lock.c revision 59300 
1/* lock.c: The opielock() library function.
2
3%%% portions-copyright-cmetz-96
4Portions of this software are Copyright 1996-1998 by Craig Metz, All Rights
5Reserved. The Inner Net License Version 2 applies to these portions of
6the software.
7You should have received a copy of the license with this software. If
8you didn't get a copy, you may request one from <license@inner.net>.
9
10Portions of this software are Copyright 1995 by Randall Atkinson and Dan
11McDonald, All Rights Reserved. All Rights under this copyright are assigned
12to the U.S. Naval Research Laboratory (NRL). The NRL Copyright Notice and
13License Agreement applies to this software.
14
15        History:
16
17	Modified by cmetz for OPIE 2.31. Put locks in a separate dir.
18            Bug fixes.
19	Modified by cmetz for OPIE 2.3. Do refcounts whether or not we
20            actually lock. Fixed USER_LOCKING=0 case.
21	Modified by cmetz for OPIE 2.22. Added reference count for locks.
22	    Changed lock filename/refcount symbol names to better indicate
23	    that they're not user serviceable.
24	Modified by cmetz for OPIE 2.2. Use FUNCTION declaration et al.
25            Use "principal" instead of "name" to make it clearer.
26            Ifdef around some headers, be more careful about allowed
27            error return values. Check open() return value properly.
28            Avoid NULL.
29        Created at NRL for OPIE 2.2 from opiesubr2.c
30
31$FreeBSD: head/contrib/opie/libopie/lock.c 59300 2000-04-17 00:01:23Z kris $
32*/
33#include "opie_cfg.h"
34#if HAVE_STRING_H
35#include <string.h>
36#endif /* HAVE_STRING_H */
37#if HAVE_UNISTD_H
38#include <unistd.h>
39#endif /* HAVE_UNISTD_H */
40#include <sys/stat.h>
41#include <syslog.h>
42#include <fcntl.h>
43#if HAVE_STDLIB_H
44#include <stdlib.h>
45#endif /* HAVE_STDLIB_H */
46#include <errno.h>
47#include "opie.h"
48
49#if !HAVE_LSTAT
50#define lstat(x, y) stat(x, y)
51#endif /* !HAVE_LSTAT */
52
53int __opie_lockrefcount = 0;
54static int do_atexit = 1;
55
56VOIDRET opiedisableaeh FUNCTION_NOARGS
57{
58  do_atexit = 0;
59}
60#if USER_LOCKING
61char *__opie_lockfilename = (char *)0;
62
63/* atexit() handler for opielock() */
64VOIDRET opieunlockaeh FUNCTION_NOARGS
65{
66  if (__opie_lockfilename) {
67    __opie_lockrefcount = 0;
68    opieunlock();
69  }
70}
71#endif /* USER_LOCKING */
72
73/*
74   Serialize (we hope) authentication of user to prevent race conditions.
75   Creates a lock file with a name of OPIE_LOCK_PREFIX with the user name
76   appended. This file contains the pid of the lock's owner and a time()
77   stamp. We use the former to check for dead owners and the latter to
78   provide an upper bound on the lock duration. If there are any problems,
79   we assume the lock is bogus.
80
81   The value of this locking and its security implications are still not
82   completely clear and require further study.
83
84   One could conceivably hack this facility to provide locking of user
85   accounts after several authentication failures.
86
87   Return -1 on low-level error, 0 if ok, 1 on locking failure.
88*/
89int opielock FUNCTION((principal), char *principal)
90{
91#if USER_LOCKING
92  int fh, waits = 0, rval = -1, pid, t, i;
93  char buffer[128], buffer2[128], *c, *c2;
94  struct stat statbuf[2];
95
96  if (getuid() && geteuid()) {
97#if DEBUG
98    syslog(LOG_DEBUG, "opielock: requires superuser priveleges");
99#endif /* DEBUG */
100    return -1;
101  };
102
103  if (__opie_lockfilename) {
104    __opie_lockrefcount++;
105    return 0;
106  }
107
108  if (!(__opie_lockfilename = (char *)malloc(sizeof(OPIE_LOCK_DIR) + 1 + strlen(principal))))
109    return -1;
110
111  strcpy(__opie_lockfilename, OPIE_LOCK_DIR);
112
113  if (mkdir(__opie_lockfilename, 0700) < 0)
114    if (errno != EEXIST)
115      return -1;
116
117  if (lstat(__opie_lockfilename, &statbuf[0]) < 0)
118    return -1;
119
120  if (statbuf[0].st_uid) {
121#if DEBUG
122    syslog(LOG_DEBUG, "opielock: %s isn't owned by the superuser.", __opie_lockfilename);
123#endif /* DEBUG */
124    return -1;
125  };
126
127  if (!S_ISDIR(statbuf[0].st_mode)) {
128#if DEBUG
129    syslog(LOG_DEBUG, "opielock: %s isn't a directory.", __opie_lockfilename);
130#endif /* DEBUG */
131    return -1;
132  };
133
134  if ((statbuf[0].st_mode & 0777) != 00700) {
135#if DEBUG
136    syslog(LOG_DEBUG, "opielock: permissions on %s are not correct.", __opie_lockfilename);
137#endif /* DEBUG */
138    return -1;
139  };
140
141  strcat(__opie_lockfilename, "/");
142  strcat(__opie_lockfilename, principal);
143
144  fh = -1;
145  while (fh < 0) {
146    if (!lstat(__opie_lockfilename, &statbuf[0]))
147      if (!S_ISREG(statbuf[0].st_mode))
148        goto lockret;
149
150    if ((fh = open(__opie_lockfilename, O_WRONLY | O_CREAT | O_EXCL, 0600)) < 0) {
151      if (lstat(__opie_lockfilename, &statbuf[1]) < 0)
152        goto lockret;
153      if (statbuf[0].st_ino != statbuf[1].st_ino)
154        goto lockret;
155      if (statbuf[0].st_mode != statbuf[1].st_mode)
156        goto lockret;
157      if ((fh = open(__opie_lockfilename, O_RDONLY, 0600)) < 0)
158        goto lockret;
159      if ((i = read(fh, buffer, sizeof(buffer))) <= 0)
160        goto lockret;
161
162      buffer[sizeof(buffer) - 1] = 0;
163      buffer[i - 1] = 0;
164
165      if (!(c = strchr(buffer, '\n')))
166        break;
167
168      *(c++) = 0;
169
170      if (!(c2 = strchr(c, '\n')))
171        break;
172
173      *(c2++) = 0;
174
175      if (!(pid = atoi(buffer)))
176        break;
177
178      if (!(t = atoi(c)))
179        break;
180
181      if ((t + OPIE_LOCK_TIMEOUT) < time(0))
182        break;
183
184      if (kill(pid, 0))
185        break;
186
187      close(fh);
188      fh = 0;
189      sleep(1);
190      if (waits++ > 3) {
191        rval = 1;
192        goto lockret;
193      };
194    };
195  };
196
197  if (lstat(__opie_lockfilename, &statbuf[0]) < 0)
198    goto lockret;
199  if (fstat(fh, &statbuf[1]) < 0)
200    goto lockret;
201  if (!S_ISREG(statbuf[0].st_mode) || (statbuf[0].st_mode != statbuf[1].st_mode) || (statbuf[0].st_ino != statbuf[1].st_ino))
202    goto lockret;
203
204  sprintf(buffer, "%d\n%d\n", getpid(), time(0));
205  i = strlen(buffer) + 1;
206  if (lseek(fh, 0, SEEK_SET)) {
207    close(fh);
208    unlink(__opie_lockfilename);
209    fh = 0;
210    goto lockret;
211  };
212  if (write(fh, buffer, i) != i) {
213    close(fh);
214    unlink(__opie_lockfilename);
215    fh = 0;
216    goto lockret;
217  };
218  close(fh);
219  if ((fh = open(__opie_lockfilename, O_RDWR, 0600)) < 0) {
220    unlink(__opie_lockfilename);
221    goto lockret;
222  };
223  if (read(fh, buffer2, i) != i) {
224    close(fh);
225    unlink(__opie_lockfilename);
226    fh = 0;
227    goto lockret;
228  };
229  close(fh);
230  if (memcmp(buffer, buffer2, i)) {
231    unlink(__opie_lockfilename);
232    goto lockret;
233  };
234
235  __opie_lockrefcount++;
236  rval = 0;
237  if (do_atexit)
238    atexit(opieunlockaeh);
239
240lockret:
241  if (fh >= 0)
242    close(fh);
243  if (!__opie_lockrefcount) {
244    free (__opie_lockfilename);
245    __opie_lockfilename = NULL;
246  };
247  return rval;
248#else /* USER_LOCKING */
249  __opie_lockrefcount++;
250  return 0;
251#endif /* USER_LOCKING */
252}
253