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mbedtls/library/pem.c
Paul Elliott 557b8d663a Remove Extraneous bytes from buffer post pem write 
In order to remove large buffers from the stack, the der data is written
into the same buffer that the pem is eventually written into, however
although the pem data is zero terminated, there is now data left in the
buffer after the zero termination, which can cause
mbedtls_x509_crt_parse to fail to parse the same buffer if passed back
in. Patches also applied to mbedtls_pk_write_pubkey_pem, and
mbedtls_pk_write_key_pem, which use similar methods of writing der data
to the same buffer, and tests modified to hopefully catch any future
regression on this.

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
2020-12-07 17:29:42 +00:00

490 lines
14 KiB
C
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/*
* 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_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_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 */
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