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mbedtls/library/pem.c
Manuel Pégourié-Gonnard 7d4e5b739e Simplify password check in pem_read_buffer()
2013-07-09 16:42:35 +02:00

370 lines
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C
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/*
* Privacy Enhanced Mail (PEM) decoding
*
* Copyright (C) 2006-2013, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "polarssl/config.h"
#if defined(POLARSSL_PEM_C)
#include "polarssl/pem.h"
#include "polarssl/base64.h"
#include "polarssl/des.h"
#include "polarssl/aes.h"
#include "polarssl/md5.h"
#include "polarssl/cipher.h"
#if defined(POLARSSL_MEMORY_C)
#include "polarssl/memory.h"
#else
#define polarssl_malloc malloc
#define polarssl_free free
#endif
#include <stdlib.h>
void pem_init( pem_context *ctx )
{
memset( ctx, 0, sizeof( pem_context ) );
}
#if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_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( POLARSSL_ERR_PEM_INVALID_ENC_IV );
k = ( ( i & 1 ) != 0 ) ? j : j << 4;
iv[i >> 1] = (unsigned char)( iv[i >> 1] | k );
}
return( 0 );
}
static void pem_pbkdf1( unsigned char *key, size_t keylen,
unsigned char *iv,
const unsigned char *pwd, size_t pwdlen )
{
md5_context md5_ctx;
unsigned char md5sum[16];
size_t use_len;
/*
* key[ 0..15] = MD5(pwd || IV)
*/
md5_starts( &md5_ctx );
md5_update( &md5_ctx, pwd, pwdlen );
md5_update( &md5_ctx, iv, 8 );
md5_finish( &md5_ctx, md5sum );
if( keylen <= 16 )
{
memcpy( key, md5sum, keylen );
memset( &md5_ctx, 0, sizeof( md5_ctx ) );
memset( md5sum, 0, 16 );
return;
}
memcpy( key, md5sum, 16 );
/*
* key[16..23] = MD5(key[ 0..15] || pwd || IV])
*/
md5_starts( &md5_ctx );
md5_update( &md5_ctx, md5sum, 16 );
md5_update( &md5_ctx, pwd, pwdlen );
md5_update( &md5_ctx, iv, 8 );
md5_finish( &md5_ctx, md5sum );
use_len = 16;
if( keylen < 32 )
use_len = keylen - 16;
memcpy( key + 16, md5sum, use_len );
memset( &md5_ctx, 0, sizeof( md5_ctx ) );
memset( md5sum, 0, 16 );
}
#if defined(POLARSSL_DES_C)
/*
* Decrypt with DES-CBC, using PBKDF1 for key derivation
*/
static void pem_des_decrypt( unsigned char des_iv[8],
unsigned char *buf, size_t buflen,
const unsigned char *pwd, size_t pwdlen )
{
des_context des_ctx;
unsigned char des_key[8];
pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen );
des_setkey_dec( &des_ctx, des_key );
des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
des_iv, buf, buf );
memset( &des_ctx, 0, sizeof( des_ctx ) );
memset( des_key, 0, 8 );
}
/*
* Decrypt with 3DES-CBC, using PBKDF1 for key derivation
*/
static void pem_des3_decrypt( unsigned char des3_iv[8],
unsigned char *buf, size_t buflen,
const unsigned char *pwd, size_t pwdlen )
{
des3_context des3_ctx;
unsigned char des3_key[24];
pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen );
des3_set3key_dec( &des3_ctx, des3_key );
des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
des3_iv, buf, buf );
memset( &des3_ctx, 0, sizeof( des3_ctx ) );
memset( des3_key, 0, 24 );
}
#endif /* POLARSSL_DES_C */
#if defined(POLARSSL_AES_C)
/*
* Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
*/
static void pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
unsigned char *buf, size_t buflen,
const unsigned char *pwd, size_t pwdlen )
{
aes_context aes_ctx;
unsigned char aes_key[32];
pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen );
aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 );
aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
aes_iv, buf, buf );
memset( &aes_ctx, 0, sizeof( aes_ctx ) );
memset( aes_key, 0, keylen );
}
#endif /* POLARSSL_AES_C */
#endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
int pem_read_buffer( 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(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
unsigned char pem_iv[16];
cipher_type_t enc_alg = POLARSSL_CIPHER_NONE;
#else
((void) pwd);
((void) pwdlen);
#endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
if( ctx == NULL )
return( POLARSSL_ERR_PEM_BAD_INPUT_DATA );
s1 = (unsigned char *) strstr( (const char *) data, header );
if( s1 == NULL )
return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );
s2 = (unsigned char *) strstr( (const char *) data, footer );
if( s2 == NULL || s2 <= s1 )
return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );
s1 += strlen( header );
if( *s1 == '\r' ) s1++;
if( *s1 == '\n' ) s1++;
else return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );
end = s2;
end += strlen( footer );
if( *end == '\r' ) end++;
if( *end == '\n' ) end++;
*use_len = end - data;
enc = 0;
if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
{
#if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
enc++;
s1 += 22;
if( *s1 == '\r' ) s1++;
if( *s1 == '\n' ) s1++;
else return( POLARSSL_ERR_PEM_INVALID_DATA );
#if defined(POLARSSL_DES_C)
if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
{
enc_alg = POLARSSL_CIPHER_DES_EDE3_CBC;
s1 += 23;
if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
return( POLARSSL_ERR_PEM_INVALID_ENC_IV );
s1 += 16;
}
else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
{
enc_alg = POLARSSL_CIPHER_DES_CBC;
s1 += 18;
if( pem_get_iv( s1, pem_iv, 8) != 0 )
return( POLARSSL_ERR_PEM_INVALID_ENC_IV );
s1 += 16;
}
#endif /* POLARSSL_DES_C */
#if defined(POLARSSL_AES_C)
if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
{
if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
enc_alg = POLARSSL_CIPHER_AES_128_CBC;
else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
enc_alg = POLARSSL_CIPHER_AES_192_CBC;
else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
enc_alg = POLARSSL_CIPHER_AES_256_CBC;
else
return( POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG );
s1 += 22;
if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
return( POLARSSL_ERR_PEM_INVALID_ENC_IV );
s1 += 32;
}
#endif /* POLARSSL_AES_C */
if( enc_alg == POLARSSL_CIPHER_NONE )
return( POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG );
if( *s1 == '\r' ) s1++;
if( *s1 == '\n' ) s1++;
else return( POLARSSL_ERR_PEM_INVALID_DATA );
#else
return( POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE );
#endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
}
len = 0;
ret = base64_decode( NULL, &len, s1, s2 - s1 );
if( ret == POLARSSL_ERR_BASE64_INVALID_CHARACTER )
return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
if( ( buf = (unsigned char *) polarssl_malloc( len ) ) == NULL )
return( POLARSSL_ERR_PEM_MALLOC_FAILED );
if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
{
polarssl_free( buf );
return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
}
if( enc != 0 )
{
#if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
if( pwd == NULL )
{
polarssl_free( buf );
return( POLARSSL_ERR_PEM_PASSWORD_REQUIRED );
}
#if defined(POLARSSL_DES_C)
if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
#endif /* POLARSSL_DES_C */
#if defined(POLARSSL_AES_C)
if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
#endif /* POLARSSL_AES_C */
/*
* 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 heurisitic to try detecting password mismatchs.
*/
if( len <= 2 || buf[0] != 0x30 || buf[1] > 0x83 )
{
polarssl_free( buf );
return( POLARSSL_ERR_PEM_PASSWORD_MISMATCH );
}
#else
polarssl_free( buf );
return( POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE );
#endif
}
ctx->buf = buf;
ctx->buflen = len;
return( 0 );
}
void pem_free( pem_context *ctx )
{
if( ctx->buf )
polarssl_free( ctx->buf );
if( ctx->info )
polarssl_free( ctx->info );
memset( ctx, 0, sizeof( pem_context ) );
}
#endif
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