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-rw-r--r--lib/asn1_decoder.c487
1 files changed, 487 insertions, 0 deletions
diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c
new file mode 100644
index 000000000000..de2c8b5a715b
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+++ b/lib/asn1_decoder.c
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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 (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
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_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,
36 [ASN1_OP_RETURN] = 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,
45};
46
47/*
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
54 */
55static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
56 size_t *_dp, size_t *_len,
57 const char **_errmsg)
58{
59 unsigned char tag, tmp;
60 size_t dp = *_dp, len, n;
61 int indef_level = 1;
62
63next_tag:
64 if (unlikely(datalen - dp < 2)) {
65 if (datalen == dp)
66 goto missing_eoc;
67 goto data_overrun_error;
68 }
69
70 /* Extract a tag from the data */
71 tag = data[dp++];
72 if (tag == 0) {
73 /* It appears to be an EOC. */
74 if (data[dp++] != 0)
75 goto invalid_eoc;
76 if (--indef_level <= 0) {
77 *_len = dp - *_dp;
78 *_dp = dp;
79 return 0;
80 }
81 goto next_tag;
82 }
83
84 if (unlikely((tag & 0x1f) == 0x1f)) {
85 do {
86 if (unlikely(datalen - dp < 2))
87 goto data_overrun_error;
88 tmp = data[dp++];
89 } while (tmp & 0x80);
90 }
91
92 /* Extract the length */
93 len = data[dp++];
94 if (len < 0x7f) {
95 dp += len;
96 goto next_tag;
97 }
98
99 if (unlikely(len == 0x80)) {
100 /* Indefinite length */
101 if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
102 goto indefinite_len_primitive;
103 indef_level++;
104 goto next_tag;
105 }
106
107 n = len - 0x80;
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--) {
113 len <<= 8;
114 len |= data[dp++];
115 }
116 dp += len;
117 goto next_tag;
118
119length_too_long:
120 *_errmsg = "Unsupported length";
121 goto error;
122indefinite_len_primitive:
123 *_errmsg = "Indefinite len primitive not permitted";
124 goto error;
125invalid_eoc:
126 *_errmsg = "Invalid length EOC";
127 goto error;
128data_overrun_error:
129 *_errmsg = "Data overrun error";
130 goto error;
131missing_eoc:
132 *_errmsg = "Missing EOC in indefinite len cons";
133error:
134 *_dp = dp;
135 return -1;
136}
137
138/**
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 * @datasize: The size of the encoded data
144 *
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.
148 *
149 * LIMITATIONS:
150 *
151 * To keep down the amount of stack used by this function, the following limits
152 * have been imposed:
153 *
154 * (1) This won't handle datalen > 65535 without increasing the size of the
155 * cons stack elements and length_too_long checking.
156 *
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.
159 *
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.
162 */
163int asn1_ber_decoder(const struct asn1_decoder *decoder,
164 void *context,
165 const unsigned char *data,
166 size_t datalen)
167{
168 const unsigned char *machine = decoder->machine;
169 const asn1_action_t *actions = decoder->actions;
170 size_t machlen = decoder->machlen;
171 enum asn1_opcode op;
172 unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
173 const char *errmsg;
174 size_t pc = 0, dp = 0, tdp = 0, len = 0;
175 int ret;
176
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
182 * a compound type.
183 */
184
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];
191
192 if (datalen > 65535)
193 return -EMSGSIZE;
194
195next_op:
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;
200 op = machine[pc];
201 if (unlikely(pc + asn1_op_lengths[op] > machlen))
202 goto machine_overrun_error;
203
204 /* If this command is meant to match a tag, then do that before
205 * evaluating the command.
206 */
207 if (op <= ASN1_OP__MATCHES_TAG) {
208 unsigned char tmp;
209
210 /* Skip conditional matches if possible */
211 if ((op & ASN1_OP_MATCH__COND &&
212 flags & FLAG_MATCHED) ||
213 dp == datalen) {
214 pc += asn1_op_lengths[op];
215 goto next_op;
216 }
217
218 flags = 0;
219 hdr = 2;
220
221 /* Extract a tag from the data */
222 if (unlikely(dp >= datalen - 1))
223 goto data_overrun_error;
224 tag = data[dp++];
225 if (unlikely((tag & 0x1f) == 0x1f))
226 goto long_tag_not_supported;
227
228 if (op & ASN1_OP_MATCH__ANY) {
229 pr_debug("- any %02x\n", tag);
230 } else {
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
234 * is mandatory.
235 */
236 optag = machine[pc + 1];
237 flags |= optag & FLAG_CONS;
238
239 /* Determine whether the tag matched */
240 tmp = optag ^ tag;
241 tmp &= ~(optag & ASN1_CONS_BIT);
242 pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
243 if (tmp != 0) {
244 /* All odd-numbered tags are MATCH_OR_SKIP. */
245 if (op & ASN1_OP_MATCH__SKIP) {
246 pc += asn1_op_lengths[op];
247 dp--;
248 goto next_op;
249 }
250 goto tag_mismatch;
251 }
252 }
253 flags |= FLAG_MATCHED;
254
255 len = data[dp++];
256 if (len > 0x7f) {
257 if (unlikely(len == 0x80)) {
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;
264 } else {
265 int n = len - 0x80;
266 if (unlikely(n > 2))
267 goto length_too_long;
268 if (unlikely(dp >= datalen - n))
269 goto data_overrun_error;
270 hdr += n;
271 for (len = 0; n > 0; n--) {
272 len <<= 8;
273 len |= data[dp++];
274 }
275 if (unlikely(len > datalen - dp))
276 goto data_overrun_error;
277 }
278 }
279
280 if (flags & FLAG_CONS) {
281 /* For expected compound forms, we stack the positions
282 * of the start and end of the data.
283 */
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;
290 datalen = dp + len;
291 } else {
292 cons_datalen_stack[csp] = 0;
293 }
294 csp++;
295 }
296
297 pr_debug("- TAG: %02x %zu%s\n",
298 tag, len, flags & FLAG_CONS ? " CONS" : "");
299 tdp = dp;
300 }
301
302 /* Decide how to handle the operation */
303 switch (op) {
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);
307 if (ret < 0)
308 return ret;
309 goto skip_data;
310
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);
315 if (ret < 0)
316 return ret;
317 goto skip_data;
318
319 case ASN1_OP_MATCH:
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:
324 skip_data:
325 if (!(flags & FLAG_CONS)) {
326 if (flags & FLAG_INDEFINITE_LENGTH) {
327 ret = asn1_find_indefinite_length(
328 data, datalen, &dp, &len, &errmsg);
329 if (ret < 0)
330 goto error;
331 } else {
332 dp += len;
333 }
334 pr_debug("- LEAF: %zu\n", len);
335 }
336 pc += asn1_op_lengths[op];
337 goto next_op;
338
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];
347 goto next_op;
348
349 case ASN1_OP_COND_FAIL:
350 if (unlikely(!(flags & FLAG_MATCHED)))
351 goto tag_mismatch;
352 pc += asn1_op_lengths[op];
353 goto next_op;
354
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",
358 jsp, csp);
359 return -EBADMSG;
360 }
361 return 0;
362
363 case ASN1_OP_END_SET:
364 case ASN1_OP_END_SET_ACT:
365 if (unlikely(!(flags & FLAG_MATCHED)))
366 goto tag_mismatch;
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;
375 csp--;
376 tdp = cons_dp_stack[csp];
377 hdr = cons_hdrlen_stack[csp];
378 len = datalen;
379 datalen = cons_datalen_stack[csp];
380 pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
381 tdp, dp, len, datalen);
382 if (datalen == 0) {
383 /* Indefinite length - check for the EOC. */
384 datalen = len;
385 if (unlikely(datalen - dp < 2))
386 goto data_overrun_error;
387 if (data[dp++] != 0) {
388 if (op & ASN1_OP_END__OF) {
389 dp--;
390 csp++;
391 pc = machine[pc + 1];
392 pr_debug("- continue\n");
393 goto next_op;
394 }
395 goto missing_eoc;
396 }
397 if (data[dp++] != 0)
398 goto invalid_eoc;
399 len = dp - tdp - 2;
400 } else {
401 if (dp < len && (op & ASN1_OP_END__OF)) {
402 datalen = len;
403 csp++;
404 pc = machine[pc + 1];
405 pr_debug("- continue\n");
406 goto next_op;
407 }
408 if (dp != len)
409 goto cons_length_error;
410 len -= tdp;
411 pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
412 }
413
414 if (op & ASN1_OP_END__ACT) {
415 unsigned char act;
416 if (op & ASN1_OP_END__OF)
417 act = machine[pc + 2];
418 else
419 act = machine[pc + 1];
420 ret = actions[act](context, hdr, 0, data + tdp, len);
421 }
422 pc += asn1_op_lengths[op];
423 goto next_op;
424
425 case ASN1_OP_ACT:
426 ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
427 pc += asn1_op_lengths[op];
428 goto next_op;
429
430 case ASN1_OP_RETURN:
431 if (unlikely(jsp <= 0))
432 goto jump_stack_underflow;
433 pc = jump_stack[--jsp];
434 goto next_op;
435
436 default:
437 break;
438 }
439
440 /* Shouldn't reach here */
441 pr_err("ASN.1 decoder error: Found reserved opcode (%u)\n", op);
442 return -EBADMSG;
443
444data_overrun_error:
445 errmsg = "Data overrun error";
446 goto error;
447machine_overrun_error:
448 errmsg = "Machine overrun error";
449 goto error;
450jump_stack_underflow:
451 errmsg = "Jump stack underflow";
452 goto error;
453jump_stack_overflow:
454 errmsg = "Jump stack overflow";
455 goto error;
456cons_stack_underflow:
457 errmsg = "Cons stack underflow";
458 goto error;
459cons_stack_overflow:
460 errmsg = "Cons stack overflow";
461 goto error;
462cons_length_error:
463 errmsg = "Cons length error";
464 goto error;
465missing_eoc:
466 errmsg = "Missing EOC in indefinite len cons";
467 goto error;
468invalid_eoc:
469 errmsg = "Invalid length EOC";
470 goto error;
471length_too_long:
472 errmsg = "Unsupported length";
473 goto error;
474indefinite_len_primitive:
475 errmsg = "Indefinite len primitive not permitted";
476 goto error;
477tag_mismatch:
478 errmsg = "Unexpected tag";
479 goto error;
480long_tag_not_supported:
481 errmsg = "Long tag not supported";
482error:
483 pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
484 errmsg, pc, dp, optag, tag, len);
485 return -EBADMSG;
486}
487EXPORT_SYMBOL_GPL(asn1_ber_decoder);
generated by cgit v1.2.2 (git 2.25.0) at 2025-09-11 16:18:51 -0400