| 1 | /* |
| 2 | * nss-icmp or libnss_icmp - GNU C Library NSS module to query host |
| 3 | * names by ICMP. |
| 4 | * Copyright (C) 2005 Fredrik Tolf <fredrik@dolda2000.com> |
| 5 | * |
| 6 | * This library is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU Library General Public |
| 8 | * License as published by the Free Software Foundation; either |
| 9 | * version 2 of the License, or (at your option) any later version. |
| 10 | * |
| 11 | * This library is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | * Library General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU Library General Public |
| 17 | * License along with this library; if not, write to the Free |
| 18 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 19 | * MA 02111-1307, USA |
| 20 | */ |
| 21 | |
| 22 | #include <stdlib.h> |
| 23 | #include <stdio.h> |
| 24 | #include <unistd.h> |
| 25 | #include <string.h> |
| 26 | #include <errno.h> |
| 27 | #include <time.h> |
| 28 | #include <sys/socket.h> |
| 29 | #include <netinet/in.h> |
| 30 | #include <netdb.h> |
| 31 | #include <arpa/inet.h> |
| 32 | #include <nss.h> |
| 33 | #include <sys/types.h> |
| 34 | #include <fcntl.h> |
| 35 | #include <sys/wait.h> |
| 36 | #include "config.h" |
| 37 | |
| 38 | #ifndef CONFIGFILE |
| 39 | #define CONFIGFILE "/etc/nss-icmp.conf" |
| 40 | #endif |
| 41 | |
| 42 | #if 0 |
| 43 | #define DEBUGP(format...) fprintf(stderr, "nss-icmp: " format); |
| 44 | #else |
| 45 | #define DEBUGP(format...) |
| 46 | #endif |
| 47 | |
| 48 | struct cache { |
| 49 | struct cache *next, *prev; |
| 50 | char *addr; |
| 51 | socklen_t addrlen; |
| 52 | int af; |
| 53 | int notfound; |
| 54 | char **names; |
| 55 | time_t at, ttl; |
| 56 | }; |
| 57 | |
| 58 | static int inited = 0; |
| 59 | static int timeout = -1; |
| 60 | static int usecache = 1; |
| 61 | static time_t nfttl = 300; |
| 62 | static struct cache *cache = NULL; |
| 63 | |
| 64 | static void readconfig(void) |
| 65 | { |
| 66 | FILE *f; |
| 67 | char linebuf[1024]; |
| 68 | char *p, *p2; |
| 69 | |
| 70 | if((f = fopen(CONFIGFILE, "r")) == NULL) |
| 71 | return; |
| 72 | |
| 73 | while(fgets(linebuf, sizeof(linebuf), f) != NULL) { |
| 74 | if(linebuf[0] == '#') |
| 75 | continue; |
| 76 | if((p = strchr(linebuf, '\n')) != NULL) |
| 77 | *p = 0; |
| 78 | if((p = strchr(linebuf, ' ')) != NULL) { |
| 79 | p2 = p + 1; |
| 80 | *p = 0; |
| 81 | } |
| 82 | if(!strcmp(linebuf, "timeout")) { |
| 83 | if(p2 == NULL) |
| 84 | continue; |
| 85 | timeout = atoi(p2); |
| 86 | } |
| 87 | if(!strcmp(linebuf, "ttlnotfound")) { |
| 88 | if(p2 == NULL) |
| 89 | continue; |
| 90 | nfttl = atoi(p2); |
| 91 | } |
| 92 | if(!strcmp(linebuf, "nocache")) { |
| 93 | usecache = 0; |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | fclose(f); |
| 98 | } |
| 99 | |
| 100 | static void freecache(struct cache *cc) |
| 101 | { |
| 102 | int i; |
| 103 | |
| 104 | if(cc->next != NULL) |
| 105 | cc->next->prev = cc->prev; |
| 106 | if(cc->prev != NULL) |
| 107 | cc->prev->next = cc->next; |
| 108 | if(cc == cache) |
| 109 | cache = cc->next; |
| 110 | if(cc->addr != NULL) |
| 111 | free(cc->addr); |
| 112 | if(cc->names != NULL) { |
| 113 | for(i = 0; cc->names[i] != NULL; i++) |
| 114 | free(cc->names[i]); |
| 115 | free(cc->names); |
| 116 | } |
| 117 | free(cc); |
| 118 | } |
| 119 | |
| 120 | static void cachenotfound(const void *addr, socklen_t len, int af, time_t ttl) |
| 121 | { |
| 122 | struct cache *cc; |
| 123 | |
| 124 | for(cc = cache; cc != NULL; cc = cc->next) { |
| 125 | if((cc->af == af) && (cc->addrlen == len) && !memcmp(cc->addr, addr, len)) |
| 126 | break; |
| 127 | } |
| 128 | if(cc == NULL) { |
| 129 | if((cc = malloc(sizeof(*cc))) == NULL) |
| 130 | return; |
| 131 | memset(cc, 0, sizeof(*cc)); |
| 132 | if((cc->addr = malloc(len)) == NULL) { |
| 133 | freecache(cc); |
| 134 | return; |
| 135 | } |
| 136 | memcpy(cc->addr, addr, len); |
| 137 | cc->addrlen = len; |
| 138 | cc->af = af; |
| 139 | cc->at = time(NULL); |
| 140 | cc->ttl = ttl; |
| 141 | |
| 142 | cc->notfound = 1; |
| 143 | |
| 144 | cc->next = cache; |
| 145 | if(cache != NULL) |
| 146 | cache->prev = cc; |
| 147 | cache = cc; |
| 148 | } |
| 149 | } |
| 150 | |
| 151 | static void updatecache(const void *addr, socklen_t len, int af, char **names, time_t ttl) |
| 152 | { |
| 153 | int i; |
| 154 | struct cache *cc; |
| 155 | |
| 156 | for(cc = cache; cc != NULL; cc = cc->next) { |
| 157 | if((cc->af == af) && (cc->addrlen == len) && !memcmp(cc->addr, addr, len)) |
| 158 | break; |
| 159 | } |
| 160 | if(cc == NULL) { |
| 161 | if((cc = malloc(sizeof(*cc))) == NULL) |
| 162 | return; |
| 163 | memset(cc, 0, sizeof(*cc)); |
| 164 | if((cc->addr = malloc(len)) == NULL) { |
| 165 | freecache(cc); |
| 166 | return; |
| 167 | } |
| 168 | memcpy(cc->addr, addr, len); |
| 169 | cc->addrlen = len; |
| 170 | cc->af = af; |
| 171 | cc->at = time(NULL); |
| 172 | cc->ttl = ttl; |
| 173 | |
| 174 | for(i = 0; names[i] != NULL; i++); |
| 175 | if((cc->names = malloc(sizeof(*(cc->names)) * (i + 1))) == NULL) { |
| 176 | freecache(cc); |
| 177 | return; |
| 178 | } |
| 179 | memset(cc->names, 0, sizeof(*(cc->names)) * (i + 1)); |
| 180 | for(i = 0; names[i] != NULL; i++) { |
| 181 | if((cc->names[i] = malloc(strlen(names[i]) + 1)) == NULL) { |
| 182 | freecache(cc); |
| 183 | return; |
| 184 | } |
| 185 | strcpy(cc->names[i], names[i]); |
| 186 | } |
| 187 | |
| 188 | cc->next = cache; |
| 189 | if(cache != NULL) |
| 190 | cache->prev = cc; |
| 191 | cache = cc; |
| 192 | } |
| 193 | } |
| 194 | |
| 195 | static void expirecache(void) |
| 196 | { |
| 197 | struct cache *cc, *next; |
| 198 | time_t now; |
| 199 | |
| 200 | now = time(NULL); |
| 201 | for(cc = cache; cc != NULL; cc = next) { |
| 202 | next = cc->next; |
| 203 | if(now - cc->at > cc->ttl) { |
| 204 | freecache(cc); |
| 205 | continue; |
| 206 | } |
| 207 | } |
| 208 | } |
| 209 | |
| 210 | enum nss_status _nss_icmp_gethostbyaddr_r(const void *addr, socklen_t len, int af, struct hostent *result, char *buffer, size_t buflen, int *errnop, int *h_errnop) |
| 211 | { |
| 212 | int i, ret; |
| 213 | struct retstruct { |
| 214 | char *aliaslist[16]; |
| 215 | char *addrlist[2]; |
| 216 | char retaddr[16]; |
| 217 | } *retbuf; |
| 218 | char addrbuf[1024]; |
| 219 | int an, thislen, ttl; |
| 220 | char *p, *p2, *p3; |
| 221 | u_int8_t *ap; |
| 222 | pid_t child; |
| 223 | int pfd[2]; |
| 224 | int rl; |
| 225 | int status; |
| 226 | struct cache *cc; |
| 227 | |
| 228 | if(!inited) { |
| 229 | readconfig(); |
| 230 | inited = 1; |
| 231 | } |
| 232 | |
| 233 | retbuf = (struct retstruct *)buffer; |
| 234 | if((buflen < sizeof(*retbuf)) || (len > sizeof(retbuf->retaddr))) { |
| 235 | *errnop = ENOMEM; |
| 236 | *h_errnop = NETDB_INTERNAL; |
| 237 | return(NSS_STATUS_UNAVAIL); |
| 238 | } |
| 239 | |
| 240 | DEBUGP("starting lookup\n"); |
| 241 | |
| 242 | if(usecache) { |
| 243 | expirecache(); |
| 244 | for(cc = cache; cc != NULL; cc = cc->next) { |
| 245 | if((cc->af == af) && (cc->addrlen == len) && !memcmp(cc->addr, addr, len)) |
| 246 | break; |
| 247 | } |
| 248 | } else { |
| 249 | cc = NULL; |
| 250 | } |
| 251 | |
| 252 | if(cc == NULL) { |
| 253 | DEBUGP("address not in cache, looking up for real\n"); |
| 254 | ap = (u_int8_t *)addr; |
| 255 | if(inet_ntop(af, addr, addrbuf, sizeof(addrbuf)) == NULL) { |
| 256 | *errnop = errno; |
| 257 | *h_errnop = NETDB_INTERNAL; |
| 258 | return(NSS_STATUS_UNAVAIL); |
| 259 | } |
| 260 | DEBUGP("address is %s\n", addrbuf); |
| 261 | |
| 262 | if(pipe(pfd)) { |
| 263 | *errnop = errno; |
| 264 | *h_errnop = NETDB_INTERNAL; |
| 265 | return(NSS_STATUS_UNAVAIL); |
| 266 | } |
| 267 | /* I honestly don't know if it is considered OK to fork in other |
| 268 | * people's programs. We need a SUID worker, though, so there's |
| 269 | * little choice that I can see. */ |
| 270 | if((child = fork()) < 0) { |
| 271 | *errnop = errno; |
| 272 | *h_errnop = NETDB_INTERNAL; |
| 273 | return(NSS_STATUS_UNAVAIL); |
| 274 | } |
| 275 | |
| 276 | if(child == 0) { |
| 277 | int i, fd; |
| 278 | char timeoutbuf[128]; |
| 279 | |
| 280 | if((fd = open("/dev/null", O_WRONLY)) < 0) |
| 281 | exit(127); |
| 282 | close(pfd[0]); |
| 283 | dup2(pfd[1], 1); |
| 284 | dup2(fd, 2); |
| 285 | for(i = 3; i < FD_SETSIZE; i++) |
| 286 | close(i); |
| 287 | |
| 288 | if(timeout != -1) { |
| 289 | snprintf(timeoutbuf, sizeof(timeoutbuf), "%i", timeout); |
| 290 | execlp("idnlookup", "idnlookup", "-Tt", timeoutbuf, addrbuf, NULL); |
| 291 | } else { |
| 292 | execlp("idnlookup", "idnlookup", "-T", addrbuf, NULL); |
| 293 | } |
| 294 | exit(127); |
| 295 | } |
| 296 | |
| 297 | close(pfd[1]); |
| 298 | |
| 299 | rl = 0; |
| 300 | do { |
| 301 | ret = read(pfd[0], addrbuf + rl, sizeof(addrbuf) - rl); |
| 302 | if(ret < 0) { |
| 303 | *errnop = errno; |
| 304 | *h_errnop = NETDB_INTERNAL; |
| 305 | close(pfd[0]); |
| 306 | return(NSS_STATUS_UNAVAIL); |
| 307 | } |
| 308 | rl += ret; |
| 309 | if(rl >= sizeof(addrbuf) - 1) { |
| 310 | *errnop = ENOMEM; |
| 311 | *h_errnop = NETDB_INTERNAL; |
| 312 | close(pfd[0]); |
| 313 | return(NSS_STATUS_UNAVAIL); |
| 314 | } |
| 315 | } while(ret != 0); |
| 316 | addrbuf[rl] = 0; |
| 317 | close(pfd[0]); |
| 318 | |
| 319 | waitpid(child, &status, 0); |
| 320 | |
| 321 | if((p = strchr(addrbuf, '\n')) == NULL) { |
| 322 | if(usecache) |
| 323 | cachenotfound(addr, len, af, nfttl); |
| 324 | *h_errnop = TRY_AGAIN; /* XXX: Is this correct? */ |
| 325 | return(NSS_STATUS_NOTFOUND); |
| 326 | } |
| 327 | *(p++) = 0; |
| 328 | ttl = atoi(addrbuf); |
| 329 | |
| 330 | an = 0; |
| 331 | p3 = buffer + sizeof(*retbuf); |
| 332 | while((p2 = strchr(p, '\n')) != NULL) { |
| 333 | *p2 = 0; |
| 334 | thislen = p2 - p; |
| 335 | if(thislen == 0) |
| 336 | continue; |
| 337 | if((p3 - buffer) + thislen + 1 > buflen) { |
| 338 | *errnop = ENOMEM; |
| 339 | *h_errnop = NETDB_INTERNAL; |
| 340 | return(NSS_STATUS_UNAVAIL); |
| 341 | } |
| 342 | memcpy(p3, p, thislen + 1); |
| 343 | retbuf->aliaslist[an] = p3; |
| 344 | p3 += thislen + 1; |
| 345 | p = p2 + 1; |
| 346 | if(++an == 16) { |
| 347 | *errnop = ENOMEM; |
| 348 | *h_errnop = NETDB_INTERNAL; |
| 349 | return(NSS_STATUS_UNAVAIL); |
| 350 | } |
| 351 | } |
| 352 | if(an == 0) { |
| 353 | if(usecache) |
| 354 | cachenotfound(addr, len, af, nfttl); |
| 355 | *h_errnop = TRY_AGAIN; /* XXX: Is this correct? */ |
| 356 | return(NSS_STATUS_NOTFOUND); |
| 357 | } |
| 358 | retbuf->aliaslist[an] = NULL; |
| 359 | |
| 360 | if(usecache) |
| 361 | updatecache(addr, len, af, retbuf->aliaslist, ttl); |
| 362 | } else { |
| 363 | DEBUGP("address found in cache\n"); |
| 364 | if(cc->notfound) { |
| 365 | *h_errnop = TRY_AGAIN; /* XXX: Is this correct? */ |
| 366 | return(NSS_STATUS_NOTFOUND); |
| 367 | } |
| 368 | |
| 369 | p3 = buffer + sizeof(*retbuf); |
| 370 | for(i = 0; cc->names[i] != NULL; i++) { |
| 371 | thislen = strlen(cc->names[i]); |
| 372 | DEBUGP("filling in address %s, length %i\n", cc->names[i], thislen); |
| 373 | if((p3 - buffer) + thislen + 1 > buflen) { |
| 374 | *errnop = ENOMEM; |
| 375 | *h_errnop = NETDB_INTERNAL; |
| 376 | return(NSS_STATUS_UNAVAIL); |
| 377 | } |
| 378 | memcpy(p3, cc->names[i], thislen + 1); |
| 379 | retbuf->aliaslist[i] = p3; |
| 380 | p3 += thislen + 1; |
| 381 | } |
| 382 | retbuf->aliaslist[i] = NULL; |
| 383 | } |
| 384 | |
| 385 | DEBUGP("returning hostent\n"); |
| 386 | memcpy(retbuf->retaddr, addr, len); |
| 387 | retbuf->addrlist[0] = retbuf->retaddr; |
| 388 | retbuf->addrlist[1] = NULL; |
| 389 | result->h_name = retbuf->aliaslist[0]; |
| 390 | result->h_aliases = retbuf->aliaslist; |
| 391 | result->h_addr_list = retbuf->addrlist; |
| 392 | result->h_addrtype = af; |
| 393 | result->h_length = len; |
| 394 | |
| 395 | *h_errnop = NETDB_SUCCESS; |
| 396 | DEBUGP("returning\n"); |
| 397 | return(NSS_STATUS_SUCCESS); |
| 398 | } |
| 399 | |
| 400 | /* |
| 401 | * Local Variables: |
| 402 | * compile-command: "gcc -shared -Wall -g -o libnss_icmp.so.2 nss-icmp.c" |
| 403 | * End: |
| 404 | */ |