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