contrib/libpcap/pcap-netfilter-linux.c

   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 this is not fatal */
 456                 if (errno == EAFNOSUPPORT)
 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