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[mirror_ubuntu-artful-kernel.git] / lib / asn1_decoder.c
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/asn1_decoder.h>
16 #include <linux/asn1_ber_bytecode.h>
17
18 static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
19 /* OPC TAG JMP ACT */
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,
41 [ASN1_OP_RETURN] = 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,
50 };
51
52 /*
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
59 */
60 static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
61 size_t *_dp, size_t *_len,
62 const char **_errmsg)
63 {
64 unsigned char tag, tmp;
65 size_t dp = *_dp, len, n;
66 int indef_level = 1;
67
68 next_tag:
69 if (unlikely(datalen - dp < 2)) {
70 if (datalen == dp)
71 goto missing_eoc;
72 goto data_overrun_error;
73 }
74
75 /* Extract a tag from the data */
76 tag = data[dp++];
77 if (tag == ASN1_EOC) {
78 /* It appears to be an EOC. */
79 if (data[dp++] != 0)
80 goto invalid_eoc;
81 if (--indef_level <= 0) {
82 *_len = dp - *_dp;
83 *_dp = dp;
84 return 0;
85 }
86 goto next_tag;
87 }
88
89 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
90 do {
91 if (unlikely(datalen - dp < 2))
92 goto data_overrun_error;
93 tmp = data[dp++];
94 } while (tmp & 0x80);
95 }
96
97 /* Extract the length */
98 len = data[dp++];
99 if (len <= 0x7f)
100 goto check_length;
101
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;
106 indef_level++;
107 goto next_tag;
108 }
109
110 n = len - 0x80;
111 if (unlikely(n > sizeof(len) - 1))
112 goto length_too_long;
113 if (unlikely(n > datalen - dp))
114 goto data_overrun_error;
115 len = 0;
116 for (; n > 0; n--) {
117 len <<= 8;
118 len |= data[dp++];
119 }
120 check_length:
121 if (len > datalen - dp)
122 goto data_overrun_error;
123 dp += len;
124 goto next_tag;
125
126 length_too_long:
127 *_errmsg = "Unsupported length";
128 goto error;
129 indefinite_len_primitive:
130 *_errmsg = "Indefinite len primitive not permitted";
131 goto error;
132 invalid_eoc:
133 *_errmsg = "Invalid length EOC";
134 goto error;
135 data_overrun_error:
136 *_errmsg = "Data overrun error";
137 goto error;
138 missing_eoc:
139 *_errmsg = "Missing EOC in indefinite len cons";
140 error:
141 *_dp = dp;
142 return -1;
143 }
144
145 /**
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
151 *
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.
155 *
156 * LIMITATIONS:
157 *
158 * To keep down the amount of stack used by this function, the following limits
159 * have been imposed:
160 *
161 * (1) This won't handle datalen > 65535 without increasing the size of the
162 * cons stack elements and length_too_long checking.
163 *
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.
166 *
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.
169 */
170 int asn1_ber_decoder(const struct asn1_decoder *decoder,
171 void *context,
172 const unsigned char *data,
173 size_t datalen)
174 {
175 const unsigned char *machine = decoder->machine;
176 const asn1_action_t *actions = decoder->actions;
177 size_t machlen = decoder->machlen;
178 enum asn1_opcode op;
179 unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
180 const char *errmsg;
181 size_t pc = 0, dp = 0, tdp = 0, len = 0;
182 int ret;
183
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
190 * a compound type.
191 */
192
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];
199
200 if (datalen > 65535)
201 return -EMSGSIZE;
202
203 next_op:
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;
208 op = machine[pc];
209 if (unlikely(pc + asn1_op_lengths[op] > machlen))
210 goto machine_overrun_error;
211
212 /* If this command is meant to match a tag, then do that before
213 * evaluating the command.
214 */
215 if (op <= ASN1_OP__MATCHES_TAG) {
216 unsigned char tmp;
217
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];
223 goto next_op;
224 }
225
226 flags = 0;
227 hdr = 2;
228
229 /* Extract a tag from the data */
230 if (unlikely(dp >= datalen - 1))
231 goto data_overrun_error;
232 tag = data[dp++];
233 if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
234 goto long_tag_not_supported;
235
236 if (op & ASN1_OP_MATCH__ANY) {
237 pr_debug("- any %02x\n", tag);
238 } else {
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
242 * is mandatory.
243 */
244 optag = machine[pc + 1];
245 flags |= optag & FLAG_CONS;
246
247 /* Determine whether the tag matched */
248 tmp = optag ^ tag;
249 tmp &= ~(optag & ASN1_CONS_BIT);
250 pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
251 if (tmp != 0) {
252 /* All odd-numbered tags are MATCH_OR_SKIP. */
253 if (op & ASN1_OP_MATCH__SKIP) {
254 pc += asn1_op_lengths[op];
255 dp--;
256 goto next_op;
257 }
258 goto tag_mismatch;
259 }
260 }
261 flags |= FLAG_MATCHED;
262
263 len = data[dp++];
264 if (len > 0x7f) {
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;
272 } else {
273 int n = len - 0x80;
274 if (unlikely(n > 2))
275 goto length_too_long;
276 if (unlikely(dp >= datalen - n))
277 goto data_overrun_error;
278 hdr += n;
279 for (len = 0; n > 0; n--) {
280 len <<= 8;
281 len |= data[dp++];
282 }
283 if (unlikely(len > datalen - dp))
284 goto data_overrun_error;
285 }
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_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);
317 if (ret < 0)
318 return ret;
319 goto skip_data;
320
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);
325 if (ret < 0)
326 return ret;
327 goto skip_data;
328
329 case ASN1_OP_MATCH:
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:
336 skip_data:
337 if (!(flags & FLAG_CONS)) {
338 if (flags & FLAG_INDEFINITE_LENGTH) {
339 ret = asn1_find_indefinite_length(
340 data, datalen, &dp, &len, &errmsg);
341 if (ret < 0)
342 goto error;
343 } else {
344 dp += len;
345 }
346 pr_debug("- LEAF: %zu\n", len);
347 }
348 pc += asn1_op_lengths[op];
349 goto next_op;
350
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];
359 goto next_op;
360
361 case ASN1_OP_COND_FAIL:
362 if (unlikely(!(flags & FLAG_MATCHED)))
363 goto tag_mismatch;
364 pc += asn1_op_lengths[op];
365 goto next_op;
366
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",
370 jsp, csp);
371 return -EBADMSG;
372 }
373 return 0;
374
375 case ASN1_OP_END_SET:
376 case ASN1_OP_END_SET_ACT:
377 if (unlikely(!(flags & FLAG_MATCHED)))
378 goto tag_mismatch;
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;
387 csp--;
388 tdp = cons_dp_stack[csp];
389 hdr = cons_hdrlen_stack[csp];
390 len = datalen;
391 datalen = cons_datalen_stack[csp];
392 pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
393 tdp, dp, len, datalen);
394 if (datalen == 0) {
395 /* Indefinite length - check for the EOC. */
396 datalen = len;
397 if (unlikely(datalen - dp < 2))
398 goto data_overrun_error;
399 if (data[dp++] != 0) {
400 if (op & ASN1_OP_END__OF) {
401 dp--;
402 csp++;
403 pc = machine[pc + 1];
404 pr_debug("- continue\n");
405 goto next_op;
406 }
407 goto missing_eoc;
408 }
409 if (data[dp++] != 0)
410 goto invalid_eoc;
411 len = dp - tdp - 2;
412 } else {
413 if (dp < len && (op & ASN1_OP_END__OF)) {
414 datalen = len;
415 csp++;
416 pc = machine[pc + 1];
417 pr_debug("- continue\n");
418 goto next_op;
419 }
420 if (dp != len)
421 goto cons_length_error;
422 len -= tdp;
423 pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
424 }
425
426 if (op & ASN1_OP_END__ACT) {
427 unsigned char act;
428 if (op & ASN1_OP_END__OF)
429 act = machine[pc + 2];
430 else
431 act = machine[pc + 1];
432 ret = actions[act](context, hdr, 0, data + tdp, len);
433 }
434 pc += asn1_op_lengths[op];
435 goto next_op;
436
437 case ASN1_OP_MAYBE_ACT:
438 if (!(flags & FLAG_LAST_MATCHED)) {
439 pc += asn1_op_lengths[op];
440 goto next_op;
441 }
442 case ASN1_OP_ACT:
443 ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
444 if (ret < 0)
445 return ret;
446 pc += asn1_op_lengths[op];
447 goto next_op;
448
449 case ASN1_OP_RETURN:
450 if (unlikely(jsp <= 0))
451 goto jump_stack_underflow;
452 pc = jump_stack[--jsp];
453 flags |= FLAG_MATCHED | FLAG_LAST_MATCHED;
454 goto next_op;
455
456 default:
457 break;
458 }
459
460 /* Shouldn't reach here */
461 pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
462 op, pc);
463 return -EBADMSG;
464
465 data_overrun_error:
466 errmsg = "Data overrun error";
467 goto error;
468 machine_overrun_error:
469 errmsg = "Machine overrun error";
470 goto error;
471 jump_stack_underflow:
472 errmsg = "Jump stack underflow";
473 goto error;
474 jump_stack_overflow:
475 errmsg = "Jump stack overflow";
476 goto error;
477 cons_stack_underflow:
478 errmsg = "Cons stack underflow";
479 goto error;
480 cons_stack_overflow:
481 errmsg = "Cons stack overflow";
482 goto error;
483 cons_length_error:
484 errmsg = "Cons length error";
485 goto error;
486 missing_eoc:
487 errmsg = "Missing EOC in indefinite len cons";
488 goto error;
489 invalid_eoc:
490 errmsg = "Invalid length EOC";
491 goto error;
492 length_too_long:
493 errmsg = "Unsupported length";
494 goto error;
495 indefinite_len_primitive:
496 errmsg = "Indefinite len primitive not permitted";
497 goto error;
498 tag_mismatch:
499 errmsg = "Unexpected tag";
500 goto error;
501 long_tag_not_supported:
502 errmsg = "Long tag not supported";
503 error:
504 pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
505 errmsg, pc, dp, optag, tag, len);
506 return -EBADMSG;
507 }
508 EXPORT_SYMBOL_GPL(asn1_ber_decoder);
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