1 /* $OpenBSD: privsep_pcap.c,v 1.15 2008/04/18 21:35:11 djm Exp $ */ 2 3 /* 4 * Copyright (c) 2004 Can Erkin Acar 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * - Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * - Redistributions in binary form must reproduce the above 14 * copyright notice, this list of conditions and the following 15 * disclaimer in the documentation and/or other materials provided 16 * with the distribution. 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 21 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 22 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 24 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 26 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 28 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/types.h> 33 #include <sys/ioctl.h> 34 #include <sys/socket.h> 35 #include <net/if.h> 36 37 #include <err.h> 38 #include <errno.h> 39 #include <fcntl.h> 40 #include <pcap-int.h> 41 #include <pcap.h> 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include <string.h> 45 #include <unistd.h> 46 47 #include "privsep.h" 48 49 /* 50 * privileged part of priv_pcap_setfilter, compile the filter 51 * expression, and return it to the parent. Note that we fake an hpcap 52 * and use it to capture the error messages, and pass the error back 53 * to client. 54 */ 55 int 56 setfilter(int bpfd, int sock, char *filter) 57 { 58 struct bpf_program fcode; 59 int oflag, snap, link; 60 u_int32_t netmask; 61 pcap_t hpcap; 62 63 must_read(sock, &oflag, sizeof(oflag)); 64 must_read(sock, &netmask, sizeof(netmask)); 65 must_read(sock, &snap, sizeof(snap)); 66 must_read(sock, &link, sizeof(link)); 67 68 if (snap < 0) { 69 snprintf(hpcap.errbuf, PCAP_ERRBUF_SIZE, "invalid snaplen"); 70 goto err; 71 } 72 73 /* fake hpcap, it only needs errbuf, snaplen, and linktype to 74 * compile a filter expression */ 75 /* XXX messing with pcap internals */ 76 hpcap.snapshot = snap; 77 hpcap.linktype = link; 78 if (pcap_compile(&hpcap, &fcode, filter, oflag, netmask)) 79 goto err; 80 81 /* if bpf descriptor is open, set the filter XXX check oflag? */ 82 if (bpfd >= 0 && ioctl(bpfd, BIOCSETF, &fcode)) { 83 snprintf(hpcap.errbuf, PCAP_ERRBUF_SIZE, 84 "ioctl: BIOCSETF: %s", strerror(errno)); 85 pcap_freecode(&fcode); 86 goto err; 87 } 88 if (fcode.bf_len > 0) { 89 /* write the filter */ 90 must_write(sock, &fcode.bf_len, sizeof(fcode.bf_len)); 91 must_write(sock, fcode.bf_insns, 92 fcode.bf_len * sizeof(struct bpf_insn)); 93 } else { 94 snprintf(hpcap.errbuf, PCAP_ERRBUF_SIZE, "Invalid filter size"); 95 pcap_freecode(&fcode); 96 goto err; 97 } 98 99 100 pcap_freecode(&fcode); 101 return (0); 102 103 err: 104 fcode.bf_len = 0; 105 must_write(sock, &fcode.bf_len, sizeof(fcode.bf_len)); 106 107 /* write back the error string */ 108 write_string(sock, hpcap.errbuf); 109 return (1); 110 } 111 112 /* 113 * filter is compiled and set in the privileged process. 114 * get the compiled output and set it locally for filtering dumps etc. 115 */ 116 struct bpf_program * 117 priv_pcap_setfilter(pcap_t *hpcap, int oflag, u_int32_t netmask) 118 { 119 struct bpf_program *fcode = NULL; 120 int snap, link; 121 char *ebuf; 122 123 if (priv_fd < 0) 124 errx(1, "%s: called from privileged portion", __func__); 125 126 ebuf = pcap_geterr(hpcap); 127 snap = pcap_snapshot(hpcap); 128 link = pcap_datalink(hpcap); 129 130 fcode = calloc(1, sizeof(*fcode)); 131 if (fcode == NULL) { 132 snprintf(ebuf, PCAP_ERRBUF_SIZE, "out of memory"); 133 return (NULL); 134 } 135 136 write_command(priv_fd, PRIV_SETFILTER); 137 138 /* send oflag, netmask, snaplen and linktype */ 139 must_write(priv_fd, &oflag, sizeof(oflag)); 140 must_write(priv_fd, &netmask, sizeof(netmask)); 141 must_write(priv_fd, &snap, sizeof(snap)); 142 must_write(priv_fd, &link, sizeof(link)); 143 144 /* receive compiled filter */ 145 must_read(priv_fd, &fcode->bf_len, sizeof(fcode->bf_len)); 146 if (fcode->bf_len <= 0) { 147 int len; 148 149 len = read_string(priv_fd, ebuf, PCAP_ERRBUF_SIZE, __func__); 150 if (len == 0) 151 snprintf(ebuf, PCAP_ERRBUF_SIZE, "pcap compile error"); 152 goto err; 153 } 154 155 fcode->bf_insns = calloc(fcode->bf_len, sizeof(struct bpf_insn)); 156 if (fcode->bf_insns == NULL) { 157 snprintf(ebuf, PCAP_ERRBUF_SIZE, "out of memory"); 158 goto err; 159 } 160 161 must_read(priv_fd, fcode->bf_insns, 162 fcode->bf_len * sizeof(struct bpf_insn)); 163 164 pcap_setfilter(hpcap, fcode); 165 return (fcode); 166 167 err: 168 free(fcode); 169 return (NULL); 170 } 171 172 173 /* privileged part of priv_pcap_live */ 174 int 175 pcap_live(const char *device, int snaplen, int promisc, u_int dlt, 176 u_int dirfilt) 177 { 178 char bpf[sizeof "/dev/bpf0000000000"]; 179 int fd, n = 0; 180 struct ifreq ifr; 181 unsigned v; 182 183 if (device == NULL || snaplen <= 0) 184 return (-1); 185 186 do { 187 snprintf(bpf, sizeof(bpf), "/dev/bpf%d", n++); 188 fd = open(bpf, O_RDONLY); 189 } while (fd < 0 && errno == EBUSY); 190 191 if (fd < 0) 192 return (-1); 193 194 v = 32768; /* XXX this should be a user-accessible hook */ 195 ioctl(fd, BIOCSBLEN, &v); 196 197 strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); 198 if (ioctl(fd, BIOCSETIF, &ifr) < 0) 199 goto error; 200 201 if (dlt != (u_int) -1 && ioctl(fd, BIOCSDLT, &dlt)) 202 goto error; 203 204 if (promisc) 205 /* this is allowed to fail */ 206 ioctl(fd, BIOCPROMISC, NULL); 207 if (ioctl(fd, BIOCSDIRFILT, &dirfilt) < 0) 208 goto error; 209 210 /* lock the descriptor */ 211 if (ioctl(fd, BIOCLOCK, NULL) < 0) 212 goto error; 213 return (fd); 214 215 error: 216 close(fd); 217 return (-1); 218 } 219 220 221 /* 222 * XXX reimplement pcap_open_live with privsep, this is the 223 * unprivileged part. 224 */ 225 pcap_t * 226 priv_pcap_live(const char *dev, int slen, int prom, int to_ms, 227 char *ebuf, u_int dlt, u_int dirfilt) 228 { 229 int fd, err; 230 struct bpf_version bv; 231 u_int v; 232 pcap_t *p; 233 234 if (priv_fd < 0) 235 errx(1, "%s: called from privileged portion", __func__); 236 237 if (dev == NULL) 238 snprintf(ebuf, PCAP_ERRBUF_SIZE, "No interface specified"); 239 240 p = (pcap_t *)malloc(sizeof(*p)); 241 if (p == NULL) { 242 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", 243 pcap_strerror(errno)); 244 return (NULL); 245 } 246 247 bzero(p, sizeof(*p)); 248 249 write_command(priv_fd, PRIV_OPEN_BPF); 250 must_write(priv_fd, &slen, sizeof(int)); 251 must_write(priv_fd, &prom, sizeof(int)); 252 must_write(priv_fd, &dlt, sizeof(u_int)); 253 must_write(priv_fd, &dirfilt, sizeof(u_int)); 254 write_string(priv_fd, dev); 255 256 fd = receive_fd(priv_fd); 257 must_read(priv_fd, &err, sizeof(int)); 258 if (fd < 0) { 259 snprintf(ebuf, PCAP_ERRBUF_SIZE, 260 "Failed to open bpf device for %s: %s", 261 dev, strerror(err)); 262 goto bad; 263 } 264 265 /* fd is locked, can only use 'safe' ioctls */ 266 if (ioctl(fd, BIOCVERSION, &bv) < 0) { 267 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s", 268 pcap_strerror(errno)); 269 goto bad; 270 } 271 272 if (bv.bv_major != BPF_MAJOR_VERSION || 273 bv.bv_minor < BPF_MINOR_VERSION) { 274 snprintf(ebuf, PCAP_ERRBUF_SIZE, 275 "kernel bpf filter out of date"); 276 goto bad; 277 } 278 279 p->fd = fd; 280 p->snapshot = slen; 281 282 /* Get the data link layer type. */ 283 if (ioctl(fd, BIOCGDLT, &v) < 0) { 284 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s", 285 pcap_strerror(errno)); 286 goto bad; 287 } 288 #if _BSDI_VERSION - 0 >= 199510 289 /* The SLIP and PPP link layer header changed in BSD/OS 2.1 */ 290 switch (v) { 291 292 case DLT_SLIP: 293 v = DLT_SLIP_BSDOS; 294 break; 295 296 case DLT_PPP: 297 v = DLT_PPP_BSDOS; 298 break; 299 } 300 #endif 301 p->linktype = v; 302 303 /* set timeout */ 304 if (to_ms != 0) { 305 struct timeval to; 306 to.tv_sec = to_ms / 1000; 307 to.tv_usec = (to_ms * 1000) % 1000000; 308 if (ioctl(p->fd, BIOCSRTIMEOUT, &to) < 0) { 309 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s", 310 pcap_strerror(errno)); 311 goto bad; 312 } 313 } 314 315 if (ioctl(fd, BIOCGBLEN, &v) < 0) { 316 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s", 317 pcap_strerror(errno)); 318 goto bad; 319 } 320 p->bufsize = v; 321 p->buffer = (u_char *)malloc(p->bufsize); 322 if (p->buffer == NULL) { 323 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", 324 pcap_strerror(errno)); 325 goto bad; 326 } 327 return (p); 328 329 bad: 330 if (fd >= 0) 331 close(fd); 332 free(p); 333 return (NULL); 334 } 335 336 337 338 /* 339 * reimplement pcap_open_offline with privsep, this is the 340 * unprivileged part. 341 * XXX merge with above? 342 */ 343 static void 344 swap_hdr(struct pcap_file_header *hp) 345 { 346 hp->version_major = swap16(hp->version_major); 347 hp->version_minor = swap16(hp->version_minor); 348 hp->thiszone = swap32(hp->thiszone); 349 hp->sigfigs = swap32(hp->sigfigs); 350 hp->snaplen = swap32(hp->snaplen); 351 hp->linktype = swap32(hp->linktype); 352 } 353 354 pcap_t * 355 priv_pcap_offline(const char *fname, char *errbuf) 356 { 357 pcap_t *p; 358 FILE *fp = NULL; 359 struct pcap_file_header hdr; 360 int linklen, err; 361 362 if (priv_fd < 0) 363 errx(1, "%s: called from privileged portion", __func__); 364 365 p = (pcap_t *)malloc(sizeof(*p)); 366 if (p == NULL) { 367 strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE); 368 return (NULL); 369 } 370 371 memset((char *)p, 0, sizeof(*p)); 372 373 if (fname[0] == '-' && fname[1] == '\0') { 374 p->fd = -1; 375 fp = stdin; 376 } else { 377 write_command(priv_fd, PRIV_OPEN_DUMP); 378 p->fd = receive_fd(priv_fd); 379 must_read(priv_fd, &err, sizeof(int)); 380 if (p->fd < 0) { 381 snprintf(errbuf, PCAP_ERRBUF_SIZE, 382 "Failed to open input file %s: %s", 383 fname, strerror(err)); 384 goto bad; 385 } 386 387 fp = fdopen(p->fd, "r"); 388 if (fp == NULL) { 389 snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname, 390 pcap_strerror(errno)); 391 close(p->fd); 392 p->fd = -1; 393 goto bad; 394 } 395 } 396 if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) { 397 snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s", 398 pcap_strerror(errno)); 399 goto bad; 400 } 401 402 if (hdr.magic != TCPDUMP_MAGIC) { 403 if (swap32(hdr.magic) != TCPDUMP_MAGIC) { 404 snprintf(errbuf, PCAP_ERRBUF_SIZE, 405 "bad dump file format"); 406 goto bad; 407 } 408 p->sf.swapped = 1; 409 swap_hdr(&hdr); 410 } 411 if (hdr.version_major < PCAP_VERSION_MAJOR) { 412 snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format"); 413 goto bad; 414 } 415 416 p->tzoff = hdr.thiszone; 417 p->snapshot = hdr.snaplen; 418 p->linktype = hdr.linktype; 419 p->sf.rfile = fp; 420 p->bufsize = hdr.snaplen; 421 422 /* Align link header as required for proper data alignment */ 423 /* XXX should handle all types */ 424 switch (p->linktype) { 425 426 case DLT_EN10MB: 427 linklen = 14; 428 break; 429 430 case DLT_FDDI: 431 linklen = 13 + 8; /* fddi_header + llc */ 432 break; 433 434 case DLT_NULL: 435 default: 436 linklen = 0; 437 break; 438 } 439 440 if (p->bufsize < 0) 441 p->bufsize = BPF_MAXBUFSIZE; 442 p->sf.base = (u_char *)malloc(p->bufsize + BPF_ALIGNMENT); 443 if (p->sf.base == NULL) { 444 strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE); 445 goto bad; 446 } 447 p->buffer = p->sf.base + BPF_ALIGNMENT - (linklen % BPF_ALIGNMENT); 448 p->sf.version_major = hdr.version_major; 449 p->sf.version_minor = hdr.version_minor; 450 #ifdef PCAP_FDDIPAD 451 /* XXX what to do with this? */ 452 /* XXX padding only needed for kernel fcode */ 453 pcap_fddipad = 0; 454 #endif 455 return (p); 456 457 bad: 458 if (fp != NULL && p->fd != -1) 459 fclose(fp); 460 free(p); 461 return (NULL); 462 } 463 464 465 static int 466 sf_write_header(FILE *fp, int linktype, int thiszone, int snaplen) 467 { 468 struct pcap_file_header hdr; 469 470 bzero(&hdr, sizeof hdr); 471 hdr.magic = TCPDUMP_MAGIC; 472 hdr.version_major = PCAP_VERSION_MAJOR; 473 hdr.version_minor = PCAP_VERSION_MINOR; 474 475 hdr.thiszone = thiszone; 476 hdr.snaplen = snaplen; 477 hdr.sigfigs = 0; 478 hdr.linktype = linktype; 479 480 if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1) 481 return (-1); 482 483 return (0); 484 } 485 486 pcap_dumper_t * 487 priv_pcap_dump_open(pcap_t *p, char *fname) 488 { 489 int fd, err; 490 FILE *f; 491 492 if (priv_fd < 0) 493 errx(1, "%s: called from privileged portion", __func__); 494 495 if (fname[0] == '-' && fname[1] == '\0') { 496 f = stdout; 497 priv_init_done(); 498 } else { 499 write_command(priv_fd, PRIV_OPEN_OUTPUT); 500 fd = receive_fd(priv_fd); 501 must_read(priv_fd, &err, sizeof(err)); 502 if (fd < 0) { 503 snprintf(p->errbuf, PCAP_ERRBUF_SIZE, 504 "Failed to open output file %s: %s", 505 fname, strerror(err)); 506 return (NULL); 507 } 508 f = fdopen(fd, "w"); 509 if (f == NULL) { 510 snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "%s: %s", 511 fname, pcap_strerror(errno)); 512 close(fd); 513 return (NULL); 514 } 515 } 516 517 (void)sf_write_header(f, p->linktype, p->tzoff, p->snapshot); 518 return ((pcap_dumper_t *)f); 519 } 520