1 /*
2 * Privacy Enhanced Mail (PEM) decoding
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 */
7
8 #include "common.h"
9
10 #if defined(MBEDTLS_PEM_PARSE_C) || defined(MBEDTLS_PEM_WRITE_C)
11
12 #include "mbedtls/pem.h"
13 #include "mbedtls/base64.h"
14 #include "mbedtls/des.h"
15 #include "mbedtls/aes.h"
16 #include "mbedtls/md.h"
17 #include "mbedtls/cipher.h"
18 #include "mbedtls/platform_util.h"
19 #include "mbedtls/error.h"
20
21 #include <string.h>
22
23 #include "mbedtls/platform.h"
24
25 #if defined(MBEDTLS_USE_PSA_CRYPTO)
26 #include "psa/crypto.h"
27 #endif
28
29 #if defined(MBEDTLS_MD_CAN_MD5) && \
30 defined(MBEDTLS_CIPHER_MODE_CBC) && \
31 (defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C))
32 #define PEM_RFC1421
33 #endif /* MBEDTLS_MD_CAN_MD5 &&
34 MBEDTLS_CIPHER_MODE_CBC &&
35 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
36
37 #if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_init(mbedtls_pem_context * ctx)38 void mbedtls_pem_init(mbedtls_pem_context *ctx)
39 {
40 memset(ctx, 0, sizeof(mbedtls_pem_context));
41 }
42
43 #if defined(PEM_RFC1421)
44 /*
45 * Read a 16-byte hex string and convert it to binary
46 */
pem_get_iv(const unsigned char * s,unsigned char * iv,size_t iv_len)47 static int pem_get_iv(const unsigned char *s, unsigned char *iv,
48 size_t iv_len)
49 {
50 size_t i, j, k;
51
52 memset(iv, 0, iv_len);
53
54 for (i = 0; i < iv_len * 2; i++, s++) {
55 if (*s >= '0' && *s <= '9') {
56 j = *s - '0';
57 } else
58 if (*s >= 'A' && *s <= 'F') {
59 j = *s - '7';
60 } else
61 if (*s >= 'a' && *s <= 'f') {
62 j = *s - 'W';
63 } else {
64 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
65 }
66
67 k = ((i & 1) != 0) ? j : j << 4;
68
69 iv[i >> 1] = (unsigned char) (iv[i >> 1] | k);
70 }
71
72 return 0;
73 }
74
pem_pbkdf1(unsigned char * key,size_t keylen,unsigned char * iv,const unsigned char * pwd,size_t pwdlen)75 static int pem_pbkdf1(unsigned char *key, size_t keylen,
76 unsigned char *iv,
77 const unsigned char *pwd, size_t pwdlen)
78 {
79 mbedtls_md_context_t md5_ctx;
80 const mbedtls_md_info_t *md5_info;
81 unsigned char md5sum[16];
82 size_t use_len;
83 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
84
85 mbedtls_md_init(&md5_ctx);
86
87 /* Prepare the context. (setup() errors gracefully on NULL info.) */
88 md5_info = mbedtls_md_info_from_type(MBEDTLS_MD_MD5);
89 if ((ret = mbedtls_md_setup(&md5_ctx, md5_info, 0)) != 0) {
90 goto exit;
91 }
92
93 /*
94 * key[ 0..15] = MD5(pwd || IV)
95 */
96 if ((ret = mbedtls_md_starts(&md5_ctx)) != 0) {
97 goto exit;
98 }
99 if ((ret = mbedtls_md_update(&md5_ctx, pwd, pwdlen)) != 0) {
100 goto exit;
101 }
102 if ((ret = mbedtls_md_update(&md5_ctx, iv, 8)) != 0) {
103 goto exit;
104 }
105 if ((ret = mbedtls_md_finish(&md5_ctx, md5sum)) != 0) {
106 goto exit;
107 }
108
109 if (keylen <= 16) {
110 memcpy(key, md5sum, keylen);
111 goto exit;
112 }
113
114 memcpy(key, md5sum, 16);
115
116 /*
117 * key[16..23] = MD5(key[ 0..15] || pwd || IV])
118 */
119 if ((ret = mbedtls_md_starts(&md5_ctx)) != 0) {
120 goto exit;
121 }
122 if ((ret = mbedtls_md_update(&md5_ctx, md5sum, 16)) != 0) {
123 goto exit;
124 }
125 if ((ret = mbedtls_md_update(&md5_ctx, pwd, pwdlen)) != 0) {
126 goto exit;
127 }
128 if ((ret = mbedtls_md_update(&md5_ctx, iv, 8)) != 0) {
129 goto exit;
130 }
131 if ((ret = mbedtls_md_finish(&md5_ctx, md5sum)) != 0) {
132 goto exit;
133 }
134
135 use_len = 16;
136 if (keylen < 32) {
137 use_len = keylen - 16;
138 }
139
140 memcpy(key + 16, md5sum, use_len);
141
142 exit:
143 mbedtls_md_free(&md5_ctx);
144 mbedtls_platform_zeroize(md5sum, 16);
145
146 return ret;
147 }
148
149 #if defined(MBEDTLS_DES_C)
150 /*
151 * Decrypt with DES-CBC, using PBKDF1 for key derivation
152 */
pem_des_decrypt(unsigned char des_iv[8],unsigned char * buf,size_t buflen,const unsigned char * pwd,size_t pwdlen)153 static int pem_des_decrypt(unsigned char des_iv[8],
154 unsigned char *buf, size_t buflen,
155 const unsigned char *pwd, size_t pwdlen)
156 {
157 mbedtls_des_context des_ctx;
158 unsigned char des_key[8];
159 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
160
161 mbedtls_des_init(&des_ctx);
162
163 if ((ret = pem_pbkdf1(des_key, 8, des_iv, pwd, pwdlen)) != 0) {
164 goto exit;
165 }
166
167 if ((ret = mbedtls_des_setkey_dec(&des_ctx, des_key)) != 0) {
168 goto exit;
169 }
170 ret = mbedtls_des_crypt_cbc(&des_ctx, MBEDTLS_DES_DECRYPT, buflen,
171 des_iv, buf, buf);
172
173 exit:
174 mbedtls_des_free(&des_ctx);
175 mbedtls_platform_zeroize(des_key, 8);
176
177 return ret;
178 }
179
180 /*
181 * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
182 */
pem_des3_decrypt(unsigned char des3_iv[8],unsigned char * buf,size_t buflen,const unsigned char * pwd,size_t pwdlen)183 static int pem_des3_decrypt(unsigned char des3_iv[8],
184 unsigned char *buf, size_t buflen,
185 const unsigned char *pwd, size_t pwdlen)
186 {
187 mbedtls_des3_context des3_ctx;
188 unsigned char des3_key[24];
189 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
190
191 mbedtls_des3_init(&des3_ctx);
192
193 if ((ret = pem_pbkdf1(des3_key, 24, des3_iv, pwd, pwdlen)) != 0) {
194 goto exit;
195 }
196
197 if ((ret = mbedtls_des3_set3key_dec(&des3_ctx, des3_key)) != 0) {
198 goto exit;
199 }
200 ret = mbedtls_des3_crypt_cbc(&des3_ctx, MBEDTLS_DES_DECRYPT, buflen,
201 des3_iv, buf, buf);
202
203 exit:
204 mbedtls_des3_free(&des3_ctx);
205 mbedtls_platform_zeroize(des3_key, 24);
206
207 return ret;
208 }
209 #endif /* MBEDTLS_DES_C */
210
211 #if defined(MBEDTLS_AES_C)
212 /*
213 * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
214 */
pem_aes_decrypt(unsigned char aes_iv[16],unsigned int keylen,unsigned char * buf,size_t buflen,const unsigned char * pwd,size_t pwdlen)215 static int pem_aes_decrypt(unsigned char aes_iv[16], unsigned int keylen,
216 unsigned char *buf, size_t buflen,
217 const unsigned char *pwd, size_t pwdlen)
218 {
219 mbedtls_aes_context aes_ctx;
220 unsigned char aes_key[32];
221 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
222
223 mbedtls_aes_init(&aes_ctx);
224
225 if ((ret = pem_pbkdf1(aes_key, keylen, aes_iv, pwd, pwdlen)) != 0) {
226 goto exit;
227 }
228
229 if ((ret = mbedtls_aes_setkey_dec(&aes_ctx, aes_key, keylen * 8)) != 0) {
230 goto exit;
231 }
232 ret = mbedtls_aes_crypt_cbc(&aes_ctx, MBEDTLS_AES_DECRYPT, buflen,
233 aes_iv, buf, buf);
234
235 exit:
236 mbedtls_aes_free(&aes_ctx);
237 mbedtls_platform_zeroize(aes_key, keylen);
238
239 return ret;
240 }
241 #endif /* MBEDTLS_AES_C */
242
243 #if defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C)
pem_check_pkcs_padding(unsigned char * input,size_t input_len,size_t * data_len)244 static int pem_check_pkcs_padding(unsigned char *input, size_t input_len, size_t *data_len)
245 {
246 /* input_len > 0 is guaranteed by mbedtls_pem_read_buffer(). */
247 size_t pad_len = input[input_len - 1];
248 size_t i;
249
250 if (pad_len > input_len) {
251 return MBEDTLS_ERR_PEM_PASSWORD_MISMATCH;
252 }
253
254 *data_len = input_len - pad_len;
255
256 for (i = *data_len; i < input_len; i++) {
257 if (input[i] != pad_len) {
258 return MBEDTLS_ERR_PEM_PASSWORD_MISMATCH;
259 }
260 }
261
262 return 0;
263 }
264 #endif /* MBEDTLS_DES_C || MBEDTLS_AES_C */
265
266 #endif /* PEM_RFC1421 */
267
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)268 int mbedtls_pem_read_buffer(mbedtls_pem_context *ctx, const char *header, const char *footer,
269 const unsigned char *data, const unsigned char *pwd,
270 size_t pwdlen, size_t *use_len)
271 {
272 int ret, enc;
273 size_t len;
274 unsigned char *buf;
275 const unsigned char *s1, *s2, *end;
276 #if defined(PEM_RFC1421)
277 unsigned char pem_iv[16];
278 mbedtls_cipher_type_t enc_alg = MBEDTLS_CIPHER_NONE;
279 #else
280 ((void) pwd);
281 ((void) pwdlen);
282 #endif /* PEM_RFC1421 */
283
284 if (ctx == NULL) {
285 return MBEDTLS_ERR_PEM_BAD_INPUT_DATA;
286 }
287
288 s1 = (unsigned char *) strstr((const char *) data, header);
289
290 if (s1 == NULL) {
291 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
292 }
293
294 s2 = (unsigned char *) strstr((const char *) data, footer);
295
296 if (s2 == NULL || s2 <= s1) {
297 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
298 }
299
300 s1 += strlen(header);
301 if (*s1 == ' ') {
302 s1++;
303 }
304 if (*s1 == '\r') {
305 s1++;
306 }
307 if (*s1 == '\n') {
308 s1++;
309 } else {
310 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
311 }
312
313 end = s2;
314 end += strlen(footer);
315 if (*end == ' ') {
316 end++;
317 }
318 if (*end == '\r') {
319 end++;
320 }
321 if (*end == '\n') {
322 end++;
323 }
324 *use_len = (size_t) (end - data);
325
326 enc = 0;
327
328 if (s2 - s1 >= 22 && memcmp(s1, "Proc-Type: 4,ENCRYPTED", 22) == 0) {
329 #if defined(PEM_RFC1421)
330 enc++;
331
332 s1 += 22;
333 if (*s1 == '\r') {
334 s1++;
335 }
336 if (*s1 == '\n') {
337 s1++;
338 } else {
339 return MBEDTLS_ERR_PEM_INVALID_DATA;
340 }
341
342
343 #if defined(MBEDTLS_DES_C)
344 if (s2 - s1 >= 23 && memcmp(s1, "DEK-Info: DES-EDE3-CBC,", 23) == 0) {
345 enc_alg = MBEDTLS_CIPHER_DES_EDE3_CBC;
346
347 s1 += 23;
348 if (s2 - s1 < 16 || pem_get_iv(s1, pem_iv, 8) != 0) {
349 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
350 }
351
352 s1 += 16;
353 } else if (s2 - s1 >= 18 && memcmp(s1, "DEK-Info: DES-CBC,", 18) == 0) {
354 enc_alg = MBEDTLS_CIPHER_DES_CBC;
355
356 s1 += 18;
357 if (s2 - s1 < 16 || pem_get_iv(s1, pem_iv, 8) != 0) {
358 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
359 }
360
361 s1 += 16;
362 }
363 #endif /* MBEDTLS_DES_C */
364
365 #if defined(MBEDTLS_AES_C)
366 if (s2 - s1 >= 14 && memcmp(s1, "DEK-Info: AES-", 14) == 0) {
367 if (s2 - s1 < 22) {
368 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG;
369 } else if (memcmp(s1, "DEK-Info: AES-128-CBC,", 22) == 0) {
370 enc_alg = MBEDTLS_CIPHER_AES_128_CBC;
371 } else if (memcmp(s1, "DEK-Info: AES-192-CBC,", 22) == 0) {
372 enc_alg = MBEDTLS_CIPHER_AES_192_CBC;
373 } else if (memcmp(s1, "DEK-Info: AES-256-CBC,", 22) == 0) {
374 enc_alg = MBEDTLS_CIPHER_AES_256_CBC;
375 } else {
376 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG;
377 }
378
379 s1 += 22;
380 if (s2 - s1 < 32 || pem_get_iv(s1, pem_iv, 16) != 0) {
381 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
382 }
383
384 s1 += 32;
385 }
386 #endif /* MBEDTLS_AES_C */
387
388 if (enc_alg == MBEDTLS_CIPHER_NONE) {
389 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG;
390 }
391
392 if (*s1 == '\r') {
393 s1++;
394 }
395 if (*s1 == '\n') {
396 s1++;
397 } else {
398 return MBEDTLS_ERR_PEM_INVALID_DATA;
399 }
400 #else
401 return MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE;
402 #endif /* PEM_RFC1421 */
403 }
404
405 if (s1 >= s2) {
406 return MBEDTLS_ERR_PEM_INVALID_DATA;
407 }
408
409 ret = mbedtls_base64_decode(NULL, 0, &len, s1, (size_t) (s2 - s1));
410
411 if (ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER) {
412 return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret);
413 }
414
415 if (len == 0) {
416 return MBEDTLS_ERR_PEM_BAD_INPUT_DATA;
417 }
418
419 if ((buf = mbedtls_calloc(1, len)) == NULL) {
420 return MBEDTLS_ERR_PEM_ALLOC_FAILED;
421 }
422
423 if ((ret = mbedtls_base64_decode(buf, len, &len, s1, (size_t) (s2 - s1))) != 0) {
424 mbedtls_zeroize_and_free(buf, len);
425 return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret);
426 }
427
428 if (enc != 0) {
429 #if defined(PEM_RFC1421)
430 if (pwd == NULL) {
431 mbedtls_zeroize_and_free(buf, len);
432 return MBEDTLS_ERR_PEM_PASSWORD_REQUIRED;
433 }
434
435 ret = 0;
436
437 #if defined(MBEDTLS_DES_C)
438 if (enc_alg == MBEDTLS_CIPHER_DES_EDE3_CBC) {
439 ret = pem_des3_decrypt(pem_iv, buf, len, pwd, pwdlen);
440 } else if (enc_alg == MBEDTLS_CIPHER_DES_CBC) {
441 ret = pem_des_decrypt(pem_iv, buf, len, pwd, pwdlen);
442 }
443 #endif /* MBEDTLS_DES_C */
444
445 #if defined(MBEDTLS_AES_C)
446 if (enc_alg == MBEDTLS_CIPHER_AES_128_CBC) {
447 ret = pem_aes_decrypt(pem_iv, 16, buf, len, pwd, pwdlen);
448 } else if (enc_alg == MBEDTLS_CIPHER_AES_192_CBC) {
449 ret = pem_aes_decrypt(pem_iv, 24, buf, len, pwd, pwdlen);
450 } else if (enc_alg == MBEDTLS_CIPHER_AES_256_CBC) {
451 ret = pem_aes_decrypt(pem_iv, 32, buf, len, pwd, pwdlen);
452 }
453 #endif /* MBEDTLS_AES_C */
454
455 if (ret != 0) {
456 mbedtls_zeroize_and_free(buf, len);
457 return ret;
458 }
459
460 /* Check PKCS padding and update data length based on padding info.
461 * This can be used to detect invalid padding data and password
462 * mismatches. */
463 size_t unpadded_len;
464 ret = pem_check_pkcs_padding(buf, len, &unpadded_len);
465 if (ret != 0) {
466 mbedtls_zeroize_and_free(buf, len);
467 return ret;
468 }
469 len = unpadded_len;
470 #else
471 mbedtls_zeroize_and_free(buf, len);
472 return MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE;
473 #endif /* PEM_RFC1421 */
474 }
475
476 ctx->buf = buf;
477 ctx->buflen = len;
478
479 return 0;
480 }
481
mbedtls_pem_free(mbedtls_pem_context * ctx)482 void mbedtls_pem_free(mbedtls_pem_context *ctx)
483 {
484 if (ctx->buf != NULL) {
485 mbedtls_zeroize_and_free(ctx->buf, ctx->buflen);
486 }
487 mbedtls_free(ctx->info);
488
489 mbedtls_platform_zeroize(ctx, sizeof(mbedtls_pem_context));
490 }
491 #endif /* MBEDTLS_PEM_PARSE_C */
492
493 #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)494 int mbedtls_pem_write_buffer(const char *header, const char *footer,
495 const unsigned char *der_data, size_t der_len,
496 unsigned char *buf, size_t buf_len, size_t *olen)
497 {
498 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
499 unsigned char *encode_buf = NULL, *c, *p = buf;
500 size_t len = 0, use_len, add_len = 0;
501
502 mbedtls_base64_encode(NULL, 0, &use_len, der_data, der_len);
503 add_len = strlen(header) + strlen(footer) + (((use_len > 2) ? (use_len - 2) : 0) / 64) + 1;
504
505 if (use_len + add_len > buf_len) {
506 *olen = use_len + add_len;
507 return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
508 }
509
510 if (use_len != 0 &&
511 ((encode_buf = mbedtls_calloc(1, use_len)) == NULL)) {
512 return MBEDTLS_ERR_PEM_ALLOC_FAILED;
513 }
514
515 if ((ret = mbedtls_base64_encode(encode_buf, use_len, &use_len, der_data,
516 der_len)) != 0) {
517 mbedtls_free(encode_buf);
518 return ret;
519 }
520
521 memcpy(p, header, strlen(header));
522 p += strlen(header);
523 c = encode_buf;
524
525 while (use_len) {
526 len = (use_len > 64) ? 64 : use_len;
527 memcpy(p, c, len);
528 use_len -= len;
529 p += len;
530 c += len;
531 *p++ = '\n';
532 }
533
534 memcpy(p, footer, strlen(footer));
535 p += strlen(footer);
536
537 *p++ = '\0';
538 *olen = (size_t) (p - buf);
539
540 /* Clean any remaining data previously written to the buffer */
541 memset(buf + *olen, 0, buf_len - *olen);
542
543 mbedtls_free(encode_buf);
544 return 0;
545 }
546 #endif /* MBEDTLS_PEM_WRITE_C */
547 #endif /* MBEDTLS_PEM_PARSE_C || MBEDTLS_PEM_WRITE_C */
548
