1 /* Provide a working getlogin_r for systems which lack it.
2
3 Copyright (C) 2005-2007, 2010-2021 Free Software Foundation, Inc.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
17
18 /* Written by Paul Eggert, Derek Price, and Bruno Haible. */
19
20 #include <config.h>
21
22 /* Specification. */
23 #include <unistd.h>
24
25 #include <errno.h>
26 #include <string.h>
27
28 #include "malloca.h"
29
30 #if defined _WIN32 && ! defined __CYGWIN__
31 # define WIN32_LEAN_AND_MEAN
32 # include <windows.h>
33 /* Don't assume that UNICODE is not defined. */
34 # undef GetUserName
35 # define GetUserName GetUserNameA
36 #else
37 # if !HAVE_DECL_GETLOGIN
38 extern char *getlogin (void);
39 # endif
40 #endif
41
42 /* See unistd.in.h for documentation. */
43 int
getlogin_r(char * name,size_t size)44 getlogin_r (char *name, size_t size)
45 {
46 #undef getlogin_r
47 #if defined _WIN32 && ! defined __CYGWIN__
48 /* Native Windows platform. */
49 DWORD sz;
50
51 /* When size > 0x7fff, the doc says that GetUserName will fail.
52 Actually, on Windows XP SP3, it succeeds. But let's be safe,
53 for the sake of older Windows versions. */
54 if (size > 0x7fff)
55 size = 0x7fff;
56 sz = size;
57 if (!GetUserName (name, &sz))
58 {
59 if (GetLastError () == ERROR_INSUFFICIENT_BUFFER)
60 /* In this case, the doc says that sz contains the required size, but
61 actually, on Windows XP SP3, it contains 2 * the required size. */
62 return ERANGE;
63 else
64 return ENOENT;
65 }
66 return 0;
67 #elif HAVE_GETLOGIN_R
68 /* Platform with a getlogin_r() function. */
69 int ret = getlogin_r (name, size);
70
71 if (ret == 0)
72 {
73 const char *nul = memchr (name, '\0', size);
74 if (nul == NULL)
75 /* name contains a truncated result. */
76 return ERANGE;
77 if (size > 0 && nul == name + size - 1)
78 {
79 /* strlen(name) == size-1. Determine whether the untruncated result
80 would have had length size-1 or size. */
81 char *room = (char *) malloca (size + 1);
82 if (room == NULL)
83 return ENOMEM;
84 ret = getlogin_r (room, size + 1);
85 /* The untruncated result should be the same as in the first call. */
86 if (ret == 0 && memcmp (name, room, size) != 0)
87 /* The untruncated result would have been different. */
88 ret = ERANGE;
89 freea (room);
90 }
91 }
92 return ret;
93 #else
94 /* Platform with a getlogin() function. */
95 char *n;
96 size_t nlen;
97
98 errno = 0;
99 n = getlogin ();
100 if (!n)
101 /* ENOENT is a reasonable errno value if getlogin returns NULL. */
102 return (errno != 0 ? errno : ENOENT);
103
104 nlen = strlen (n);
105 if (size <= nlen)
106 return ERANGE;
107 memcpy (name, n, nlen + 1);
108 return 0;
109 #endif
110 }
111