1 /* $NetBSD: ns_verify.c,v 1.4 2022/04/19 20:32:17 rillig Exp $ */ 2 3 /* 4 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 5 * Copyright (c) 1999 by Internet Software Consortium, Inc. 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 17 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 20 #include <sys/cdefs.h> 21 __RCSID("Id: ns_verify.c,v 1.5 2006/03/09 23:57:56 marka Exp "); 22 23 /* Import. */ 24 25 #include "port_before.h" 26 #include "fd_setsize.h" 27 28 #include <sys/types.h> 29 #include <sys/param.h> 30 31 #include <netinet/in.h> 32 #include <arpa/nameser.h> 33 #include <arpa/inet.h> 34 35 #include <errno.h> 36 #include <netdb.h> 37 #include <resolv.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include <time.h> 42 #include <unistd.h> 43 44 #include <isc/dst.h> 45 46 #include "port_after.h" 47 48 /* Private. */ 49 50 #define BOUNDS_CHECK(ptr, count) \ 51 do { \ 52 if ((ptr) + (count) > eom) { \ 53 return (NS_TSIG_ERROR_FORMERR); \ 54 } \ 55 } while (0) 56 57 /* Public. */ 58 59 u_char * 60 ns_find_tsig(u_char *msg, u_char *eom) { 61 HEADER *hp = (void *)msg; 62 int n, type; 63 u_char *cp = msg, *start; 64 65 if (msg == NULL || eom == NULL || msg > eom) 66 return (NULL); 67 68 if (cp + HFIXEDSZ >= eom) 69 return (NULL); 70 71 if (hp->arcount == 0) 72 return (NULL); 73 74 cp += HFIXEDSZ; 75 76 n = ns_skiprr(cp, eom, ns_s_qd, ntohs(hp->qdcount)); 77 if (n < 0) 78 return (NULL); 79 cp += n; 80 81 n = ns_skiprr(cp, eom, ns_s_an, ntohs(hp->ancount)); 82 if (n < 0) 83 return (NULL); 84 cp += n; 85 86 n = ns_skiprr(cp, eom, ns_s_ns, ntohs(hp->nscount)); 87 if (n < 0) 88 return (NULL); 89 cp += n; 90 91 n = ns_skiprr(cp, eom, ns_s_ar, ntohs(hp->arcount) - 1); 92 if (n < 0) 93 return (NULL); 94 cp += n; 95 96 start = cp; 97 n = dn_skipname(cp, eom); 98 if (n < 0) 99 return (NULL); 100 cp += n; 101 if (cp + INT16SZ >= eom) 102 return (NULL); 103 104 GETSHORT(type, cp); 105 if (type != ns_t_tsig) 106 return (NULL); 107 return (start); 108 } 109 110 /* ns_verify 111 * 112 * Parameters: 113 *\li statp res stuff 114 *\li msg received message 115 *\li msglen length of message 116 *\li key tsig key used for verifying. 117 *\li querysig (response), the signature in the query 118 *\li querysiglen (response), the length of the signature in the query 119 *\li sig (query), a buffer to hold the signature 120 *\li siglen (query), input - length of signature buffer 121 * output - length of signature 122 * 123 * Errors: 124 *\li - bad input (-1) 125 *\li - invalid dns message (NS_TSIG_ERROR_FORMERR) 126 *\li - TSIG is not present (NS_TSIG_ERROR_NO_TSIG) 127 *\li - key doesn't match (-ns_r_badkey) 128 *\li - TSIG verification fails with BADKEY (-ns_r_badkey) 129 *\li - TSIG verification fails with BADSIG (-ns_r_badsig) 130 *\li - TSIG verification fails with BADTIME (-ns_r_badtime) 131 *\li - TSIG verification succeeds, error set to BAKEY (ns_r_badkey) 132 *\li - TSIG verification succeeds, error set to BADSIG (ns_r_badsig) 133 *\li - TSIG verification succeeds, error set to BADTIME (ns_r_badtime) 134 */ 135 int 136 ns_verify(u_char *msg, int *msglen, void *k, 137 const u_char *querysig, int querysiglen, u_char *sig, int *siglen, 138 time_t *timesigned, int nostrip) 139 { 140 HEADER *hp = (void *)msg; 141 DST_KEY *key = (DST_KEY *)k; 142 u_char *cp = msg, *eom; 143 char name[MAXDNAME], alg[MAXDNAME]; 144 u_char *recstart, *rdatastart; 145 u_char *sigstart, *otherstart; 146 int n; 147 int error; 148 u_int16_t type, length; 149 u_int16_t fudge, sigfieldlen, otherfieldlen; 150 151 dst_init(); 152 if (msg == NULL || msglen == NULL || *msglen < 0) 153 return (-1); 154 155 eom = msg + *msglen; 156 157 recstart = ns_find_tsig(msg, eom); 158 if (recstart == NULL) 159 return (NS_TSIG_ERROR_NO_TSIG); 160 161 cp = recstart; 162 163 /* Read the key name. */ 164 n = dn_expand(msg, eom, cp, name, MAXDNAME); 165 if (n < 0) 166 return (NS_TSIG_ERROR_FORMERR); 167 cp += n; 168 169 /* Read the type. */ 170 BOUNDS_CHECK(cp, 2*INT16SZ + INT32SZ + INT16SZ); 171 GETSHORT(type, cp); 172 if (type != ns_t_tsig) 173 return (NS_TSIG_ERROR_NO_TSIG); 174 175 /* Skip the class and TTL, save the length. */ 176 cp += INT16SZ + INT32SZ; 177 GETSHORT(length, cp); 178 if (eom - cp != length) 179 return (NS_TSIG_ERROR_FORMERR); 180 181 /* Read the algorithm name. */ 182 rdatastart = cp; 183 n = dn_expand(msg, eom, cp, alg, MAXDNAME); 184 if (n < 0) 185 return (NS_TSIG_ERROR_FORMERR); 186 if (ns_samename(alg, NS_TSIG_ALG_HMAC_MD5) != 1) 187 return (-ns_r_badkey); 188 cp += n; 189 190 /* Read the time signed and fudge. */ 191 BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ); 192 cp += INT16SZ; 193 GETLONG((*timesigned), cp); 194 GETSHORT(fudge, cp); 195 196 /* Read the signature. */ 197 BOUNDS_CHECK(cp, INT16SZ); 198 GETSHORT(sigfieldlen, cp); 199 BOUNDS_CHECK(cp, sigfieldlen); 200 sigstart = cp; 201 cp += sigfieldlen; 202 203 /* Skip id and read error. */ 204 BOUNDS_CHECK(cp, 2*INT16SZ); 205 cp += INT16SZ; 206 GETSHORT(error, cp); 207 208 /* Parse the other data. */ 209 BOUNDS_CHECK(cp, INT16SZ); 210 GETSHORT(otherfieldlen, cp); 211 BOUNDS_CHECK(cp, otherfieldlen); 212 otherstart = cp; 213 cp += otherfieldlen; 214 215 if (cp != eom) 216 return (NS_TSIG_ERROR_FORMERR); 217 218 /* Verify that the key used is OK. */ 219 if (key != NULL) { 220 if (key->dk_alg != KEY_HMAC_MD5) 221 return (-ns_r_badkey); 222 if (error != ns_r_badsig && error != ns_r_badkey) { 223 if (ns_samename(key->dk_key_name, name) != 1) 224 return (-ns_r_badkey); 225 } 226 } 227 228 hp->arcount = htons(ntohs(hp->arcount) - 1); 229 230 /* 231 * Do the verification. 232 */ 233 234 if (key != NULL && error != ns_r_badsig && error != ns_r_badkey) { 235 void *ctx; 236 u_char buf[MAXDNAME]; 237 u_char buf2[MAXDNAME]; 238 239 /* Digest the query signature, if this is a response. */ 240 dst_verify_data(SIG_MODE_INIT, key, &ctx, NULL, 0, NULL, 0); 241 if (querysiglen > 0 && querysig != NULL) { 242 u_int16_t len_n = htons(querysiglen); 243 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 244 (void *)&len_n, INT16SZ, NULL, 0); 245 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 246 querysig, querysiglen, NULL, 0); 247 } 248 249 /* Digest the message. */ 250 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, msg, 251 (int)(recstart - msg), NULL, 0); 252 253 /* Digest the key name. */ 254 n = ns_name_pton(name, buf2, sizeof(buf2)); 255 if (n < 0) 256 return (-1); 257 n = ns_name_ntol(buf2, buf, sizeof(buf)); 258 if (n < 0) 259 return (-1); 260 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, buf, n, NULL, 0); 261 262 /* Digest the class and TTL. */ 263 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 264 recstart + dn_skipname(recstart, eom) + INT16SZ, 265 INT16SZ + INT32SZ, NULL, 0); 266 267 /* Digest the algorithm. */ 268 n = ns_name_pton(alg, buf2, sizeof(buf2)); 269 if (n < 0) 270 return (-1); 271 n = ns_name_ntol(buf2, buf, sizeof(buf)); 272 if (n < 0) 273 return (-1); 274 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, buf, n, NULL, 0); 275 276 /* Digest the time signed and fudge. */ 277 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 278 rdatastart + dn_skipname(rdatastart, eom), 279 INT16SZ + INT32SZ + INT16SZ, NULL, 0); 280 281 /* Digest the error and other data. */ 282 dst_verify_data(SIG_MODE_UPDATE, key, &ctx, 283 otherstart - INT16SZ - INT16SZ, 284 otherfieldlen + INT16SZ + INT16SZ, NULL, 0); 285 286 n = dst_verify_data(SIG_MODE_FINAL, key, &ctx, NULL, 0, 287 sigstart, sigfieldlen); 288 289 if (n < 0) 290 return (-ns_r_badsig); 291 292 if (sig != NULL && siglen != NULL) { 293 if (*siglen < sigfieldlen) 294 return (NS_TSIG_ERROR_NO_SPACE); 295 memcpy(sig, sigstart, sigfieldlen); 296 *siglen = sigfieldlen; 297 } 298 } else { 299 if (sigfieldlen > 0) 300 return (NS_TSIG_ERROR_FORMERR); 301 if (sig != NULL && siglen != NULL) 302 *siglen = 0; 303 } 304 305 /* Reset the counter, since we still need to check for badtime. */ 306 hp->arcount = htons(ntohs(hp->arcount) + 1); 307 308 /* Verify the time. */ 309 if (abs((int)((*timesigned) - time(NULL))) > fudge) 310 return (-ns_r_badtime); 311 312 if (nostrip == 0) { 313 *msglen = (int)(recstart - msg); 314 hp->arcount = htons(ntohs(hp->arcount) - 1); 315 } 316 317 if (error != NOERROR) 318 return (error); 319 320 return (0); 321 } 322 323 int 324 ns_verify_tcp_init(void *k, const u_char *querysig, int querysiglen, 325 ns_tcp_tsig_state *state) 326 { 327 dst_init(); 328 if (state == NULL || k == NULL || querysig == NULL || querysiglen < 0) 329 return (-1); 330 state->counter = -1; 331 state->key = k; 332 if (state->key->dk_alg != KEY_HMAC_MD5) 333 return (-ns_r_badkey); 334 if (querysiglen > (int)sizeof(state->sig)) 335 return (-1); 336 memcpy(state->sig, querysig, querysiglen); 337 state->siglen = querysiglen; 338 return (0); 339 } 340 341 int 342 ns_verify_tcp(u_char *msg, int *msglen, ns_tcp_tsig_state *state, 343 int required) 344 { 345 HEADER *hp = (void *)msg; 346 u_char *recstart, *sigstart; 347 unsigned int sigfieldlen, otherfieldlen; 348 u_char *cp, *eom, *cp2; 349 char name[MAXDNAME], alg[MAXDNAME]; 350 u_char buf[MAXDNAME]; 351 int n, type, length, fudge, error; 352 time_t timesigned; 353 354 if (msg == NULL || msglen == NULL || state == NULL) 355 return (-1); 356 357 eom = msg + *msglen; 358 359 state->counter++; 360 if (state->counter == 0) 361 return (ns_verify(msg, msglen, state->key, 362 state->sig, state->siglen, 363 state->sig, &state->siglen, ×igned, 0)); 364 365 if (state->siglen > 0) { 366 u_int16_t siglen_n = htons(state->siglen); 367 368 dst_verify_data(SIG_MODE_INIT, state->key, &state->ctx, 369 NULL, 0, NULL, 0); 370 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 371 (void *)&siglen_n, INT16SZ, NULL, 0); 372 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 373 state->sig, state->siglen, NULL, 0); 374 state->siglen = 0; 375 } 376 377 cp = recstart = ns_find_tsig(msg, eom); 378 379 if (recstart == NULL) { 380 if (required) 381 return (NS_TSIG_ERROR_NO_TSIG); 382 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 383 msg, *msglen, NULL, 0); 384 return (0); 385 } 386 387 hp->arcount = htons(ntohs(hp->arcount) - 1); 388 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 389 msg, (int)(recstart - msg), NULL, 0); 390 391 /* Read the key name. */ 392 n = dn_expand(msg, eom, cp, name, MAXDNAME); 393 if (n < 0) 394 return (NS_TSIG_ERROR_FORMERR); 395 cp += n; 396 397 /* Read the type. */ 398 BOUNDS_CHECK(cp, 2*INT16SZ + INT32SZ + INT16SZ); 399 GETSHORT(type, cp); 400 if (type != ns_t_tsig) 401 return (NS_TSIG_ERROR_NO_TSIG); 402 403 /* Skip the class and TTL, save the length. */ 404 cp += INT16SZ + INT32SZ; 405 GETSHORT(length, cp); 406 if (eom - cp != length) 407 return (NS_TSIG_ERROR_FORMERR); 408 409 /* Read the algorithm name. */ 410 n = dn_expand(msg, eom, cp, alg, MAXDNAME); 411 if (n < 0) 412 return (NS_TSIG_ERROR_FORMERR); 413 if (ns_samename(alg, NS_TSIG_ALG_HMAC_MD5) != 1) 414 return (-ns_r_badkey); 415 cp += n; 416 417 /* Verify that the key used is OK. */ 418 if ((ns_samename(state->key->dk_key_name, name) != 1 || 419 state->key->dk_alg != KEY_HMAC_MD5)) 420 return (-ns_r_badkey); 421 422 /* Read the time signed and fudge. */ 423 BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ); 424 cp += INT16SZ; 425 GETLONG(timesigned, cp); 426 GETSHORT(fudge, cp); 427 428 /* Read the signature. */ 429 BOUNDS_CHECK(cp, INT16SZ); 430 GETSHORT(sigfieldlen, cp); 431 BOUNDS_CHECK(cp, sigfieldlen); 432 sigstart = cp; 433 cp += sigfieldlen; 434 435 /* Skip id and read error. */ 436 BOUNDS_CHECK(cp, 2*INT16SZ); 437 cp += INT16SZ; 438 GETSHORT(error, cp); 439 440 /* Parse the other data. */ 441 BOUNDS_CHECK(cp, INT16SZ); 442 GETSHORT(otherfieldlen, cp); 443 BOUNDS_CHECK(cp, otherfieldlen); 444 cp += otherfieldlen; 445 446 if (cp != eom) 447 return (NS_TSIG_ERROR_FORMERR); 448 449 /* 450 * Do the verification. 451 */ 452 453 /* Digest the time signed and fudge. */ 454 cp2 = buf; 455 PUTSHORT(0, cp2); /*%< Top 16 bits of time. */ 456 PUTLONG(timesigned, cp2); 457 PUTSHORT(NS_TSIG_FUDGE, cp2); 458 459 dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx, 460 buf, (int)(cp2 - buf), NULL, 0); 461 462 n = dst_verify_data(SIG_MODE_FINAL, state->key, &state->ctx, NULL, 0, 463 sigstart, (int)sigfieldlen); 464 if (n < 0) 465 return (-ns_r_badsig); 466 467 if (sigfieldlen > sizeof(state->sig)) 468 return (NS_TSIG_ERROR_NO_SPACE); 469 470 memcpy(state->sig, sigstart, sigfieldlen); 471 state->siglen = sigfieldlen; 472 473 /* Verify the time. */ 474 if (abs((int)(timesigned - time(NULL))) > fudge) 475 return (-ns_r_badtime); 476 477 *msglen = (int)(recstart - msg); 478 479 if (error != NOERROR) 480 return (error); 481 482 return (0); 483 } 484 485 /*! \file */ 486
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