
150
151 doispty = 1;
152 }
153
154 /* Prepare the result buffer. */
155 memcpy (buf, "/dev/pts/", sizeof ("/dev/pts/"));
156 buflen -= sizeof ("/dev/pts/") - 1;
157
158 if (__stat64_time64 (buf, &st1) == 0 && S_ISDIR (st1.st_mode))
159 {
160 ret = getttyname_r (buf, buflen, &st, save,
161 &dostat);
162 }
163 else
164 {
165 __set_errno (save);
166 ret = ENOENT;
167 }
168
169 if (ret && dostat != -1)
170 {
171 buf[sizeof ("/dev/") - 1] = '\0';
172 buflen += sizeof ("pts/") - 1;
173 ret = getttyname_r (buf, buflen, &st, save,
174 &dostat);
175 }
176
177 if (ret && dostat != -1)
178 {
179 buf[sizeof ("/dev/") - 1] = '\0';
180 dostat = 1;
181 ret = getttyname_r (buf, buflen, &st,
182 save, &dostat);
183 }
184
185 if (ret && doispty && is_pty (&st))
186 {
187 /* We failed to figure out the TTY's name, but we can at least
188 signal that we did verify that it really is a PTY slave.
189 This happens when we have inherited the file descriptor from
190 a different mount namespace. */
191 __set_errno (ENODEV);
192 return ENODEV;
193 }
194
195 return ret;
196}
197libc_hidden_def (__ttyname_r)
198weak_alias (__ttyname_r, ttyname_r)
199