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
49 * @data: The data buffer
50 * @datalen: The end of the innermost containing element in the buffer
51 * @_dp: The data parse cursor (updated before returning)
52 * @_len: Where to return the size of the element.
53 * @_errmsg: Where to return a pointer to an error message on error
55 static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
56 size_t *_dp, size_t *_len,
59 unsigned char tag, tmp;
60 size_t dp = *_dp, len, n;
64 if (unlikely(datalen - dp < 2)) {
67 goto data_overrun_error;
70 /* Extract a tag from the data */
73 /* It appears to be an EOC. */
76 if (--indef_level <= 0) {
84 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
86 if (unlikely(datalen - dp < 2))
87 goto data_overrun_error;
92 /* Extract the length */
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;
108 if (unlikely(n > sizeof(size_t) - 1))
109 goto length_too_long;
110 if (unlikely(n > datalen - dp))
111 goto data_overrun_error;
112 for (len = 0; n > 0; n--) {
120 *_errmsg = "Unsupported length";
122 indefinite_len_primitive:
123 *_errmsg = "Indefinite len primitive not permitted";
126 *_errmsg = "Invalid length EOC";
129 *_errmsg = "Data overrun error";
132 *_errmsg = "Missing EOC in indefinite len cons";
139 * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
140 * @decoder: The decoder definition (produced by asn1_compiler)
141 * @context: The caller's context (to be passed to the action functions)
142 * @data: The encoded data
143 * @datalen: The size of the encoded data
145 * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
146 * produced by asn1_compiler. Action functions are called on marked tags to
147 * allow the caller to retrieve significant data.
151 * To keep down the amount of stack used by this function, the following limits
154 * (1) This won't handle datalen > 65535 without increasing the size of the
155 * cons stack elements and length_too_long checking.
157 * (2) The stack of constructed types is 10 deep. If the depth of non-leaf
158 * constructed types exceeds this, the decode will fail.
160 * (3) The SET type (not the SET OF type) isn't really supported as tracking
161 * what members of the set have been seen is a pain.
163 int asn1_ber_decoder(const struct asn1_decoder *decoder,
165 const unsigned char *data,
168 const unsigned char *machine = decoder->machine;
169 const asn1_action_t *actions = decoder->actions;
170 size_t machlen = decoder->machlen;
172 unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
174 size_t pc = 0, dp = 0, tdp = 0, len = 0;
177 unsigned char flags = 0;
178 #define FLAG_INDEFINITE_LENGTH 0x01
179 #define FLAG_MATCHED 0x02
180 #define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
181 * - ie. whether or not we are going to parse
185 #define NR_CONS_STACK 10
186 unsigned short cons_dp_stack[NR_CONS_STACK];
187 unsigned short cons_datalen_stack[NR_CONS_STACK];
188 unsigned char cons_hdrlen_stack[NR_CONS_STACK];
189 #define NR_JUMP_STACK 10
190 unsigned char jump_stack[NR_JUMP_STACK];
196 pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
197 pc, machlen, dp, datalen, csp, jsp);
198 if (unlikely(pc >= machlen))
199 goto machine_overrun_error;
201 if (unlikely(pc + asn1_op_lengths[op] > machlen))
202 goto machine_overrun_error;
204 /* If this command is meant to match a tag, then do that before
205 * evaluating the command.
207 if (op <= ASN1_OP__MATCHES_TAG) {
210 /* Skip conditional matches if possible */
211 if ((op & ASN1_OP_MATCH__COND &&
212 flags & FLAG_MATCHED) ||
214 pc += asn1_op_lengths[op];
221 /* Extract a tag from the data */
222 if (unlikely(dp >= datalen - 1))
223 goto data_overrun_error;
225 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
226 goto long_tag_not_supported;
228 if (op & ASN1_OP_MATCH__ANY) {
229 pr_debug("- any %02x\n", tag);
231 /* Extract the tag from the machine
232 * - Either CONS or PRIM are permitted in the data if
233 * CONS is not set in the op stream, otherwise CONS
236 optag = machine[pc + 1];
237 flags |= optag & FLAG_CONS;
239 /* Determine whether the tag matched */
241 tmp &= ~(optag & ASN1_CONS_BIT);
242 pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
244 /* All odd-numbered tags are MATCH_OR_SKIP. */
245 if (op & ASN1_OP_MATCH__SKIP) {
246 pc += asn1_op_lengths[op];
253 flags |= FLAG_MATCHED;
257 if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
258 /* Indefinite length */
259 if (unlikely(!(tag & ASN1_CONS_BIT)))
260 goto indefinite_len_primitive;
261 flags |= FLAG_INDEFINITE_LENGTH;
262 if (unlikely(2 > datalen - dp))
263 goto data_overrun_error;
267 goto length_too_long;
268 if (unlikely(dp >= datalen - n))
269 goto data_overrun_error;
271 for (len = 0; n > 0; n--) {
275 if (unlikely(len > datalen - dp))
276 goto data_overrun_error;
280 if (flags & FLAG_CONS) {
281 /* For expected compound forms, we stack the positions
282 * of the start and end of the data.
284 if (unlikely(csp >= NR_CONS_STACK))
285 goto cons_stack_overflow;
286 cons_dp_stack[csp] = dp;
287 cons_hdrlen_stack[csp] = hdr;
288 if (!(flags & FLAG_INDEFINITE_LENGTH)) {
289 cons_datalen_stack[csp] = datalen;
292 cons_datalen_stack[csp] = 0;
297 pr_debug("- TAG: %02x %zu%s\n",
298 tag, len, flags & FLAG_CONS ? " CONS" : "");
302 /* Decide how to handle the operation */
304 case ASN1_OP_MATCH_ANY_ACT:
305 case ASN1_OP_COND_MATCH_ANY_ACT:
306 ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
311 case ASN1_OP_MATCH_ACT:
312 case ASN1_OP_MATCH_ACT_OR_SKIP:
313 case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
314 ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
320 case ASN1_OP_MATCH_OR_SKIP:
321 case ASN1_OP_MATCH_ANY:
322 case ASN1_OP_COND_MATCH_OR_SKIP:
323 case ASN1_OP_COND_MATCH_ANY:
325 if (!(flags & FLAG_CONS)) {
326 if (flags & FLAG_INDEFINITE_LENGTH) {
327 ret = asn1_find_indefinite_length(
328 data, datalen, &dp, &len, &errmsg);
334 pr_debug("- LEAF: %zu\n", len);
336 pc += asn1_op_lengths[op];
339 case ASN1_OP_MATCH_JUMP:
340 case ASN1_OP_MATCH_JUMP_OR_SKIP:
341 case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
342 pr_debug("- MATCH_JUMP\n");
343 if (unlikely(jsp == NR_JUMP_STACK))
344 goto jump_stack_overflow;
345 jump_stack[jsp++] = pc + asn1_op_lengths[op];
346 pc = machine[pc + 2];
349 case ASN1_OP_COND_FAIL:
350 if (unlikely(!(flags & FLAG_MATCHED)))
352 pc += asn1_op_lengths[op];
355 case ASN1_OP_COMPLETE:
356 if (unlikely(jsp != 0 || csp != 0)) {
357 pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
363 case ASN1_OP_END_SET:
364 case ASN1_OP_END_SET_ACT:
365 if (unlikely(!(flags & FLAG_MATCHED)))
367 case ASN1_OP_END_SEQ:
368 case ASN1_OP_END_SET_OF:
369 case ASN1_OP_END_SEQ_OF:
370 case ASN1_OP_END_SEQ_ACT:
371 case ASN1_OP_END_SET_OF_ACT:
372 case ASN1_OP_END_SEQ_OF_ACT:
373 if (unlikely(csp <= 0))
374 goto cons_stack_underflow;
376 tdp = cons_dp_stack[csp];
377 hdr = cons_hdrlen_stack[csp];
379 datalen = cons_datalen_stack[csp];
380 pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
381 tdp, dp, len, datalen);
383 /* Indefinite length - check for the EOC. */
385 if (unlikely(datalen - dp < 2))
386 goto data_overrun_error;
387 if (data[dp++] != 0) {
388 if (op & ASN1_OP_END__OF) {
391 pc = machine[pc + 1];
392 pr_debug("- continue\n");
401 if (dp < len && (op & ASN1_OP_END__OF)) {
404 pc = machine[pc + 1];
405 pr_debug("- continue\n");
409 goto cons_length_error;
411 pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
414 if (op & ASN1_OP_END__ACT) {
416 if (op & ASN1_OP_END__OF)
417 act = machine[pc + 2];
419 act = machine[pc + 1];
420 ret = actions[act](context, hdr, 0, data + tdp, len);
422 pc += asn1_op_lengths[op];
426 ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
427 pc += asn1_op_lengths[op];
431 if (unlikely(jsp <= 0))
432 goto jump_stack_underflow;
433 pc = jump_stack[--jsp];
440 /* Shouldn't reach here */
441 pr_err("ASN.1 decoder error: Found reserved opcode (%u)\n", op);
445 errmsg = "Data overrun error";
447 machine_overrun_error:
448 errmsg = "Machine overrun error";
450 jump_stack_underflow:
451 errmsg = "Jump stack underflow";
454 errmsg = "Jump stack overflow";
456 cons_stack_underflow:
457 errmsg = "Cons stack underflow";
460 errmsg = "Cons stack overflow";
463 errmsg = "Cons length error";
466 errmsg = "Missing EOC in indefinite len cons";
469 errmsg = "Invalid length EOC";
472 errmsg = "Unsupported length";
474 indefinite_len_primitive:
475 errmsg = "Indefinite len primitive not permitted";
478 errmsg = "Unexpected tag";
480 long_tag_not_supported:
481 errmsg = "Long tag not supported";
483 pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
484 errmsg, pc, dp, optag, tag, len);
487 EXPORT_SYMBOL_GPL(asn1_ber_decoder);