1/* Copyright (C) 1996-2024 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 <assert.h>
19#include <errno.h>
20#include <limits.h>
21#include <string.h>
22#include <unistd.h>
23#include <stdlib.h>
24#include <utmp.h>
25#include <shlib-compat.h>
26
27/* Return the result of ttyname in the buffer pointed to by TTY, which should
28 be of length BUF_LEN. If it is too long to fit in this buffer, a
29 sufficiently long buffer is allocated using malloc, and returned in TTY.
30 0 is returned upon success, -1 otherwise. */
31static int
32tty_name (int fd, char **tty, size_t buf_len)
33{
34 int rv; /* Return value. 0 = success. */
35 char *buf = *tty; /* Buffer for ttyname, initially the user's. */
36
37 for (;;)
38 {
39 char *new_buf;
40
41 if (buf_len)
42 {
43 rv = __ttyname_r (fd, buf, buf_len);
44
45 if (rv != 0 || memchr (buf, '\0', buf_len))
46 /* We either got an error, or we succeeded and the
47 returned name fit in the buffer. */
48 break;
49
50 /* Try again with a longer buffer. */
51 buf_len += buf_len; /* Double it */
52 }
53 else
54 /* No initial buffer; start out by mallocing one. */
55 buf_len = 128; /* First time guess. */
56
57 if (buf != *tty)
58 /* We've already malloced another buffer at least once. */
59 new_buf = realloc (ptr: buf, size: buf_len);
60 else
61 new_buf = malloc (size: buf_len);
62 if (! new_buf)
63 {
64 rv = -1;
65 __set_errno (ENOMEM);
66 break;
67 }
68 buf = new_buf;
69 }
70
71 if (rv == 0)
72 *tty = buf; /* Return buffer to the user. */
73 else if (buf != *tty)
74 free (ptr: buf); /* Free what we malloced when returning an error. */
75
76 return rv;
77}
78
79void
80__login (const struct utmp *ut)
81{
82#ifdef PATH_MAX
83 char _tty[PATH_MAX + UT_LINESIZE];
84#else
85 char _tty[512 + UT_LINESIZE];
86#endif
87 char *tty = _tty;
88 int found_tty;
89 const char *ttyp;
90 struct utmp copy = *ut;
91
92 /* Fill in those fields we supply. */
93 copy.ut_type = USER_PROCESS;
94 copy.ut_pid = getpid ();
95
96 /* Seek tty. */
97 found_tty = tty_name (STDIN_FILENO, tty: &tty, buf_len: sizeof (_tty));
98 if (found_tty < 0)
99 found_tty = tty_name (STDOUT_FILENO, tty: &tty, buf_len: sizeof (_tty));
100 if (found_tty < 0)
101 found_tty = tty_name (STDERR_FILENO, tty: &tty, buf_len: sizeof (_tty));
102
103 if (found_tty >= 0)
104 {
105 /* We only want to insert the name of the tty without path.
106 But take care of name like /dev/pts/3. */
107 if (strncmp (tty, "/dev/", 5) == 0)
108 ttyp = tty + 5; /* Skip the "/dev/". */
109 else
110 ttyp = basename (tty);
111
112 /* Position to record for this tty. */
113 strncpy (copy.ut_line, ttyp, UT_LINESIZE);
114
115 /* Tell that we want to use the UTMP file. */
116 if (__utmpname (_PATH_UTMP) == 0)
117 {
118 /* Open UTMP file. */
119 __setutent ();
120
121 /* Write the entry. */
122 __pututline (&copy);
123
124 /* Close UTMP file. */
125 __endutent ();
126 }
127
128 if (tty != _tty)
129 free (ptr: tty); /* Free buffer malloced by tty_name. */
130 }
131 else
132 /* We provide a default value so that the output does not contain
133 an random bytes in this field. */
134 strncpy (copy.ut_line, "???", UT_LINESIZE);
135
136 /* Update the WTMP file. Here we have to add a new entry. */
137 __updwtmp (_PATH_WTMP, &copy);
138}
139versioned_symbol (libc, __login, login, GLIBC_2_34);
140libc_hidden_ver (__login, login)
141
142#if OTHER_SHLIB_COMPAT (libutil, GLIBC_2_0, GLIBC_2_34)
143compat_symbol (libutil, __login, login, GLIBC_2_0);
144#endif
145

source code of glibc/login/login.c