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1041a39338
mbedtls/library/ssl_ticket.c
Manuel Pégourié-Gonnard 1041a39338 Use AES-GCM-256 for session ticket protection
2015-05-20 20:19:42 +02:00

397 lines
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/*
* TLS server tickets callbacks implementation
*
* Copyright (C) 2015, ARM Limited, All Rights Reserved
*
* This file is part of mbed TLS (https://tls.mbed.org)
*
* 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.
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_SSL_TICKET_C)
#include "mbedtls/ssl_ticket.h"
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#define mbedtls_malloc malloc
#define mbedtls_free free
#endif
#include <string.h>
/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
/*
* Initialze context
*/
void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
{
memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
}
/*
* Setup context for actual use
*/
int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
uint32_t lifetime )
{
int ret;
unsigned char buf[32];
ctx->f_rng = f_rng;
ctx->p_rng = p_rng;
ctx->ticket_lifetime = lifetime;
if( ( ret = mbedtls_cipher_setup( &ctx->cipher,
mbedtls_cipher_info_from_type(
MBEDTLS_CIPHER_AES_256_GCM ) ) ) != 0 )
{
goto cleanup;
}
if( ( ret = f_rng( p_rng, buf, sizeof( buf ) ) != 0 ) )
{
goto cleanup;
}
/* With GCM and CCM, same context can encrypt & decrypt */
if( ( ret = mbedtls_cipher_setkey( &ctx->cipher, buf, 256,
MBEDTLS_ENCRYPT ) ) != 0 )
{
goto cleanup;
}
cleanup:
mbedtls_zeroize( buf, sizeof( buf ) );
if( ret != 0 )
mbedtls_ssl_ticket_free( ctx );
return( ret );
}
/*
* Serialize a session in the following format:
* 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session)
* n . n+2 peer_cert length = m (0 if no certificate)
* n+3 . n+2+m peer cert ASN.1
*/
static int ssl_save_session( const mbedtls_ssl_session *session,
unsigned char *buf, size_t buf_len,
size_t *olen )
{
unsigned char *p = buf;
size_t left = buf_len;
#if defined(MBEDTLS_X509_CRT_PARSE_C)
size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( left < sizeof( mbedtls_ssl_session ) )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
memcpy( p, session, sizeof( mbedtls_ssl_session ) );
p += sizeof( mbedtls_ssl_session );
left -= sizeof( mbedtls_ssl_session );
#if defined(MBEDTLS_X509_CRT_PARSE_C)
if( session->peer_cert == NULL )
cert_len = 0;
else
cert_len = session->peer_cert->raw.len;
if( left < 3 + cert_len )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
*p++ = (unsigned char)( cert_len >> 16 & 0xFF );
*p++ = (unsigned char)( cert_len >> 8 & 0xFF );
*p++ = (unsigned char)( cert_len & 0xFF );
if( session->peer_cert != NULL )
memcpy( p, session->peer_cert->raw.p, cert_len );
p += cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */
*olen = p - buf;
return( 0 );
}
/*
* Unserialise session, see ssl_save_session()
*/
static int ssl_load_session( mbedtls_ssl_session *session,
const unsigned char *buf, size_t len )
{
const unsigned char *p = buf;
const unsigned char * const end = buf + len;
#if defined(MBEDTLS_X509_CRT_PARSE_C)
size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( p + sizeof( mbedtls_ssl_session ) > end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
memcpy( session, p, sizeof( mbedtls_ssl_session ) );
p += sizeof( mbedtls_ssl_session );
#if defined(MBEDTLS_X509_CRT_PARSE_C)
if( p + 3 > end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
p += 3;
if( cert_len == 0 )
{
session->peer_cert = NULL;
}
else
{
int ret;
if( p + cert_len > end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
session->peer_cert = mbedtls_malloc( sizeof( mbedtls_x509_crt ) );
if( session->peer_cert == NULL )
return( MBEDTLS_ERR_SSL_MALLOC_FAILED );
mbedtls_x509_crt_init( session->peer_cert );
if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
p, cert_len ) ) != 0 )
{
mbedtls_x509_crt_free( session->peer_cert );
mbedtls_free( session->peer_cert );
session->peer_cert = NULL;
return( ret );
}
p += cert_len;
}
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( p != end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
return( 0 );
}
/*
* Create session ticket, with the following structure:
*
* struct {
* opaque key_name[4];
* opaque iv[12];
* opaque encrypted_state<0..2^16-1>;
* opaque tag[16];
* } ticket;
*
* The key_name, iv, and length of encrypted_state are the additional
* authenticated data.
*/
int mbedtls_ssl_ticket_write( void *p_ticket,
const mbedtls_ssl_session *session,
unsigned char *start,
const unsigned char *end,
size_t *tlen,
uint32_t *ticket_lifetime )
{
int ret;
mbedtls_ssl_ticket_context *ctx = p_ticket;
unsigned char *key_name = start;
unsigned char *iv = start + 4;
unsigned char *state_len_bytes = iv + 12;
unsigned char *state = state_len_bytes + 2;
unsigned char *tag;
size_t clear_len, ciph_len;
*tlen = 0;
if( ctx == NULL || ctx->f_rng == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
/* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
* in addition to session itself, that will be checked when writing it. */
if( end - start < 4 + 12 + 2 + 16 )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
*ticket_lifetime = ctx->ticket_lifetime;
memcpy( key_name, ctx->key_name, 4 );
if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
goto cleanup;
/* Dump session state */
if( ( ret = ssl_save_session( session,
state, end - state, &clear_len ) ) != 0 ||
(unsigned long) clear_len > 65535 )
{
goto cleanup;
}
state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
state_len_bytes[1] = ( clear_len ) & 0xff;
/* Encrypt and authenticate */
tag = state + clear_len;
if( ( ret = mbedtls_cipher_auth_encrypt( &ctx->cipher,
iv, 12, key_name, 4 + 12 + 2,
state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 )
{
goto cleanup;
}
if( ciph_len != clear_len )
{
ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
goto cleanup;
}
*tlen = 4 + 12 + 2 + 16 + ciph_len;
cleanup:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Load session ticket (see mbedtls_ssl_ticket_write for structure)
*/
int mbedtls_ssl_ticket_parse( void *p_ticket,
mbedtls_ssl_session *session,
unsigned char *buf,
size_t len )
{
int ret;
mbedtls_ssl_ticket_context *ctx = p_ticket;
unsigned char *key_name = buf;
unsigned char *iv = buf + 4;
unsigned char *enc_len_p = iv + 12;
unsigned char *ticket = enc_len_p + 2;
unsigned char *tag;
size_t enc_len, clear_len;
if( ctx == NULL || ctx->f_rng == NULL ||
len < 4 + 12 + 2 + 16 )
{
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
tag = ticket + enc_len;
if( len != 4 + 12 + 2 + enc_len + 16 )
{
ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
goto cleanup;
}
/* Check name (public data) */
if( memcmp( key_name, ctx->key_name, 4 ) != 0 )
{
ret = MBEDTLS_ERR_SSL_INVALID_MAC;
goto cleanup;
}
/* Decrypt and authenticate */
if( ( ret = mbedtls_cipher_auth_decrypt( &ctx->cipher, iv, 12,
key_name, 4 + 12 + 2, ticket, enc_len,
ticket, &clear_len, tag, 16 ) ) != 0 )
{
/* TODO: convert AUTH_FAILED to INVALID_MAC */
goto cleanup;
}
if( clear_len != enc_len )
{
ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
goto cleanup;
}
/* Actually load session */
if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
goto cleanup;
#if defined(MBEDTLS_HAVE_TIME)
{
/* Check for expiration */
time_t current_time = time( NULL );
if( current_time < session->start ||
(uint32_t)( current_time - session->start ) > ctx->ticket_lifetime )
{
ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
goto cleanup;
}
}
#endif
cleanup:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Free context
*/
void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
{
mbedtls_cipher_free( &ctx->cipher );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex );
#endif
mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
}
#endif /* MBEDTLS_SSL_TICKET_C */
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