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Add TLS 1.3 second level key derivations

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This commit adds helper functions to ssl_tls13_keys.[ch]
allowing to derive the secrets specific to each stage of
a TLS 1.3 handshake (early, handshake, application) from
the corresponding master secret (early secret, handshake
secret, master secret).

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This commit is contained in:
Hanno Becker
2021-05-24 06:39:41 +01:00
parent f823722af4
commit ef5235bc2e
2 changed files with 413 additions and 0 deletions
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219
library/ssl_tls13_keys.c
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@ -24,6 +24,7 @@
#include "mbedtls/hkdf.h"
#include "ssl_misc.h"
#include "ssl_tls13_keys.h"
#include "mbedtls/debug.h"
#include <stdint.h>
#include <string.h>
@ -346,4 +347,222 @@ int mbedtls_ssl_tls1_3_evolve_secret(
return( ret );
}
int mbedtls_ssl_tls1_3_derive_early_secrets(
mbedtls_md_type_t md_type,
unsigned char const *early_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls1_3_early_secrets *derived )
{
int ret;
mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
/* We should never call this function with an unknown hash,
* but add an assertion anyway. */
if( md_info == 0 )
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
/*
* 0
* |
* v
* PSK -> HKDF-Extract = Early Secret
* |
* +-----> Derive-Secret(., "ext binder" | "res binder", "")
* | = binder_key
* |
* +-----> Derive-Secret(., "c e traffic", ClientHello)
* | = client_early_traffic_secret
* |
* +-----> Derive-Secret(., "e exp master", ClientHello)
* | = early_exporter_master_secret
* v
*/
/* Create client_early_traffic_secret */
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
early_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( c_e_traffic ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->client_early_traffic_secret,
md_size );
if( ret != 0 )
return( ret );
/* Create early exporter */
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
early_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( e_exp_master ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->early_exporter_master_secret,
md_size );
if( ret != 0 )
return( ret );
return( 0 );
}
int mbedtls_ssl_tls1_3_derive_handshake_secrets(
mbedtls_md_type_t md_type,
unsigned char const *handshake_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls1_3_handshake_secrets *derived )
{
int ret;
mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
/* We should never call this function with an unknown hash,
* but add an assertion anyway. */
if( md_info == 0 )
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
/*
*
* Handshake Secret
* |
* +-----> Derive-Secret( ., "c hs traffic",
* | ClientHello...ServerHello )
* | = client_handshake_traffic_secret
* |
* +-----> Derive-Secret( ., "s hs traffic",
* | ClientHello...ServerHello )
* | = server_handshake_traffic_secret
*
*/
/*
* Compute client_handshake_traffic_secret with
* Derive-Secret( ., "c hs traffic", ClientHello...ServerHello )
*/
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
handshake_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( c_hs_traffic ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->client_handshake_traffic_secret,
md_size );
if( ret != 0 )
return( ret );
/*
* Compute server_handshake_traffic_secret with
* Derive-Secret( ., "s hs traffic", ClientHello...ServerHello )
*/
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
handshake_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( s_hs_traffic ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->server_handshake_traffic_secret,
md_size );
if( ret != 0 )
return( ret );
return( 0 );
}
int mbedtls_ssl_tls1_3_derive_application_secrets(
mbedtls_md_type_t md_type,
unsigned char const *application_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls1_3_application_secrets *derived )
{
int ret;
mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
/* We should never call this function with an unknown hash,
* but add an assertion anyway. */
if( md_info == 0 )
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
/* Generate {client,server}_application_traffic_secret_0
*
* Master Secret
* |
* +-----> Derive-Secret( ., "c ap traffic",
* | ClientHello...server Finished )
* | = client_application_traffic_secret_0
* |
* +-----> Derive-Secret( ., "s ap traffic",
* | ClientHello...Server Finished )
* | = server_application_traffic_secret_0
* |
* +-----> Derive-Secret( ., "exp master",
* | ClientHello...server Finished)
* | = exporter_master_secret
*
*/
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
application_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( c_ap_traffic ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->client_application_traffic_secret_N,
md_size );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
application_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( s_ap_traffic ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->server_application_traffic_secret_N,
md_size );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
application_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( exp_master ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->exporter_master_secret,
md_size );
if( ret != 0 )
return( ret );
return( 0 );
}
/* Generate resumption_master_secret for use with the ticket exchange.
*
* This is not integrated with mbedtls_ssl_tls1_3_derive_application_secrets()
* because it uses the transcript hash up to and including ClientFinished. */
int mbedtls_ssl_tls1_3_derive_resumption_master_secret(
mbedtls_md_type_t md_type,
unsigned char const *application_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls1_3_application_secrets *derived )
{
int ret;
mbedtls_md_info_t const * const md_info = mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
/* We should never call this function with an unknown hash,
* but add an assertion anyway. */
if( md_info == 0 )
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
ret = mbedtls_ssl_tls1_3_derive_secret( md_type,
application_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( res_master ),
transcript, transcript_len,
MBEDTLS_SSL_TLS1_3_CONTEXT_HASHED,
derived->resumption_master_secret,
md_size );
if( ret != 0 )
return( ret );
return( 0 );
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */