1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Decoder for ASN.1 BER/DER/CER encoded bytestream
3 *
4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #ifdef __UBOOT__
9 #include <linux/compat.h>
10 #else
11 #include <linux/export.h>
12 #endif
13 #include <linux/kernel.h>
14 #include <linux/errno.h>
15 #ifndef __UBOOT__
16 #include <linux/module.h>
17 #endif
18 #include <linux/asn1_decoder.h>
19 #include <linux/asn1_ber_bytecode.h>
20
21 static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
22 /* OPC TAG JMP ACT */
23 [ASN1_OP_MATCH] = 1 + 1,
24 [ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
25 [ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
26 [ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
27 [ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
28 [ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
29 [ASN1_OP_MATCH_ANY] = 1,
30 [ASN1_OP_MATCH_ANY_OR_SKIP] = 1,
31 [ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
32 [ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
33 [ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
34 [ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
35 [ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
36 [ASN1_OP_COND_MATCH_ANY] = 1,
37 [ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1,
38 [ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
39 [ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
40 [ASN1_OP_COND_FAIL] = 1,
41 [ASN1_OP_COMPLETE] = 1,
42 [ASN1_OP_ACT] = 1 + 1,
43 [ASN1_OP_MAYBE_ACT] = 1 + 1,
44 [ASN1_OP_RETURN] = 1,
45 [ASN1_OP_END_SEQ] = 1,
46 [ASN1_OP_END_SEQ_OF] = 1 + 1,
47 [ASN1_OP_END_SET] = 1,
48 [ASN1_OP_END_SET_OF] = 1 + 1,
49 [ASN1_OP_END_SEQ_ACT] = 1 + 1,
50 [ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
51 [ASN1_OP_END_SET_ACT] = 1 + 1,
52 [ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
53 };
54
55 /*
56 * Find the length of an indefinite length object
57 * @data: The data buffer
58 * @datalen: The end of the innermost containing element in the buffer
59 * @_dp: The data parse cursor (updated before returning)
60 * @_len: Where to return the size of the element.
61 * @_errmsg: Where to return a pointer to an error message on error
62 */
asn1_find_indefinite_length(const unsigned char * data,size_t datalen,size_t * _dp,size_t * _len,const char ** _errmsg)63 static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
64 size_t *_dp, size_t *_len,
65 const char **_errmsg)
66 {
67 unsigned char tag, tmp;
68 size_t dp = *_dp, len, n;
69 int indef_level = 1;
70
71 next_tag:
72 if (unlikely(datalen - dp < 2)) {
73 if (datalen == dp)
74 goto missing_eoc;
75 goto data_overrun_error;
76 }
77
78 /* Extract a tag from the data */
79 tag = data[dp++];
80 if (tag == ASN1_EOC) {
81 /* It appears to be an EOC. */
82 if (data[dp++] != 0)
83 goto invalid_eoc;
84 if (--indef_level <= 0) {
85 *_len = dp - *_dp;
86 *_dp = dp;
87 return 0;
88 }
89 goto next_tag;
90 }
91
92 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
93 do {
94 if (unlikely(datalen - dp < 2))
95 goto data_overrun_error;
96 tmp = data[dp++];
97 } while (tmp & 0x80);
98 }
99
100 /* Extract the length */
101 len = data[dp++];
102 if (len <= 0x7f)
103 goto check_length;
104
105 if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
106 /* Indefinite length */
107 if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
108 goto indefinite_len_primitive;
109 indef_level++;
110 goto next_tag;
111 }
112
113 n = len - 0x80;
114 if (unlikely(n > sizeof(len) - 1))
115 goto length_too_long;
116 if (unlikely(n > datalen - dp))
117 goto data_overrun_error;
118 len = 0;
119 for (; n > 0; n--) {
120 len <<= 8;
121 len |= data[dp++];
122 }
123 check_length:
124 if (len > datalen - dp)
125 goto data_overrun_error;
126 dp += len;
127 goto next_tag;
128
129 length_too_long:
130 *_errmsg = "Unsupported length";
131 goto error;
132 indefinite_len_primitive:
133 *_errmsg = "Indefinite len primitive not permitted";
134 goto error;
135 invalid_eoc:
136 *_errmsg = "Invalid length EOC";
137 goto error;
138 data_overrun_error:
139 *_errmsg = "Data overrun error";
140 goto error;
141 missing_eoc:
142 *_errmsg = "Missing EOC in indefinite len cons";
143 error:
144 *_dp = dp;
145 return -1;
146 }
147
148 /**
149 * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
150 * @decoder: The decoder definition (produced by asn1_compiler)
151 * @context: The caller's context (to be passed to the action functions)
152 * @data: The encoded data
153 * @datalen: The size of the encoded data
154 *
155 * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
156 * produced by asn1_compiler. Action functions are called on marked tags to
157 * allow the caller to retrieve significant data.
158 *
159 * LIMITATIONS:
160 *
161 * To keep down the amount of stack used by this function, the following limits
162 * have been imposed:
163 *
164 * (1) This won't handle datalen > 65535 without increasing the size of the
165 * cons stack elements and length_too_long checking.
166 *
167 * (2) The stack of constructed types is 10 deep. If the depth of non-leaf
168 * constructed types exceeds this, the decode will fail.
169 *
170 * (3) The SET type (not the SET OF type) isn't really supported as tracking
171 * what members of the set have been seen is a pain.
172 */
asn1_ber_decoder(const struct asn1_decoder * decoder,void * context,const unsigned char * data,size_t datalen)173 int asn1_ber_decoder(const struct asn1_decoder *decoder,
174 void *context,
175 const unsigned char *data,
176 size_t datalen)
177 {
178 const unsigned char *machine = decoder->machine;
179 const asn1_action_t *actions = decoder->actions;
180 size_t machlen = decoder->machlen;
181 enum asn1_opcode op;
182 unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
183 const char *errmsg;
184 size_t pc = 0, dp = 0, tdp = 0, len = 0;
185 int ret;
186
187 unsigned char flags = 0;
188 #define FLAG_INDEFINITE_LENGTH 0x01
189 #define FLAG_MATCHED 0x02
190 #define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
191 #define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
192 * - ie. whether or not we are going to parse
193 * a compound type.
194 */
195
196 #define NR_CONS_STACK 10
197 unsigned short cons_dp_stack[NR_CONS_STACK];
198 unsigned short cons_datalen_stack[NR_CONS_STACK];
199 unsigned char cons_hdrlen_stack[NR_CONS_STACK];
200 #define NR_JUMP_STACK 10
201 unsigned char jump_stack[NR_JUMP_STACK];
202
203 if (datalen > 65535)
204 return -EMSGSIZE;
205
206 next_op:
207 pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
208 pc, machlen, dp, datalen, csp, jsp);
209 if (unlikely(pc >= machlen))
210 goto machine_overrun_error;
211 op = machine[pc];
212 if (unlikely(pc + asn1_op_lengths[op] > machlen))
213 goto machine_overrun_error;
214
215 /* If this command is meant to match a tag, then do that before
216 * evaluating the command.
217 */
218 if (op <= ASN1_OP__MATCHES_TAG) {
219 unsigned char tmp;
220
221 /* Skip conditional matches if possible */
222 if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) ||
223 (op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
224 flags &= ~FLAG_LAST_MATCHED;
225 pc += asn1_op_lengths[op];
226 goto next_op;
227 }
228
229 flags = 0;
230 hdr = 2;
231
232 /* Extract a tag from the data */
233 if (unlikely(datalen - dp < 2))
234 goto data_overrun_error;
235 tag = data[dp++];
236 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
237 goto long_tag_not_supported;
238
239 if (op & ASN1_OP_MATCH__ANY) {
240 pr_debug("- any %02x\n", tag);
241 } else {
242 /* Extract the tag from the machine
243 * - Either CONS or PRIM are permitted in the data if
244 * CONS is not set in the op stream, otherwise CONS
245 * is mandatory.
246 */
247 optag = machine[pc + 1];
248 flags |= optag & FLAG_CONS;
249
250 /* Determine whether the tag matched */
251 tmp = optag ^ tag;
252 tmp &= ~(optag & ASN1_CONS_BIT);
253 pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
254 if (tmp != 0) {
255 /* All odd-numbered tags are MATCH_OR_SKIP. */
256 if (op & ASN1_OP_MATCH__SKIP) {
257 pc += asn1_op_lengths[op];
258 dp--;
259 goto next_op;
260 }
261 goto tag_mismatch;
262 }
263 }
264 flags |= FLAG_MATCHED;
265
266 len = data[dp++];
267 if (len > 0x7f) {
268 if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
269 /* Indefinite length */
270 if (unlikely(!(tag & ASN1_CONS_BIT)))
271 goto indefinite_len_primitive;
272 flags |= FLAG_INDEFINITE_LENGTH;
273 if (unlikely(2 > datalen - dp))
274 goto data_overrun_error;
275 } else {
276 int n = len - 0x80;
277 if (unlikely(n > 2))
278 goto length_too_long;
279 if (unlikely(n > datalen - dp))
280 goto data_overrun_error;
281 hdr += n;
282 for (len = 0; n > 0; n--) {
283 len <<= 8;
284 len |= data[dp++];
285 }
286 if (unlikely(len > datalen - dp))
287 goto data_overrun_error;
288 }
289 } else {
290 if (unlikely(len > datalen - dp))
291 goto data_overrun_error;
292 }
293
294 if (flags & FLAG_CONS) {
295 /* For expected compound forms, we stack the positions
296 * of the start and end of the data.
297 */
298 if (unlikely(csp >= NR_CONS_STACK))
299 goto cons_stack_overflow;
300 cons_dp_stack[csp] = dp;
301 cons_hdrlen_stack[csp] = hdr;
302 if (!(flags & FLAG_INDEFINITE_LENGTH)) {
303 cons_datalen_stack[csp] = datalen;
304 datalen = dp + len;
305 } else {
306 cons_datalen_stack[csp] = 0;
307 }
308 csp++;
309 }
310
311 pr_debug("- TAG: %02x %zu%s\n",
312 tag, len, flags & FLAG_CONS ? " CONS" : "");
313 tdp = dp;
314 }
315
316 /* Decide how to handle the operation */
317 switch (op) {
318 case ASN1_OP_MATCH:
319 case ASN1_OP_MATCH_OR_SKIP:
320 case ASN1_OP_MATCH_ACT:
321 case ASN1_OP_MATCH_ACT_OR_SKIP:
322 case ASN1_OP_MATCH_ANY:
323 case ASN1_OP_MATCH_ANY_OR_SKIP:
324 case ASN1_OP_MATCH_ANY_ACT:
325 case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
326 case ASN1_OP_COND_MATCH_OR_SKIP:
327 case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
328 case ASN1_OP_COND_MATCH_ANY:
329 case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
330 case ASN1_OP_COND_MATCH_ANY_ACT:
331 case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
332
333 if (!(flags & FLAG_CONS)) {
334 if (flags & FLAG_INDEFINITE_LENGTH) {
335 size_t tmp = dp;
336
337 ret = asn1_find_indefinite_length(
338 data, datalen, &tmp, &len, &errmsg);
339 if (ret < 0)
340 goto error;
341 }
342 pr_debug("- LEAF: %zu\n", len);
343 }
344
345 if (op & ASN1_OP_MATCH__ACT) {
346 unsigned char act;
347
348 if (op & ASN1_OP_MATCH__ANY)
349 act = machine[pc + 1];
350 else
351 act = machine[pc + 2];
352 ret = actions[act](context, hdr, tag, data + dp, len);
353 if (ret < 0)
354 return ret;
355 }
356
357 if (!(flags & FLAG_CONS))
358 dp += len;
359 pc += asn1_op_lengths[op];
360 goto next_op;
361
362 case ASN1_OP_MATCH_JUMP:
363 case ASN1_OP_MATCH_JUMP_OR_SKIP:
364 case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
365 pr_debug("- MATCH_JUMP\n");
366 if (unlikely(jsp == NR_JUMP_STACK))
367 goto jump_stack_overflow;
368 jump_stack[jsp++] = pc + asn1_op_lengths[op];
369 pc = machine[pc + 2];
370 goto next_op;
371
372 case ASN1_OP_COND_FAIL:
373 if (unlikely(!(flags & FLAG_MATCHED)))
374 goto tag_mismatch;
375 pc += asn1_op_lengths[op];
376 goto next_op;
377
378 case ASN1_OP_COMPLETE:
379 if (unlikely(jsp != 0 || csp != 0)) {
380 pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
381 jsp, csp);
382 return -EBADMSG;
383 }
384 return 0;
385
386 case ASN1_OP_END_SET:
387 case ASN1_OP_END_SET_ACT:
388 if (unlikely(!(flags & FLAG_MATCHED)))
389 goto tag_mismatch;
390 /* fall through */
391
392 case ASN1_OP_END_SEQ:
393 case ASN1_OP_END_SET_OF:
394 case ASN1_OP_END_SEQ_OF:
395 case ASN1_OP_END_SEQ_ACT:
396 case ASN1_OP_END_SET_OF_ACT:
397 case ASN1_OP_END_SEQ_OF_ACT:
398 if (unlikely(csp <= 0))
399 goto cons_stack_underflow;
400 csp--;
401 tdp = cons_dp_stack[csp];
402 hdr = cons_hdrlen_stack[csp];
403 len = datalen;
404 datalen = cons_datalen_stack[csp];
405 pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
406 tdp, dp, len, datalen);
407 if (datalen == 0) {
408 /* Indefinite length - check for the EOC. */
409 datalen = len;
410 if (unlikely(datalen - dp < 2))
411 goto data_overrun_error;
412 if (data[dp++] != 0) {
413 if (op & ASN1_OP_END__OF) {
414 dp--;
415 csp++;
416 pc = machine[pc + 1];
417 pr_debug("- continue\n");
418 goto next_op;
419 }
420 goto missing_eoc;
421 }
422 if (data[dp++] != 0)
423 goto invalid_eoc;
424 len = dp - tdp - 2;
425 } else {
426 if (dp < len && (op & ASN1_OP_END__OF)) {
427 datalen = len;
428 csp++;
429 pc = machine[pc + 1];
430 pr_debug("- continue\n");
431 goto next_op;
432 }
433 if (dp != len)
434 goto cons_length_error;
435 len -= tdp;
436 pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
437 }
438
439 if (op & ASN1_OP_END__ACT) {
440 unsigned char act;
441 if (op & ASN1_OP_END__OF)
442 act = machine[pc + 2];
443 else
444 act = machine[pc + 1];
445 ret = actions[act](context, hdr, 0, data + tdp, len);
446 if (ret < 0)
447 return ret;
448 }
449 pc += asn1_op_lengths[op];
450 goto next_op;
451
452 case ASN1_OP_MAYBE_ACT:
453 if (!(flags & FLAG_LAST_MATCHED)) {
454 pc += asn1_op_lengths[op];
455 goto next_op;
456 }
457 /* fall through */
458
459 case ASN1_OP_ACT:
460 ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
461 if (ret < 0)
462 return ret;
463 pc += asn1_op_lengths[op];
464 goto next_op;
465
466 case ASN1_OP_RETURN:
467 if (unlikely(jsp <= 0))
468 goto jump_stack_underflow;
469 pc = jump_stack[--jsp];
470 flags |= FLAG_MATCHED | FLAG_LAST_MATCHED;
471 goto next_op;
472
473 default:
474 break;
475 }
476
477 /* Shouldn't reach here */
478 pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
479 op, pc);
480 return -EBADMSG;
481
482 data_overrun_error:
483 errmsg = "Data overrun error";
484 goto error;
485 machine_overrun_error:
486 errmsg = "Machine overrun error";
487 goto error;
488 jump_stack_underflow:
489 errmsg = "Jump stack underflow";
490 goto error;
491 jump_stack_overflow:
492 errmsg = "Jump stack overflow";
493 goto error;
494 cons_stack_underflow:
495 errmsg = "Cons stack underflow";
496 goto error;
497 cons_stack_overflow:
498 errmsg = "Cons stack overflow";
499 goto error;
500 cons_length_error:
501 errmsg = "Cons length error";
502 goto error;
503 missing_eoc:
504 errmsg = "Missing EOC in indefinite len cons";
505 goto error;
506 invalid_eoc:
507 errmsg = "Invalid length EOC";
508 goto error;
509 length_too_long:
510 errmsg = "Unsupported length";
511 goto error;
512 indefinite_len_primitive:
513 errmsg = "Indefinite len primitive not permitted";
514 goto error;
515 tag_mismatch:
516 errmsg = "Unexpected tag";
517 goto error;
518 long_tag_not_supported:
519 errmsg = "Long tag not supported";
520 error:
521 pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
522 errmsg, pc, dp, optag, tag, len);
523 return -EBADMSG;
524 }
525 EXPORT_SYMBOL_GPL(asn1_ber_decoder);
526
527 MODULE_LICENSE("GPL");
528