1/* Copyright (C) 2010-2016 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 <http://www.gnu.org/licenses/>. */
17
18#include <pwd.h>
19#include <unistd.h>
20#include <not-cancel.h>
21
22#define STATIC static
23static int getlogin_r_fd0 (char *name, size_t namesize);
24#define __getlogin_r getlogin_r_fd0
25#include <sysdeps/unix/getlogin_r.c>
26#undef __getlogin_r
27
28
29/* Try to determine login name from /proc/self/loginuid and return 0
30 if successful. If /proc/self/loginuid cannot be read return -1.
31 Otherwise return the error number. */
32
33int
34attribute_hidden
35__getlogin_r_loginuid (char *name, size_t namesize)
36{
37 int fd = open_not_cancel_2 ("/proc/self/loginuid", O_RDONLY);
38 if (fd == -1)
39 return -1;
40
41 /* We are reading a 32-bit number. 12 bytes are enough for the text
42 representation. If not, something is wrong. */
43 char uidbuf[12];
44 ssize_t n = TEMP_FAILURE_RETRY (read_not_cancel (fd, uidbuf,
45 sizeof (uidbuf)));
46 close_not_cancel_no_status (fd);
47
48 uid_t uid;
49 char *endp;
50 if (n <= 0
51 || n == sizeof (uidbuf)
52 || (uidbuf[n] = '\0',
53 uid = strtoul (uidbuf, &endp, 10),
54 endp == uidbuf || *endp != '\0'))
55 return -1;
56
57 size_t buflen = 1024;
58 char *buf = alloca (buflen);
59 bool use_malloc = false;
60 struct passwd pwd;
61 struct passwd *tpwd;
62 int result = 0;
63 int res;
64
65 while ((res = __getpwuid_r (uid, &pwd, buf, buflen, &tpwd)) == ERANGE)
66 if (__libc_use_alloca (2 * buflen))
67 buf = extend_alloca (buf, buflen, 2 * buflen);
68 else
69 {
70 buflen *= 2;
71 char *newp = realloc (use_malloc ? buf : NULL, buflen);
72 if (newp == NULL)
73 {
74 result = ENOMEM;
75 goto out;
76 }
77 buf = newp;
78 use_malloc = true;
79 }
80
81 if (res != 0 || tpwd == NULL)
82 {
83 result = -1;
84 goto out;
85 }
86
87 size_t needed = strlen (pwd.pw_name) + 1;
88 if (needed > namesize)
89 {
90 __set_errno (ERANGE);
91 result = ERANGE;
92 goto out;
93 }
94
95 memcpy (name, pwd.pw_name, needed);
96
97 out:
98 if (use_malloc)
99 free (buf);
100
101 return result;
102}
103
104
105/* Return at most NAME_LEN characters of the login name of the user in NAME.
106 If it cannot be determined or some other error occurred, return the error
107 code. Otherwise return 0. */
108
109int
110__getlogin_r (char *name, size_t namesize)
111{
112 int res = __getlogin_r_loginuid (name, namesize);
113 if (res >= 0)
114 return res;
115
116 return getlogin_r_fd0 (name, namesize);
117}
118libc_hidden_def (__getlogin_r)
119weak_alias (__getlogin_r, getlogin_r)
120libc_hidden_weak (getlogin_r)
121