lock.c revision 92914
1/* lock.c: The opielock() library function. 2 3%%% portions-copyright-cmetz-96 4Portions of this software are Copyright 1996-1999 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 2.4. Use snprintf. 18 Modified by cmetz for OPIE 2.31. Put locks in a separate dir. 19 Bug fixes. 20 Modified by cmetz for OPIE 2.3. Do refcounts whether or not we 21 actually lock. Fixed USER_LOCKING=0 case. 22 Modified by cmetz for OPIE 2.22. Added reference count for locks. 23 Changed lock filename/refcount symbol names to better indicate 24 that they're not user serviceable. 25 Modified by cmetz for OPIE 2.2. Use FUNCTION declaration et al. 26 Use "principal" instead of "name" to make it clearer. 27 Ifdef around some headers, be more careful about allowed 28 error return values. Check open() return value properly. 29 Avoid NULL. 30 Created at NRL for OPIE 2.2 from opiesubr2.c 31 32$FreeBSD: head/contrib/opie/libopie/lock.c 92914 2002-03-21 23:42:52Z markm $ 33*/ 34#include "opie_cfg.h" 35#if HAVE_STRING_H 36#include <string.h> 37#endif /* HAVE_STRING_H */ 38#if HAVE_UNISTD_H 39#include <unistd.h> 40#endif /* HAVE_UNISTD_H */ 41#include <sys/stat.h> 42#include <syslog.h> 43#include <fcntl.h> 44#if HAVE_STDLIB_H 45#include <stdlib.h> 46#endif /* HAVE_STDLIB_H */ 47#include <errno.h> 48#include "opie.h" 49 50#if !HAVE_LSTAT 51#define lstat(x, y) stat(x, y) 52#endif /* !HAVE_LSTAT */ 53 54int __opie_lockrefcount = 0; 55static int do_atexit = 1; 56 57VOIDRET opiedisableaeh FUNCTION_NOARGS 58{ 59 do_atexit = 0; 60} 61#if USER_LOCKING 62char *__opie_lockfilename = (char *)0; 63 64/* atexit() handler for opielock() */ 65VOIDRET opieunlockaeh FUNCTION_NOARGS 66{ 67 if (__opie_lockfilename) { 68 __opie_lockrefcount = 0; 69 opieunlock(); 70 } 71} 72#endif /* USER_LOCKING */ 73 74/* 75 Serialize (we hope) authentication of user to prevent race conditions. 76 Creates a lock file with a name of OPIE_LOCK_PREFIX with the user name 77 appended. This file contains the pid of the lock's owner and a time() 78 stamp. We use the former to check for dead owners and the latter to 79 provide an upper bound on the lock duration. If there are any problems, 80 we assume the lock is bogus. 81 82 The value of this locking and its security implications are still not 83 completely clear and require further study. 84 85 One could conceivably hack this facility to provide locking of user 86 accounts after several authentication failures. 87 88 Return -1 on low-level error, 0 if ok, 1 on locking failure. 89*/ 90int opielock FUNCTION((principal), char *principal) 91{ 92#if USER_LOCKING 93 int fh, waits = 0, rval = -1, pid, t, i; 94 char buffer[128], buffer2[128], *c, *c2; 95 struct stat statbuf[2]; 96 97 if (getuid() && geteuid()) { 98#if DEBUG 99 syslog(LOG_DEBUG, "opielock: requires superuser priveleges"); 100#endif /* DEBUG */ 101 return -1; 102 }; 103 104 if (__opie_lockfilename) { 105 __opie_lockrefcount++; 106 return 0; 107 } 108 109 if (!(__opie_lockfilename = (char *)malloc(sizeof(OPIE_LOCK_DIR) + 1 + strlen(principal)))) 110 return -1; 111 112 strcpy(__opie_lockfilename, OPIE_LOCK_DIR); 113 114 if (mkdir(__opie_lockfilename, 0700) < 0) 115 if (errno != EEXIST) 116 return -1; 117 118 if (lstat(__opie_lockfilename, &statbuf[0]) < 0) 119 return -1; 120 121 if (statbuf[0].st_uid) { 122#if DEBUG 123 syslog(LOG_DEBUG, "opielock: %s isn't owned by the superuser.", __opie_lockfilename); 124#endif /* DEBUG */ 125 return -1; 126 }; 127 128 if (!S_ISDIR(statbuf[0].st_mode)) { 129#if DEBUG 130 syslog(LOG_DEBUG, "opielock: %s isn't a directory.", __opie_lockfilename); 131#endif /* DEBUG */ 132 return -1; 133 }; 134 135 if ((statbuf[0].st_mode & 0777) != 00700) { 136#if DEBUG 137 syslog(LOG_DEBUG, "opielock: permissions on %s are not correct.", __opie_lockfilename); 138#endif /* DEBUG */ 139 return -1; 140 }; 141 142 strcat(__opie_lockfilename, "/"); 143 strcat(__opie_lockfilename, principal); 144 145 fh = -1; 146 while (fh < 0) { 147 if (!lstat(__opie_lockfilename, &statbuf[0])) 148 if (!S_ISREG(statbuf[0].st_mode)) 149 goto lockret; 150 151 if ((fh = open(__opie_lockfilename, O_WRONLY | O_CREAT | O_EXCL, 0600)) < 0) { 152 if (lstat(__opie_lockfilename, &statbuf[1]) < 0) 153 goto lockret; 154 if (statbuf[0].st_ino != statbuf[1].st_ino) 155 goto lockret; 156 if (statbuf[0].st_mode != statbuf[1].st_mode) 157 goto lockret; 158 if ((fh = open(__opie_lockfilename, O_RDONLY, 0600)) < 0) 159 goto lockret; 160 if ((i = read(fh, buffer, sizeof(buffer))) <= 0) 161 goto lockret; 162 163 buffer[sizeof(buffer) - 1] = 0; 164 buffer[i - 1] = 0; 165 166 if (!(c = strchr(buffer, '\n'))) 167 break; 168 169 *(c++) = 0; 170 171 if (!(c2 = strchr(c, '\n'))) 172 break; 173 174 *(c2++) = 0; 175 176 if (!(pid = atoi(buffer))) 177 break; 178 179 if (!(t = atoi(c))) 180 break; 181 182 if ((t + OPIE_LOCK_TIMEOUT) < time(0)) 183 break; 184 185 if (kill(pid, 0)) 186 break; 187 188 close(fh); 189 fh = 0; 190 sleep(1); 191 if (waits++ > 3) { 192 rval = 1; 193 goto lockret; 194 }; 195 }; 196 }; 197 198 if (lstat(__opie_lockfilename, &statbuf[0]) < 0) 199 goto lockret; 200 if (fstat(fh, &statbuf[1]) < 0) 201 goto lockret; 202 if (!S_ISREG(statbuf[0].st_mode) || (statbuf[0].st_mode != statbuf[1].st_mode) || (statbuf[0].st_ino != statbuf[1].st_ino)) 203 goto lockret; 204 205 if (snprintf(buffer, sizeof(buffer), "%d\n%d\n", getpid(), time(0)) >= sizeof(buffer)) 206 goto lockret; 207 208 i = strlen(buffer) + 1; 209 if (lseek(fh, 0, SEEK_SET)) { 210 close(fh); 211 unlink(__opie_lockfilename); 212 fh = 0; 213 goto lockret; 214 }; 215 if (write(fh, buffer, i) != i) { 216 close(fh); 217 unlink(__opie_lockfilename); 218 fh = 0; 219 goto lockret; 220 }; 221 close(fh); 222 if ((fh = open(__opie_lockfilename, O_RDWR, 0600)) < 0) { 223 unlink(__opie_lockfilename); 224 goto lockret; 225 }; 226 if (read(fh, buffer2, i) != i) { 227 close(fh); 228 unlink(__opie_lockfilename); 229 fh = 0; 230 goto lockret; 231 }; 232 close(fh); 233 if (memcmp(buffer, buffer2, i)) { 234 unlink(__opie_lockfilename); 235 goto lockret; 236 }; 237 238 __opie_lockrefcount++; 239 rval = 0; 240 if (do_atexit) 241 atexit(opieunlockaeh); 242 243lockret: 244 if (fh >= 0) 245 close(fh); 246 if (!__opie_lockrefcount) { 247 free (__opie_lockfilename); 248 __opie_lockfilename = NULL; 249 }; 250 return rval; 251#else /* USER_LOCKING */ 252 __opie_lockrefcount++; 253 return 0; 254#endif /* USER_LOCKING */ 255} 256