1 /*
2 * ASN.1 buffer writing functionality
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 #include "common.h"
21
22 #if defined(MBEDTLS_ASN1_WRITE_C)
23
24 #include "mbedtls/asn1write.h"
25 #include "mbedtls/error.h"
26
27 #include <string.h>
28
29 #if defined(MBEDTLS_PLATFORM_C)
30 #include "mbedtls/platform.h"
31 #else
32 #include <stdlib.h>
33 #define mbedtls_calloc calloc
34 #define mbedtls_free free
35 #endif
36
mbedtls_asn1_write_len(unsigned char ** p,unsigned char * start,size_t len)37 int mbedtls_asn1_write_len( unsigned char **p, unsigned char *start, size_t len )
38 {
39 if( len < 0x80 )
40 {
41 if( *p - start < 1 )
42 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
43
44 *--(*p) = (unsigned char) len;
45 return( 1 );
46 }
47
48 if( len <= 0xFF )
49 {
50 if( *p - start < 2 )
51 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
52
53 *--(*p) = (unsigned char) len;
54 *--(*p) = 0x81;
55 return( 2 );
56 }
57
58 if( len <= 0xFFFF )
59 {
60 if( *p - start < 3 )
61 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
62
63 *--(*p) = MBEDTLS_BYTE_0( len );
64 *--(*p) = MBEDTLS_BYTE_1( len );
65 *--(*p) = 0x82;
66 return( 3 );
67 }
68
69 if( len <= 0xFFFFFF )
70 {
71 if( *p - start < 4 )
72 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
73
74 *--(*p) = MBEDTLS_BYTE_0( len );
75 *--(*p) = MBEDTLS_BYTE_1( len );
76 *--(*p) = MBEDTLS_BYTE_2( len );
77 *--(*p) = 0x83;
78 return( 4 );
79 }
80
81 #if SIZE_MAX > 0xFFFFFFFF
82 if( len <= 0xFFFFFFFF )
83 #endif
84 {
85 if( *p - start < 5 )
86 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
87
88 *--(*p) = MBEDTLS_BYTE_0( len );
89 *--(*p) = MBEDTLS_BYTE_1( len );
90 *--(*p) = MBEDTLS_BYTE_2( len );
91 *--(*p) = MBEDTLS_BYTE_3( len );
92 *--(*p) = 0x84;
93 return( 5 );
94 }
95
96 #if SIZE_MAX > 0xFFFFFFFF
97 return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
98 #endif
99 }
100
mbedtls_asn1_write_tag(unsigned char ** p,unsigned char * start,unsigned char tag)101 int mbedtls_asn1_write_tag( unsigned char **p, unsigned char *start, unsigned char tag )
102 {
103 if( *p - start < 1 )
104 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
105
106 *--(*p) = tag;
107
108 return( 1 );
109 }
110
mbedtls_asn1_write_raw_buffer(unsigned char ** p,unsigned char * start,const unsigned char * buf,size_t size)111 int mbedtls_asn1_write_raw_buffer( unsigned char **p, unsigned char *start,
112 const unsigned char *buf, size_t size )
113 {
114 size_t len = 0;
115
116 if( *p < start || (size_t)( *p - start ) < size )
117 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
118
119 len = size;
120 (*p) -= len;
121 memcpy( *p, buf, len );
122
123 return( (int) len );
124 }
125
126 #if defined(MBEDTLS_BIGNUM_C)
mbedtls_asn1_write_mpi(unsigned char ** p,unsigned char * start,const mbedtls_mpi * X)127 int mbedtls_asn1_write_mpi( unsigned char **p, unsigned char *start, const mbedtls_mpi *X )
128 {
129 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
130 size_t len = 0;
131
132 // Write the MPI
133 //
134 len = mbedtls_mpi_size( X );
135
136 /* DER represents 0 with a sign bit (0=nonnegative) and 7 value bits, not
137 * as 0 digits. We need to end up with 020100, not with 0200. */
138 if( len == 0 )
139 len = 1;
140
141 if( *p < start || (size_t)( *p - start ) < len )
142 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
143
144 (*p) -= len;
145 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) );
146
147 // DER format assumes 2s complement for numbers, so the leftmost bit
148 // should be 0 for positive numbers and 1 for negative numbers.
149 //
150 if( X->s ==1 && **p & 0x80 )
151 {
152 if( *p - start < 1 )
153 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
154
155 *--(*p) = 0x00;
156 len += 1;
157 }
158
159 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
160 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
161
162 ret = (int) len;
163
164 cleanup:
165 return( ret );
166 }
167 #endif /* MBEDTLS_BIGNUM_C */
168
mbedtls_asn1_write_null(unsigned char ** p,unsigned char * start)169 int mbedtls_asn1_write_null( unsigned char **p, unsigned char *start )
170 {
171 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
172 size_t len = 0;
173
174 // Write NULL
175 //
176 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) );
177 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) );
178
179 return( (int) len );
180 }
181
mbedtls_asn1_write_oid(unsigned char ** p,unsigned char * start,const char * oid,size_t oid_len)182 int mbedtls_asn1_write_oid( unsigned char **p, unsigned char *start,
183 const char *oid, size_t oid_len )
184 {
185 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
186 size_t len = 0;
187
188 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
189 (const unsigned char *) oid, oid_len ) );
190 MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_len( p, start, len ) );
191 MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OID ) );
192
193 return( (int) len );
194 }
195
mbedtls_asn1_write_algorithm_identifier(unsigned char ** p,unsigned char * start,const char * oid,size_t oid_len,size_t par_len)196 int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start,
197 const char *oid, size_t oid_len,
198 size_t par_len )
199 {
200 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
201 size_t len = 0;
202
203 if( par_len == 0 )
204 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) );
205 else
206 len += par_len;
207
208 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
209
210 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
211 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start,
212 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
213
214 return( (int) len );
215 }
216
mbedtls_asn1_write_bool(unsigned char ** p,unsigned char * start,int boolean)217 int mbedtls_asn1_write_bool( unsigned char **p, unsigned char *start, int boolean )
218 {
219 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
220 size_t len = 0;
221
222 if( *p - start < 1 )
223 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
224
225 *--(*p) = (boolean) ? 255 : 0;
226 len++;
227
228 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
229 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BOOLEAN ) );
230
231 return( (int) len );
232 }
233
asn1_write_tagged_int(unsigned char ** p,unsigned char * start,int val,int tag)234 static int asn1_write_tagged_int( unsigned char **p, unsigned char *start, int val, int tag )
235 {
236 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
237 size_t len = 0;
238
239 do
240 {
241 if( *p - start < 1 )
242 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
243 len += 1;
244 *--(*p) = val & 0xff;
245 val >>= 8;
246 }
247 while( val > 0 );
248
249 if( **p & 0x80 )
250 {
251 if( *p - start < 1 )
252 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
253 *--(*p) = 0x00;
254 len += 1;
255 }
256
257 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
258 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
259
260 return( (int) len );
261 }
262
mbedtls_asn1_write_int(unsigned char ** p,unsigned char * start,int val)263 int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val )
264 {
265 return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_INTEGER ) );
266 }
267
mbedtls_asn1_write_enum(unsigned char ** p,unsigned char * start,int val)268 int mbedtls_asn1_write_enum( unsigned char **p, unsigned char *start, int val )
269 {
270 return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_ENUMERATED ) );
271 }
272
mbedtls_asn1_write_tagged_string(unsigned char ** p,unsigned char * start,int tag,const char * text,size_t text_len)273 int mbedtls_asn1_write_tagged_string( unsigned char **p, unsigned char *start, int tag,
274 const char *text, size_t text_len )
275 {
276 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
277 size_t len = 0;
278
279 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
280 (const unsigned char *) text, text_len ) );
281
282 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
283 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
284
285 return( (int) len );
286 }
287
mbedtls_asn1_write_utf8_string(unsigned char ** p,unsigned char * start,const char * text,size_t text_len)288 int mbedtls_asn1_write_utf8_string( unsigned char **p, unsigned char *start,
289 const char *text, size_t text_len )
290 {
291 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len) );
292 }
293
mbedtls_asn1_write_printable_string(unsigned char ** p,unsigned char * start,const char * text,size_t text_len)294 int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start,
295 const char *text, size_t text_len )
296 {
297 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len) );
298 }
299
mbedtls_asn1_write_ia5_string(unsigned char ** p,unsigned char * start,const char * text,size_t text_len)300 int mbedtls_asn1_write_ia5_string( unsigned char **p, unsigned char *start,
301 const char *text, size_t text_len )
302 {
303 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len) );
304 }
305
mbedtls_asn1_write_named_bitstring(unsigned char ** p,unsigned char * start,const unsigned char * buf,size_t bits)306 int mbedtls_asn1_write_named_bitstring( unsigned char **p,
307 unsigned char *start,
308 const unsigned char *buf,
309 size_t bits )
310 {
311 size_t unused_bits, byte_len;
312 const unsigned char *cur_byte;
313 unsigned char cur_byte_shifted;
314 unsigned char bit;
315
316 byte_len = ( bits + 7 ) / 8;
317 unused_bits = ( byte_len * 8 ) - bits;
318
319 /*
320 * Named bitstrings require that trailing 0s are excluded in the encoding
321 * of the bitstring. Trailing 0s are considered part of the 'unused' bits
322 * when encoding this value in the first content octet
323 */
324 if( bits != 0 )
325 {
326 cur_byte = buf + byte_len - 1;
327 cur_byte_shifted = *cur_byte >> unused_bits;
328
329 for( ; ; )
330 {
331 bit = cur_byte_shifted & 0x1;
332 cur_byte_shifted >>= 1;
333
334 if( bit != 0 )
335 break;
336
337 bits--;
338 if( bits == 0 )
339 break;
340
341 if( bits % 8 == 0 )
342 cur_byte_shifted = *--cur_byte;
343 }
344 }
345
346 return( mbedtls_asn1_write_bitstring( p, start, buf, bits ) );
347 }
348
mbedtls_asn1_write_bitstring(unsigned char ** p,unsigned char * start,const unsigned char * buf,size_t bits)349 int mbedtls_asn1_write_bitstring( unsigned char **p, unsigned char *start,
350 const unsigned char *buf, size_t bits )
351 {
352 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
353 size_t len = 0;
354 size_t unused_bits, byte_len;
355
356 byte_len = ( bits + 7 ) / 8;
357 unused_bits = ( byte_len * 8 ) - bits;
358
359 if( *p < start || (size_t)( *p - start ) < byte_len + 1 )
360 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
361
362 len = byte_len + 1;
363
364 /* Write the bitstring. Ensure the unused bits are zeroed */
365 if( byte_len > 0 )
366 {
367 byte_len--;
368 *--( *p ) = buf[byte_len] & ~( ( 0x1 << unused_bits ) - 1 );
369 ( *p ) -= byte_len;
370 memcpy( *p, buf, byte_len );
371 }
372
373 /* Write unused bits */
374 *--( *p ) = (unsigned char)unused_bits;
375
376 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
377 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BIT_STRING ) );
378
379 return( (int) len );
380 }
381
mbedtls_asn1_write_octet_string(unsigned char ** p,unsigned char * start,const unsigned char * buf,size_t size)382 int mbedtls_asn1_write_octet_string( unsigned char **p, unsigned char *start,
383 const unsigned char *buf, size_t size )
384 {
385 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
386 size_t len = 0;
387
388 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, size ) );
389
390 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
391 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OCTET_STRING ) );
392
393 return( (int) len );
394 }
395
396
397 /* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(),
398 * which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */
asn1_find_named_data(mbedtls_asn1_named_data * list,const char * oid,size_t len)399 static mbedtls_asn1_named_data *asn1_find_named_data(
400 mbedtls_asn1_named_data *list,
401 const char *oid, size_t len )
402 {
403 while( list != NULL )
404 {
405 if( list->oid.len == len &&
406 memcmp( list->oid.p, oid, len ) == 0 )
407 {
408 break;
409 }
410
411 list = list->next;
412 }
413
414 return( list );
415 }
416
mbedtls_asn1_store_named_data(mbedtls_asn1_named_data ** head,const char * oid,size_t oid_len,const unsigned char * val,size_t val_len)417 mbedtls_asn1_named_data *mbedtls_asn1_store_named_data(
418 mbedtls_asn1_named_data **head,
419 const char *oid, size_t oid_len,
420 const unsigned char *val,
421 size_t val_len )
422 {
423 mbedtls_asn1_named_data *cur;
424
425 if( ( cur = asn1_find_named_data( *head, oid, oid_len ) ) == NULL )
426 {
427 // Add new entry if not present yet based on OID
428 //
429 cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1,
430 sizeof(mbedtls_asn1_named_data) );
431 if( cur == NULL )
432 return( NULL );
433
434 cur->oid.len = oid_len;
435 cur->oid.p = mbedtls_calloc( 1, oid_len );
436 if( cur->oid.p == NULL )
437 {
438 mbedtls_free( cur );
439 return( NULL );
440 }
441
442 memcpy( cur->oid.p, oid, oid_len );
443
444 cur->val.len = val_len;
445 if( val_len != 0 )
446 {
447 cur->val.p = mbedtls_calloc( 1, val_len );
448 if( cur->val.p == NULL )
449 {
450 mbedtls_free( cur->oid.p );
451 mbedtls_free( cur );
452 return( NULL );
453 }
454 }
455
456 cur->next = *head;
457 *head = cur;
458 }
459 else if( val_len == 0 )
460 {
461 mbedtls_free( cur->val.p );
462 cur->val.p = NULL;
463 }
464 else if( cur->val.len != val_len )
465 {
466 /*
467 * Enlarge existing value buffer if needed
468 * Preserve old data until the allocation succeeded, to leave list in
469 * a consistent state in case allocation fails.
470 */
471 void *p = mbedtls_calloc( 1, val_len );
472 if( p == NULL )
473 return( NULL );
474
475 mbedtls_free( cur->val.p );
476 cur->val.p = p;
477 cur->val.len = val_len;
478 }
479
480 if( val != NULL && val_len != 0 )
481 memcpy( cur->val.p, val, val_len );
482
483 return( cur );
484 }
485 #endif /* MBEDTLS_ASN1_WRITE_C */
486