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#include "mbedtls/platform.h"
36
37#if defined(MBEDTLS_PEM_PARSE_C)
38void mbedtls_pem_init(mbedtls_pem_context *ctx)
39{
40 memset(ctx, 0, sizeof(mbedtls_pem_context));
41}
42
43#if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
44 (defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C))
45/*
46 * Read a 16-byte hex string and convert it to binary
47 */
48static int pem_get_iv(const unsigned char *s, unsigned char *iv,
49 size_t iv_len)
50{
51 size_t i, j, k;
52
53 memset(iv, 0, iv_len);
54
55 for (i = 0; i < iv_len * 2; i++, s++) {
56 if (*s >= '0' && *s <= '9') {
57 j = *s - '0';
58 } else
59 if (*s >= 'A' && *s <= 'F') {
60 j = *s - '7';
61 } else
62 if (*s >= 'a' && *s <= 'f') {
63 j = *s - 'W';
64 } else {
65 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
66 }
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
76static 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 }
93 if ((ret = mbedtls_md5_update_ret(&md5_ctx, pwd, pwdlen)) != 0) {
94 goto exit;
95 }
96 if ((ret = mbedtls_md5_update_ret(&md5_ctx, iv, 8)) != 0) {
97 goto exit;
98 }
99 if ((ret = mbedtls_md5_finish_ret(&md5_ctx, md5sum)) != 0) {
100 goto exit;
101 }
102
103 if (keylen <= 16) {
104 memcpy(key, md5sum, keylen);
105 goto exit;
106 }
107
108 memcpy(key, md5sum, 16);
109
110 /*
111 * key[16..23] = MD5(key[ 0..15] || pwd || IV])
112 */
113 if ((ret = mbedtls_md5_starts_ret(&md5_ctx)) != 0) {
114 goto exit;
115 }
116 if ((ret = mbedtls_md5_update_ret(&md5_ctx, md5sum, 16)) != 0) {
117 goto exit;
118 }
119 if ((ret = mbedtls_md5_update_ret(&md5_ctx, pwd, pwdlen)) != 0) {
120 goto exit;
121 }
122 if ((ret = mbedtls_md5_update_ret(&md5_ctx, iv, 8)) != 0) {
123 goto exit;
124 }
125 if ((ret = mbedtls_md5_finish_ret(&md5_ctx, md5sum)) != 0) {
126 goto exit;
127 }
128
129 use_len = 16;
130 if (keylen < 32) {
131 use_len = keylen - 16;
132 }
133
134 memcpy(key + 16, md5sum, use_len);
135
136exit:
137 mbedtls_md5_free(&md5_ctx);
138 mbedtls_platform_zeroize(md5sum, 16);
139
140 return ret;
141}
142
143#if defined(MBEDTLS_DES_C)
144/*
145 * Decrypt with DES-CBC, using PBKDF1 for key derivation
146 */
147static int pem_des_decrypt(unsigned char des_iv[8],
148 unsigned char *buf, size_t buflen,
149 const unsigned char *pwd, size_t pwdlen)
150{
151 mbedtls_des_context des_ctx;
152 unsigned char des_key[8];
153 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
154
155 mbedtls_des_init(&des_ctx);
156
157 if ((ret = pem_pbkdf1(des_key, 8, des_iv, pwd, pwdlen)) != 0) {
158 goto exit;
159 }
160
161 if ((ret = mbedtls_des_setkey_dec(&des_ctx, des_key)) != 0) {
162 goto exit;
163 }
164 ret = mbedtls_des_crypt_cbc(&des_ctx, MBEDTLS_DES_DECRYPT, buflen,
165 des_iv, buf, buf);
166
167exit:
168 mbedtls_des_free(&des_ctx);
169 mbedtls_platform_zeroize(des_key, 8);
170
171 return ret;
172}
173
174/*
175 * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
176 */
177static int pem_des3_decrypt(unsigned char des3_iv[8],
178 unsigned char *buf, size_t buflen,
179 const unsigned char *pwd, size_t pwdlen)
180{
181 mbedtls_des3_context des3_ctx;
182 unsigned char des3_key[24];
183 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
184
185 mbedtls_des3_init(&des3_ctx);
186
187 if ((ret = pem_pbkdf1(des3_key, 24, des3_iv, pwd, pwdlen)) != 0) {
188 goto exit;
189 }
190
191 if ((ret = mbedtls_des3_set3key_dec(&des3_ctx, des3_key)) != 0) {
192 goto exit;
193 }
194 ret = mbedtls_des3_crypt_cbc(&des3_ctx, MBEDTLS_DES_DECRYPT, buflen,
195 des3_iv, buf, buf);
196
197exit:
198 mbedtls_des3_free(&des3_ctx);
199 mbedtls_platform_zeroize(des3_key, 24);
200
201 return ret;
202}
203#endif /* MBEDTLS_DES_C */
204
205#if defined(MBEDTLS_AES_C)
206/*
207 * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
208 */
209static int pem_aes_decrypt(unsigned char aes_iv[16], unsigned int keylen,
210 unsigned char *buf, size_t buflen,
211 const unsigned char *pwd, size_t pwdlen)
212{
213 mbedtls_aes_context aes_ctx;
214 unsigned char aes_key[32];
215 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
216
217 mbedtls_aes_init(&aes_ctx);
218
219 if ((ret = pem_pbkdf1(aes_key, keylen, aes_iv, pwd, pwdlen)) != 0) {
220 goto exit;
221 }
222
223 if ((ret = mbedtls_aes_setkey_dec(&aes_ctx, aes_key, keylen * 8)) != 0) {
224 goto exit;
225 }
226 ret = mbedtls_aes_crypt_cbc(&aes_ctx, MBEDTLS_AES_DECRYPT, buflen,
227 aes_iv, buf, buf);
228
229exit:
230 mbedtls_aes_free(&aes_ctx);
231 mbedtls_platform_zeroize(aes_key, keylen);
232
233 return ret;
234}
235#endif /* MBEDTLS_AES_C */
236
237#endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
238 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
239
240int mbedtls_pem_read_buffer(mbedtls_pem_context *ctx, const char *header, const char *footer,
241 const unsigned char *data, const unsigned char *pwd,
242 size_t pwdlen, size_t *use_len)
243{
244 int ret, enc;
245 size_t len;
246 unsigned char *buf;
247 const unsigned char *s1, *s2, *end;
248#if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
249 (defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C))
250 unsigned char pem_iv[16];
251 mbedtls_cipher_type_t enc_alg = MBEDTLS_CIPHER_NONE;
252#else
253 ((void) pwd);
254 ((void) pwdlen);
255#endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
256 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
257
258 if (ctx == NULL) {
259 return MBEDTLS_ERR_PEM_BAD_INPUT_DATA;
260 }
261
262 s1 = (unsigned char *) strstr((const char *) data, header);
263
264 if (s1 == NULL) {
265 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
266 }
267
268 s2 = (unsigned char *) strstr((const char *) data, footer);
269
270 if (s2 == NULL || s2 <= s1) {
271 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
272 }
273
274 s1 += strlen(header);
275 if (*s1 == ' ') {
276 s1++;
277 }
278 if (*s1 == '\r') {
279 s1++;
280 }
281 if (*s1 == '\n') {
282 s1++;
283 } else {
284 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
285 }
286
287 end = s2;
288 end += strlen(footer);
289 if (*end == ' ') {
290 end++;
291 }
292 if (*end == '\r') {
293 end++;
294 }
295 if (*end == '\n') {
296 end++;
297 }
298 *use_len = end - data;
299
300 enc = 0;
301
302 if (s2 - s1 >= 22 && memcmp(s1, "Proc-Type: 4,ENCRYPTED", 22) == 0) {
303#if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
304 (defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C))
305 enc++;
306
307 s1 += 22;
308 if (*s1 == '\r') {
309 s1++;
310 }
311 if (*s1 == '\n') {
312 s1++;
313 } else {
314 return MBEDTLS_ERR_PEM_INVALID_DATA;
315 }
316
317
318#if defined(MBEDTLS_DES_C)
319 if (s2 - s1 >= 23 && memcmp(s1, "DEK-Info: DES-EDE3-CBC,", 23) == 0) {
320 enc_alg = MBEDTLS_CIPHER_DES_EDE3_CBC;
321
322 s1 += 23;
323 if (s2 - s1 < 16 || pem_get_iv(s1, pem_iv, 8) != 0) {
324 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
325 }
326
327 s1 += 16;
328 } else if (s2 - s1 >= 18 && memcmp(s1, "DEK-Info: DES-CBC,", 18) == 0) {
329 enc_alg = MBEDTLS_CIPHER_DES_CBC;
330
331 s1 += 18;
332 if (s2 - s1 < 16 || pem_get_iv(s1, pem_iv, 8) != 0) {
333 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
334 }
335
336 s1 += 16;
337 }
338#endif /* MBEDTLS_DES_C */
339
340#if defined(MBEDTLS_AES_C)
341 if (s2 - s1 >= 14 && memcmp(s1, "DEK-Info: AES-", 14) == 0) {
342 if (s2 - s1 < 22) {
343 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG;
344 } else if (memcmp(s1, "DEK-Info: AES-128-CBC,", 22) == 0) {
345 enc_alg = MBEDTLS_CIPHER_AES_128_CBC;
346 } else if (memcmp(s1, "DEK-Info: AES-192-CBC,", 22) == 0) {
347 enc_alg = MBEDTLS_CIPHER_AES_192_CBC;
348 } else if (memcmp(s1, "DEK-Info: AES-256-CBC,", 22) == 0) {
349 enc_alg = MBEDTLS_CIPHER_AES_256_CBC;
350 } else {
351 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG;
352 }
353
354 s1 += 22;
355 if (s2 - s1 < 32 || pem_get_iv(s1, pem_iv, 16) != 0) {
356 return MBEDTLS_ERR_PEM_INVALID_ENC_IV;
357 }
358
359 s1 += 32;
360 }
361#endif /* MBEDTLS_AES_C */
362
363 if (enc_alg == MBEDTLS_CIPHER_NONE) {
364 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG;
365 }
366
367 if (*s1 == '\r') {
368 s1++;
369 }
370 if (*s1 == '\n') {
371 s1++;
372 } else {
373 return MBEDTLS_ERR_PEM_INVALID_DATA;
374 }
375#else
376 return MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE;
377#endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
378 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
379 }
380
381 if (s1 >= s2) {
382 return MBEDTLS_ERR_PEM_INVALID_DATA;
383 }
384
385 ret = mbedtls_base64_decode(NULL, 0, &len, s1, s2 - s1);
386
387 if (ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER) {
388 return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret);
389 }
390
391 if ((buf = mbedtls_calloc(1, len)) == NULL) {
392 return MBEDTLS_ERR_PEM_ALLOC_FAILED;
393 }
394
395 if ((ret = mbedtls_base64_decode(buf, len, &len, s1, s2 - s1)) != 0) {
396 mbedtls_platform_zeroize(buf, len);
397 mbedtls_free(buf);
398 return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret);
399 }
400
401 if (enc != 0) {
402#if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \
403 (defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C))
404 if (pwd == NULL) {
405 mbedtls_platform_zeroize(buf, len);
406 mbedtls_free(buf);
407 return MBEDTLS_ERR_PEM_PASSWORD_REQUIRED;
408 }
409
410 ret = 0;
411
412#if defined(MBEDTLS_DES_C)
413 if (enc_alg == MBEDTLS_CIPHER_DES_EDE3_CBC) {
414 ret = pem_des3_decrypt(pem_iv, buf, len, pwd, pwdlen);
415 } else if (enc_alg == MBEDTLS_CIPHER_DES_CBC) {
416 ret = pem_des_decrypt(pem_iv, buf, len, pwd, pwdlen);
417 }
418#endif /* MBEDTLS_DES_C */
419
420#if defined(MBEDTLS_AES_C)
421 if (enc_alg == MBEDTLS_CIPHER_AES_128_CBC) {
422 ret = pem_aes_decrypt(pem_iv, 16, buf, len, pwd, pwdlen);
423 } else if (enc_alg == MBEDTLS_CIPHER_AES_192_CBC) {
424 ret = pem_aes_decrypt(pem_iv, 24, buf, len, pwd, pwdlen);
425 } else if (enc_alg == MBEDTLS_CIPHER_AES_256_CBC) {
426 ret = pem_aes_decrypt(pem_iv, 32, buf, len, pwd, pwdlen);
427 }
428#endif /* MBEDTLS_AES_C */
429
430 if (ret != 0) {
431 mbedtls_free(buf);
432 return ret;
433 }
434
435 /*
436 * The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3
437 * length bytes (allow 4 to be sure) in all known use cases.
438 *
439 * Use that as a heuristic to try to detect password mismatches.
440 */
441 if (len <= 2 || buf[0] != 0x30 || buf[1] > 0x83) {
442 mbedtls_platform_zeroize(buf, len);
443 mbedtls_free(buf);
444 return MBEDTLS_ERR_PEM_PASSWORD_MISMATCH;
445 }
446#else
447 mbedtls_platform_zeroize(buf, len);
448 mbedtls_free(buf);
449 return MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE;
450#endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC &&
451 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */
452 }
453
454 ctx->buf = buf;
455 ctx->buflen = len;
456
457 return 0;
458}
459
460void mbedtls_pem_free(mbedtls_pem_context *ctx)
461{
462 if (ctx->buf != NULL) {
463 mbedtls_platform_zeroize(ctx->buf, ctx->buflen);
464 mbedtls_free(ctx->buf);
465 }
466 mbedtls_free(ctx->info);
467
468 mbedtls_platform_zeroize(ctx, sizeof(mbedtls_pem_context));
469}
470#endif /* MBEDTLS_PEM_PARSE_C */
471
472#if defined(MBEDTLS_PEM_WRITE_C)
473int mbedtls_pem_write_buffer(const char *header, const char *footer,
474 const unsigned char *der_data, size_t der_len,
475 unsigned char *buf, size_t buf_len, size_t *olen)
476{
477 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
478 unsigned char *encode_buf = NULL, *c, *p = buf;
479 size_t len = 0, use_len, add_len = 0;
480
481 mbedtls_base64_encode(NULL, 0, &use_len, der_data, der_len);
482 add_len = strlen(header) + strlen(footer) + (use_len / 64) + 1;
483
484 if (use_len + add_len > buf_len) {
485 *olen = use_len + add_len;
486 return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
487 }
488
489 if (use_len != 0 &&
490 ((encode_buf = mbedtls_calloc(1, use_len)) == NULL)) {
491 return MBEDTLS_ERR_PEM_ALLOC_FAILED;
492 }
493
494 if ((ret = mbedtls_base64_encode(encode_buf, use_len, &use_len, der_data,
495 der_len)) != 0) {
496 mbedtls_free(encode_buf);
497 return ret;
498 }
499
500 memcpy(p, header, strlen(header));
501 p += strlen(header);
502 c = encode_buf;
503
504 while (use_len) {
505 len = (use_len > 64) ? 64 : use_len;
506 memcpy(p, c, len);
507 use_len -= len;
508 p += len;
509 c += len;
510 *p++ = '\n';
511 }
512
513 memcpy(p, footer, strlen(footer));
514 p += strlen(footer);
515
516 *p++ = '\0';
517 *olen = p - buf;
518
519 /* Clean any remaining data previously written to the buffer */
520 memset(buf + *olen, 0, buf_len - *olen);
521
522 mbedtls_free(encode_buf);
523 return 0;
524}
525#endif /* MBEDTLS_PEM_WRITE_C */
526#endif /* MBEDTLS_PEM_PARSE_C || MBEDTLS_PEM_WRITE_C */
527