1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from the Stanford/CMU enet packet filter,
8 * (net/enet.c) distributed as part of 4.3BSD, and code contributed
9 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
10 * Berkeley Laboratory.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
37 */
38
39 #include <sys/cdefs.h>
40 #include <sys/param.h>
41
42 #if !defined(_KERNEL)
43 #include <strings.h>
44 #endif
45 #if !defined(_KERNEL) || defined(sun)
46 #include <netinet/in.h>
47 #endif
48
49 #ifndef __i386__
50 #define BPF_ALIGN
51 #endif
52
53 #ifndef BPF_ALIGN
54 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
55 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
56 #else
57 #define EXTRACT_SHORT(p)\
58 ((u_int16_t)\
59 ((u_int16_t)*((u_char *)p+0)<<8|\
60 (u_int16_t)*((u_char *)p+1)<<0))
61 #define EXTRACT_LONG(p)\
62 ((u_int32_t)*((u_char *)p+0)<<24|\
63 (u_int32_t)*((u_char *)p+1)<<16|\
64 (u_int32_t)*((u_char *)p+2)<<8|\
65 (u_int32_t)*((u_char *)p+3)<<0)
66 #endif
67
68 #ifdef _KERNEL
69 #include <sys/mbuf.h>
70 #else
71 #include <stdlib.h>
72 #endif
73 #include <net/bpf.h>
74 #ifdef _KERNEL
75 #define MINDEX(m, k) \
76 { \
77 int len = m->m_len; \
78 \
79 while (k >= len) { \
80 k -= len; \
81 m = m->m_next; \
82 if (m == 0) \
83 return (0); \
84 len = m->m_len; \
85 } \
86 }
87
88 static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err);
89 static u_int32_t m_xword(struct mbuf *m, bpf_u_int32 k, int *err);
90
91 static u_int32_t
m_xword(struct mbuf * m,bpf_u_int32 k,int * err)92 m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
93 {
94 size_t len;
95 u_char *cp, *np;
96 struct mbuf *m0;
97
98 len = m->m_len;
99 while (k >= len) {
100 k -= len;
101 m = m->m_next;
102 if (m == NULL)
103 goto bad;
104 len = m->m_len;
105 }
106 cp = mtod(m, u_char *) + k;
107 if (len - k >= 4) {
108 *err = 0;
109 return (EXTRACT_LONG(cp));
110 }
111 m0 = m->m_next;
112 if (m0 == NULL || m0->m_len + len - k < 4)
113 goto bad;
114 *err = 0;
115 np = mtod(m0, u_char *);
116 switch (len - k) {
117 case 1:
118 return (((u_int32_t)cp[0] << 24) |
119 ((u_int32_t)np[0] << 16) |
120 ((u_int32_t)np[1] << 8) |
121 (u_int32_t)np[2]);
122
123 case 2:
124 return (((u_int32_t)cp[0] << 24) |
125 ((u_int32_t)cp[1] << 16) |
126 ((u_int32_t)np[0] << 8) |
127 (u_int32_t)np[1]);
128
129 default:
130 return (((u_int32_t)cp[0] << 24) |
131 ((u_int32_t)cp[1] << 16) |
132 ((u_int32_t)cp[2] << 8) |
133 (u_int32_t)np[0]);
134 }
135 bad:
136 *err = 1;
137 return (0);
138 }
139
140 static u_int16_t
m_xhalf(struct mbuf * m,bpf_u_int32 k,int * err)141 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
142 {
143 size_t len;
144 u_char *cp;
145 struct mbuf *m0;
146
147 len = m->m_len;
148 while (k >= len) {
149 k -= len;
150 m = m->m_next;
151 if (m == NULL)
152 goto bad;
153 len = m->m_len;
154 }
155 cp = mtod(m, u_char *) + k;
156 if (len - k >= 2) {
157 *err = 0;
158 return (EXTRACT_SHORT(cp));
159 }
160 m0 = m->m_next;
161 if (m0 == NULL)
162 goto bad;
163 *err = 0;
164 return ((cp[0] << 8) | mtod(m0, u_char *)[0]);
165 bad:
166 *err = 1;
167 return (0);
168 }
169 #endif
170
171 /*
172 * Execute the filter program starting at pc on the packet p
173 * wirelen is the length of the original packet
174 * buflen is the amount of data present
175 */
176 u_int
bpf_filter(const struct bpf_insn * pc,u_char * p,u_int wirelen,u_int buflen)177 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
178 {
179 u_int32_t A = 0, X = 0;
180 bpf_u_int32 k;
181 u_int32_t mem[BPF_MEMWORDS];
182
183 bzero(mem, sizeof(mem));
184
185 if (pc == NULL)
186 /*
187 * No filter means accept all.
188 */
189 return ((u_int)-1);
190
191 --pc;
192 while (1) {
193 ++pc;
194 switch (pc->code) {
195 default:
196 #ifdef _KERNEL
197 return (0);
198 #else
199 abort();
200 #endif
201
202 case BPF_RET|BPF_K:
203 return ((u_int)pc->k);
204
205 case BPF_RET|BPF_A:
206 return ((u_int)A);
207
208 case BPF_LD|BPF_W|BPF_ABS:
209 k = pc->k;
210 if (k > buflen || sizeof(int32_t) > buflen - k) {
211 #ifdef _KERNEL
212 int merr;
213
214 if (buflen != 0)
215 return (0);
216 A = m_xword((struct mbuf *)p, k, &merr);
217 if (merr != 0)
218 return (0);
219 continue;
220 #else
221 return (0);
222 #endif
223 }
224 #ifdef BPF_ALIGN
225 if (((intptr_t)(p + k) & 3) != 0)
226 A = EXTRACT_LONG(&p[k]);
227 else
228 #endif
229 A = ntohl(*(int32_t *)(p + k));
230 continue;
231
232 case BPF_LD|BPF_H|BPF_ABS:
233 k = pc->k;
234 if (k > buflen || sizeof(int16_t) > buflen - k) {
235 #ifdef _KERNEL
236 int merr;
237
238 if (buflen != 0)
239 return (0);
240 A = m_xhalf((struct mbuf *)p, k, &merr);
241 continue;
242 #else
243 return (0);
244 #endif
245 }
246 A = EXTRACT_SHORT(&p[k]);
247 continue;
248
249 case BPF_LD|BPF_B|BPF_ABS:
250 k = pc->k;
251 if (k >= buflen) {
252 #ifdef _KERNEL
253 struct mbuf *m;
254
255 if (buflen != 0)
256 return (0);
257 m = (struct mbuf *)p;
258 MINDEX(m, k);
259 A = mtod(m, u_char *)[k];
260 continue;
261 #else
262 return (0);
263 #endif
264 }
265 A = p[k];
266 continue;
267
268 case BPF_LD|BPF_W|BPF_LEN:
269 A = wirelen;
270 continue;
271
272 case BPF_LDX|BPF_W|BPF_LEN:
273 X = wirelen;
274 continue;
275
276 case BPF_LD|BPF_W|BPF_IND:
277 k = X + pc->k;
278 if (pc->k > buflen || X > buflen - pc->k ||
279 sizeof(int32_t) > buflen - k) {
280 #ifdef _KERNEL
281 int merr;
282
283 if (buflen != 0)
284 return (0);
285 A = m_xword((struct mbuf *)p, k, &merr);
286 if (merr != 0)
287 return (0);
288 continue;
289 #else
290 return (0);
291 #endif
292 }
293 #ifdef BPF_ALIGN
294 if (((intptr_t)(p + k) & 3) != 0)
295 A = EXTRACT_LONG(&p[k]);
296 else
297 #endif
298 A = ntohl(*(int32_t *)(p + k));
299 continue;
300
301 case BPF_LD|BPF_H|BPF_IND:
302 k = X + pc->k;
303 if (X > buflen || pc->k > buflen - X ||
304 sizeof(int16_t) > buflen - k) {
305 #ifdef _KERNEL
306 int merr;
307
308 if (buflen != 0)
309 return (0);
310 A = m_xhalf((struct mbuf *)p, k, &merr);
311 if (merr != 0)
312 return (0);
313 continue;
314 #else
315 return (0);
316 #endif
317 }
318 A = EXTRACT_SHORT(&p[k]);
319 continue;
320
321 case BPF_LD|BPF_B|BPF_IND:
322 k = X + pc->k;
323 if (pc->k >= buflen || X >= buflen - pc->k) {
324 #ifdef _KERNEL
325 struct mbuf *m;
326
327 if (buflen != 0)
328 return (0);
329 m = (struct mbuf *)p;
330 MINDEX(m, k);
331 A = mtod(m, u_char *)[k];
332 continue;
333 #else
334 return (0);
335 #endif
336 }
337 A = p[k];
338 continue;
339
340 case BPF_LDX|BPF_MSH|BPF_B:
341 k = pc->k;
342 if (k >= buflen) {
343 #ifdef _KERNEL
344 struct mbuf *m;
345
346 if (buflen != 0)
347 return (0);
348 m = (struct mbuf *)p;
349 MINDEX(m, k);
350 X = (mtod(m, u_char *)[k] & 0xf) << 2;
351 continue;
352 #else
353 return (0);
354 #endif
355 }
356 X = (p[pc->k] & 0xf) << 2;
357 continue;
358
359 case BPF_LD|BPF_IMM:
360 A = pc->k;
361 continue;
362
363 case BPF_LDX|BPF_IMM:
364 X = pc->k;
365 continue;
366
367 case BPF_LD|BPF_MEM:
368 A = mem[pc->k];
369 continue;
370
371 case BPF_LDX|BPF_MEM:
372 X = mem[pc->k];
373 continue;
374
375 case BPF_ST:
376 mem[pc->k] = A;
377 continue;
378
379 case BPF_STX:
380 mem[pc->k] = X;
381 continue;
382
383 case BPF_JMP|BPF_JA:
384 pc += pc->k;
385 continue;
386
387 case BPF_JMP|BPF_JGT|BPF_K:
388 pc += (A > pc->k) ? pc->jt : pc->jf;
389 continue;
390
391 case BPF_JMP|BPF_JGE|BPF_K:
392 pc += (A >= pc->k) ? pc->jt : pc->jf;
393 continue;
394
395 case BPF_JMP|BPF_JEQ|BPF_K:
396 pc += (A == pc->k) ? pc->jt : pc->jf;
397 continue;
398
399 case BPF_JMP|BPF_JSET|BPF_K:
400 pc += (A & pc->k) ? pc->jt : pc->jf;
401 continue;
402
403 case BPF_JMP|BPF_JGT|BPF_X:
404 pc += (A > X) ? pc->jt : pc->jf;
405 continue;
406
407 case BPF_JMP|BPF_JGE|BPF_X:
408 pc += (A >= X) ? pc->jt : pc->jf;
409 continue;
410
411 case BPF_JMP|BPF_JEQ|BPF_X:
412 pc += (A == X) ? pc->jt : pc->jf;
413 continue;
414
415 case BPF_JMP|BPF_JSET|BPF_X:
416 pc += (A & X) ? pc->jt : pc->jf;
417 continue;
418
419 case BPF_ALU|BPF_ADD|BPF_X:
420 A += X;
421 continue;
422
423 case BPF_ALU|BPF_SUB|BPF_X:
424 A -= X;
425 continue;
426
427 case BPF_ALU|BPF_MUL|BPF_X:
428 A *= X;
429 continue;
430
431 case BPF_ALU|BPF_DIV|BPF_X:
432 if (X == 0)
433 return (0);
434 A /= X;
435 continue;
436
437 case BPF_ALU|BPF_MOD|BPF_X:
438 if (X == 0)
439 return (0);
440 A %= X;
441 continue;
442
443 case BPF_ALU|BPF_AND|BPF_X:
444 A &= X;
445 continue;
446
447 case BPF_ALU|BPF_OR|BPF_X:
448 A |= X;
449 continue;
450
451 case BPF_ALU|BPF_XOR|BPF_X:
452 A ^= X;
453 continue;
454
455 case BPF_ALU|BPF_LSH|BPF_X:
456 A <<= X;
457 continue;
458
459 case BPF_ALU|BPF_RSH|BPF_X:
460 A >>= X;
461 continue;
462
463 case BPF_ALU|BPF_ADD|BPF_K:
464 A += pc->k;
465 continue;
466
467 case BPF_ALU|BPF_SUB|BPF_K:
468 A -= pc->k;
469 continue;
470
471 case BPF_ALU|BPF_MUL|BPF_K:
472 A *= pc->k;
473 continue;
474
475 case BPF_ALU|BPF_DIV|BPF_K:
476 A /= pc->k;
477 continue;
478
479 case BPF_ALU|BPF_MOD|BPF_K:
480 A %= pc->k;
481 continue;
482
483 case BPF_ALU|BPF_AND|BPF_K:
484 A &= pc->k;
485 continue;
486
487 case BPF_ALU|BPF_OR|BPF_K:
488 A |= pc->k;
489 continue;
490
491 case BPF_ALU|BPF_XOR|BPF_K:
492 A ^= pc->k;
493 continue;
494
495 case BPF_ALU|BPF_LSH|BPF_K:
496 A <<= pc->k;
497 continue;
498
499 case BPF_ALU|BPF_RSH|BPF_K:
500 A >>= pc->k;
501 continue;
502
503 case BPF_ALU|BPF_NEG:
504 A = -A;
505 continue;
506
507 case BPF_MISC|BPF_TAX:
508 X = A;
509 continue;
510
511 case BPF_MISC|BPF_TXA:
512 A = X;
513 continue;
514 }
515 }
516 }
517
518 #ifdef _KERNEL
519 static const u_short bpf_code_map[] = {
520 0x10ff, /* 0x00-0x0f: 1111111100001000 */
521 0x3070, /* 0x10-0x1f: 0000111000001100 */
522 0x3131, /* 0x20-0x2f: 1000110010001100 */
523 0x3031, /* 0x30-0x3f: 1000110000001100 */
524 0x3131, /* 0x40-0x4f: 1000110010001100 */
525 0x1011, /* 0x50-0x5f: 1000100000001000 */
526 0x1013, /* 0x60-0x6f: 1100100000001000 */
527 0x1010, /* 0x70-0x7f: 0000100000001000 */
528 0x0093, /* 0x80-0x8f: 1100100100000000 */
529 0x1010, /* 0x90-0x9f: 0000100000001000 */
530 0x1010, /* 0xa0-0xaf: 0000100000001000 */
531 0x0002, /* 0xb0-0xbf: 0100000000000000 */
532 0x0000, /* 0xc0-0xcf: 0000000000000000 */
533 0x0000, /* 0xd0-0xdf: 0000000000000000 */
534 0x0000, /* 0xe0-0xef: 0000000000000000 */
535 0x0000 /* 0xf0-0xff: 0000000000000000 */
536 };
537
538 #define BPF_VALIDATE_CODE(c) \
539 ((c) <= 0xff && (bpf_code_map[(c) >> 4] & (1 << ((c) & 0xf))) != 0)
540
541 /*
542 * Return true if the 'fcode' is a valid filter program.
543 * The constraints are that each jump be forward and to a valid
544 * code. The code must terminate with either an accept or reject.
545 *
546 * The kernel needs to be able to verify an application's filter code.
547 * Otherwise, a bogus program could easily crash the system.
548 */
549 int
bpf_validate(const struct bpf_insn * f,int len)550 bpf_validate(const struct bpf_insn *f, int len)
551 {
552 int i;
553 const struct bpf_insn *p;
554
555 /* Do not accept negative length filter. */
556 if (len < 0)
557 return (0);
558
559 /* An empty filter means accept all. */
560 if (len == 0)
561 return (1);
562
563 for (i = 0; i < len; ++i) {
564 p = &f[i];
565 /*
566 * Check that the code is valid.
567 */
568 if (!BPF_VALIDATE_CODE(p->code))
569 return (0);
570 /*
571 * Check that the jumps are forward, and within
572 * the code block.
573 */
574 if (BPF_CLASS(p->code) == BPF_JMP) {
575 u_int offset;
576
577 if (p->code == (BPF_JMP|BPF_JA))
578 offset = p->k;
579 else
580 offset = p->jt > p->jf ? p->jt : p->jf;
581 if (offset >= (u_int)(len - i) - 1)
582 return (0);
583 continue;
584 }
585 /*
586 * Check that memory operations use valid addresses.
587 */
588 if (p->code == BPF_ST || p->code == BPF_STX ||
589 p->code == (BPF_LD|BPF_MEM) ||
590 p->code == (BPF_LDX|BPF_MEM)) {
591 if (p->k >= BPF_MEMWORDS)
592 return (0);
593 continue;
594 }
595 /*
596 * Check for constant division by 0.
597 */
598 if ((p->code == (BPF_ALU|BPF_DIV|BPF_K) ||
599 p->code == (BPF_ALU|BPF_MOD|BPF_K)) && p->k == 0)
600 return (0);
601 }
602 return (BPF_CLASS(f[len - 1].code) == BPF_RET);
603 }
604 #endif
605