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Implement TLS 1.3 traffic key generation

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See the documentation in library/ssl_tls13_keys.h.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This commit is contained in:
Hanno Becker
2020-08-21 13:03:34 +01:00
parent 39ff4928ff
commit 3385a4d5cf
3 changed files with 125 additions and 0 deletions
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64
library/ssl_tls13_keys.c
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@ -26,6 +26,7 @@
#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
#include "mbedtls/hkdf.h"
#include "mbedtls/ssl_internal.h"
#include "ssl_tls13_keys.h"
#include <stdint.h>
@ -179,4 +180,67 @@ int mbedtls_ssl_tls1_3_hkdf_expand_label(
buf, blen ) );
}
/*
* The traffic keying material is generated from the following inputs:
*
* - One secret value per sender.
* - A purpose value indicating the specific value being generated
* - The desired lengths of key and IV.
*
* The expansion itself is based on HKDF:
*
* [sender]_write_key = HKDF-Expand-Label( Secret, "key", "", key_length )
* [sender]_write_iv = HKDF-Expand-Label( Secret, "iv" , "", iv_length )
*
* [sender] denotes the sending side and the Secret value is provided
* by the function caller. Note that we generate server and client side
* keys in a single function call.
*/
int mbedtls_ssl_tls1_3_make_traffic_keys(
mbedtls_md_type_t hash_alg,
const unsigned char *client_secret,
const unsigned char *server_secret,
size_t slen, size_t keyLen, size_t ivLen,
mbedtls_ssl_key_set *keys )
{
int ret = 0;
ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg,
client_secret, slen,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( key ),
NULL, 0,
keys->client_write_key, keyLen );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg,
server_secret, slen,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( key ),
NULL, 0,
keys->server_write_key, keyLen );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg,
client_secret, slen,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( iv ),
NULL, 0,
keys->client_write_iv, ivLen );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls1_3_hkdf_expand_label( hash_alg,
server_secret, slen,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( iv ),
NULL, 0,
keys->server_write_iv, ivLen );
if( ret != 0 )
return( ret );
keys->keyLen = keyLen;
keys->ivLen = ivLen;
return( 0 );
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */