1 /* 2 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 3 * Copyright (c) 1999 by Internet Software Consortium, Inc. 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 15 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 #ifndef lint 19 static const char rcsid[] = "$Id: ns_verify.c,v 1.5 2006/03/09 23:57:56 marka Exp $"; 20 #endif 21 22 /* Import. */ 23 24 #include "port_before.h" 25 #include "fd_setsize.h" 26 27 #include <sys/types.h> 28 #include <sys/param.h> 29 30 #include <netinet/in.h> 31 #include <arpa/nameser.h> 32 #include <arpa/inet.h> 33 34 #include <errno.h> 35 #include <netdb.h> 36 #include <resolv.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include <time.h> 41 #include <unistd.h> 42 43 #include <isc/dst.h> 44 45 #include "port_after.h" 46 47 /* Private. */ 48 49 #define BOUNDS_CHECK(ptr, count) \ 50 do { \ 51 if ((ptr) + (count) > eom) { \ 52 return (NS_TSIG_ERROR_FORMERR); \ 53 } \ 54 } while (0) 55 56 /* Public. */ 57 58 u_char * 59 ns_find_tsig(u_char *msg, u_char *eom) { 60 HEADER *hp = (HEADER *)msg; 61 int n, type; 62 u_char *cp = msg, *start; 63 64 if (msg == NULL || eom == NULL || msg > eom) 65 return (NULL); 66 67 if (cp + HFIXEDSZ >= eom) 68 return (NULL); 69 70 if (hp->arcount == 0) 71 return (NULL); 72 73 cp += HFIXEDSZ; 74 75 n = ns_skiprr(cp, eom, ns_s_qd, ntohs(hp->qdcount)); 76 if (n < 0) 77 return (NULL); 78 cp += n; 79 80 n = ns_skiprr(cp, eom, ns_s_an, ntohs(hp->ancount)); 81 if (n < 0) 82 return (NULL); 83 cp += n; 84 85 n = ns_skiprr(cp, eom, ns_s_ns, ntohs(hp->nscount)); 86 if (n < 0) 87 return (NULL); 88 cp += n; 89 90 n = ns_skiprr(cp, eom, ns_s_ar, ntohs(hp->arcount) - 1); 91 if (n < 0) 92 return (NULL); 93 cp += n; 94 95 start = cp; 96 n = dn_skipname(cp, eom); 97 if (n < 0) 98 return (NULL); 99 cp += n; 100 if (cp + INT16SZ >= eom) 101 return (NULL); 102 103 GETSHORT(type, cp); 104 if (type != ns_t_tsig) 105 return (NULL); 106 return (start); 107 } 108 109 /* ns_verify 110 * 111 * Parameters: 112 *\li statp res stuff 113 *\li msg received message 114 *\li msglen length of message 115 *\li key tsig key used for verifying. 116 *\li querysig (response), the signature in the query 117 *\li querysiglen (response), the length of the signature in the query 118 *\li sig (query), a buffer to hold the signature 119 *\li siglen (query), input - length of signature buffer 120 * output - length of signature 121 * 122 * Errors: 123 *\li - bad input (-1) 124 *\li - invalid dns message (NS_TSIG_ERROR_FORMERR) 125 *\li - TSIG is not present (NS_TSIG_ERROR_NO_TSIG) 126 *\li - key doesn't match (-ns_r_badkey) 127 *\li - TSIG verification fails with BADKEY (-ns_r_badkey) 128 *\li - TSIG verification fails with BADSIG (-ns_r_badsig) 129 *\li - TSIG verification fails with BADTIME (-ns_r_badtime) 130 *\li - TSIG verification succeeds, error set to BAKEY (ns_r_badkey) 131 *\li - TSIG verification succeeds, error set to BADSIG (ns_r_badsig) 132 *\li - TSIG verification succeeds, error set to BADTIME (ns_r_badtime) 133 */ 134 int 135 ns_verify(u_char *msg, int *msglen, void *k, 136 const u_char *querysig, int querysiglen, u_char *sig, int *siglen, 137 time_t *timesigned, int nostrip) 138 { 139 HEADER *hp = (HEADER *)msg; 140 DST_KEY *key = (DST_KEY *)k; 141 u_char *cp = msg, *eom; 142 char name[MAXDNAME], alg[MAXDNAME]; 143 u_char *recstart, *rdatastart; 144 u_char *sigstart, *otherstart; 145 int n; 146 int error; 147 u_int16_t type, length; 148 u_int16_t fudge, sigfieldlen, otherfieldlen; 149 150 dst_init(); 151 if (msg == NULL || msglen == NULL || *msglen < 0) 152 return (-1); 153 154 eom = msg + *msglen; 155 156 recstart = ns_find_tsig(msg, eom); 157 if (recstart == NULL) 158 return (NS_TSIG_ERROR_NO_TSIG); 159 160 cp = recstart; 161 162 /* Read the key name. */ 163 n = dn_expand(msg, eom, cp, name, MAXDNAME); 164 if (n < 0) 165 return (NS_TSIG_ERROR_FORMERR); 166 cp += n; 167 168 /* Read the type. */ 169 BOUNDS_CHECK(cp, 2*INT16SZ + INT32SZ + INT16SZ); 170 GETSHORT(type, cp); 171 if (type != ns_t_tsig) 172 return (NS_TSIG_ERROR_NO_TSIG); 173 174 /* Skip the class and TTL, save the length. */ 175 cp += INT16SZ + INT32SZ; 176 GETSHORT(length, cp); 177 if (eom - cp != length) 178 return (NS_TSIG_ERROR_FORMERR); 179 180 /* Read the algorithm name. */ 181 rdatastart = cp; 182 n = dn_expand(msg, eom, cp, alg, MAXDNAME); 183 if (n < 0) 184 return (NS_TSIG_ERROR_FORMERR); 185 if (ns_samename(alg, NS_TSIG_ALG_HMAC_MD5) != 1) 186 return (-ns_r_badkey); 187 cp += n; 188 189 /* Read the time signed and fudge. */ 190 BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ); 191 cp += INT16SZ; 192 GETLONG((*timesigned), cp); 193 GETSHORT(fudge, cp); 194 195 /* Read the signature. */ 196 BOUNDS_CHECK(cp, INT16SZ); 197 GETSHORT(sigfieldlen, cp); 198 BOUNDS_CHECK(cp, sigfieldlen); 199 sigstart = cp; 200 cp += sigfieldlen; 201 202 /* Skip id and read error. */ 203 BOUNDS_CHECK(cp, 2*INT16SZ); 204 cp += INT16SZ; 205 GETSHORT(error, cp); 206 207 /* Parse the other data. */ 208 BOUNDS_CHECK(cp, INT16SZ); 209 GETSHORT(otherfieldlen, cp); 210 BOUNDS_CHECK(cp, otherfieldlen); 211 otherstart = cp; 212 cp += otherfieldlen; 213 214 if (cp != eom) 215 return (NS_TSIG_ERROR_FORMERR); 216 217 /* Verify that the key used is OK. */ 218 if (key != NULL) { 219 if (key->dk_alg != KEY_HMAC_MD5) 220 return (-ns_r_badkey); 221 if (error != ns_r_badsig && error != ns_r_badkey) { 222 if (ns_samename(key->dk_key_name, name) != 1) 223 return (-ns_r_badkey); 224 } 225 } 226 227 hp->arcount = htons(ntohs(hp->arcount) - 1); 228 229 /* 230 * Do the verification. 231 */ 232 233 if (key != NULL && error != ns_r_badsig && error != ns_r_badkey) { 234 void *ctx; 235 u_char buf[MAXDNAME]; 236 u_char buf2[MAXDNAME]; 237 238 /* Digest the query signature, if this is a response. */ 239 dst_verify_data(SIG_MODE_INIT, key, &ctx, NULL, 0, NULL, 0); 240 if (querysiglen > 0 && querysig != NULL) { 241 u_int16_t len_n = htons(querysiglen); 242 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 243 (u_char *)&len_n, INT16SZ, NULL, 0); 244 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 245 querysig, querysiglen, NULL, 0); 246 } 247 248 /* Digest the message. */ 249 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, msg, recstart - msg, 250 NULL, 0); 251 252 /* Digest the key name. */ 253 n = ns_name_pton(name, buf2, sizeof(buf2)); 254 if (n < 0) 255 return (-1); 256 n = ns_name_ntol(buf2, buf, sizeof(buf)); 257 if (n < 0) 258 return (-1); 259 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, buf, n, NULL, 0); 260 261 /* Digest the class and TTL. */ 262 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 263 recstart + dn_skipname(recstart, eom) + INT16SZ, 264 INT16SZ + INT32SZ, NULL, 0); 265 266 /* Digest the algorithm. */ 267 n = ns_name_pton(alg, buf2, sizeof(buf2)); 268 if (n < 0) 269 return (-1); 270 n = ns_name_ntol(buf2, buf, sizeof(buf)); 271 if (n < 0) 272 return (-1); 273 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, buf, n, NULL, 0); 274 275 /* Digest the time signed and fudge. */ 276 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 277 rdatastart + dn_skipname(rdatastart, eom), 278 INT16SZ + INT32SZ + INT16SZ, NULL, 0); 279 280 /* Digest the error and other data. */ 281 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 282 otherstart - INT16SZ - INT16SZ, 283 otherfieldlen + INT16SZ + INT16SZ, NULL, 0); 284 285 n = dst_verify_data(SIG_MODE_FINAL, key, &ctx, NULL, 0, 286 sigstart, sigfieldlen); 287 288 if (n < 0) 289 return (-ns_r_badsig); 290 291 if (sig != NULL && siglen != NULL) { 292 if (*siglen < sigfieldlen) 293 return (NS_TSIG_ERROR_NO_SPACE); 294 memcpy(sig, sigstart, sigfieldlen); 295 *siglen = sigfieldlen; 296 } 297 } else { 298 if (sigfieldlen > 0) 299 return (NS_TSIG_ERROR_FORMERR); 300 if (sig != NULL && siglen != NULL) 301 *siglen = 0; 302 } 303 304 /* Reset the counter, since we still need to check for badtime. */ 305 hp->arcount = htons(ntohs(hp->arcount) + 1); 306 307 /* Verify the time. */ 308 if (abs((*timesigned) - time(NULL)) > fudge) 309 return (-ns_r_badtime); 310 311 if (nostrip == 0) { 312 *msglen = recstart - msg; 313 hp->arcount = htons(ntohs(hp->arcount) - 1); 314 } 315 316 if (error != NOERROR) 317 return (error); 318 319 return (0); 320 } 321 322 int 323 ns_verify_tcp_init(void *k, const u_char *querysig, int querysiglen, 324 ns_tcp_tsig_state *state) 325 { 326 dst_init(); 327 if (state == NULL || k == NULL || querysig == NULL || querysiglen < 0) 328 return (-1); 329 state->counter = -1; 330 state->key = k; 331 if (state->key->dk_alg != KEY_HMAC_MD5) 332 return (-ns_r_badkey); 333 if (querysiglen > (int)sizeof(state->sig)) 334 return (-1); 335 memcpy(state->sig, querysig, querysiglen); 336 state->siglen = querysiglen; 337 return (0); 338 } 339 340 int 341 ns_verify_tcp(u_char *msg, int *msglen, ns_tcp_tsig_state *state, 342 int required) 343 { 344 HEADER *hp = (HEADER *)msg; 345 u_char *recstart, *sigstart; 346 unsigned int sigfieldlen, otherfieldlen; 347 u_char *cp, *eom, *cp2; 348 char name[MAXDNAME], alg[MAXDNAME]; 349 u_char buf[MAXDNAME]; 350 int n, type, length, fudge, error; 351 time_t timesigned; 352 353 if (msg == NULL || msglen == NULL || state == NULL) 354 return (-1); 355 356 eom = msg + *msglen; 357 358 state->counter++; 359 if (state->counter == 0) 360 return (ns_verify(msg, msglen, state->key, 361 state->sig, state->siglen, 362 state->sig, &state->siglen, ×igned, 0)); 363 364 if (state->siglen > 0) { 365 u_int16_t siglen_n = htons(state->siglen); 366 367 dst_verify_data(SIG_MODE_INIT, state->key, &state->ctx, 368 NULL, 0, NULL, 0); 369 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 370 (u_char *)&siglen_n, INT16SZ, NULL, 0); 371 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 372 state->sig, state->siglen, NULL, 0); 373 state->siglen = 0; 374 } 375 376 cp = recstart = ns_find_tsig(msg, eom); 377 378 if (recstart == NULL) { 379 if (required) 380 return (NS_TSIG_ERROR_NO_TSIG); 381 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 382 msg, *msglen, NULL, 0); 383 return (0); 384 } 385 386 hp->arcount = htons(ntohs(hp->arcount) - 1); 387 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 388 msg, recstart - msg, NULL, 0); 389 390 /* Read the key name. */ 391 n = dn_expand(msg, eom, cp, name, MAXDNAME); 392 if (n < 0) 393 return (NS_TSIG_ERROR_FORMERR); 394 cp += n; 395 396 /* Read the type. */ 397 BOUNDS_CHECK(cp, 2*INT16SZ + INT32SZ + INT16SZ); 398 GETSHORT(type, cp); 399 if (type != ns_t_tsig) 400 return (NS_TSIG_ERROR_NO_TSIG); 401 402 /* Skip the class and TTL, save the length. */ 403 cp += INT16SZ + INT32SZ; 404 GETSHORT(length, cp); 405 if (eom - cp != length) 406 return (NS_TSIG_ERROR_FORMERR); 407 408 /* Read the algorithm name. */ 409 n = dn_expand(msg, eom, cp, alg, MAXDNAME); 410 if (n < 0) 411 return (NS_TSIG_ERROR_FORMERR); 412 if (ns_samename(alg, NS_TSIG_ALG_HMAC_MD5) != 1) 413 return (-ns_r_badkey); 414 cp += n; 415 416 /* Verify that the key used is OK. */ 417 if ((ns_samename(state->key->dk_key_name, name) != 1 || 418 state->key->dk_alg != KEY_HMAC_MD5)) 419 return (-ns_r_badkey); 420 421 /* Read the time signed and fudge. */ 422 BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ); 423 cp += INT16SZ; 424 GETLONG(timesigned, cp); 425 GETSHORT(fudge, cp); 426 427 /* Read the signature. */ 428 BOUNDS_CHECK(cp, INT16SZ); 429 GETSHORT(sigfieldlen, cp); 430 BOUNDS_CHECK(cp, sigfieldlen); 431 sigstart = cp; 432 cp += sigfieldlen; 433 434 /* Skip id and read error. */ 435 BOUNDS_CHECK(cp, 2*INT16SZ); 436 cp += INT16SZ; 437 GETSHORT(error, cp); 438 439 /* Parse the other data. */ 440 BOUNDS_CHECK(cp, INT16SZ); 441 GETSHORT(otherfieldlen, cp); 442 BOUNDS_CHECK(cp, otherfieldlen); 443 cp += otherfieldlen; 444 445 if (cp != eom) 446 return (NS_TSIG_ERROR_FORMERR); 447 448 /* 449 * Do the verification. 450 */ 451 452 /* Digest the time signed and fudge. */ 453 cp2 = buf; 454 PUTSHORT(0, cp2); /*%< Top 16 bits of time. */ 455 PUTLONG(timesigned, cp2); 456 PUTSHORT(NS_TSIG_FUDGE, cp2); 457 458 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 459 buf, cp2 - buf, NULL, 0); 460 461 n = dst_verify_data(SIG_MODE_FINAL, state->key, &state->ctx, NULL, 0, 462 sigstart, sigfieldlen); 463 if (n < 0) 464 return (-ns_r_badsig); 465 466 if (sigfieldlen > sizeof(state->sig)) 467 return (NS_TSIG_ERROR_NO_SPACE); 468 469 memcpy(state->sig, sigstart, sigfieldlen); 470 state->siglen = sigfieldlen; 471 472 /* Verify the time. */ 473 if (abs(timesigned - time(NULL)) > fudge) 474 return (-ns_r_badtime); 475 476 *msglen = recstart - msg; 477 478 if (error != NOERROR) 479 return (error); 480 481 return (0); 482 } 483 484 /*! \file */ 485