1 /* 2 * Privacy Enhanced Mail (PEM) decoding 3 * 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 5 * SPDX-License-Identifier: GPL-2.0 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License along 18 * with this program; if not, write to the Free Software Foundation, Inc., 19 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * This file is part of mbed TLS (https://tls.mbed.org) 22 */ 23 24 #if !defined(MBEDTLS_CONFIG_FILE) 25 #include "mbedtls/config.h" 26 #else 27 #include MBEDTLS_CONFIG_FILE 28 #endif 29 30 #if defined(MBEDTLS_PEM_PARSE_C) || defined(MBEDTLS_PEM_WRITE_C) 31 32 #include "mbedtls/pem.h" 33 #include "mbedtls/base64.h" 34 #include "mbedtls/des.h" 35 #include "mbedtls/aes.h" 36 #include "mbedtls/md5.h" 37 #include "mbedtls/cipher.h" 38 39 #include <string.h> 40 41 #if defined(MBEDTLS_PLATFORM_C) 42 #include "mbedtls/platform.h" 43 #else 44 #include <stdlib.h> 45 #define mbedtls_calloc calloc 46 #define mbedtls_free free 47 #endif 48 49 #if defined(MBEDTLS_PEM_PARSE_C) 50 /* Implementation that should never be optimized out by the compiler */ 51 static void mbedtls_zeroize( void *v, size_t n ) { 52 volatile unsigned char *p = v; while( n-- ) *p++ = 0; 53 } 54 55 void mbedtls_pem_init( mbedtls_pem_context *ctx ) 56 { 57 memset( ctx, 0, sizeof( mbedtls_pem_context ) ); 58 } 59 60 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ 61 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) 62 /* 63 * Read a 16-byte hex string and convert it to binary 64 */ 65 static int pem_get_iv( const unsigned char *s, unsigned char *iv, 66 size_t iv_len ) 67 { 68 size_t i, j, k; 69 70 memset( iv, 0, iv_len ); 71 72 for( i = 0; i < iv_len * 2; i++, s++ ) 73 { 74 if( *s >= '0' && *s <= '9' ) j = *s - '0'; else 75 if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else 76 if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else 77 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); 78 79 k = ( ( i & 1 ) != 0 ) ? j : j << 4; 80 81 iv[i >> 1] = (unsigned char)( iv[i >> 1] | k ); 82 } 83 84 return( 0 ); 85 } 86 87 static int pem_pbkdf1( unsigned char *key, size_t keylen, 88 unsigned char *iv, 89 const unsigned char *pwd, size_t pwdlen ) 90 { 91 mbedtls_md5_context md5_ctx; 92 unsigned char md5sum[16]; 93 size_t use_len; 94 int ret; 95 96 mbedtls_md5_init( &md5_ctx ); 97 98 /* 99 * key[ 0..15] = MD5(pwd || IV) 100 */ 101 if( ( ret = mbedtls_md5_starts_ret( &md5_ctx ) ) != 0 ) 102 goto exit; 103 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, pwd, pwdlen ) ) != 0 ) 104 goto exit; 105 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, iv, 8 ) ) != 0 ) 106 goto exit; 107 if( ( ret = mbedtls_md5_finish_ret( &md5_ctx, md5sum ) ) != 0 ) 108 goto exit; 109 110 if( keylen <= 16 ) 111 { 112 memcpy( key, md5sum, keylen ); 113 goto exit; 114 } 115 116 memcpy( key, md5sum, 16 ); 117 118 /* 119 * key[16..23] = MD5(key[ 0..15] || pwd || IV]) 120 */ 121 if( ( ret = mbedtls_md5_starts_ret( &md5_ctx ) ) != 0 ) 122 goto exit; 123 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, md5sum, 16 ) ) != 0 ) 124 goto exit; 125 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, pwd, pwdlen ) ) != 0 ) 126 goto exit; 127 if( ( ret = mbedtls_md5_update_ret( &md5_ctx, iv, 8 ) ) != 0 ) 128 goto exit; 129 if( ( ret = mbedtls_md5_finish_ret( &md5_ctx, md5sum ) ) != 0 ) 130 goto exit; 131 132 use_len = 16; 133 if( keylen < 32 ) 134 use_len = keylen - 16; 135 136 memcpy( key + 16, md5sum, use_len ); 137 138 exit: 139 mbedtls_md5_free( &md5_ctx ); 140 mbedtls_zeroize( md5sum, 16 ); 141 142 return( ret ); 143 } 144 145 #if defined(MBEDTLS_DES_C) 146 /* 147 * Decrypt with DES-CBC, using PBKDF1 for key derivation 148 */ 149 static int pem_des_decrypt( unsigned char des_iv[8], 150 unsigned char *buf, size_t buflen, 151 const unsigned char *pwd, size_t pwdlen ) 152 { 153 mbedtls_des_context des_ctx; 154 unsigned char des_key[8]; 155 int ret; 156 157 mbedtls_des_init( &des_ctx ); 158 159 if( ( ret = pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen ) ) != 0 ) 160 goto exit; 161 162 if( ( ret = mbedtls_des_setkey_dec( &des_ctx, des_key ) ) != 0 ) 163 goto exit; 164 ret = mbedtls_des_crypt_cbc( &des_ctx, MBEDTLS_DES_DECRYPT, buflen, 165 des_iv, buf, buf ); 166 167 exit: 168 mbedtls_des_free( &des_ctx ); 169 mbedtls_zeroize( des_key, 8 ); 170 171 return( ret ); 172 } 173 174 /* 175 * Decrypt with 3DES-CBC, using PBKDF1 for key derivation 176 */ 177 static 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; 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 if( ( ret = mbedtls_des3_set3key_dec( &des3_ctx, des3_key ) ) != 0 ) 191 goto exit; 192 ret = mbedtls_des3_crypt_cbc( &des3_ctx, MBEDTLS_DES_DECRYPT, buflen, 193 des3_iv, buf, buf ); 194 195 exit: 196 mbedtls_des3_free( &des3_ctx ); 197 mbedtls_zeroize( des3_key, 24 ); 198 199 return( ret ); 200 } 201 #endif /* MBEDTLS_DES_C */ 202 203 #if defined(MBEDTLS_AES_C) 204 /* 205 * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation 206 */ 207 static int pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen, 208 unsigned char *buf, size_t buflen, 209 const unsigned char *pwd, size_t pwdlen ) 210 { 211 mbedtls_aes_context aes_ctx; 212 unsigned char aes_key[32]; 213 int ret; 214 215 mbedtls_aes_init( &aes_ctx ); 216 217 if( ( ret = pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen ) ) != 0 ) 218 goto exit; 219 220 if( ( ret = mbedtls_aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 ) ) != 0 ) 221 goto exit; 222 ret = mbedtls_aes_crypt_cbc( &aes_ctx, MBEDTLS_AES_DECRYPT, buflen, 223 aes_iv, buf, buf ); 224 225 exit: 226 mbedtls_aes_free( &aes_ctx ); 227 mbedtls_zeroize( aes_key, keylen ); 228 229 return( ret ); 230 } 231 #endif /* MBEDTLS_AES_C */ 232 233 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && 234 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ 235 236 int mbedtls_pem_read_buffer( mbedtls_pem_context *ctx, const char *header, const char *footer, 237 const unsigned char *data, const unsigned char *pwd, 238 size_t pwdlen, size_t *use_len ) 239 { 240 int ret, enc; 241 size_t len; 242 unsigned char *buf; 243 const unsigned char *s1, *s2, *end; 244 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ 245 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) 246 unsigned char pem_iv[16]; 247 mbedtls_cipher_type_t enc_alg = MBEDTLS_CIPHER_NONE; 248 #else 249 ((void) pwd); 250 ((void) pwdlen); 251 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && 252 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ 253 254 if( ctx == NULL ) 255 return( MBEDTLS_ERR_PEM_BAD_INPUT_DATA ); 256 257 s1 = (unsigned char *) strstr( (const char *) data, header ); 258 259 if( s1 == NULL ) 260 return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT ); 261 262 s2 = (unsigned char *) strstr( (const char *) data, footer ); 263 264 if( s2 == NULL || s2 <= s1 ) 265 return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT ); 266 267 s1 += strlen( header ); 268 if( *s1 == ' ' ) s1++; 269 if( *s1 == '\r' ) s1++; 270 if( *s1 == '\n' ) s1++; 271 else return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT ); 272 273 end = s2; 274 end += strlen( footer ); 275 if( *end == ' ' ) end++; 276 if( *end == '\r' ) end++; 277 if( *end == '\n' ) end++; 278 *use_len = end - data; 279 280 enc = 0; 281 282 if( s2 - s1 >= 22 && memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 ) 283 { 284 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ 285 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) 286 enc++; 287 288 s1 += 22; 289 if( *s1 == '\r' ) s1++; 290 if( *s1 == '\n' ) s1++; 291 else return( MBEDTLS_ERR_PEM_INVALID_DATA ); 292 293 294 #if defined(MBEDTLS_DES_C) 295 if( s2 - s1 >= 23 && memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 ) 296 { 297 enc_alg = MBEDTLS_CIPHER_DES_EDE3_CBC; 298 299 s1 += 23; 300 if( s2 - s1 < 16 || pem_get_iv( s1, pem_iv, 8 ) != 0 ) 301 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); 302 303 s1 += 16; 304 } 305 else if( s2 - s1 >= 18 && memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 ) 306 { 307 enc_alg = MBEDTLS_CIPHER_DES_CBC; 308 309 s1 += 18; 310 if( s2 - s1 < 16 || pem_get_iv( s1, pem_iv, 8) != 0 ) 311 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); 312 313 s1 += 16; 314 } 315 #endif /* MBEDTLS_DES_C */ 316 317 #if defined(MBEDTLS_AES_C) 318 if( s2 - s1 >= 14 && memcmp( s1, "DEK-Info: AES-", 14 ) == 0 ) 319 { 320 if( s2 - s1 < 22 ) 321 return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG ); 322 else if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 ) 323 enc_alg = MBEDTLS_CIPHER_AES_128_CBC; 324 else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 ) 325 enc_alg = MBEDTLS_CIPHER_AES_192_CBC; 326 else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 ) 327 enc_alg = MBEDTLS_CIPHER_AES_256_CBC; 328 else 329 return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG ); 330 331 s1 += 22; 332 if( s2 - s1 < 32 || pem_get_iv( s1, pem_iv, 16 ) != 0 ) 333 return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); 334 335 s1 += 32; 336 } 337 #endif /* MBEDTLS_AES_C */ 338 339 if( enc_alg == MBEDTLS_CIPHER_NONE ) 340 return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG ); 341 342 if( *s1 == '\r' ) s1++; 343 if( *s1 == '\n' ) s1++; 344 else return( MBEDTLS_ERR_PEM_INVALID_DATA ); 345 #else 346 return( MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE ); 347 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && 348 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ 349 } 350 351 if( s1 >= s2 ) 352 return( MBEDTLS_ERR_PEM_INVALID_DATA ); 353 354 ret = mbedtls_base64_decode( NULL, 0, &len, s1, s2 - s1 ); 355 356 if( ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER ) 357 return( MBEDTLS_ERR_PEM_INVALID_DATA + ret ); 358 359 if( ( buf = mbedtls_calloc( 1, len ) ) == NULL ) 360 return( MBEDTLS_ERR_PEM_ALLOC_FAILED ); 361 362 if( ( ret = mbedtls_base64_decode( buf, len, &len, s1, s2 - s1 ) ) != 0 ) 363 { 364 mbedtls_zeroize( buf, len ); 365 mbedtls_free( buf ); 366 return( MBEDTLS_ERR_PEM_INVALID_DATA + ret ); 367 } 368 369 if( enc != 0 ) 370 { 371 #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ 372 ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) 373 if( pwd == NULL ) 374 { 375 mbedtls_zeroize( buf, len ); 376 mbedtls_free( buf ); 377 return( MBEDTLS_ERR_PEM_PASSWORD_REQUIRED ); 378 } 379 380 ret = 0; 381 382 #if defined(MBEDTLS_DES_C) 383 if( enc_alg == MBEDTLS_CIPHER_DES_EDE3_CBC ) 384 ret = pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen ); 385 else if( enc_alg == MBEDTLS_CIPHER_DES_CBC ) 386 ret = pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen ); 387 #endif /* MBEDTLS_DES_C */ 388 389 #if defined(MBEDTLS_AES_C) 390 if( enc_alg == MBEDTLS_CIPHER_AES_128_CBC ) 391 ret = pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen ); 392 else if( enc_alg == MBEDTLS_CIPHER_AES_192_CBC ) 393 ret = pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen ); 394 else if( enc_alg == MBEDTLS_CIPHER_AES_256_CBC ) 395 ret = pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen ); 396 #endif /* MBEDTLS_AES_C */ 397 398 if( ret != 0 ) 399 { 400 mbedtls_free( buf ); 401 return( ret ); 402 } 403 404 /* 405 * The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3 406 * length bytes (allow 4 to be sure) in all known use cases. 407 * 408 * Use that as heurisitic to try detecting password mismatchs. 409 */ 410 if( len <= 2 || buf[0] != 0x30 || buf[1] > 0x83 ) 411 { 412 mbedtls_zeroize( buf, len ); 413 mbedtls_free( buf ); 414 return( MBEDTLS_ERR_PEM_PASSWORD_MISMATCH ); 415 } 416 #else 417 mbedtls_zeroize( buf, len ); 418 mbedtls_free( buf ); 419 return( MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE ); 420 #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && 421 ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ 422 } 423 424 ctx->buf = buf; 425 ctx->buflen = len; 426 427 return( 0 ); 428 } 429 430 void mbedtls_pem_free( mbedtls_pem_context *ctx ) 431 { 432 if( ctx->buf != NULL ) 433 mbedtls_zeroize( ctx->buf, ctx->buflen ); 434 mbedtls_free( ctx->buf ); 435 mbedtls_free( ctx->info ); 436 437 mbedtls_zeroize( ctx, sizeof( mbedtls_pem_context ) ); 438 } 439 #endif /* MBEDTLS_PEM_PARSE_C */ 440 441 #if defined(MBEDTLS_PEM_WRITE_C) 442 int mbedtls_pem_write_buffer( const char *header, const char *footer, 443 const unsigned char *der_data, size_t der_len, 444 unsigned char *buf, size_t buf_len, size_t *olen ) 445 { 446 int ret; 447 unsigned char *encode_buf = NULL, *c, *p = buf; 448 size_t len = 0, use_len, add_len = 0; 449 450 mbedtls_base64_encode( NULL, 0, &use_len, der_data, der_len ); 451 add_len = strlen( header ) + strlen( footer ) + ( use_len / 64 ) + 1; 452 453 if( use_len + add_len > buf_len ) 454 { 455 *olen = use_len + add_len; 456 return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL ); 457 } 458 459 if( use_len != 0 && 460 ( ( encode_buf = mbedtls_calloc( 1, use_len ) ) == NULL ) ) 461 return( MBEDTLS_ERR_PEM_ALLOC_FAILED ); 462 463 if( ( ret = mbedtls_base64_encode( encode_buf, use_len, &use_len, der_data, 464 der_len ) ) != 0 ) 465 { 466 mbedtls_free( encode_buf ); 467 return( ret ); 468 } 469 470 memcpy( p, header, strlen( header ) ); 471 p += strlen( header ); 472 c = encode_buf; 473 474 while( use_len ) 475 { 476 len = ( use_len > 64 ) ? 64 : use_len; 477 memcpy( p, c, len ); 478 use_len -= len; 479 p += len; 480 c += len; 481 *p++ = '\n'; 482 } 483 484 memcpy( p, footer, strlen( footer ) ); 485 p += strlen( footer ); 486 487 *p++ = '\0'; 488 *olen = p - buf; 489 490 mbedtls_free( encode_buf ); 491 return( 0 ); 492 } 493 #endif /* MBEDTLS_PEM_WRITE_C */ 494 #endif /* MBEDTLS_PEM_PARSE_C || MBEDTLS_PEM_WRITE_C */ 495