projects/linux·blob v4.5-rc2 · refs

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