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mbedtls/library/ssl_ticket.c
Hanno Becker 6883874013 Fix typo in SSL ticket documentation
2019-02-26 14:38:09 +00:00

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/*
* TLS server tickets callbacks implementation
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* 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.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_SSL_TICKET_C)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
#include "mbedtls/ssl_ticket.h"
#include "mbedtls/platform_util.h"
#include <string.h>
/*
* 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
}
#define MAX_KEY_BYTES 32 /* 256 bits */
#define TICKET_KEY_NAME_BYTES 4
#define TICKET_IV_BYTES 12
#define TICKET_CRYPT_LEN_BYTES 2
#define TICKET_AUTH_TAG_BYTES 16
#define TICKET_MIN_LEN ( TICKET_KEY_NAME_BYTES + \
TICKET_IV_BYTES + \
TICKET_CRYPT_LEN_BYTES + \
TICKET_AUTH_TAG_BYTES )
#define TICKET_ADD_DATA_LEN ( TICKET_KEY_NAME_BYTES + \
TICKET_IV_BYTES + \
TICKET_CRYPT_LEN_BYTES )
/*
* Generate/update a key
*/
static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
unsigned char index )
{
int ret;
unsigned char buf[MAX_KEY_BYTES];
mbedtls_ssl_ticket_key *key = ctx->keys + index;
#if defined(MBEDTLS_HAVE_TIME)
key->generation_time = (uint32_t) mbedtls_time( NULL );
#endif
if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 )
return( ret );
if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 )
return( ret );
/* With GCM and CCM, same context can encrypt & decrypt */
ret = mbedtls_cipher_setkey( &key->ctx, buf,
mbedtls_cipher_get_key_bitlen( &key->ctx ),
MBEDTLS_ENCRYPT );
mbedtls_platform_zeroize( buf, sizeof( buf ) );
return( ret );
}
/*
* Rotate/generate keys if necessary
*/
static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
{
#if !defined(MBEDTLS_HAVE_TIME)
((void) ctx);
#else
if( ctx->ticket_lifetime != 0 )
{
uint32_t current_time = (uint32_t) mbedtls_time( NULL );
uint32_t key_time = ctx->keys[ctx->active].generation_time;
if( current_time >= key_time &&
current_time - key_time < ctx->ticket_lifetime )
{
return( 0 );
}
ctx->active = 1 - ctx->active;
return( ssl_ticket_gen_key( ctx, ctx->active ) );
}
else
#endif /* MBEDTLS_HAVE_TIME */
return( 0 );
}
/*
* 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,
mbedtls_cipher_type_t cipher,
uint32_t lifetime )
{
int ret;
const mbedtls_cipher_info_t *cipher_info;
ctx->f_rng = f_rng;
ctx->p_rng = p_rng;
ctx->ticket_lifetime = lifetime;
cipher_info = mbedtls_cipher_info_from_type( cipher);
if( cipher_info == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( cipher_info->mode != MBEDTLS_MODE_GCM &&
cipher_info->mode != MBEDTLS_MODE_CCM )
{
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
if( cipher_info->key_bitlen > 8 * MAX_KEY_BYTES )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
#if defined(MBEDTLS_USE_PSA_CRYPTO)
ret = mbedtls_cipher_setup_psa( &ctx->keys[0].ctx,
cipher_info, TICKET_AUTH_TAG_BYTES );
if( ret != 0 && ret != MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE )
return( ret );
/* We don't yet expect to support all ciphers through PSA,
* so allow fallback to ordinary mbedtls_cipher_setup(). */
if( ret == MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE )
#endif /* MBEDTLS_USE_PSA_CRYPTO */
if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 )
return( ret );
#if defined(MBEDTLS_USE_PSA_CRYPTO)
ret = mbedtls_cipher_setup_psa( &ctx->keys[1].ctx,
cipher_info, TICKET_AUTH_TAG_BYTES );
if( ret != 0 && ret != MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE )
return( ret );
if( ret == MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE )
#endif /* MBEDTLS_USE_PSA_CRYPTO */
if( ( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 )
return( ret );
if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 ||
( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 )
{
return( ret );
}
return( 0 );
}
/*
* Serialize a session in the following format:
*
* - If MBEDTLS_SSL_KEEP_PEER_CERTIFICATE is enabled:
* 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
*
* - If MBEDTLS_SSL_KEEP_PEER_CERTIFICATE is disabled:
* 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session)
* n . n length of peer certificate digest = k (0 if no digest)
* n+1 . n+k peer certificate digest (digest type encoded in session)
*/
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)
#if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
size_t cert_len;
#else
size_t cert_digest_len;
#endif /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( left < sizeof( mbedtls_ssl_session ) )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
/* This also copies the values of pointer fields in the
* session to be serialized, but they'll be ignored when
* loading the session through ssl_load_session(). */
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 defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
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 );
left -= 3;
if( session->peer_cert != NULL )
memcpy( p, session->peer_cert->raw.p, cert_len );
p += cert_len;
left -= cert_len;
#else /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
if( session->peer_cert_digest != NULL )
cert_digest_len = 0;
else
cert_digest_len = session->peer_cert_digest_len;
if( left < 1 + cert_digest_len )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
*p++ = (unsigned char) cert_digest_len;
left--;
if( session->peer_cert_digest != NULL )
memcpy( p, session->peer_cert_digest, cert_digest_len );
p += cert_digest_len;
left -= cert_digest_len;
#endif /* !MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
#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)
#if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
size_t cert_len;
#else
size_t cert_digest_len;
#endif /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( sizeof( mbedtls_ssl_session ) > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
memcpy( session, p, sizeof( mbedtls_ssl_session ) );
p += sizeof( mbedtls_ssl_session );
/* Non-NULL pointer fields of `session` are meaningless
* and potentially harmful. Zeroize them for safety. */
#if defined(MBEDTLS_X509_CRT_PARSE_C)
#if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
session->peer_cert = NULL;
#else
session->peer_cert_digest = NULL;
#endif /* !MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
#endif /* MBEDTLS_X509_CRT_PARSE_C */
#if defined(MBEDTLS_SSL_SESSION_TICKETS) && defined(MBEDTLS_SSL_CLI_C)
session->ticket = NULL;
#endif /* MBEDTLS_SSL_SESSION_TICKETS && MBEDTLS_SSL_CLI_C */
#if defined(MBEDTLS_X509_CRT_PARSE_C)
#if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
/* Deserialize CRT from the end of the ticket. */
if( 3 > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
p += 3;
if( cert_len != 0 )
{
int ret;
if( cert_len > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
if( session->peer_cert == NULL )
return( MBEDTLS_ERR_SSL_ALLOC_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;
}
#else /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
/* Deserialize CRT digest from the end of the ticket. */
if( 1 > (size_t)( end - p ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
cert_digest_len = (size_t) p[0];
p++;
if( cert_digest_len != 0 )
{
if( cert_digest_len > (size_t)( end - p ) ||
cert_digest_len != session->peer_cert_digest_len )
{
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
session->peer_cert_digest = mbedtls_calloc( 1, cert_digest_len );
if( session->peer_cert_digest == NULL )
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
memcpy( session->peer_cert_digest, p, cert_digest_len );
p += cert_digest_len;
}
#endif /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
#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;
mbedtls_ssl_ticket_key *key;
unsigned char *key_name = start;
unsigned char *iv = start + TICKET_KEY_NAME_BYTES;
unsigned char *state_len_bytes = iv + TICKET_IV_BYTES;
unsigned char *state = state_len_bytes + TICKET_CRYPT_LEN_BYTES;
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 < TICKET_MIN_LEN )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
goto cleanup;
key = &ctx->keys[ctx->active];
*ticket_lifetime = ctx->ticket_lifetime;
memcpy( key_name, key->name, TICKET_KEY_NAME_BYTES );
if( ( ret = ctx->f_rng( ctx->p_rng, iv, TICKET_IV_BYTES ) ) != 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( &key->ctx,
iv, TICKET_IV_BYTES,
/* Additional data: key name, IV and length */
key_name, TICKET_ADD_DATA_LEN,
state, clear_len, state, &ciph_len,
tag, TICKET_AUTH_TAG_BYTES ) ) != 0 )
{
goto cleanup;
}
if( ciph_len != clear_len )
{
ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
goto cleanup;
}
*tlen = TICKET_MIN_LEN + ciph_len;
cleanup:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Select key based on name
*/
static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
mbedtls_ssl_ticket_context *ctx,
const unsigned char name[4] )
{
unsigned char i;
for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
return( &ctx->keys[i] );
return( NULL );
}
/*
* 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;
mbedtls_ssl_ticket_key *key;
unsigned char *key_name = buf;
unsigned char *iv = buf + TICKET_KEY_NAME_BYTES;
unsigned char *enc_len_p = iv + TICKET_IV_BYTES;
unsigned char *ticket = enc_len_p + TICKET_CRYPT_LEN_BYTES;
unsigned char *tag;
size_t enc_len, clear_len;
if( ctx == NULL || ctx->f_rng == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( len < TICKET_MIN_LEN )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
goto cleanup;
enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
tag = ticket + enc_len;
if( len != TICKET_MIN_LEN + enc_len )
{
ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
goto cleanup;
}
/* Select key */
if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
{
/* We can't know for sure but this is a likely option unless we're
* under attack - this is only informative anyway */
ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
goto cleanup;
}
/* Decrypt and authenticate */
if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx,
iv, TICKET_IV_BYTES,
/* Additional data: key name, IV and length */
key_name, TICKET_ADD_DATA_LEN,
ticket, enc_len,
ticket, &clear_len,
tag, TICKET_AUTH_TAG_BYTES ) ) != 0 )
{
if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
ret = MBEDTLS_ERR_SSL_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 */
mbedtls_time_t current_time = mbedtls_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->keys[0].ctx );
mbedtls_cipher_free( &ctx->keys[1].ctx );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex );
#endif
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
}
#endif /* MBEDTLS_SSL_TICKET_C */
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