/* * Privacy Enhanced Mail (PEM) decoding * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "common.h" #if defined(MBEDTLS_PEM_PARSE_C) || defined(MBEDTLS_PEM_WRITE_C) #include "mbedtls/pem.h" #include "mbedtls/base64.h" #include "mbedtls/des.h" #include "mbedtls/aes.h" #include "mbedtls/md5.h" #include "mbedtls/cipher.h" #include "mbedtls/platform_util.h" #include "mbedtls/error.h" #include <string.h> #if defined(MBEDTLS_PLATFORM_C) #include "mbedtls/platform.h" #else #include <stdlib.h> #define mbedtls_calloc calloc #define mbedtls_free free #endif #if defined(MBEDTLS_PEM_PARSE_C) void mbedtls_pem_init( mbedtls_pem_context *ctx ) { memset( ctx, 0, sizeof( mbedtls_pem_context ) ); } #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) /* * Read a 16-byte hex string and convert it to binary */ static int pem_get_iv( const unsigned char *s, unsigned char *iv, size_t iv_len ) { size_t i, j, k; memset( iv, 0, iv_len ); for( i = 0; i < iv_len * 2; i++, s++ ) { if( *s >= '0' && *s <= '9' ) j = *s - '0'; else if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); k = ( ( i & 1 ) != 0 ) ? j : j << 4; iv[i >> 1] = (unsigned char)( iv[i >> 1] | k ); } return( 0 ); } static int pem_pbkdf1( unsigned char *key, size_t keylen, unsigned char *iv, const unsigned char *pwd, size_t pwdlen ) { mbedtls_md5_context md5_ctx; unsigned char md5sum[16]; size_t use_len; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_md5_init( &md5_ctx ); /* * key[ 0..15] = MD5(pwd || IV) */ if( ( ret = mbedtls_md5_starts_ret( &md5_ctx ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_update_ret( &md5_ctx, pwd, pwdlen ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_update_ret( &md5_ctx, iv, 8 ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_finish_ret( &md5_ctx, md5sum ) ) != 0 ) goto exit; if( keylen <= 16 ) { memcpy( key, md5sum, keylen ); goto exit; } memcpy( key, md5sum, 16 ); /* * key[16..23] = MD5(key[ 0..15] || pwd || IV]) */ if( ( ret = mbedtls_md5_starts_ret( &md5_ctx ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_update_ret( &md5_ctx, md5sum, 16 ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_update_ret( &md5_ctx, pwd, pwdlen ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_update_ret( &md5_ctx, iv, 8 ) ) != 0 ) goto exit; if( ( ret = mbedtls_md5_finish_ret( &md5_ctx, md5sum ) ) != 0 ) goto exit; use_len = 16; if( keylen < 32 ) use_len = keylen - 16; memcpy( key + 16, md5sum, use_len ); exit: mbedtls_md5_free( &md5_ctx ); mbedtls_platform_zeroize( md5sum, 16 ); return( ret ); } #if defined(MBEDTLS_DES_C) /* * Decrypt with DES-CBC, using PBKDF1 for key derivation */ static int pem_des_decrypt( unsigned char des_iv[8], unsigned char *buf, size_t buflen, const unsigned char *pwd, size_t pwdlen ) { mbedtls_des_context des_ctx; unsigned char des_key[8]; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_des_init( &des_ctx ); if( ( ret = pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen ) ) != 0 ) goto exit; if( ( ret = mbedtls_des_setkey_dec( &des_ctx, des_key ) ) != 0 ) goto exit; ret = mbedtls_des_crypt_cbc( &des_ctx, MBEDTLS_DES_DECRYPT, buflen, des_iv, buf, buf ); exit: mbedtls_des_free( &des_ctx ); mbedtls_platform_zeroize( des_key, 8 ); return( ret ); } /* * Decrypt with 3DES-CBC, using PBKDF1 for key derivation */ static int pem_des3_decrypt( unsigned char des3_iv[8], unsigned char *buf, size_t buflen, const unsigned char *pwd, size_t pwdlen ) { mbedtls_des3_context des3_ctx; unsigned char des3_key[24]; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_des3_init( &des3_ctx ); if( ( ret = pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen ) ) != 0 ) goto exit; if( ( ret = mbedtls_des3_set3key_dec( &des3_ctx, des3_key ) ) != 0 ) goto exit; ret = mbedtls_des3_crypt_cbc( &des3_ctx, MBEDTLS_DES_DECRYPT, buflen, des3_iv, buf, buf ); exit: mbedtls_des3_free( &des3_ctx ); mbedtls_platform_zeroize( des3_key, 24 ); return( ret ); } #endif /* MBEDTLS_DES_C */ #if defined(MBEDTLS_AES_C) /* * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation */ static int pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen, unsigned char *buf, size_t buflen, const unsigned char *pwd, size_t pwdlen ) { mbedtls_aes_context aes_ctx; unsigned char aes_key[32]; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_aes_init( &aes_ctx ); if( ( ret = pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen ) ) != 0 ) goto exit; if( ( ret = mbedtls_aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 ) ) != 0 ) goto exit; ret = mbedtls_aes_crypt_cbc( &aes_ctx, MBEDTLS_AES_DECRYPT, buflen, aes_iv, buf, buf ); exit: mbedtls_aes_free( &aes_ctx ); mbedtls_platform_zeroize( aes_key, keylen ); return( ret ); } #endif /* MBEDTLS_AES_C */ #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ int 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 ) { int ret, enc; size_t len; unsigned char *buf; const unsigned char *s1, *s2, *end; #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) unsigned char pem_iv[16]; mbedtls_cipher_type_t enc_alg = MBEDTLS_CIPHER_NONE; #else ((void) pwd); ((void) pwdlen); #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ if( ctx == NULL ) return( MBEDTLS_ERR_PEM_BAD_INPUT_DATA ); s1 = (unsigned char *) strstr( (const char *) data, header ); if( s1 == NULL ) return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT ); s2 = (unsigned char *) strstr( (const char *) data, footer ); if( s2 == NULL || s2 <= s1 ) return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT ); s1 += strlen( header ); if( *s1 == ' ' ) s1++; if( *s1 == '\r' ) s1++; if( *s1 == '\n' ) s1++; else return( MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT ); end = s2; end += strlen( footer ); if( *end == ' ' ) end++; if( *end == '\r' ) end++; if( *end == '\n' ) end++; *use_len = end - data; enc = 0; if( s2 - s1 >= 22 && memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 ) { #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) enc++; s1 += 22; if( *s1 == '\r' ) s1++; if( *s1 == '\n' ) s1++; else return( MBEDTLS_ERR_PEM_INVALID_DATA ); #if defined(MBEDTLS_DES_C) if( s2 - s1 >= 23 && memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 ) { enc_alg = MBEDTLS_CIPHER_DES_EDE3_CBC; s1 += 23; if( s2 - s1 < 16 || pem_get_iv( s1, pem_iv, 8 ) != 0 ) return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); s1 += 16; } else if( s2 - s1 >= 18 && memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 ) { enc_alg = MBEDTLS_CIPHER_DES_CBC; s1 += 18; if( s2 - s1 < 16 || pem_get_iv( s1, pem_iv, 8) != 0 ) return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); s1 += 16; } #endif /* MBEDTLS_DES_C */ #if defined(MBEDTLS_AES_C) if( s2 - s1 >= 14 && memcmp( s1, "DEK-Info: AES-", 14 ) == 0 ) { if( s2 - s1 < 22 ) return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG ); else if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 ) enc_alg = MBEDTLS_CIPHER_AES_128_CBC; else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 ) enc_alg = MBEDTLS_CIPHER_AES_192_CBC; else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 ) enc_alg = MBEDTLS_CIPHER_AES_256_CBC; else return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG ); s1 += 22; if( s2 - s1 < 32 || pem_get_iv( s1, pem_iv, 16 ) != 0 ) return( MBEDTLS_ERR_PEM_INVALID_ENC_IV ); s1 += 32; } #endif /* MBEDTLS_AES_C */ if( enc_alg == MBEDTLS_CIPHER_NONE ) return( MBEDTLS_ERR_PEM_UNKNOWN_ENC_ALG ); if( *s1 == '\r' ) s1++; if( *s1 == '\n' ) s1++; else return( MBEDTLS_ERR_PEM_INVALID_DATA ); #else return( MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE ); #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ } if( s1 >= s2 ) return( MBEDTLS_ERR_PEM_INVALID_DATA ); ret = mbedtls_base64_decode( NULL, 0, &len, s1, s2 - s1 ); if( ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER ) return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PEM_INVALID_DATA, ret ) ); if( ( buf = mbedtls_calloc( 1, len ) ) == NULL ) return( MBEDTLS_ERR_PEM_ALLOC_FAILED ); if( ( ret = mbedtls_base64_decode( buf, len, &len, s1, s2 - s1 ) ) != 0 ) { mbedtls_platform_zeroize( buf, len ); mbedtls_free( buf ); return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PEM_INVALID_DATA, ret ) ); } if( enc != 0 ) { #if defined(MBEDTLS_MD5_C) && defined(MBEDTLS_CIPHER_MODE_CBC) && \ ( defined(MBEDTLS_DES_C) || defined(MBEDTLS_AES_C) ) if( pwd == NULL ) { mbedtls_platform_zeroize( buf, len ); mbedtls_free( buf ); return( MBEDTLS_ERR_PEM_PASSWORD_REQUIRED ); } ret = 0; #if defined(MBEDTLS_DES_C) if( enc_alg == MBEDTLS_CIPHER_DES_EDE3_CBC ) ret = pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen ); else if( enc_alg == MBEDTLS_CIPHER_DES_CBC ) ret = pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen ); #endif /* MBEDTLS_DES_C */ #if defined(MBEDTLS_AES_C) if( enc_alg == MBEDTLS_CIPHER_AES_128_CBC ) ret = pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen ); else if( enc_alg == MBEDTLS_CIPHER_AES_192_CBC ) ret = pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen ); else if( enc_alg == MBEDTLS_CIPHER_AES_256_CBC ) ret = pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen ); #endif /* MBEDTLS_AES_C */ if( ret != 0 ) { mbedtls_free( buf ); return( ret ); } /* * The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3 * length bytes (allow 4 to be sure) in all known use cases. * * Use that as a heuristic to try to detect password mismatches. */ if( len <= 2 || buf[0] != 0x30 || buf[1] > 0x83 ) { mbedtls_platform_zeroize( buf, len ); mbedtls_free( buf ); return( MBEDTLS_ERR_PEM_PASSWORD_MISMATCH ); } #else mbedtls_platform_zeroize( buf, len ); mbedtls_free( buf ); return( MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE ); #endif /* MBEDTLS_MD5_C && MBEDTLS_CIPHER_MODE_CBC && ( MBEDTLS_AES_C || MBEDTLS_DES_C ) */ } ctx->buf = buf; ctx->buflen = len; return( 0 ); } void mbedtls_pem_free( mbedtls_pem_context *ctx ) { if ( ctx->buf != NULL ) { mbedtls_platform_zeroize( ctx->buf, ctx->buflen ); mbedtls_free( ctx->buf ); } mbedtls_free( ctx->info ); mbedtls_platform_zeroize( ctx, sizeof( mbedtls_pem_context ) ); } #endif /* MBEDTLS_PEM_PARSE_C */ #if defined(MBEDTLS_PEM_WRITE_C) int 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 ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *encode_buf = NULL, *c, *p = buf; size_t len = 0, use_len, add_len = 0; mbedtls_base64_encode( NULL, 0, &use_len, der_data, der_len ); add_len = strlen( header ) + strlen( footer ) + ( use_len / 64 ) + 1; if( use_len + add_len > buf_len ) { *olen = use_len + add_len; return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL ); } if( use_len != 0 && ( ( encode_buf = mbedtls_calloc( 1, use_len ) ) == NULL ) ) return( MBEDTLS_ERR_PEM_ALLOC_FAILED ); if( ( ret = mbedtls_base64_encode( encode_buf, use_len, &use_len, der_data, der_len ) ) != 0 ) { mbedtls_free( encode_buf ); return( ret ); } memcpy( p, header, strlen( header ) ); p += strlen( header ); c = encode_buf; while( use_len ) { len = ( use_len > 64 ) ? 64 : use_len; memcpy( p, c, len ); use_len -= len; p += len; c += len; *p++ = '\n'; } memcpy( p, footer, strlen( footer ) ); p += strlen( footer ); *p++ = '\0'; *olen = p - buf; /* Clean any remaining data previously written to the buffer */ memset( buf + *olen, 0, buf_len - *olen ); mbedtls_free( encode_buf ); return( 0 ); } #endif /* MBEDTLS_PEM_WRITE_C */ #endif /* MBEDTLS_PEM_PARSE_C || MBEDTLS_PEM_WRITE_C */