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_ACT] = 1 + 1,
28 [ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
29 [ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
30 [ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
31 [ASN1_OP_COND_MATCH_ANY] = 1,
32 [ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
33 [ASN1_OP_COND_FAIL] = 1,
34 [ASN1_OP_COMPLETE] = 1,
35 [ASN1_OP_ACT] = 1 + 1,
37 [ASN1_OP_END_SEQ] = 1,
38 [ASN1_OP_END_SEQ_OF] = 1 + 1,
39 [ASN1_OP_END_SET] = 1,
40 [ASN1_OP_END_SET_OF] = 1 + 1,
41 [ASN1_OP_END_SEQ_ACT] = 1 + 1,
42 [ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
43 [ASN1_OP_END_SET_ACT] = 1 + 1,
44 [ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
48 * Find the length of an indefinite length object
50 static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
51 const char **_errmsg, size_t *_err_dp)
53 unsigned char tag, tmp;
54 size_t dp = 0, len, n;
58 if (unlikely(datalen - dp < 2)) {
61 goto data_overrun_error;
64 /* Extract a tag from the data */
67 /* It appears to be an EOC. */
70 if (--indef_level <= 0)
75 if (unlikely((tag & 0x1f) == 0x1f)) {
77 if (unlikely(datalen - dp < 2))
78 goto data_overrun_error;
83 /* Extract the length */
90 if (unlikely(len == 0x80)) {
91 /* Indefinite length */
92 if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
93 goto indefinite_len_primitive;
99 if (unlikely(n > sizeof(size_t) - 1))
100 goto length_too_long;
101 if (unlikely(n > datalen - dp))
102 goto data_overrun_error;
103 for (len = 0; n > 0; n--) {
111 *_errmsg = "Unsupported length";
113 indefinite_len_primitive:
114 *_errmsg = "Indefinite len primitive not permitted";
117 *_errmsg = "Invalid length EOC";
120 *_errmsg = "Data overrun error";
123 *_errmsg = "Missing EOC in indefinite len cons";
130 * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
131 * @decoder: The decoder definition (produced by asn1_compiler)
132 * @context: The caller's context (to be passed to the action functions)
133 * @data: The encoded data
134 * @datasize: The size of the encoded data
136 * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
137 * produced by asn1_compiler. Action functions are called on marked tags to
138 * allow the caller to retrieve significant data.
142 * To keep down the amount of stack used by this function, the following limits
145 * (1) This won't handle datalen > 65535 without increasing the size of the
146 * cons stack elements and length_too_long checking.
148 * (2) The stack of constructed types is 10 deep. If the depth of non-leaf
149 * constructed types exceeds this, the decode will fail.
151 * (3) The SET type (not the SET OF type) isn't really supported as tracking
152 * what members of the set have been seen is a pain.
154 int asn1_ber_decoder(const struct asn1_decoder *decoder,
156 const unsigned char *data,
159 const unsigned char *machine = decoder->machine;
160 const asn1_action_t *actions = decoder->actions;
161 size_t machlen = decoder->machlen;
163 unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
165 size_t pc = 0, dp = 0, tdp = 0, len = 0;
168 unsigned char flags = 0;
169 #define FLAG_INDEFINITE_LENGTH 0x01
170 #define FLAG_MATCHED 0x02
171 #define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
172 * - ie. whether or not we are going to parse
176 #define NR_CONS_STACK 10
177 unsigned short cons_dp_stack[NR_CONS_STACK];
178 unsigned short cons_datalen_stack[NR_CONS_STACK];
179 unsigned char cons_hdrlen_stack[NR_CONS_STACK];
180 #define NR_JUMP_STACK 10
181 unsigned char jump_stack[NR_JUMP_STACK];
187 pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
188 pc, machlen, dp, datalen, csp, jsp);
189 if (unlikely(pc >= machlen))
190 goto machine_overrun_error;
192 if (unlikely(pc + asn1_op_lengths[op] > machlen))
193 goto machine_overrun_error;
195 /* If this command is meant to match a tag, then do that before
196 * evaluating the command.
198 if (op <= ASN1_OP__MATCHES_TAG) {
201 /* Skip conditional matches if possible */
202 if ((op & ASN1_OP_MATCH__COND &&
203 flags & FLAG_MATCHED) ||
205 pc += asn1_op_lengths[op];
212 /* Extract a tag from the data */
213 if (unlikely(dp >= datalen - 1))
214 goto data_overrun_error;
216 if (unlikely((tag & 0x1f) == 0x1f))
217 goto long_tag_not_supported;
219 if (op & ASN1_OP_MATCH__ANY) {
220 pr_debug("- any %02x\n", tag);
222 /* Extract the tag from the machine
223 * - Either CONS or PRIM are permitted in the data if
224 * CONS is not set in the op stream, otherwise CONS
227 optag = machine[pc + 1];
228 flags |= optag & FLAG_CONS;
230 /* Determine whether the tag matched */
232 tmp &= ~(optag & ASN1_CONS_BIT);
233 pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
235 /* All odd-numbered tags are MATCH_OR_SKIP. */
236 if (op & ASN1_OP_MATCH__SKIP) {
237 pc += asn1_op_lengths[op];
244 flags |= FLAG_MATCHED;
248 if (unlikely(len == 0x80)) {
249 /* Indefinite length */
250 if (unlikely(!(tag & ASN1_CONS_BIT)))
251 goto indefinite_len_primitive;
252 flags |= FLAG_INDEFINITE_LENGTH;
253 if (unlikely(2 > datalen - dp))
254 goto data_overrun_error;
258 goto length_too_long;
259 if (unlikely(dp >= datalen - n))
260 goto data_overrun_error;
262 for (len = 0; n > 0; n--) {
266 if (unlikely(len > datalen - dp))
267 goto data_overrun_error;
271 if (flags & FLAG_CONS) {
272 /* For expected compound forms, we stack the positions
273 * of the start and end of the data.
275 if (unlikely(csp >= NR_CONS_STACK))
276 goto cons_stack_overflow;
277 cons_dp_stack[csp] = dp;
278 cons_hdrlen_stack[csp] = hdr;
279 if (!(flags & FLAG_INDEFINITE_LENGTH)) {
280 cons_datalen_stack[csp] = datalen;
283 cons_datalen_stack[csp] = 0;
288 pr_debug("- TAG: %02x %zu%s\n",
289 tag, len, flags & FLAG_CONS ? " CONS" : "");
293 /* Decide how to handle the operation */
295 case ASN1_OP_MATCH_ANY_ACT:
296 case ASN1_OP_COND_MATCH_ANY_ACT:
297 ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
302 case ASN1_OP_MATCH_ACT:
303 case ASN1_OP_MATCH_ACT_OR_SKIP:
304 case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
305 ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
311 case ASN1_OP_MATCH_OR_SKIP:
312 case ASN1_OP_MATCH_ANY:
313 case ASN1_OP_COND_MATCH_OR_SKIP:
314 case ASN1_OP_COND_MATCH_ANY:
316 if (!(flags & FLAG_CONS)) {
317 if (flags & FLAG_INDEFINITE_LENGTH) {
318 len = asn1_find_indefinite_length(
319 data + dp, datalen - dp, &errmsg, &dp);
323 pr_debug("- LEAF: %zu\n", len);
326 pc += asn1_op_lengths[op];
329 case ASN1_OP_MATCH_JUMP:
330 case ASN1_OP_MATCH_JUMP_OR_SKIP:
331 case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
332 pr_debug("- MATCH_JUMP\n");
333 if (unlikely(jsp == NR_JUMP_STACK))
334 goto jump_stack_overflow;
335 jump_stack[jsp++] = pc + asn1_op_lengths[op];
336 pc = machine[pc + 2];
339 case ASN1_OP_COND_FAIL:
340 if (unlikely(!(flags & FLAG_MATCHED)))
342 pc += asn1_op_lengths[op];
345 case ASN1_OP_COMPLETE:
346 if (unlikely(jsp != 0 || csp != 0)) {
347 pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
353 case ASN1_OP_END_SET:
354 case ASN1_OP_END_SET_ACT:
355 if (unlikely(!(flags & FLAG_MATCHED)))
357 case ASN1_OP_END_SEQ:
358 case ASN1_OP_END_SET_OF:
359 case ASN1_OP_END_SEQ_OF:
360 case ASN1_OP_END_SEQ_ACT:
361 case ASN1_OP_END_SET_OF_ACT:
362 case ASN1_OP_END_SEQ_OF_ACT:
363 if (unlikely(csp <= 0))
364 goto cons_stack_underflow;
366 tdp = cons_dp_stack[csp];
367 hdr = cons_hdrlen_stack[csp];
369 datalen = cons_datalen_stack[csp];
370 pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
371 tdp, dp, len, datalen);
373 /* Indefinite length - check for the EOC. */
375 if (unlikely(datalen - dp < 2))
376 goto data_overrun_error;
377 if (data[dp++] != 0) {
378 if (op & ASN1_OP_END__OF) {
381 pc = machine[pc + 1];
382 pr_debug("- continue\n");
391 if (dp < len && (op & ASN1_OP_END__OF)) {
394 pc = machine[pc + 1];
395 pr_debug("- continue\n");
399 goto cons_length_error;
401 pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
404 if (op & ASN1_OP_END__ACT) {
406 if (op & ASN1_OP_END__OF)
407 act = machine[pc + 2];
409 act = machine[pc + 1];
410 ret = actions[act](context, hdr, 0, data + tdp, len);
412 pc += asn1_op_lengths[op];
416 ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
417 pc += asn1_op_lengths[op];
421 if (unlikely(jsp <= 0))
422 goto jump_stack_underflow;
423 pc = jump_stack[--jsp];
430 /* Shouldn't reach here */
431 pr_err("ASN.1 decoder error: Found reserved opcode (%u)\n", op);
435 errmsg = "Data overrun error";
437 machine_overrun_error:
438 errmsg = "Machine overrun error";
440 jump_stack_underflow:
441 errmsg = "Jump stack underflow";
444 errmsg = "Jump stack overflow";
446 cons_stack_underflow:
447 errmsg = "Cons stack underflow";
450 errmsg = "Cons stack overflow";
453 errmsg = "Cons length error";
456 errmsg = "Missing EOC in indefinite len cons";
459 errmsg = "Invalid length EOC";
462 errmsg = "Unsupported length";
464 indefinite_len_primitive:
465 errmsg = "Indefinite len primitive not permitted";
468 errmsg = "Unexpected tag";
470 long_tag_not_supported:
471 errmsg = "Long tag not supported";
473 pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
474 errmsg, pc, dp, optag, tag, len);
477 EXPORT_SYMBOL_GPL(asn1_ber_decoder);