1 /* $OpenBSD: privsep_pcap.c,v 1.19 2015/10/01 13:18:40 jsg 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 return (NULL); 240 } 241 242 p = malloc(sizeof(*p)); 243 if (p == NULL) { 244 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", 245 pcap_strerror(errno)); 246 return (NULL); 247 } 248 249 bzero(p, sizeof(*p)); 250 251 write_command(priv_fd, PRIV_OPEN_BPF); 252 must_write(priv_fd, &slen, sizeof(int)); 253 must_write(priv_fd, &prom, sizeof(int)); 254 must_write(priv_fd, &dlt, sizeof(u_int)); 255 must_write(priv_fd, &dirfilt, sizeof(u_int)); 256 write_string(priv_fd, dev); 257 258 fd = receive_fd(priv_fd); 259 must_read(priv_fd, &err, sizeof(int)); 260 if (fd < 0) { 261 snprintf(ebuf, PCAP_ERRBUF_SIZE, 262 "Failed to open bpf device for %s: %s", 263 dev, strerror(err)); 264 goto bad; 265 } 266 267 /* fd is locked, can only use 'safe' ioctls */ 268 if (ioctl(fd, BIOCVERSION, &bv) < 0) { 269 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s", 270 pcap_strerror(errno)); 271 goto bad; 272 } 273 274 if (bv.bv_major != BPF_MAJOR_VERSION || 275 bv.bv_minor < BPF_MINOR_VERSION) { 276 snprintf(ebuf, PCAP_ERRBUF_SIZE, 277 "kernel bpf filter out of date"); 278 goto bad; 279 } 280 281 p->fd = fd; 282 p->snapshot = slen; 283 284 /* Get the data link layer type. */ 285 if (ioctl(fd, BIOCGDLT, &v) < 0) { 286 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s", 287 pcap_strerror(errno)); 288 goto bad; 289 } 290 p->linktype = v; 291 292 /* XXX hack */ 293 if (p->linktype == DLT_PFLOG && p->snapshot < 160) 294 p->snapshot = 160; 295 296 /* set timeout */ 297 if (to_ms != 0) { 298 struct timeval to; 299 to.tv_sec = to_ms / 1000; 300 to.tv_usec = (to_ms * 1000) % 1000000; 301 if (ioctl(p->fd, BIOCSRTIMEOUT, &to) < 0) { 302 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s", 303 pcap_strerror(errno)); 304 goto bad; 305 } 306 } 307 308 if (ioctl(fd, BIOCGBLEN, &v) < 0) { 309 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s", 310 pcap_strerror(errno)); 311 goto bad; 312 } 313 p->bufsize = v; 314 p->buffer = malloc(p->bufsize); 315 if (p->buffer == NULL) { 316 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", 317 pcap_strerror(errno)); 318 goto bad; 319 } 320 return (p); 321 322 bad: 323 if (fd >= 0) 324 close(fd); 325 free(p); 326 return (NULL); 327 } 328 329 330 331 /* 332 * reimplement pcap_open_offline with privsep, this is the 333 * unprivileged part. 334 * XXX merge with above? 335 */ 336 static void 337 swap_hdr(struct pcap_file_header *hp) 338 { 339 hp->version_major = swap16(hp->version_major); 340 hp->version_minor = swap16(hp->version_minor); 341 hp->thiszone = swap32(hp->thiszone); 342 hp->sigfigs = swap32(hp->sigfigs); 343 hp->snaplen = swap32(hp->snaplen); 344 hp->linktype = swap32(hp->linktype); 345 } 346 347 pcap_t * 348 priv_pcap_offline(const char *fname, char *errbuf) 349 { 350 pcap_t *p; 351 FILE *fp = NULL; 352 struct pcap_file_header hdr; 353 int linklen, err; 354 355 if (priv_fd < 0) 356 errx(1, "%s: called from privileged portion", __func__); 357 358 p = malloc(sizeof(*p)); 359 if (p == NULL) { 360 strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE); 361 return (NULL); 362 } 363 364 memset((char *)p, 0, sizeof(*p)); 365 366 if (fname[0] == '-' && fname[1] == '\0') { 367 p->fd = -1; 368 fp = stdin; 369 } else { 370 write_command(priv_fd, PRIV_OPEN_DUMP); 371 p->fd = receive_fd(priv_fd); 372 must_read(priv_fd, &err, sizeof(int)); 373 if (p->fd < 0) { 374 snprintf(errbuf, PCAP_ERRBUF_SIZE, 375 "Failed to open input file %s: %s", 376 fname, strerror(err)); 377 goto bad; 378 } 379 380 fp = fdopen(p->fd, "r"); 381 if (fp == NULL) { 382 snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname, 383 pcap_strerror(errno)); 384 close(p->fd); 385 p->fd = -1; 386 goto bad; 387 } 388 } 389 if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) { 390 snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s", 391 pcap_strerror(errno)); 392 goto bad; 393 } 394 395 if (hdr.magic != TCPDUMP_MAGIC) { 396 if (swap32(hdr.magic) != TCPDUMP_MAGIC) { 397 snprintf(errbuf, PCAP_ERRBUF_SIZE, 398 "bad dump file format"); 399 goto bad; 400 } 401 p->sf.swapped = 1; 402 swap_hdr(&hdr); 403 } 404 if (hdr.version_major < PCAP_VERSION_MAJOR) { 405 snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format"); 406 goto bad; 407 } 408 409 p->tzoff = hdr.thiszone; 410 p->snapshot = hdr.snaplen; 411 p->linktype = hdr.linktype; 412 p->sf.rfile = fp; 413 p->bufsize = hdr.snaplen; 414 415 /* Align link header as required for proper data alignment */ 416 /* XXX should handle all types */ 417 switch (p->linktype) { 418 419 case DLT_EN10MB: 420 linklen = 14; 421 break; 422 423 case DLT_FDDI: 424 linklen = 13 + 8; /* fddi_header + llc */ 425 break; 426 427 case DLT_NULL: 428 default: 429 linklen = 0; 430 break; 431 } 432 433 if (p->bufsize < 0) 434 p->bufsize = BPF_MAXBUFSIZE; 435 p->sf.base = malloc(p->bufsize + BPF_ALIGNMENT); 436 if (p->sf.base == NULL) { 437 strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE); 438 goto bad; 439 } 440 p->buffer = p->sf.base + BPF_ALIGNMENT - (linklen % BPF_ALIGNMENT); 441 p->sf.version_major = hdr.version_major; 442 p->sf.version_minor = hdr.version_minor; 443 #ifdef PCAP_FDDIPAD 444 /* XXX what to do with this? */ 445 /* XXX padding only needed for kernel fcode */ 446 pcap_fddipad = 0; 447 #endif 448 return (p); 449 450 bad: 451 if (fp != NULL && p->fd != -1) 452 fclose(fp); 453 free(p); 454 return (NULL); 455 } 456 457 458 static int 459 sf_write_header(FILE *fp, int linktype, int thiszone, int snaplen) 460 { 461 struct pcap_file_header hdr; 462 463 bzero(&hdr, sizeof hdr); 464 hdr.magic = TCPDUMP_MAGIC; 465 hdr.version_major = PCAP_VERSION_MAJOR; 466 hdr.version_minor = PCAP_VERSION_MINOR; 467 468 hdr.thiszone = thiszone; 469 hdr.snaplen = snaplen; 470 hdr.sigfigs = 0; 471 hdr.linktype = linktype; 472 473 if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1) 474 return (-1); 475 476 return (0); 477 } 478 479 pcap_dumper_t * 480 priv_pcap_dump_open(pcap_t *p, char *fname) 481 { 482 int fd, err; 483 FILE *f; 484 485 if (priv_fd < 0) 486 errx(1, "%s: called from privileged portion", __func__); 487 488 if (fname[0] == '-' && fname[1] == '\0') { 489 f = stdout; 490 priv_init_done(); 491 } else { 492 write_command(priv_fd, PRIV_OPEN_OUTPUT); 493 fd = receive_fd(priv_fd); 494 must_read(priv_fd, &err, sizeof(err)); 495 if (fd < 0) { 496 snprintf(p->errbuf, PCAP_ERRBUF_SIZE, 497 "Failed to open output file %s: %s", 498 fname, strerror(err)); 499 return (NULL); 500 } 501 f = fdopen(fd, "w"); 502 if (f == NULL) { 503 snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "%s: %s", 504 fname, pcap_strerror(errno)); 505 close(fd); 506 return (NULL); 507 } 508 } 509 510 (void)sf_write_header(f, p->linktype, p->tzoff, p->snapshot); 511 return ((pcap_dumper_t *)f); 512 } 513