1 /* $OpenBSD: privsep_pcap.c,v 1.22 2017/04/19 05:36:13 natano 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 int fd; 179 struct ifreq ifr; 180 unsigned v; 181 182 if (device == NULL || snaplen <= 0) 183 return (-1); 184 185 if ((fd = open("/dev/bpf", O_RDONLY)) == -1) 186 return (-1); 187 188 v = 32768; /* XXX this should be a user-accessible hook */ 189 ioctl(fd, BIOCSBLEN, &v); 190 191 strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); 192 if (ioctl(fd, BIOCSETIF, &ifr) < 0) 193 goto error; 194 195 if (dlt != (u_int) -1 && ioctl(fd, BIOCSDLT, &dlt)) 196 goto error; 197 198 if (promisc) 199 /* this is allowed to fail */ 200 ioctl(fd, BIOCPROMISC, NULL); 201 if (ioctl(fd, BIOCSDIRFILT, &dirfilt) < 0) 202 goto error; 203 204 /* lock the descriptor */ 205 if (ioctl(fd, BIOCLOCK, NULL) < 0) 206 goto error; 207 return (fd); 208 209 error: 210 close(fd); 211 return (-1); 212 } 213 214 215 /* 216 * XXX reimplement pcap_open_live with privsep, this is the 217 * unprivileged part. 218 */ 219 pcap_t * 220 priv_pcap_live(const char *dev, int slen, int prom, int to_ms, 221 char *ebuf, u_int dlt, u_int dirfilt) 222 { 223 int fd, err; 224 struct bpf_version bv; 225 u_int v; 226 pcap_t *p; 227 228 if (priv_fd < 0) 229 errx(1, "%s: called from privileged portion", __func__); 230 231 if (dev == NULL) { 232 snprintf(ebuf, PCAP_ERRBUF_SIZE, "No interface specified"); 233 return (NULL); 234 } 235 236 p = malloc(sizeof(*p)); 237 if (p == NULL) { 238 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", 239 pcap_strerror(errno)); 240 return (NULL); 241 } 242 243 bzero(p, sizeof(*p)); 244 245 write_command(priv_fd, PRIV_OPEN_BPF); 246 must_write(priv_fd, &slen, sizeof(int)); 247 must_write(priv_fd, &prom, sizeof(int)); 248 must_write(priv_fd, &dlt, sizeof(u_int)); 249 must_write(priv_fd, &dirfilt, sizeof(u_int)); 250 write_string(priv_fd, dev); 251 252 fd = receive_fd(priv_fd); 253 must_read(priv_fd, &err, sizeof(int)); 254 if (fd < 0) { 255 snprintf(ebuf, PCAP_ERRBUF_SIZE, 256 "Failed to open bpf device for %s: %s", 257 dev, strerror(err)); 258 goto bad; 259 } 260 261 /* fd is locked, can only use 'safe' ioctls */ 262 if (ioctl(fd, BIOCVERSION, &bv) < 0) { 263 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s", 264 pcap_strerror(errno)); 265 goto bad; 266 } 267 268 if (bv.bv_major != BPF_MAJOR_VERSION || 269 bv.bv_minor < BPF_MINOR_VERSION) { 270 snprintf(ebuf, PCAP_ERRBUF_SIZE, 271 "kernel bpf filter out of date"); 272 goto bad; 273 } 274 275 p->fd = fd; 276 p->snapshot = slen; 277 278 /* Get the data link layer type. */ 279 if (ioctl(fd, BIOCGDLT, &v) < 0) { 280 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s", 281 pcap_strerror(errno)); 282 goto bad; 283 } 284 p->linktype = v; 285 286 /* XXX hack */ 287 if (p->linktype == DLT_PFLOG && p->snapshot < 160) 288 p->snapshot = 160; 289 290 /* set timeout */ 291 if (to_ms != 0) { 292 struct timeval to; 293 to.tv_sec = to_ms / 1000; 294 to.tv_usec = (to_ms * 1000) % 1000000; 295 if (ioctl(p->fd, BIOCSRTIMEOUT, &to) < 0) { 296 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s", 297 pcap_strerror(errno)); 298 goto bad; 299 } 300 } 301 302 if (ioctl(fd, BIOCGBLEN, &v) < 0) { 303 snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s", 304 pcap_strerror(errno)); 305 goto bad; 306 } 307 p->bufsize = v; 308 p->buffer = malloc(p->bufsize); 309 if (p->buffer == NULL) { 310 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", 311 pcap_strerror(errno)); 312 goto bad; 313 } 314 return (p); 315 316 bad: 317 if (fd >= 0) 318 close(fd); 319 free(p); 320 return (NULL); 321 } 322 323 324 325 /* 326 * reimplement pcap_open_offline with privsep, this is the 327 * unprivileged part. 328 * XXX merge with above? 329 */ 330 static void 331 swap_hdr(struct pcap_file_header *hp) 332 { 333 hp->version_major = swap16(hp->version_major); 334 hp->version_minor = swap16(hp->version_minor); 335 hp->thiszone = swap32(hp->thiszone); 336 hp->sigfigs = swap32(hp->sigfigs); 337 hp->snaplen = swap32(hp->snaplen); 338 hp->linktype = swap32(hp->linktype); 339 } 340 341 pcap_t * 342 priv_pcap_offline(const char *fname, char *errbuf) 343 { 344 pcap_t *p; 345 FILE *fp = NULL; 346 struct pcap_file_header hdr; 347 int linklen, err; 348 349 if (priv_fd < 0) 350 errx(1, "%s: called from privileged portion", __func__); 351 352 p = malloc(sizeof(*p)); 353 if (p == NULL) { 354 strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE); 355 return (NULL); 356 } 357 358 memset((char *)p, 0, sizeof(*p)); 359 360 if (fname[0] == '-' && fname[1] == '\0') { 361 p->fd = -1; 362 fp = stdin; 363 } else { 364 write_command(priv_fd, PRIV_OPEN_DUMP); 365 p->fd = receive_fd(priv_fd); 366 must_read(priv_fd, &err, sizeof(int)); 367 if (p->fd < 0) { 368 snprintf(errbuf, PCAP_ERRBUF_SIZE, 369 "Failed to open input file %s: %s", 370 fname, strerror(err)); 371 goto bad; 372 } 373 374 fp = fdopen(p->fd, "r"); 375 if (fp == NULL) { 376 snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname, 377 pcap_strerror(errno)); 378 close(p->fd); 379 p->fd = -1; 380 goto bad; 381 } 382 } 383 if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) { 384 snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s", 385 pcap_strerror(errno)); 386 goto bad; 387 } 388 389 if (hdr.magic != TCPDUMP_MAGIC) { 390 if (swap32(hdr.magic) != TCPDUMP_MAGIC) { 391 snprintf(errbuf, PCAP_ERRBUF_SIZE, 392 "bad dump file format"); 393 goto bad; 394 } 395 p->sf.swapped = 1; 396 swap_hdr(&hdr); 397 } 398 if (hdr.version_major < PCAP_VERSION_MAJOR) { 399 snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format"); 400 goto bad; 401 } 402 403 p->tzoff = hdr.thiszone; 404 p->snapshot = hdr.snaplen; 405 p->linktype = hdr.linktype; 406 p->sf.rfile = fp; 407 p->bufsize = hdr.snaplen; 408 409 /* Align link header as required for proper data alignment */ 410 /* XXX should handle all types */ 411 switch (p->linktype) { 412 413 case DLT_EN10MB: 414 linklen = 14; 415 break; 416 417 case DLT_FDDI: 418 linklen = 13 + 8; /* fddi_header + llc */ 419 break; 420 421 case DLT_NULL: 422 default: 423 linklen = 0; 424 break; 425 } 426 427 if (p->bufsize < 0) 428 p->bufsize = BPF_MAXBUFSIZE; 429 p->sf.base = malloc(p->bufsize + BPF_ALIGNMENT); 430 if (p->sf.base == NULL) { 431 strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE); 432 goto bad; 433 } 434 p->buffer = p->sf.base + BPF_ALIGNMENT - (linklen % BPF_ALIGNMENT); 435 p->sf.version_major = hdr.version_major; 436 p->sf.version_minor = hdr.version_minor; 437 #ifdef PCAP_FDDIPAD 438 /* XXX what to do with this? */ 439 /* XXX padding only needed for kernel fcode */ 440 pcap_fddipad = 0; 441 #endif 442 return (p); 443 444 bad: 445 if (fp != NULL && p->fd != -1) 446 fclose(fp); 447 free(p); 448 return (NULL); 449 } 450 451 452 static int 453 sf_write_header(FILE *fp, int linktype, int thiszone, int snaplen) 454 { 455 struct pcap_file_header hdr; 456 457 bzero(&hdr, sizeof hdr); 458 hdr.magic = TCPDUMP_MAGIC; 459 hdr.version_major = PCAP_VERSION_MAJOR; 460 hdr.version_minor = PCAP_VERSION_MINOR; 461 462 hdr.thiszone = thiszone; 463 hdr.snaplen = snaplen; 464 hdr.sigfigs = 0; 465 hdr.linktype = linktype; 466 467 if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1) 468 return (-1); 469 470 return (0); 471 } 472 473 pcap_dumper_t * 474 priv_pcap_dump_open(pcap_t *p, char *fname) 475 { 476 int fd, err; 477 FILE *f; 478 479 if (priv_fd < 0) 480 errx(1, "%s: called from privileged portion", __func__); 481 482 if (fname[0] == '-' && fname[1] == '\0') { 483 f = stdout; 484 priv_init_done(); 485 } else { 486 write_command(priv_fd, PRIV_OPEN_OUTPUT); 487 fd = receive_fd(priv_fd); 488 must_read(priv_fd, &err, sizeof(err)); 489 if (fd < 0) { 490 snprintf(p->errbuf, PCAP_ERRBUF_SIZE, 491 "Failed to open output file %s: %s", 492 fname, strerror(err)); 493 return (NULL); 494 } 495 f = fdopen(fd, "w"); 496 if (f == NULL) { 497 snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "%s: %s", 498 fname, pcap_strerror(errno)); 499 close(fd); 500 return (NULL); 501 } 502 } 503 504 (void)sf_write_header(f, p->linktype, p->tzoff, p->snapshot); 505 return ((pcap_dumper_t *)f); 506 } 507