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Add TLS 1.3 specific key to SSL transform conversion function

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This commit adds the TLS 1.3 specific internal function

```
  mbedtls_ssl_tls13_populate_transform()
```

which creates an instance of the SSL transform structure
`mbedtls_ssl_transform` representing a TLS 1.3 record protection
mechanism.

It is analogous to the existing internal helper function

```
   ssl_tls12_populate_transform()
```

which creates transform structures representing record
protection mechanisms in TLS 1.2 and earlier.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This commit is contained in:
Hanno Becker 2021-03-22 07:50:44 +00:00
parent bd25755d2a
commit c94060c641
2 changed files with 141 additions and 0 deletions
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108
library/ssl_tls13_keys.c
View file

@ -699,4 +699,112 @@ exit:
return( ret );
}
int mbedtls_ssl_tls13_populate_transform( mbedtls_ssl_transform *transform,
int endpoint,
int ciphersuite,
mbedtls_ssl_key_set const *traffic_keys,
mbedtls_ssl_context *ssl /* DEBUG ONLY */ )
{
int ret;
mbedtls_cipher_info_t const *cipher_info;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
unsigned char const *key_enc;
unsigned char const *iv_enc;
unsigned char const *key_dec;
unsigned char const *iv_dec;
#if !defined(MBEDTLS_DEBUG_C)
ssl = NULL; /* make sure we don't use it except for those cases */
(void) ssl;
#endif
ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( ciphersuite );
cipher_info = mbedtls_cipher_info_from_type( ciphersuite_info->cipher );
if( cipher_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
/*
* Setup cipher contexts in target transform
*/
if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_enc,
cipher_info ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
return( ret );
}
if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_dec,
cipher_info ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
return( ret );
}
#if defined(MBEDTLS_SSL_SRV_C)
if( endpoint == MBEDTLS_SSL_IS_SERVER )
{
key_enc = traffic_keys->server_write_key;
key_dec = traffic_keys->client_write_key;
iv_enc = traffic_keys->server_write_iv;
iv_dec = traffic_keys->client_write_iv;
}
else
#endif /* MBEDTLS_SSL_SRV_C */
#if defined(MBEDTLS_SSL_CLI_C)
if( endpoint == MBEDTLS_SSL_IS_CLIENT )
{
key_enc = traffic_keys->client_write_key;
key_dec = traffic_keys->server_write_key;
iv_enc = traffic_keys->client_write_iv;
iv_dec = traffic_keys->server_write_iv;
}
else
#endif /* MBEDTLS_SSL_CLI_C */
{
/* should not happen */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
memcpy( transform->iv_enc, iv_enc, traffic_keys->iv_len );
memcpy( transform->iv_dec, iv_dec, traffic_keys->iv_len );
if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_enc,
key_enc, cipher_info->key_bitlen,
MBEDTLS_ENCRYPT ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
return( ret );
}
if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_dec,
key_dec, cipher_info->key_bitlen,
MBEDTLS_DECRYPT ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
return( ret );
}
/*
* Setup other fields in SSL transform
*/
if( ( ciphersuite_info->flags & MBEDTLS_CIPHERSUITE_SHORT_TAG ) != 0 )
transform->taglen = 8;
else
transform->taglen = 16;
transform->ivlen = traffic_keys->iv_len;
transform->maclen = 0;
transform->fixed_ivlen = transform->ivlen;
transform->minlen = transform->taglen + 1;
transform->minor_ver = MBEDTLS_SSL_MINOR_VERSION_4;
return( 0 );
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */

33
library/ssl_tls13_keys.h
View file

@ -498,4 +498,37 @@ int mbedtls_ssl_tls1_3_create_psk_binder( mbedtls_ssl_context *ssl,
unsigned char const *transcript,
unsigned char *result );
/**
* \bref Setup an SSL transform structure representing the
* record protection mechanism used by TLS 1.3
*
* \param transform The SSL transform structure to be created. This must have
* been initialized through mbedtls_ssl_transform_init() and
* not used in any other way prior to calling this function.
* In particular, this function does not clean up the
* transform structure prior to installing the new keys.
* \param endpoint Indicates whether the transform is for the client
* (value #MBEDTLS_SSL_IS_CLIENT) or the server
* (value #MBEDTLS_SSL_IS_SERVER).
* \param ciphersuite The numerical identifier for the ciphersuite to use.
* This must be one of the identifiers listed in
* ssl_ciphersuites.h.
* \param traffic_keys The key material to use. No reference is stored in
* the SSL transform being generated, and the caller
* should destroy the key material afterwards.
* \param ssl (Debug-only) The SSL context to use for debug output
* in case of failure. This parameter is only needed if
* #MBEDTLS_DEBUG_C is set, and is ignored otherwise.
*
* \return \c 0 on success. In this case, \p transform is ready to
* be used with mbedtls_ssl_transform_decrypt() and
* mbedtls_ssl_transform_encrypt().
* \return A negative error code on failure.
*/
int mbedtls_ssl_tls13_populate_transform( mbedtls_ssl_transform *transform,
int endpoint,
int ciphersuite,
mbedtls_ssl_key_set const *traffic_keys,
mbedtls_ssl_context *ssl );
#endif /* MBEDTLS_SSL_TLS1_3_KEYS_H */