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) 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 */ 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 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 */ 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 */ 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 */ 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 ) */ 224 225 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_ERROR_ADD( 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_ERROR_ADD( 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 } 418 419 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) 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