1 /* 2 * Copyright (c) 2011 Jakub Zawadzki 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote 15 * products derived from this software without specific prior written 16 * permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31 #ifdef HAVE_CONFIG_H 32 #include "config.h" 33 #endif 34 35 #include "pcap-int.h" 36 37 #ifdef NEED_STRERROR_H 38 #include "strerror.h" 39 #endif 40 41 #include <errno.h> 42 #include <stdlib.h> 43 #include <unistd.h> 44 #include <string.h> 45 #include <sys/socket.h> 46 #include <arpa/inet.h> 47 48 #include <time.h> 49 #include <sys/time.h> 50 #include <netinet/in.h> 51 #include <linux/types.h> 52 53 #include <linux/netlink.h> 54 #include <linux/netfilter/nfnetlink.h> 55 #include <linux/netfilter/nfnetlink_log.h> 56 57 #include "pcap-netfilter-linux.h" 58 59 #define HDR_LENGTH (NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg)))) 60 61 #define NFLOG_IFACE "nflog" 62 63 static int 64 nflog_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user) 65 { 66 const unsigned char *buf; 67 int count = 0; 68 int len; 69 70 /* ignore interrupt system call error */ 71 do { 72 len = recv(handle->fd, handle->buffer, handle->bufsize, 0); 73 if (handle->break_loop) { 74 handle->break_loop = 0; 75 return -2; 76 } 77 } while ((len == -1) && (errno == EINTR)); 78 79 if (len < 0) { 80 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't receive packet %d:%s", errno, pcap_strerror(errno)); 81 return -1; 82 } 83 84 buf = handle->buffer; 85 while (len >= NLMSG_SPACE(0)) { 86 const struct nlmsghdr *nlh = (const struct nlmsghdr *) buf; 87 u_int32_t msg_len; 88 89 if (nlh->nlmsg_len < sizeof(struct nlmsghdr) || len < nlh->nlmsg_len) { 90 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Message truncated: (got: %d) (nlmsg_len: %u)", len, nlh->nlmsg_len); 91 return -1; 92 } 93 94 if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_ULOG && 95 NFNL_MSG_TYPE(nlh->nlmsg_type) == NFULNL_MSG_PACKET) 96 { 97 const unsigned char *payload = NULL; 98 struct pcap_pkthdr pkth; 99 100 if (handle->linktype != DLT_NFLOG) { 101 const struct nfattr *payload_attr = NULL; 102 103 if (nlh->nlmsg_len < HDR_LENGTH) { 104 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Malformed message: (nlmsg_len: %u)", nlh->nlmsg_len); 105 return -1; 106 } 107 108 if (nlh->nlmsg_len > HDR_LENGTH) { 109 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh)); 110 int attr_len = nlh->nlmsg_len - NLMSG_ALIGN(HDR_LENGTH); 111 112 while (NFA_OK(attr, attr_len)) { 113 switch (NFA_TYPE(attr)) { 114 case NFULA_PAYLOAD: 115 payload_attr = attr; 116 break; 117 } 118 attr = NFA_NEXT(attr, attr_len); 119 } 120 } 121 122 if (payload_attr) { 123 payload = NFA_DATA(payload_attr); 124 pkth.len = pkth.caplen = NFA_PAYLOAD(payload_attr); 125 } 126 127 } else { 128 payload = NLMSG_DATA(nlh); 129 pkth.caplen = pkth.len = nlh->nlmsg_len-NLMSG_ALIGN(sizeof(struct nlmsghdr)); 130 } 131 132 if (payload) { 133 /* pkth.caplen = min (payload_len, handle->snapshot); */ 134 135 gettimeofday(&pkth.ts, NULL); 136 if (handle->fcode.bf_insns == NULL || 137 bpf_filter(handle->fcode.bf_insns, payload, pkth.len, pkth.caplen)) 138 { 139 handle->md.packets_read++; 140 callback(user, &pkth, payload); 141 count++; 142 } 143 } 144 } 145 146 msg_len = NLMSG_ALIGN(nlh->nlmsg_len); 147 if (msg_len > len) 148 msg_len = len; 149 150 len -= msg_len; 151 buf += msg_len; 152 } 153 return count; 154 } 155 156 static int 157 netfilter_set_datalink(pcap_t *handle, int dlt) 158 { 159 handle->linktype = dlt; 160 return 0; 161 } 162 163 static int 164 netfilter_stats_linux(pcap_t *handle, struct pcap_stat *stats) 165 { 166 stats->ps_recv = handle->md.packets_read; 167 stats->ps_drop = 0; 168 stats->ps_ifdrop = 0; 169 return 0; 170 } 171 172 static int 173 netfilter_inject_linux(pcap_t *handle, const void *buf, size_t size) 174 { 175 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "inject not supported on netfilter devices"); 176 return (-1); 177 } 178 179 struct my_nfattr { 180 u_int16_t nfa_len; 181 u_int16_t nfa_type; 182 void *data; 183 }; 184 185 static int 186 nflog_send_config_msg(const pcap_t *handle, u_int8_t family, u_int16_t res_id, const struct my_nfattr *mynfa) 187 { 188 char buf[1024] __attribute__ ((aligned)); 189 190 struct nlmsghdr *nlh = (struct nlmsghdr *) buf; 191 struct nfgenmsg *nfg = (struct nfgenmsg *) (buf + sizeof(struct nlmsghdr)); 192 193 struct sockaddr_nl snl; 194 static unsigned int seq_id; 195 196 if (!seq_id) 197 seq_id = time(NULL); 198 ++seq_id; 199 200 nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nfgenmsg)); 201 nlh->nlmsg_type = (NFNL_SUBSYS_ULOG << 8) | NFULNL_MSG_CONFIG; 202 nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK; 203 nlh->nlmsg_pid = 0; /* to kernel */ 204 nlh->nlmsg_seq = seq_id; 205 206 nfg->nfgen_family = family; 207 nfg->version = NFNETLINK_V0; 208 nfg->res_id = htons(res_id); 209 210 if (mynfa) { 211 struct nfattr *nfa = (struct nfattr *) (buf + NLMSG_ALIGN(nlh->nlmsg_len)); 212 213 nfa->nfa_type = mynfa->nfa_type; 214 nfa->nfa_len = NFA_LENGTH(mynfa->nfa_len); 215 memcpy(NFA_DATA(nfa), mynfa->data, mynfa->nfa_len); 216 nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + NFA_ALIGN(nfa->nfa_len); 217 } 218 219 memset(&snl, 0, sizeof(snl)); 220 snl.nl_family = AF_NETLINK; 221 222 if (sendto(handle->fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *) &snl, sizeof(snl)) == -1) 223 return -1; 224 225 /* waiting for reply loop */ 226 do { 227 socklen_t addrlen = sizeof(snl); 228 int len; 229 230 /* ignore interrupt system call error */ 231 do { 232 len = recvfrom(handle->fd, buf, sizeof(buf), 0, (struct sockaddr *) &snl, &addrlen); 233 } while ((len == -1) && (errno == EINTR)); 234 235 if (len <= 0) 236 return len; 237 238 if (addrlen != sizeof(snl) || snl.nl_family != AF_NETLINK) { 239 errno = EINVAL; 240 return -1; 241 } 242 243 nlh = (struct nlmsghdr *) buf; 244 if (snl.nl_pid != 0 || seq_id != nlh->nlmsg_seq) /* if not from kernel or wrong sequence skip */ 245 continue; 246 247 while (len >= NLMSG_SPACE(0) && NLMSG_OK(nlh, len)) { 248 if (nlh->nlmsg_type == NLMSG_ERROR || (nlh->nlmsg_type == NLMSG_DONE && nlh->nlmsg_flags & NLM_F_MULTI)) { 249 if (nlh->nlmsg_len < NLMSG_ALIGN(sizeof(struct nlmsgerr))) { 250 errno = EBADMSG; 251 return -1; 252 } 253 errno = -(*((int *)NLMSG_DATA(nlh))); 254 return (errno == 0) ? 0 : -1; 255 } 256 nlh = NLMSG_NEXT(nlh, len); 257 } 258 } while (1); 259 260 return -1; /* never here */ 261 } 262 263 static int 264 nflog_send_config_cmd(const pcap_t *handle, u_int16_t group_id, u_int8_t cmd, u_int8_t family) 265 { 266 struct nfulnl_msg_config_cmd msg; 267 struct my_nfattr nfa; 268 269 msg.command = cmd; 270 271 nfa.data = &msg; 272 nfa.nfa_type = NFULA_CFG_CMD; 273 nfa.nfa_len = sizeof(msg); 274 275 return nflog_send_config_msg(handle, family, group_id, &nfa); 276 } 277 278 static int 279 nflog_send_config_mode(const pcap_t *handle, u_int16_t group_id, u_int8_t copy_mode, u_int32_t copy_range) 280 { 281 struct nfulnl_msg_config_mode msg; 282 struct my_nfattr nfa; 283 284 msg.copy_range = htonl(copy_range); 285 msg.copy_mode = copy_mode; 286 287 nfa.data = &msg; 288 nfa.nfa_type = NFULA_CFG_MODE; 289 nfa.nfa_len = sizeof(msg); 290 291 return nflog_send_config_msg(handle, AF_UNSPEC, group_id, &nfa); 292 } 293 294 static int 295 nflog_activate(pcap_t* handle) 296 { 297 const char *dev = handle->opt.source; 298 unsigned short groups[32]; 299 int group_count = 0; 300 int i; 301 302 if (strncmp(dev, NFLOG_IFACE, strlen(NFLOG_IFACE)) == 0) { 303 dev += strlen(NFLOG_IFACE); 304 305 /* nflog:30,33,42 looks nice, allow it */ 306 if (*dev == ':') 307 dev++; 308 309 while (*dev) { 310 long int group_id; 311 char *end_dev; 312 313 if (group_count == 32) { 314 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, 315 "Maximum 32 netfilter groups! dev: %s", 316 handle->opt.source); 317 return PCAP_ERROR; 318 } 319 320 group_id = strtol(dev, &end_dev, 0); 321 if (end_dev != dev) { 322 if (group_id < 0 || group_id > 65535) { 323 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, 324 "Netfilter group range from 0 to 65535 (got %ld)", 325 group_id); 326 return PCAP_ERROR; 327 } 328 329 groups[group_count++] = (unsigned short) group_id; 330 dev = end_dev; 331 } 332 if (*dev != ',') 333 break; 334 dev++; 335 } 336 } 337 338 if (*dev) { 339 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, 340 "Can't get netfilter group(s) index from %s", 341 handle->opt.source); 342 return PCAP_ERROR; 343 } 344 345 /* if no groups, add default: 0 */ 346 if (!group_count) { 347 groups[0] = 0; 348 group_count = 1; 349 } 350 351 /* Initialize some components of the pcap structure. */ 352 handle->bufsize = 128 + handle->snapshot; 353 handle->offset = 0; 354 handle->linktype = DLT_NFLOG; 355 handle->read_op = nflog_read_linux; 356 handle->inject_op = netfilter_inject_linux; 357 handle->setfilter_op = install_bpf_program; /* no kernel filtering */ 358 handle->setdirection_op = NULL; 359 handle->set_datalink_op = NULL; 360 handle->set_datalink_op = netfilter_set_datalink; 361 handle->getnonblock_op = pcap_getnonblock_fd; 362 handle->setnonblock_op = pcap_setnonblock_fd; 363 handle->stats_op = netfilter_stats_linux; 364 365 /* Create netlink socket */ 366 handle->fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER); 367 if (handle->fd < 0) { 368 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't create raw socket %d:%s", errno, pcap_strerror(errno)); 369 return PCAP_ERROR; 370 } 371 372 handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2); 373 if (handle->dlt_list != NULL) { 374 handle->dlt_list[0] = DLT_NFLOG; 375 handle->dlt_list[1] = DLT_IPV4; 376 handle->dlt_count = 2; 377 } 378 379 handle->buffer = malloc(handle->bufsize); 380 if (!handle->buffer) { 381 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't allocate dump buffer: %s", pcap_strerror(errno)); 382 goto close_fail; 383 } 384 385 if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) { 386 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_UNBIND: %s", pcap_strerror(errno)); 387 goto close_fail; 388 } 389 390 if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_BIND, AF_INET) < 0) { 391 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_BIND: %s", pcap_strerror(errno)); 392 goto close_fail; 393 } 394 395 /* Bind socket to the nflog groups */ 396 for (i = 0; i < group_count; i++) { 397 if (nflog_send_config_cmd(handle, groups[i], NFULNL_CFG_CMD_BIND, AF_UNSPEC) < 0) { 398 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't listen on group group index: %s", pcap_strerror(errno)); 399 goto close_fail; 400 } 401 402 if (nflog_send_config_mode(handle, groups[i], NFULNL_COPY_PACKET, handle->snapshot) < 0) { 403 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_COPY_PACKET: %s", pcap_strerror(errno)); 404 goto close_fail; 405 } 406 } 407 408 if (handle->opt.rfmon) { 409 /* 410 * Monitor mode doesn't apply to netfilter devices. 411 */ 412 pcap_cleanup_live_common(handle); 413 return PCAP_ERROR_RFMON_NOTSUP; 414 } 415 416 if (handle->opt.buffer_size != 0) { 417 /* 418 * Set the socket buffer size to the specified value. 419 */ 420 if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF, &handle->opt.buffer_size, sizeof(handle->opt.buffer_size)) == -1) { 421 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "SO_RCVBUF: %s", pcap_strerror(errno)); 422 goto close_fail; 423 } 424 } 425 426 handle->selectable_fd = handle->fd; 427 return 0; 428 429 close_fail: 430 pcap_cleanup_live_common(handle); 431 return PCAP_ERROR; 432 } 433 434 pcap_t * 435 nflog_create(const char *device, char *ebuf) 436 { 437 pcap_t *p; 438 439 p = pcap_create_common(device, ebuf); 440 if (p == NULL) 441 return (NULL); 442 443 p->activate_op = nflog_activate; 444 return (p); 445 } 446 447 int 448 netfilter_platform_finddevs(pcap_if_t **alldevsp, char *err_str) 449 { 450 pcap_if_t *found_dev = *alldevsp; 451 int sock; 452 453 sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER); 454 if (sock < 0) { 455 /* if netlink is not supported this is not fatal */ 456 if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT) 457 return 0; 458 snprintf(err_str, PCAP_ERRBUF_SIZE, "Can't open netlink socket %d:%s", 459 errno, pcap_strerror(errno)); 460 return -1; 461 } 462 close(sock); 463 464 if (pcap_add_if(&found_dev, NFLOG_IFACE, 0, "Linux netfilter log (NFLOG) interface", err_str) < 0) 465 return -1; 466 return 0; 467 } 468 469