1 /*
2 * lib/krb5/os/lock_file.c
3 *
4 * Copyright 1990, 1998 by the Massachusetts Institute of Technology.
5 * All Rights Reserved.
6 *
7 * Export of this software from the United States of America may
8 * require a specific license from the United States Government.
9 * It is the responsibility of any person or organization contemplating
10 * export to obtain such a license before exporting.
11 *
12 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
13 * distribute this software and its documentation for any purpose and
14 * without fee is hereby granted, provided that the above copyright
15 * notice appear in all copies and that both that copyright notice and
16 * this permission notice appear in supporting documentation, and that
17 * the name of M.I.T. not be used in advertising or publicity pertaining
18 * to distribution of the software without specific, written prior
19 * permission. Furthermore if you modify this software you must label
20 * your software as modified software and not distribute it in such a
21 * fashion that it might be confused with the original M.I.T. software.
22 * M.I.T. makes no representations about the suitability of
23 * this software for any purpose. It is provided "as is" without express
24 * or implied warranty.
25 *
26 *
27 * libos: krb5_lock_file routine
28 */
29
30 #include "k5-int.h"
31 #include <stdio.h>
32
33 #if !defined(_WIN32)
34
35 /* Unix version... */
36
37 #if HAVE_UNISTD_H
38 #include <unistd.h>
39 #endif
40
41 #include <errno.h>
42
43 #ifdef HAVE_FCNTL_H
44 #include <fcntl.h>
45 #endif
46
47 #if defined(HAVE_FCNTL_H) && defined(F_SETLKW) && defined(F_RDLCK)
48 #define POSIX_FILE_LOCKS
49 #endif
50
51 #ifdef HAVE_FLOCK
52 #ifndef sysvimp
53 #include <sys/file.h>
54 #endif
55 #else
56 #ifndef LOCK_SH
57 #define LOCK_SH 0
58 #define LOCK_EX 0
59 #define LOCK_UN 0
60 #endif
61 #endif
62
63 /*ARGSUSED*/
64 krb5_error_code
krb5_lock_file(krb5_context context,int fd,int mode)65 krb5_lock_file(krb5_context context, int fd, int mode)
66 {
67 int lock_flag = -1;
68 krb5_error_code retval = 0;
69 #ifdef POSIX_FILE_LOCKS
70 int lock_cmd = F_SETLKW;
71 struct flock lock_arg = { 0 };
72 #endif
73
74 switch (mode & ~KRB5_LOCKMODE_DONTBLOCK) {
75 case KRB5_LOCKMODE_SHARED:
76 #ifdef POSIX_FILE_LOCKS
77 lock_arg.l_type = F_RDLCK;
78 #endif
79 lock_flag = LOCK_SH;
80 break;
81 case KRB5_LOCKMODE_EXCLUSIVE:
82 #ifdef POSIX_FILE_LOCKS
83 lock_arg.l_type = F_WRLCK;
84 #endif
85 lock_flag = LOCK_EX;
86 break;
87 case KRB5_LOCKMODE_UNLOCK:
88 #ifdef POSIX_FILE_LOCKS
89 lock_arg.l_type = F_UNLCK;
90 #endif
91 lock_flag = LOCK_UN;
92 break;
93 }
94
95 if (lock_flag == -1)
96 return(KRB5_LIBOS_BADLOCKFLAG);
97
98 if (mode & KRB5_LOCKMODE_DONTBLOCK) {
99 #ifdef POSIX_FILE_LOCKS
100 lock_cmd = F_SETLK;
101 #endif
102 #ifdef HAVE_FLOCK
103 lock_flag |= LOCK_NB;
104 #endif
105 }
106
107 #ifdef POSIX_FILE_LOCKS
108 lock_arg.l_whence = 0;
109 lock_arg.l_start = 0;
110 lock_arg.l_len = 0;
111 if (fcntl(fd, lock_cmd, &lock_arg) == -1) {
112 if (errno == EACCES || errno == EAGAIN) /* see POSIX/IEEE 1003.1-1988,
113 6.5.2.4 */
114 return(EAGAIN);
115 if (errno != EINVAL) /* Fall back to flock if we get EINVAL */
116 return(errno);
117 retval = errno;
118 } else
119 return 0; /* We succeeded. Yay. */
120 #endif
121
122 #ifdef HAVE_FLOCK
123 if (flock(fd, lock_flag) == -1)
124 retval = errno;
125 #endif
126
127 return retval;
128 }
129 #else /* Windows or Macintosh */
130
131 krb5_error_code
krb5_lock_file(context,fd,mode)132 krb5_lock_file(context, fd, mode)
133 krb5_context context;
134 int fd;
135 int mode;
136 {
137 return 0;
138 }
139 #endif
140