ip_dns_pxy.c revision 1.2
1 /* $NetBSD: ip_dns_pxy.c,v 1.2 2012/03/23 20:39:49 christos Exp $ */ 2 3 /* 4 * Copyright (C) 2010 by Darren Reed. 5 * 6 * See the IPFILTER.LICENCE file for details on licencing. 7 * 8 * Id: ip_dns_pxy.c,v 2.2.2.6 2012/01/29 05:30:35 darrenr Exp 9 */ 10 11 #define IPF_DNS_PROXY 12 13 /* 14 * map ... proxy port dns/udp 53 { block .cnn.com; } 15 */ 16 typedef struct ipf_dns_filter { 17 struct ipf_dns_filter *idns_next; 18 char *idns_name; 19 int idns_namelen; 20 int idns_pass; 21 } ipf_dns_filter_t; 22 23 24 typedef struct ipf_dns_softc_s { 25 ipf_dns_filter_t *ipf_p_dns_list; 26 ipfrwlock_t ipf_p_dns_rwlock; 27 u_long ipf_p_dns_compress; 28 u_long ipf_p_dns_toolong; 29 u_long ipf_p_dns_nospace; 30 } ipf_dns_softc_t; 31 32 int ipf_p_dns_allow_query(ipf_dns_softc_t *, dnsinfo_t *); 33 int ipf_p_dns_ctl(ipf_main_softc_t *, void *, ap_ctl_t *); 34 int ipf_p_dns_del(ipf_main_softc_t *, ap_session_t *); 35 int ipf_p_dns_get_name(ipf_dns_softc_t *, char *, int, char *, int); 36 int ipf_p_dns_inout(void *, fr_info_t *, ap_session_t *, nat_t *); 37 int ipf_p_dns_match(fr_info_t *, ap_session_t *, nat_t *); 38 int ipf_p_dns_match_names(ipf_dns_filter_t *, char *, int); 39 int ipf_p_dns_new(void *, fr_info_t *, ap_session_t *, nat_t *); 40 void *ipf_p_dns_soft_create(ipf_main_softc_t *); 41 void ipf_p_dns_soft_destroy(ipf_main_softc_t *, void *); 42 43 typedef struct { 44 u_char dns_id[2]; 45 u_short dns_ctlword; 46 u_short dns_qdcount; 47 u_short dns_ancount; 48 u_short dns_nscount; 49 u_short dns_arcount; 50 } ipf_dns_hdr_t; 51 52 #define DNS_QR(x) ((ntohs(x) & 0x8000) >> 15) 53 #define DNS_OPCODE(x) ((ntohs(x) & 0x7800) >> 11) 54 #define DNS_AA(x) ((ntohs(x) & 0x0400) >> 10) 55 #define DNS_TC(x) ((ntohs(x) & 0x0200) >> 9) 56 #define DNS_RD(x) ((ntohs(x) & 0x0100) >> 8) 57 #define DNS_RA(x) ((ntohs(x) & 0x0080) >> 7) 58 #define DNS_Z(x) ((ntohs(x) & 0x0070) >> 4) 59 #define DNS_RCODE(x) ((ntohs(x) & 0x000f) >> 0) 60 61 62 void * 63 ipf_p_dns_soft_create(ipf_main_softc_t *softc) 64 { 65 ipf_dns_softc_t *softd; 66 67 KMALLOC(softd, ipf_dns_softc_t *); 68 if (softd == NULL) 69 return NULL; 70 71 bzero((char *)softd, sizeof(*softd)); 72 RWLOCK_INIT(&softd->ipf_p_dns_rwlock, "ipf dns rwlock"); 73 74 return softd; 75 } 76 77 78 void 79 ipf_p_dns_soft_destroy(ipf_main_softc_t *softc, void *arg) 80 { 81 ipf_dns_softc_t *softd = arg; 82 ipf_dns_filter_t *idns; 83 84 while ((idns = softd->ipf_p_dns_list) != NULL) { 85 KFREES(idns->idns_name, idns->idns_namelen); 86 idns->idns_name = NULL; 87 idns->idns_namelen = 0; 88 softd->ipf_p_dns_list = idns->idns_next; 89 KFREE(idns); 90 } 91 RW_DESTROY(&softd->ipf_p_dns_rwlock); 92 93 KFREE(softd); 94 } 95 96 97 int 98 ipf_p_dns_ctl(ipf_main_softc_t *softc, void *arg, ap_ctl_t *ctl) 99 { 100 ipf_dns_softc_t *softd = arg; 101 ipf_dns_filter_t *tmp, *idns, **idnsp; 102 int error = 0; 103 104 /* 105 * To make locking easier. 106 */ 107 KMALLOC(tmp, ipf_dns_filter_t *); 108 109 WRITE_ENTER(&softd->ipf_p_dns_rwlock); 110 for (idnsp = &softd->ipf_p_dns_list; (idns = *idnsp) != NULL; 111 idnsp = &idns->idns_next) { 112 if (idns->idns_namelen != ctl->apc_dsize) 113 continue; 114 if (!strncmp(ctl->apc_data, idns->idns_name, 115 idns->idns_namelen)) 116 break; 117 } 118 119 switch (ctl->apc_cmd) 120 { 121 case APC_CMD_DEL : 122 if (idns == NULL) { 123 IPFERROR(80006); 124 error = ESRCH; 125 break; 126 } 127 *idnsp = idns->idns_next; 128 idns->idns_next = NULL; 129 KFREES(idns->idns_name, idns->idns_namelen); 130 idns->idns_name = NULL; 131 idns->idns_namelen = 0; 132 KFREE(idns); 133 break; 134 case APC_CMD_ADD : 135 if (idns != NULL) { 136 IPFERROR(80007); 137 error = EEXIST; 138 break; 139 } 140 if (tmp == NULL) { 141 IPFERROR(80008); 142 error = ENOMEM; 143 break; 144 } 145 idns = tmp; 146 tmp = NULL; 147 idns->idns_namelen = ctl->apc_dsize; 148 idns->idns_name = ctl->apc_data; 149 idns->idns_pass = ctl->apc_arg; 150 idns->idns_next = NULL; 151 *idnsp = idns; 152 ctl->apc_data = NULL; 153 ctl->apc_dsize = 0; 154 break; 155 default : 156 IPFERROR(80009); 157 error = EINVAL; 158 break; 159 } 160 RWLOCK_EXIT(&softd->ipf_p_dns_rwlock); 161 162 if (tmp != NULL) { 163 KFREE(tmp); 164 tmp = NULL; 165 } 166 167 return error; 168 } 169 170 171 /* ARGSUSED */ 172 int 173 ipf_p_dns_new(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat) 174 { 175 dnsinfo_t *di; 176 int dlen; 177 178 dlen = fin->fin_dlen - sizeof(udphdr_t); 179 if (dlen < sizeof(ipf_dns_hdr_t)) { 180 /* 181 * No real DNS packet is smaller than that. 182 */ 183 return -1; 184 } 185 186 aps->aps_psiz = sizeof(dnsinfo_t); 187 KMALLOCS(di, dnsinfo_t *, sizeof(dnsinfo_t)); 188 if (di == NULL) { 189 printf("ipf_dns_new:KMALLOCS(%zu) failed\n", sizeof(*di)); 190 return -1; 191 } 192 193 MUTEX_INIT(&di->dnsi_lock, "dns lock"); 194 195 aps->aps_data = di; 196 197 dlen = fin->fin_dlen - sizeof(udphdr_t); 198 COPYDATA(fin->fin_m, fin->fin_hlen + sizeof(udphdr_t), 199 MIN(dlen, sizeof(di->dnsi_buffer)), di->dnsi_buffer); 200 di->dnsi_id = (di->dnsi_buffer[0] << 8) | di->dnsi_buffer[1]; 201 return 0; 202 } 203 204 205 /* ARGSUSED */ 206 int 207 ipf_p_dns_del(ipf_main_softc_t *softc, ap_session_t *aps) 208 { 209 #ifdef USE_MUTEXES 210 dnsinfo_t *di = aps->aps_data; 211 212 MUTEX_DESTROY(&di->dnsi_lock); 213 #endif 214 KFREES(aps->aps_data, aps->aps_psiz); 215 aps->aps_data = NULL; 216 aps->aps_psiz = 0; 217 return 0; 218 } 219 220 221 /* 222 * Tries to match the base string (in our ACL) with the query from a packet. 223 */ 224 int 225 ipf_p_dns_match_names(ipf_dns_filter_t *idns, char *query, int qlen) 226 { 227 int blen; 228 char *base; 229 230 blen = idns->idns_namelen; 231 base = idns->idns_name; 232 233 if (blen > qlen) 234 return 1; 235 236 if (blen == qlen) 237 return strncasecmp(base, query, qlen); 238 239 /* 240 * If the base string string is shorter than the query, allow the 241 * tail of the base to match the same length tail of the query *if*: 242 * - the base string starts with a '*' (*cnn.com) 243 * - the base string represents a domain (.cnn.com) 244 * as otherwise it would not be possible to block just "cnn.com" 245 * without also impacting "foocnn.com", etc. 246 */ 247 if (*base == '*') { 248 base++; 249 blen--; 250 } else if (*base != '.') 251 return 1; 252 253 return strncasecmp(base, query + qlen - blen, blen); 254 } 255 256 257 int 258 ipf_p_dns_get_name(ipf_dns_softc_t *softd, char *start, int len, char *buffer, 259 int buflen) 260 { 261 char *s, *t, clen; 262 int slen, blen; 263 264 s = start; 265 t = buffer; 266 slen = len; 267 blen = buflen - 1; /* Always make room for trailing \0 */ 268 269 while (*s != '\0') { 270 clen = *s; 271 if ((clen & 0xc0) == 0xc0) { /* Doesn't do compression */ 272 softd->ipf_p_dns_compress++; 273 return 0; 274 } 275 if (clen > slen) { 276 softd->ipf_p_dns_toolong++; 277 return 0; /* Does the name run off the end? */ 278 } 279 if ((clen + 1) > blen) { 280 softd->ipf_p_dns_nospace++; 281 return 0; /* Enough room for name+.? */ 282 } 283 s++; 284 bcopy(s, t, clen); 285 t += clen; 286 s += clen; 287 *t++ = '.'; 288 slen -= clen; 289 blen -= (clen + 1); 290 } 291 292 *(t - 1) = '\0'; 293 return s - start; 294 } 295 296 297 int 298 ipf_p_dns_allow_query(ipf_dns_softc_t *softd, dnsinfo_t *dnsi) 299 { 300 ipf_dns_filter_t *idns; 301 int len; 302 303 len = strlen(dnsi->dnsi_buffer); 304 305 for (idns = softd->ipf_p_dns_list; idns != NULL; idns = idns->idns_next) 306 if (ipf_p_dns_match_names(idns, dnsi->dnsi_buffer, len) == 0) 307 return idns->idns_pass; 308 return 0; 309 } 310 311 312 /* ARGSUSED */ 313 int 314 ipf_p_dns_inout(void *arg, fr_info_t *fin, ap_session_t *aps, nat_t *nat) 315 { 316 ipf_dns_softc_t *softd = arg; 317 ipf_dns_hdr_t *dns; 318 dnsinfo_t *di; 319 char *data; 320 int dlen, q, rc = 0; 321 322 if (fin->fin_dlen < sizeof(*dns)) 323 return APR_ERR(1); 324 325 dns = (ipf_dns_hdr_t *)((char *)fin->fin_dp + sizeof(udphdr_t)); 326 327 q = dns->dns_qdcount; 328 329 data = (char *)(dns + 1); 330 dlen = fin->fin_dlen - sizeof(*dns) - sizeof(udphdr_t); 331 332 di = aps->aps_data; 333 334 READ_ENTER(&softd->ipf_p_dns_rwlock); 335 MUTEX_ENTER(&di->dnsi_lock); 336 337 for (; (dlen > 0) && (q > 0); q--) { 338 int len; 339 340 len = ipf_p_dns_get_name(softd, data, dlen, di->dnsi_buffer, 341 sizeof(di->dnsi_buffer)); 342 if (len == 0) { 343 rc = 1; 344 break; 345 } 346 rc = ipf_p_dns_allow_query(softd, di); 347 if (rc != 0) 348 break; 349 data += len; 350 dlen -= len; 351 } 352 MUTEX_EXIT(&di->dnsi_lock); 353 RWLOCK_EXIT(&softd->ipf_p_dns_rwlock); 354 355 return APR_ERR(rc); 356 } 357 358 359 /* ARGSUSED */ 360 int 361 ipf_p_dns_match(fr_info_t *fin, ap_session_t *aps, nat_t *nat) 362 { 363 dnsinfo_t *di = aps->aps_data; 364 ipf_dns_hdr_t *dnh; 365 366 if ((fin->fin_dlen < sizeof(u_short)) || (fin->fin_flx & FI_FRAG)) 367 return -1; 368 369 dnh = (ipf_dns_hdr_t *)((char *)fin->fin_dp + sizeof(udphdr_t)); 370 if (((dnh->dns_id[0] << 8) | dnh->dns_id[1]) != di->dnsi_id) 371 return -1; 372 return 0; 373 } 374
Indexes created Tue Sep 30 11:09:46 GMT 2025