1 /* Decoder for ASN.1 BER/DER/CER encoded bytestream
3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
12 #include <linux/export.h>
13 #include <linux/kernel.h>
14 #include <linux/errno.h>
15 #include <linux/asn1_decoder.h>
16 #include <linux/asn1_ber_bytecode.h>
18 static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
20 [ASN1_OP_MATCH] = 1 + 1,
21 [ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
22 [ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
23 [ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
24 [ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
25 [ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
26 [ASN1_OP_MATCH_ANY] = 1,
27 [ASN1_OP_MATCH_ANY_OR_SKIP] = 1,
28 [ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
29 [ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
30 [ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
31 [ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
32 [ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
33 [ASN1_OP_COND_MATCH_ANY] = 1,
34 [ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1,
35 [ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
36 [ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
37 [ASN1_OP_COND_FAIL] = 1,
38 [ASN1_OP_COMPLETE] = 1,
39 [ASN1_OP_ACT] = 1 + 1,
40 [ASN1_OP_MAYBE_ACT] = 1 + 1,
42 [ASN1_OP_END_SEQ] = 1,
43 [ASN1_OP_END_SEQ_OF] = 1 + 1,
44 [ASN1_OP_END_SET] = 1,
45 [ASN1_OP_END_SET_OF] = 1 + 1,
46 [ASN1_OP_END_SEQ_ACT] = 1 + 1,
47 [ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
48 [ASN1_OP_END_SET_ACT] = 1 + 1,
49 [ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
53 * Find the length of an indefinite length object
54 * @data: The data buffer
55 * @datalen: The end of the innermost containing element in the buffer
56 * @_dp: The data parse cursor (updated before returning)
57 * @_len: Where to return the size of the element.
58 * @_errmsg: Where to return a pointer to an error message on error
60 static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
61 size_t *_dp, size_t *_len,
64 unsigned char tag, tmp;
65 size_t dp = *_dp, len, n;
69 if (unlikely(datalen - dp < 2)) {
72 goto data_overrun_error;
75 /* Extract a tag from the data */
77 if (tag == ASN1_EOC) {
78 /* It appears to be an EOC. */
81 if (--indef_level <= 0) {
89 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
91 if (unlikely(datalen - dp < 2))
92 goto data_overrun_error;
97 /* Extract the length */
102 if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
103 /* Indefinite length */
104 if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
105 goto indefinite_len_primitive;
111 if (unlikely(n > sizeof(len) - 1))
112 goto length_too_long;
113 if (unlikely(n > datalen - dp))
114 goto data_overrun_error;
121 if (len > datalen - dp)
122 goto data_overrun_error;
127 *_errmsg = "Unsupported length";
129 indefinite_len_primitive:
130 *_errmsg = "Indefinite len primitive not permitted";
133 *_errmsg = "Invalid length EOC";
136 *_errmsg = "Data overrun error";
139 *_errmsg = "Missing EOC in indefinite len cons";
146 * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
147 * @decoder: The decoder definition (produced by asn1_compiler)
148 * @context: The caller's context (to be passed to the action functions)
149 * @data: The encoded data
150 * @datalen: The size of the encoded data
152 * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
153 * produced by asn1_compiler. Action functions are called on marked tags to
154 * allow the caller to retrieve significant data.
158 * To keep down the amount of stack used by this function, the following limits
161 * (1) This won't handle datalen > 65535 without increasing the size of the
162 * cons stack elements and length_too_long checking.
164 * (2) The stack of constructed types is 10 deep. If the depth of non-leaf
165 * constructed types exceeds this, the decode will fail.
167 * (3) The SET type (not the SET OF type) isn't really supported as tracking
168 * what members of the set have been seen is a pain.
170 int asn1_ber_decoder(const struct asn1_decoder *decoder,
172 const unsigned char *data,
175 const unsigned char *machine = decoder->machine;
176 const asn1_action_t *actions = decoder->actions;
177 size_t machlen = decoder->machlen;
179 unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
181 size_t pc = 0, dp = 0, tdp = 0, len = 0;
184 unsigned char flags = 0;
185 #define FLAG_INDEFINITE_LENGTH 0x01
186 #define FLAG_MATCHED 0x02
187 #define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
188 #define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
189 * - ie. whether or not we are going to parse
193 #define NR_CONS_STACK 10
194 unsigned short cons_dp_stack[NR_CONS_STACK];
195 unsigned short cons_datalen_stack[NR_CONS_STACK];
196 unsigned char cons_hdrlen_stack[NR_CONS_STACK];
197 #define NR_JUMP_STACK 10
198 unsigned char jump_stack[NR_JUMP_STACK];
204 pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
205 pc, machlen, dp, datalen, csp, jsp);
206 if (unlikely(pc >= machlen))
207 goto machine_overrun_error;
209 if (unlikely(pc + asn1_op_lengths[op] > machlen))
210 goto machine_overrun_error;
212 /* If this command is meant to match a tag, then do that before
213 * evaluating the command.
215 if (op <= ASN1_OP__MATCHES_TAG) {
218 /* Skip conditional matches if possible */
219 if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) ||
220 (op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
221 flags &= ~FLAG_LAST_MATCHED;
222 pc += asn1_op_lengths[op];
229 /* Extract a tag from the data */
230 if (unlikely(dp >= datalen - 1))
231 goto data_overrun_error;
233 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
234 goto long_tag_not_supported;
236 if (op & ASN1_OP_MATCH__ANY) {
237 pr_debug("- any %02x\n", tag);
239 /* Extract the tag from the machine
240 * - Either CONS or PRIM are permitted in the data if
241 * CONS is not set in the op stream, otherwise CONS
244 optag = machine[pc + 1];
245 flags |= optag & FLAG_CONS;
247 /* Determine whether the tag matched */
249 tmp &= ~(optag & ASN1_CONS_BIT);
250 pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
252 /* All odd-numbered tags are MATCH_OR_SKIP. */
253 if (op & ASN1_OP_MATCH__SKIP) {
254 pc += asn1_op_lengths[op];
261 flags |= FLAG_MATCHED;
265 if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
266 /* Indefinite length */
267 if (unlikely(!(tag & ASN1_CONS_BIT)))
268 goto indefinite_len_primitive;
269 flags |= FLAG_INDEFINITE_LENGTH;
270 if (unlikely(2 > datalen - dp))
271 goto data_overrun_error;
275 goto length_too_long;
276 if (unlikely(dp >= datalen - n))
277 goto data_overrun_error;
279 for (len = 0; n > 0; n--) {
283 if (unlikely(len > datalen - dp))
284 goto data_overrun_error;
288 if (flags & FLAG_CONS) {
289 /* For expected compound forms, we stack the positions
290 * of the start and end of the data.
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;
300 cons_datalen_stack[csp] = 0;
305 pr_debug("- TAG: %02x %zu%s\n",
306 tag, len, flags & FLAG_CONS ? " CONS" : "");
310 /* Decide how to handle the operation */
312 case ASN1_OP_MATCH_ANY_ACT:
313 case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
314 case ASN1_OP_COND_MATCH_ANY_ACT:
315 case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
316 ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
321 case ASN1_OP_MATCH_ACT:
322 case ASN1_OP_MATCH_ACT_OR_SKIP:
323 case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
324 ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
330 case ASN1_OP_MATCH_OR_SKIP:
331 case ASN1_OP_MATCH_ANY:
332 case ASN1_OP_MATCH_ANY_OR_SKIP:
333 case ASN1_OP_COND_MATCH_OR_SKIP:
334 case ASN1_OP_COND_MATCH_ANY:
335 case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
337 if (!(flags & FLAG_CONS)) {
338 if (flags & FLAG_INDEFINITE_LENGTH) {
339 ret = asn1_find_indefinite_length(
340 data, datalen, &dp, &len, &errmsg);
346 pr_debug("- LEAF: %zu\n", len);
348 pc += asn1_op_lengths[op];
351 case ASN1_OP_MATCH_JUMP:
352 case ASN1_OP_MATCH_JUMP_OR_SKIP:
353 case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
354 pr_debug("- MATCH_JUMP\n");
355 if (unlikely(jsp == NR_JUMP_STACK))
356 goto jump_stack_overflow;
357 jump_stack[jsp++] = pc + asn1_op_lengths[op];
358 pc = machine[pc + 2];
361 case ASN1_OP_COND_FAIL:
362 if (unlikely(!(flags & FLAG_MATCHED)))
364 pc += asn1_op_lengths[op];
367 case ASN1_OP_COMPLETE:
368 if (unlikely(jsp != 0 || csp != 0)) {
369 pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
375 case ASN1_OP_END_SET:
376 case ASN1_OP_END_SET_ACT:
377 if (unlikely(!(flags & FLAG_MATCHED)))
379 case ASN1_OP_END_SEQ:
380 case ASN1_OP_END_SET_OF:
381 case ASN1_OP_END_SEQ_OF:
382 case ASN1_OP_END_SEQ_ACT:
383 case ASN1_OP_END_SET_OF_ACT:
384 case ASN1_OP_END_SEQ_OF_ACT:
385 if (unlikely(csp <= 0))
386 goto cons_stack_underflow;
388 tdp = cons_dp_stack[csp];
389 hdr = cons_hdrlen_stack[csp];
391 datalen = cons_datalen_stack[csp];
392 pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
393 tdp, dp, len, datalen);
395 /* Indefinite length - check for the EOC. */
397 if (unlikely(datalen - dp < 2))
398 goto data_overrun_error;
399 if (data[dp++] != 0) {
400 if (op & ASN1_OP_END__OF) {
403 pc = machine[pc + 1];
404 pr_debug("- continue\n");
413 if (dp < len && (op & ASN1_OP_END__OF)) {
416 pc = machine[pc + 1];
417 pr_debug("- continue\n");
421 goto cons_length_error;
423 pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
426 if (op & ASN1_OP_END__ACT) {
428 if (op & ASN1_OP_END__OF)
429 act = machine[pc + 2];
431 act = machine[pc + 1];
432 ret = actions[act](context, hdr, 0, data + tdp, len);
434 pc += asn1_op_lengths[op];
437 case ASN1_OP_MAYBE_ACT:
438 if (!(flags & FLAG_LAST_MATCHED)) {
439 pc += asn1_op_lengths[op];
443 ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
446 pc += asn1_op_lengths[op];
450 if (unlikely(jsp <= 0))
451 goto jump_stack_underflow;
452 pc = jump_stack[--jsp];
453 flags |= FLAG_MATCHED | FLAG_LAST_MATCHED;
460 /* Shouldn't reach here */
461 pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
466 errmsg = "Data overrun error";
468 machine_overrun_error:
469 errmsg = "Machine overrun error";
471 jump_stack_underflow:
472 errmsg = "Jump stack underflow";
475 errmsg = "Jump stack overflow";
477 cons_stack_underflow:
478 errmsg = "Cons stack underflow";
481 errmsg = "Cons stack overflow";
484 errmsg = "Cons length error";
487 errmsg = "Missing EOC in indefinite len cons";
490 errmsg = "Invalid length EOC";
493 errmsg = "Unsupported length";
495 indefinite_len_primitive:
496 errmsg = "Indefinite len primitive not permitted";
499 errmsg = "Unexpected tag";
501 long_tag_not_supported:
502 errmsg = "Long tag not supported";
504 pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
505 errmsg, pc, dp, optag, tag, len);
508 EXPORT_SYMBOL_GPL(asn1_ber_decoder);