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) 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 */ 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 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 */ 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 */ 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 */ 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) 244 static int pem_check_pkcs_padding(unsigned char *input, size_t input_len, size_t *data_len) 245 { 246 /* input_len > 0 is not guaranteed by mbedtls_pem_read_buffer(). */ 247 if (input_len < 1) { 248 return MBEDTLS_ERR_PEM_INVALID_DATA; 249 } 250 size_t pad_len = input[input_len - 1]; 251 size_t i; 252 253 if (pad_len > input_len) { 254 return MBEDTLS_ERR_PEM_PASSWORD_MISMATCH; 255 } 256 257 *data_len = input_len - pad_len; 258 259 for (i = *data_len; i < input_len; i++) { 260 if (input[i] != pad_len) { 261 return MBEDTLS_ERR_PEM_PASSWORD_MISMATCH; 262 } 263 } 264 265 return 0; 266 } 267 #endif /* MBEDTLS_DES_C || MBEDTLS_AES_C */ 268 269 #endif /* PEM_RFC1421 */ 270 271 int mbedtls_pem_read_buffer(mbedtls_pem_context *ctx, const char *header, const char *footer, 272 const unsigned char *data, const unsigned char *pwd, 273 size_t pwdlen, size_t *use_len) 274 { 275 int ret, enc; 276 size_t len; 277 unsigned char *buf; 278 const unsigned char *s1, *s2, *end; 279 #if defined(PEM_RFC1421) 280 unsigned char pem_iv[16]; 281 mbedtls_cipher_type_t enc_alg = MBEDTLS_CIPHER_NONE; 282 #else 283 ((void) pwd); 284 ((void) pwdlen); 285 #endif /* PEM_RFC1421 */ 286 287 if (ctx == NULL) { 288 return MBEDTLS_ERR_PEM_BAD_INPUT_DATA; 289 } 290 291 s1 = (unsigned char *) strstr((const char *) data, header); 292 293 if (s1 == NULL) { 294 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT; 295 } 296 297 s2 = (unsigned char *) strstr((const char *) data, footer); 298 299 if (s2 == NULL || s2 <= s1) { 300 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT; 301 } 302 303 s1 += strlen(header); 304 if (*s1 == ' ') { 305 s1++; 306 } 307 if (*s1 == '\r') { 308 s1++; 309 } 310 if (*s1 == '\n') { 311 s1++; 312 } else { 313 return MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT; 314 } 315 316 end = s2; 317 end += strlen(footer); 318 if (*end == ' ') { 319 end++; 320 } 321 if (*end == '\r') { 322 end++; 323 } 324 if (*end == '\n') { 325 end++; 326 } 327 *use_len = (size_t) (end - data); 328 329 enc = 0; 330 331 if (s2 - s1 >= 22 && memcmp(s1, "Proc-Type: 4,ENCRYPTED", 22) == 0) { 332 #if defined(PEM_RFC1421) 333 enc++; 334 335 s1 += 22; 336 if (*s1 == '\r') { 337 s1++; 338 } 339 if (*s1 == '\n') { 340 s1++; 341 } else { 342 return MBEDTLS_ERR_PEM_INVALID_DATA; 343 } 344 345 346 #if defined(MBEDTLS_DES_C) 347 if (s2 - s1 >= 23 && memcmp(s1, "DEK-Info: DES-EDE3-CBC,", 23) == 0) { 348 enc_alg = MBEDTLS_CIPHER_DES_EDE3_CBC; 349 350 s1 += 23; 351 if (s2 - s1 < 16 || pem_get_iv(s1, pem_iv, 8) != 0) { 352 return MBEDTLS_ERR_PEM_INVALID_ENC_IV; 353 } 354 355 s1 += 16; 356 } else if (s2 - s1 >= 18 && memcmp(s1, "DEK-Info: DES-CBC,", 18) == 0) { 357 enc_alg = MBEDTLS_CIPHER_DES_CBC; 358 359 s1 += 18; 360 if (s2 - s1 < 16 || pem_get_iv(s1, pem_iv, 8) != 0) { 361 return MBEDTLS_ERR_PEM_INVALID_ENC_IV; 362 } 363 364 s1 += 16; 365 } 366 #endif /* MBEDTLS_DES_C */ 367 368 #if defined(MBEDTLS_AES_C) 369 if (s2 - s1 >= 14 && memcmp(s1, "DEK-Info: AES-", 14) == 0) { 370 if (s2 - s1 < 22) { 371 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG; 372 } else if (memcmp(s1, "DEK-Info: AES-128-CBC,", 22) == 0) { 373 enc_alg = MBEDTLS_CIPHER_AES_128_CBC; 374 } else if (memcmp(s1, "DEK-Info: AES-192-CBC,", 22) == 0) { 375 enc_alg = MBEDTLS_CIPHER_AES_192_CBC; 376 } else if (memcmp(s1, "DEK-Info: AES-256-CBC,", 22) == 0) { 377 enc_alg = MBEDTLS_CIPHER_AES_256_CBC; 378 } else { 379 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG; 380 } 381 382 s1 += 22; 383 if (s2 - s1 < 32 || pem_get_iv(s1, pem_iv, 16) != 0) { 384 return MBEDTLS_ERR_PEM_INVALID_ENC_IV; 385 } 386 387 s1 += 32; 388 } 389 #endif /* MBEDTLS_AES_C */ 390 391 if (enc_alg == MBEDTLS_CIPHER_NONE) { 392 return MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG; 393 } 394 395 if (*s1 == '\r') { 396 s1++; 397 } 398 if (*s1 == '\n') { 399 s1++; 400 } else { 401 return MBEDTLS_ERR_PEM_INVALID_DATA; 402 } 403 #else 404 return MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE; 405 #endif /* PEM_RFC1421 */ 406 } 407 408 if (s1 >= s2) { 409 return MBEDTLS_ERR_PEM_INVALID_DATA; 410 } 411 412 ret = mbedtls_base64_decode(NULL, 0, &len, s1, (size_t) (s2 - s1)); 413 414 if (ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER) { 415 return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret); 416 } 417 418 if (len == 0) { 419 return MBEDTLS_ERR_PEM_BAD_INPUT_DATA; 420 } 421 422 if ((buf = mbedtls_calloc(1, len)) == NULL) { 423 return MBEDTLS_ERR_PEM_ALLOC_FAILED; 424 } 425 426 if ((ret = mbedtls_base64_decode(buf, len, &len, s1, (size_t) (s2 - s1))) != 0) { 427 mbedtls_zeroize_and_free(buf, len); 428 return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PEM_INVALID_DATA, ret); 429 } 430 431 if (enc != 0) { 432 #if defined(PEM_RFC1421) 433 if (pwd == NULL) { 434 mbedtls_zeroize_and_free(buf, len); 435 return MBEDTLS_ERR_PEM_PASSWORD_REQUIRED; 436 } 437 438 ret = 0; 439 440 #if defined(MBEDTLS_DES_C) 441 if (enc_alg == MBEDTLS_CIPHER_DES_EDE3_CBC) { 442 ret = pem_des3_decrypt(pem_iv, buf, len, pwd, pwdlen); 443 } else if (enc_alg == MBEDTLS_CIPHER_DES_CBC) { 444 ret = pem_des_decrypt(pem_iv, buf, len, pwd, pwdlen); 445 } 446 #endif /* MBEDTLS_DES_C */ 447 448 #if defined(MBEDTLS_AES_C) 449 if (enc_alg == MBEDTLS_CIPHER_AES_128_CBC) { 450 ret = pem_aes_decrypt(pem_iv, 16, buf, len, pwd, pwdlen); 451 } else if (enc_alg == MBEDTLS_CIPHER_AES_192_CBC) { 452 ret = pem_aes_decrypt(pem_iv, 24, buf, len, pwd, pwdlen); 453 } else if (enc_alg == MBEDTLS_CIPHER_AES_256_CBC) { 454 ret = pem_aes_decrypt(pem_iv, 32, buf, len, pwd, pwdlen); 455 } 456 #endif /* MBEDTLS_AES_C */ 457 458 if (ret != 0) { 459 mbedtls_zeroize_and_free(buf, len); 460 return ret; 461 } 462 463 /* Check PKCS padding and update data length based on padding info. 464 * This can be used to detect invalid padding data and password 465 * mismatches. */ 466 size_t unpadded_len; 467 ret = pem_check_pkcs_padding(buf, len, &unpadded_len); 468 if (ret != 0) { 469 mbedtls_zeroize_and_free(buf, len); 470 return ret; 471 } 472 len = unpadded_len; 473 #else 474 mbedtls_zeroize_and_free(buf, len); 475 return MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE; 476 #endif /* PEM_RFC1421 */ 477 } 478 479 ctx->buf = buf; 480 ctx->buflen = len; 481 482 return 0; 483 } 484 485 void mbedtls_pem_free(mbedtls_pem_context *ctx) 486 { 487 if (ctx == NULL) { 488 return; 489 } 490 491 if (ctx->buf != NULL) { 492 mbedtls_zeroize_and_free(ctx->buf, ctx->buflen); 493 } 494 mbedtls_free(ctx->info); 495 496 mbedtls_platform_zeroize(ctx, sizeof(mbedtls_pem_context)); 497 } 498 #endif /* MBEDTLS_PEM_PARSE_C */ 499 500 #if defined(MBEDTLS_PEM_WRITE_C) 501 int mbedtls_pem_write_buffer(const char *header, const char *footer, 502 const unsigned char *der_data, size_t der_len, 503 unsigned char *buf, size_t buf_len, size_t *olen) 504 { 505 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 506 unsigned char *encode_buf = NULL, *c, *p = buf; 507 size_t len = 0, use_len, add_len = 0; 508 509 mbedtls_base64_encode(NULL, 0, &use_len, der_data, der_len); 510 add_len = strlen(header) + strlen(footer) + (((use_len > 2) ? (use_len - 2) : 0) / 64) + 1; 511 512 if (use_len + add_len > buf_len) { 513 *olen = use_len + add_len; 514 return MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL; 515 } 516 517 if (use_len != 0 && 518 ((encode_buf = mbedtls_calloc(1, use_len)) == NULL)) { 519 return MBEDTLS_ERR_PEM_ALLOC_FAILED; 520 } 521 522 if ((ret = mbedtls_base64_encode(encode_buf, use_len, &use_len, der_data, 523 der_len)) != 0) { 524 mbedtls_free(encode_buf); 525 return ret; 526 } 527 528 memcpy(p, header, strlen(header)); 529 p += strlen(header); 530 c = encode_buf; 531 532 while (use_len) { 533 len = (use_len > 64) ? 64 : use_len; 534 memcpy(p, c, len); 535 use_len -= len; 536 p += len; 537 c += len; 538 *p++ = '\n'; 539 } 540 541 memcpy(p, footer, strlen(footer)); 542 p += strlen(footer); 543 544 *p++ = '\0'; 545 *olen = (size_t) (p - buf); 546 547 /* Clean any remaining data previously written to the buffer */ 548 memset(buf + *olen, 0, buf_len - *olen); 549 550 mbedtls_free(encode_buf); 551 return 0; 552 } 553 #endif /* MBEDTLS_PEM_WRITE_C */ 554 #endif /* MBEDTLS_PEM_PARSE_C || MBEDTLS_PEM_WRITE_C */ 555