1 /*
2 * Privacy Enhanced Mail (PEM) decoding
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_PEM_PARSE_C) || defined(MBEDTLS_PEM_WRITE_C)
23
24 #include "mbedtls/pem.h"
25 #include "mbedtls/base64.h"
26 #include "mbedtls/des.h"
27 #include "mbedtls/aes.h"
28 #include "mbedtls/md5.h"
29 #include "mbedtls/cipher.h"
30 #include "mbedtls/platform_util.h"
31 #include "mbedtls/error.h"
32
33 #include <string.h>
34
35 #if defined(MBEDTLS_PLATFORM_C)
36 #include "mbedtls/platform.h"
37 #else
38 #include <stdlib.h>
39 #define mbedtls_calloc calloc
40 #define mbedtls_free free
41 #endif
42
43 #if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_init(mbedtls_pem_context * ctx)44 void mbedtls_pem_init( mbedtls_pem_context *ctx )
45 {
46 memset( ctx, 0, sizeof( mbedtls_pem_context ) );
47 }
48
49 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
50 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) )
51 /*
52 * Read a 16-byte hex string and convert it to binary
53 */
pem_get_iv(const unsigned char * s,unsigned char * iv,size_t iv_len)54 static int pem_get_iv( const unsigned char *s, unsigned char *iv,
55 size_t iv_len )
56 {
57 size_t i, j, k;
58
59 memset( iv, 0, iv_len );
60
61 for( i = 0; i < iv_len * 2; i++, s++ )
62 {
63 if( *s >= '0' && *s <= '9' ) j = *s - '0'; else
64 if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else
65 if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else
66 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV );
67
68 k = ( ( i & 1 ) != 0 ) ? j : j << 4;
69
70 iv[i >> 1] = (unsigned char)( iv[i >> 1] | k );
71 }
72
73 return( 0 );
74 }
75
pem_pbkdf1(unsigned char * key,size_t keylen,unsigned char * iv,const unsigned char * pwd,size_t pwdlen)76 static int pem_pbkdf1( unsigned char *key, size_t keylen,
77 unsigned char *iv,
78 const unsigned char *pwd, size_t pwdlen )
79 {
80 mbedtls_md5_context md5_ctx;
81 unsigned char md5sum[16];
82 size_t use_len;
83 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
84
85 mbedtls_md5_init( &md5_ctx );
86
87 /*
88 * key[ 0..15] = MD5(pwd || IV)
89 */
90 if( ( ret = mbedtls_md5_starts_ret( &md5_ctx ) ) != 0 )
91 goto exit;
92 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, pwd, pwdlen ) ) != 0 )
93 goto exit;
94 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, iv, 8 ) ) != 0 )
95 goto exit;
96 if( ( ret = mbedtls_md5_finish_ret( &md5_ctx, md5sum ) ) != 0 )
97 goto exit;
98
99 if( keylen <= 16 )
100 {
101 memcpy( key, md5sum, keylen );
102 goto exit;
103 }
104
105 memcpy( key, md5sum, 16 );
106
107 /*
108 * key[16..23] = MD5(key[ 0..15] || pwd || IV])
109 */
110 if( ( ret = mbedtls_md5_starts_ret( &md5_ctx ) ) != 0 )
111 goto exit;
112 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, md5sum, 16 ) ) != 0 )
113 goto exit;
114 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, pwd, pwdlen ) ) != 0 )
115 goto exit;
116 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, iv, 8 ) ) != 0 )
117 goto exit;
118 if( ( ret = mbedtls_md5_finish_ret( &md5_ctx, md5sum ) ) != 0 )
119 goto exit;
120
121 use_len = 16;
122 if( keylen < 32 )
123 use_len = keylen - 16;
124
125 memcpy( key + 16, md5sum, use_len );
126
127 exit:
128 mbedtls_md5_free( &md5_ctx );
129 mbedtls_platform_zeroize( md5sum, 16 );
130
131 return( ret );
132 }
133
134 #if defined(MBEDTLS_DES_C)
135 /*
136 * Decrypt with DES-CBC, using PBKDF1 for key derivation
137 */
pem_des_decrypt(unsigned char des_iv[8],unsigned char * buf,size_t buflen,const unsigned char * pwd,size_t pwdlen)138 static int pem_des_decrypt( unsigned char des_iv[8],
139 unsigned char *buf, size_t buflen,
140 const unsigned char *pwd, size_t pwdlen )
141 {
142 mbedtls_des_context des_ctx;
143 unsigned char des_key[8];
144 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
145
146 mbedtls_des_init( &des_ctx );
147
148 if( ( ret = pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen ) ) != 0 )
149 goto exit;
150
151 if( ( ret = mbedtls_des_setkey_dec( &des_ctx, des_key ) ) != 0 )
152 goto exit;
153 ret = mbedtls_des_crypt_cbc( &des_ctx, MBEDTLS_DES_DECRYPT, buflen,
154 des_iv, buf, buf );
155
156 exit:
157 mbedtls_des_free( &des_ctx );
158 mbedtls_platform_zeroize( des_key, 8 );
159
160 return( ret );
161 }
162
163 /*
164 * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
165 */
pem_des3_decrypt(unsigned char des3_iv[8],unsigned char * buf,size_t buflen,const unsigned char * pwd,size_t pwdlen)166 static int pem_des3_decrypt( unsigned char des3_iv[8],
167 unsigned char *buf, size_t buflen,
168 const unsigned char *pwd, size_t pwdlen )
169 {
170 mbedtls_des3_context des3_ctx;
171 unsigned char des3_key[24];
172 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
173
174 mbedtls_des3_init( &des3_ctx );
175
176 if( ( ret = pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen ) ) != 0 )
177 goto exit;
178
179 if( ( ret = mbedtls_des3_set3key_dec( &des3_ctx, des3_key ) ) != 0 )
180 goto exit;
181 ret = mbedtls_des3_crypt_cbc( &des3_ctx, MBEDTLS_DES_DECRYPT, buflen,
182 des3_iv, buf, buf );
183
184 exit:
185 mbedtls_des3_free( &des3_ctx );
186 mbedtls_platform_zeroize( des3_key, 24 );
187
188 return( ret );
189 }
190 #endif /* MBEDTLS_DES_C */
191
192 #if defined(MBEDTLS_AES_C)
193 /*
194 * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
195 */
pem_aes_decrypt(unsigned char aes_iv[16],unsigned int keylen,unsigned char * buf,size_t buflen,const unsigned char * pwd,size_t pwdlen)196 static int pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
197 unsigned char *buf, size_t buflen,
198 const unsigned char *pwd, size_t pwdlen )
199 {
200 mbedtls_aes_context aes_ctx;
201 unsigned char aes_key[32];
202 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
203
204 mbedtls_aes_init( &aes_ctx );
205
206 if( ( ret = pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen ) ) != 0 )
207 goto exit;
208
209 if( ( ret = mbedtls_aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 ) ) != 0 )
210 goto exit;
211 ret = mbedtls_aes_crypt_cbc( &aes_ctx, MBEDTLS_AES_DECRYPT, buflen,
212 aes_iv, buf, buf );
213
214 exit:
215 mbedtls_aes_free( &aes_ctx );
216 mbedtls_platform_zeroize( aes_key, keylen );
217
218 return( ret );
219 }
220 #endif /* MBEDTLS_AES_C */
221
222 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
223 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
224
mbedtls_pem_read_buffer(mbedtls_pem_context * ctx,const char * header,const char * footer,const unsigned char * data,const unsigned char * pwd,size_t pwdlen,size_t * use_len)225 int mbedtls_pem_read_buffer( mbedtls_pem_context *ctx, const char *header, const char *footer,
226 const unsigned char *data, const unsigned char *pwd,
227 size_t pwdlen, size_t *use_len )
228 {
229 int ret, enc;
230 size_t len;
231 unsigned char *buf;
232 const unsigned char *s1, *s2, *end;
233 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
234 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) )
235 unsigned char pem_iv[16];
236 mbedtls_cipher_type_t enc_alg = MBEDTLS_CIPHER_NONE;
237 #else
238 ((void) pwd);
239 ((void) pwdlen);
240 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
241 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
242
243 if( ctx == NULL )
244 return( MBEDTLS_ERR_PEM_BAD_INPUT_DATA );
245
246 s1 = (unsigned char *) strstr( (const char *) data, header );
247
248 if( s1 == NULL )
249 return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT );
250
251 s2 = (unsigned char *) strstr( (const char *) data, footer );
252
253 if( s2 == NULL || s2 <= s1 )
254 return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT );
255
256 s1 += strlen( header );
257 if( *s1 == ' ' ) s1++;
258 if( *s1 == '\r' ) s1++;
259 if( *s1 == '\n' ) s1++;
260 else return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT );
261
262 end = s2;
263 end += strlen( footer );
264 if( *end == ' ' ) end++;
265 if( *end == '\r' ) end++;
266 if( *end == '\n' ) end++;
267 *use_len = end - data;
268
269 enc = 0;
270
271 if( s2 - s1 >= 22 && memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
272 {
273 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
274 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) )
275 enc++;
276
277 s1 += 22;
278 if( *s1 == '\r' ) s1++;
279 if( *s1 == '\n' ) s1++;
280 else return( MBEDTLS_ERR_PEM_INVALID_DATA );
281
282
283 #if defined(MBEDTLS_DES_C)
284 if( s2 - s1 >= 23 && memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
285 {
286 enc_alg = MBEDTLS_CIPHER_DES_EDE3_CBC;
287
288 s1 += 23;
289 if( s2 - s1 < 16 || pem_get_iv( s1, pem_iv, 8 ) != 0 )
290 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV );
291
292 s1 += 16;
293 }
294 else if( s2 - s1 >= 18 && memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
295 {
296 enc_alg = MBEDTLS_CIPHER_DES_CBC;
297
298 s1 += 18;
299 if( s2 - s1 < 16 || pem_get_iv( s1, pem_iv, 8) != 0 )
300 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV );
301
302 s1 += 16;
303 }
304 #endif /* MBEDTLS_DES_C */
305
306 #if defined(MBEDTLS_AES_C)
307 if( s2 - s1 >= 14 && memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
308 {
309 if( s2 - s1 < 22 )
310 return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG );
311 else if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
312 enc_alg = MBEDTLS_CIPHER_AES_128_CBC;
313 else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
314 enc_alg = MBEDTLS_CIPHER_AES_192_CBC;
315 else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
316 enc_alg = MBEDTLS_CIPHER_AES_256_CBC;
317 else
318 return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG );
319
320 s1 += 22;
321 if( s2 - s1 < 32 || pem_get_iv( s1, pem_iv, 16 ) != 0 )
322 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV );
323
324 s1 += 32;
325 }
326 #endif /* MBEDTLS_AES_C */
327
328 if( enc_alg == MBEDTLS_CIPHER_NONE )
329 return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG );
330
331 if( *s1 == '\r' ) s1++;
332 if( *s1 == '\n' ) s1++;
333 else return( MBEDTLS_ERR_PEM_INVALID_DATA );
334 #else
335 return( MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE );
336 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
337 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
338 }
339
340 if( s1 >= s2 )
341 return( MBEDTLS_ERR_PEM_INVALID_DATA );
342
343 ret = mbedtls_base64_decode( NULL, 0, &len, s1, s2 - s1 );
344
345 if( ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER )
346 return( MBEDTLS_ERR_PEM_INVALID_DATA + ret );
347
348 if( ( buf = mbedtls_calloc( 1, len ) ) == NULL )
349 return( MBEDTLS_ERR_PEM_ALLOC_FAILED );
350
351 if( ( ret = mbedtls_base64_decode( buf, len, &len, s1, s2 - s1 ) ) != 0 )
352 {
353 mbedtls_platform_zeroize( buf, len );
354 mbedtls_free( buf );
355 return( MBEDTLS_ERR_PEM_INVALID_DATA + ret );
356 }
357
358 if( enc != 0 )
359 {
360 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
361 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) )
362 if( pwd == NULL )
363 {
364 mbedtls_platform_zeroize( buf, len );
365 mbedtls_free( buf );
366 return( MBEDTLS_ERR_PEM_PASSWORD_REQUIRED );
367 }
368
369 ret = 0;
370
371 #if defined(MBEDTLS_DES_C)
372 if( enc_alg == MBEDTLS_CIPHER_DES_EDE3_CBC )
373 ret = pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
374 else if( enc_alg == MBEDTLS_CIPHER_DES_CBC )
375 ret = pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
376 #endif /* MBEDTLS_DES_C */
377
378 #if defined(MBEDTLS_AES_C)
379 if( enc_alg == MBEDTLS_CIPHER_AES_128_CBC )
380 ret = pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
381 else if( enc_alg == MBEDTLS_CIPHER_AES_192_CBC )
382 ret = pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
383 else if( enc_alg == MBEDTLS_CIPHER_AES_256_CBC )
384 ret = pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
385 #endif /* MBEDTLS_AES_C */
386
387 if( ret != 0 )
388 {
389 mbedtls_free( buf );
390 return( ret );
391 }
392
393 /*
394 * The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3
395 * length bytes (allow 4 to be sure) in all known use cases.
396 *
397 * Use that as a heuristic to try to detect password mismatches.
398 */
399 if( len <= 2 || buf[0] != 0x30 || buf[1] > 0x83 )
400 {
401 mbedtls_platform_zeroize( buf, len );
402 mbedtls_free( buf );
403 return( MBEDTLS_ERR_PEM_PASSWORD_MISMATCH );
404 }
405 #else
406 mbedtls_platform_zeroize( buf, len );
407 mbedtls_free( buf );
408 return( MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE );
409 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
410 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
411 }
412
413 ctx->buf = buf;
414 ctx->buflen = len;
415
416 return( 0 );
417 }
418
mbedtls_pem_free(mbedtls_pem_context * ctx)419 void mbedtls_pem_free( mbedtls_pem_context *ctx )
420 {
421 if ( ctx->buf != NULL )
422 {
423 mbedtls_platform_zeroize( ctx->buf, ctx->buflen );
424 mbedtls_free( ctx->buf );
425 }
426 mbedtls_free( ctx->info );
427
428 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_pem_context ) );
429 }
430 #endif /* MBEDTLS_PEM_PARSE_C */
431
432 #if defined(MBEDTLS_PEM_WRITE_C)
mbedtls_pem_write_buffer(const char * header,const char * footer,const unsigned char * der_data,size_t der_len,unsigned char * buf,size_t buf_len,size_t * olen)433 int mbedtls_pem_write_buffer( const char *header, const char *footer,
434 const unsigned char *der_data, size_t der_len,
435 unsigned char *buf, size_t buf_len, size_t *olen )
436 {
437 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
438 unsigned char *encode_buf = NULL, *c, *p = buf;
439 size_t len = 0, use_len, add_len = 0;
440
441 mbedtls_base64_encode( NULL, 0, &use_len, der_data, der_len );
442 add_len = strlen( header ) + strlen( footer ) + ( use_len / 64 ) + 1;
443
444 if( use_len + add_len > buf_len )
445 {
446 *olen = use_len + add_len;
447 return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
448 }
449
450 if( use_len != 0 &&
451 ( ( encode_buf = mbedtls_calloc( 1, use_len ) ) == NULL ) )
452 return( MBEDTLS_ERR_PEM_ALLOC_FAILED );
453
454 if( ( ret = mbedtls_base64_encode( encode_buf, use_len, &use_len, der_data,
455 der_len ) ) != 0 )
456 {
457 mbedtls_free( encode_buf );
458 return( ret );
459 }
460
461 memcpy( p, header, strlen( header ) );
462 p += strlen( header );
463 c = encode_buf;
464
465 while( use_len )
466 {
467 len = ( use_len > 64 ) ? 64 : use_len;
468 memcpy( p, c, len );
469 use_len -= len;
470 p += len;
471 c += len;
472 *p++ = '\n';
473 }
474
475 memcpy( p, footer, strlen( footer ) );
476 p += strlen( footer );
477
478 *p++ = '\0';
479 *olen = p - buf;
480
481 /* Clean any remaining data previously written to the buffer */
482 memset( buf + *olen, 0, buf_len - *olen );
483
484 mbedtls_free( encode_buf );
485 return( 0 );
486 }
487 #endif /* MBEDTLS_PEM_WRITE_C */
488 #endif /* MBEDTLS_PEM_PARSE_C || MBEDTLS_PEM_WRITE_C */
489
490
