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mbedtls/library/ssl_tls13_keys.c
Ronald Cron 6f135e1148 Rename MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL to MBEDTLS_SSL_PROTO_TLS1_3 
As we have now a minimal viable implementation of TLS 1.3,
let's remove EXPERIMENTAL from the config option enabling
it.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
2021-12-10 13:47:55 +01:00

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/*
* TLS 1.3 key schedule
*
* Copyright The Mbed TLS Contributors
* 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.
*/
#include "common.h"
#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
#include <stdint.h>
#include <string.h>
#include "mbedtls/hkdf.h"
#include "mbedtls/debug.h"
#include "mbedtls/error.h"
#include "ssl_misc.h"
#include "ssl_tls13_keys.h"
#define MBEDTLS_SSL_TLS1_3_LABEL( name, string ) \
.name = string,
struct mbedtls_ssl_tls13_labels_struct const mbedtls_ssl_tls13_labels =
{
/* This seems to work in C, despite the string literal being one
* character too long due to the 0-termination. */
MBEDTLS_SSL_TLS1_3_LABEL_LIST
};
#undef MBEDTLS_SSL_TLS1_3_LABEL
/*
* This function creates a HkdfLabel structure used in the TLS 1.3 key schedule.
*
* The HkdfLabel is specified in RFC 8446 as follows:
*
* struct HkdfLabel {
* uint16 length; // Length of expanded key material
* opaque label<7..255>; // Always prefixed by "tls13 "
* opaque context<0..255>; // Usually a communication transcript hash
* };
*
* Parameters:
* - desired_length: Length of expanded key material
* Even though the standard allows expansion to up to
* 2**16 Bytes, TLS 1.3 never uses expansion to more than
* 255 Bytes, so we require `desired_length` to be at most
* 255. This allows us to save a few Bytes of code by
* hardcoding the writing of the high bytes.
* - (label, label_len): label + label length, without "tls13 " prefix
* The label length MUST be less than or equal to
* MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN
* It is the caller's responsibility to ensure this.
* All (label, label length) pairs used in TLS 1.3
* can be obtained via MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN().
* - (ctx, ctx_len): context + context length
* The context length MUST be less than or equal to
* MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN
* It is the caller's responsibility to ensure this.
* - dst: Target buffer for HkdfLabel structure,
* This MUST be a writable buffer of size
* at least SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN Bytes.
* - dst_len: Pointer at which to store the actual length of
* the HkdfLabel structure on success.
*/
static const char tls13_label_prefix[6] = "tls13 ";
#define SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( label_len, context_len ) \
( 2 /* expansion length */ \
+ 1 /* label length */ \
+ label_len \
+ 1 /* context length */ \
+ context_len )
#define SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN \
SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( \
sizeof(tls13_label_prefix) + \
MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN, \
MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN )
static void ssl_tls13_hkdf_encode_label(
size_t desired_length,
const unsigned char *label, size_t label_len,
const unsigned char *ctx, size_t ctx_len,
unsigned char *dst, size_t *dst_len )
{
size_t total_label_len =
sizeof(tls13_label_prefix) + label_len;
size_t total_hkdf_lbl_len =
SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN( total_label_len, ctx_len );
unsigned char *p = dst;
/* Add the size of the expanded key material.
* We're hardcoding the high byte to 0 here assuming that we never use
* TLS 1.3 HKDF key expansion to more than 255 Bytes. */
#if MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN > 255
#error "The implementation of ssl_tls13_hkdf_encode_label() is not fit for the \
value of MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN"
#endif
*p++ = 0;
*p++ = MBEDTLS_BYTE_0( desired_length );
/* Add label incl. prefix */
*p++ = MBEDTLS_BYTE_0( total_label_len );
memcpy( p, tls13_label_prefix, sizeof(tls13_label_prefix) );
p += sizeof(tls13_label_prefix);
memcpy( p, label, label_len );
p += label_len;
/* Add context value */
*p++ = MBEDTLS_BYTE_0( ctx_len );
if( ctx_len != 0 )
memcpy( p, ctx, ctx_len );
/* Return total length to the caller. */
*dst_len = total_hkdf_lbl_len;
}
int mbedtls_ssl_tls13_hkdf_expand_label(
mbedtls_md_type_t hash_alg,
const unsigned char *secret, size_t secret_len,
const unsigned char *label, size_t label_len,
const unsigned char *ctx, size_t ctx_len,
unsigned char *buf, size_t buf_len )
{
const mbedtls_md_info_t *md_info;
unsigned char hkdf_label[ SSL_TLS1_3_KEY_SCHEDULE_MAX_HKDF_LABEL_LEN ];
size_t hkdf_label_len;
if( label_len > MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_LABEL_LEN )
{
/* Should never happen since this is an internal
* function, and we know statically which labels
* are allowed. */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
if( ctx_len > MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_CONTEXT_LEN )
{
/* Should not happen, as above. */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
if( buf_len > MBEDTLS_SSL_TLS1_3_KEY_SCHEDULE_MAX_EXPANSION_LEN )
{
/* Should not happen, as above. */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
md_info = mbedtls_md_info_from_type( hash_alg );
if( md_info == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
ssl_tls13_hkdf_encode_label( buf_len,
label, label_len,
ctx, ctx_len,
hkdf_label,
&hkdf_label_len );
return( mbedtls_hkdf_expand( md_info,
secret, secret_len,
hkdf_label, hkdf_label_len,
buf, buf_len ) );
}
/*
* 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_tls13_make_traffic_keys(
mbedtls_md_type_t hash_alg,
const unsigned char *client_secret,
const unsigned char *server_secret, size_t secret_len,
size_t key_len, size_t iv_len,
mbedtls_ssl_key_set *keys )
{
int ret = 0;
ret = mbedtls_ssl_tls13_hkdf_expand_label( hash_alg,
client_secret, secret_len,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( key ),
NULL, 0,
keys->client_write_key, key_len );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls13_hkdf_expand_label( hash_alg,
server_secret, secret_len,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( key ),
NULL, 0,
keys->server_write_key, key_len );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls13_hkdf_expand_label( hash_alg,
client_secret, secret_len,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( iv ),
NULL, 0,
keys->client_write_iv, iv_len );
if( ret != 0 )
return( ret );
ret = mbedtls_ssl_tls13_hkdf_expand_label( hash_alg,
server_secret, secret_len,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( iv ),
NULL, 0,
keys->server_write_iv, iv_len );
if( ret != 0 )
return( ret );
keys->key_len = key_len;
keys->iv_len = iv_len;
return( 0 );
}
int mbedtls_ssl_tls13_derive_secret(
mbedtls_md_type_t hash_alg,
const unsigned char *secret, size_t secret_len,
const unsigned char *label, size_t label_len,
const unsigned char *ctx, size_t ctx_len,
int ctx_hashed,
unsigned char *dstbuf, size_t dstbuf_len )
{
int ret;
unsigned char hashed_context[ MBEDTLS_MD_MAX_SIZE ];
const mbedtls_md_info_t *md_info;
md_info = mbedtls_md_info_from_type( hash_alg );
if( md_info == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( ctx_hashed == MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED )
{
ret = mbedtls_md( md_info, ctx, ctx_len, hashed_context );
if( ret != 0 )
return( ret );
ctx_len = mbedtls_md_get_size( md_info );
}
else
{
if( ctx_len > sizeof(hashed_context) )
{
/* This should never happen since this function is internal
* and the code sets `ctx_hashed` correctly.
* Let's double-check nonetheless to not run at the risk
* of getting a stack overflow. */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
memcpy( hashed_context, ctx, ctx_len );
}
return( mbedtls_ssl_tls13_hkdf_expand_label( hash_alg,
secret, secret_len,
label, label_len,
hashed_context, ctx_len,
dstbuf, dstbuf_len ) );
}
int mbedtls_ssl_tls13_evolve_secret(
mbedtls_md_type_t hash_alg,
const unsigned char *secret_old,
const unsigned char *input, size_t input_len,
unsigned char *secret_new )
{
int ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
size_t hlen, ilen;
unsigned char tmp_secret[ MBEDTLS_MD_MAX_SIZE ] = { 0 };
unsigned char tmp_input [ MBEDTLS_ECP_MAX_BYTES ] = { 0 };
const mbedtls_md_info_t *md_info;
md_info = mbedtls_md_info_from_type( hash_alg );
if( md_info == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
hlen = mbedtls_md_get_size( md_info );
/* For non-initial runs, call Derive-Secret( ., "derived", "")
* on the old secret. */
if( secret_old != NULL )
{
ret = mbedtls_ssl_tls13_derive_secret(
hash_alg,
secret_old, hlen,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( derived ),
NULL, 0, /* context */
MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED,
tmp_secret, hlen );
if( ret != 0 )
goto cleanup;
}
if( input != NULL )
{
memcpy( tmp_input, input, input_len );
ilen = input_len;
}
else
{
ilen = hlen;
}
/* HKDF-Extract takes a salt and input key material.
* The salt is the old secret, and the input key material
* is the input secret (PSK / ECDHE). */
ret = mbedtls_hkdf_extract( md_info,
tmp_secret, hlen,
tmp_input, ilen,
secret_new );
if( ret != 0 )
goto cleanup;
ret = 0;
cleanup:
mbedtls_platform_zeroize( tmp_secret, sizeof(tmp_secret) );
mbedtls_platform_zeroize( tmp_input, sizeof(tmp_input) );
return( ret );
}
int mbedtls_ssl_tls13_derive_early_secrets(
mbedtls_md_type_t md_type,
unsigned char const *early_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls13_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(., "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_tls13_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_tls13_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_tls13_derive_handshake_secrets(
mbedtls_md_type_t md_type,
unsigned char const *handshake_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls13_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_tls13_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_tls13_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_tls13_derive_application_secrets(
mbedtls_md_type_t md_type,
unsigned char const *application_secret,
unsigned char const *transcript, size_t transcript_len,
mbedtls_ssl_tls13_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_tls13_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_tls13_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_tls13_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_tls13_derive_application_secrets()
* because it uses the transcript hash up to and including ClientFinished. */
int mbedtls_ssl_tls13_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_tls13_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_tls13_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 );
}
int mbedtls_ssl_tls13_key_schedule_stage_application( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
mbedtls_md_type_t const md_type = handshake->ciphersuite_info->mac;
#if defined(MBEDTLS_DEBUG_C)
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 );
#endif /* MBEDTLS_DEBUG_C */
/*
* Compute MasterSecret
*/
ret = mbedtls_ssl_tls13_evolve_secret( md_type,
handshake->tls13_master_secrets.handshake,
NULL, 0,
handshake->tls13_master_secrets.app );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_evolve_secret", ret );
return( ret );
}
MBEDTLS_SSL_DEBUG_BUF( 4, "Master secret",
handshake->tls13_master_secrets.app, md_size );
return( 0 );
}
static int ssl_tls13_calc_finished_core( mbedtls_md_type_t md_type,
unsigned char const *base_key,
unsigned char const *transcript,
unsigned char *dst )
{
const mbedtls_md_info_t* const md_info = mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
unsigned char finished_key[MBEDTLS_MD_MAX_SIZE];
int ret;
/* 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 );
/* TLS 1.3 Finished message
*
* struct {
* opaque verify_data[Hash.length];
* } Finished;
*
* verify_data =
* HMAC( finished_key,
* Hash( Handshake Context +
* Certificate* +
* CertificateVerify* )
* )
*
* finished_key =
* HKDF-Expand-Label( BaseKey, "finished", "", Hash.length )
*/
ret = mbedtls_ssl_tls13_hkdf_expand_label(
md_type, base_key, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( finished ),
NULL, 0,
finished_key, md_size );
if( ret != 0 )
goto exit;
ret = mbedtls_md_hmac( md_info, finished_key, md_size, transcript, md_size, dst );
if( ret != 0 )
goto exit;
exit:
mbedtls_platform_zeroize( finished_key, sizeof( finished_key ) );
return( ret );
}
int mbedtls_ssl_tls13_calculate_verify_data( mbedtls_ssl_context* ssl,
unsigned char* dst,
size_t dst_len,
size_t *actual_len,
int from )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char transcript[MBEDTLS_TLS1_3_MD_MAX_SIZE];
size_t transcript_len;
unsigned char *base_key = NULL;
size_t base_key_len = 0;
mbedtls_ssl_tls13_handshake_secrets *tls13_hs_secrets =
&ssl->handshake->tls13_hs_secrets;
mbedtls_md_type_t const md_type = ssl->handshake->ciphersuite_info->mac;
const mbedtls_md_info_t* const md_info =
mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_tls13_calculate_verify_data" ) );
if( from == MBEDTLS_SSL_IS_CLIENT )
{
base_key = tls13_hs_secrets->client_handshake_traffic_secret;
base_key_len = sizeof( tls13_hs_secrets->client_handshake_traffic_secret );
}
else
{
base_key = tls13_hs_secrets->server_handshake_traffic_secret;
base_key_len = sizeof( tls13_hs_secrets->server_handshake_traffic_secret );
}
if( dst_len < md_size )
{
ret = MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
goto exit;
}
ret = mbedtls_ssl_get_handshake_transcript( ssl, md_type,
transcript, sizeof( transcript ),
&transcript_len );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_get_handshake_transcript", ret );
goto exit;
}
MBEDTLS_SSL_DEBUG_BUF( 4, "handshake hash", transcript, transcript_len );
ret = ssl_tls13_calc_finished_core( md_type, base_key, transcript, dst );
if( ret != 0 )
goto exit;
*actual_len = md_size;
MBEDTLS_SSL_DEBUG_BUF( 3, "verify_data for finished message", dst, md_size );
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_tls13_calculate_verify_data" ) );
exit:
/* Erase handshake secrets */
mbedtls_platform_zeroize( base_key, base_key_len );
mbedtls_platform_zeroize( transcript, sizeof( transcript ) );
return( ret );
}
int mbedtls_ssl_tls13_create_psk_binder( mbedtls_ssl_context *ssl,
const mbedtls_md_type_t md_type,
unsigned char const *psk, size_t psk_len,
int psk_type,
unsigned char const *transcript,
unsigned char *result )
{
int ret = 0;
unsigned char binder_key[MBEDTLS_MD_MAX_SIZE];
unsigned char early_secret[MBEDTLS_MD_MAX_SIZE];
mbedtls_md_info_t const *md_info = mbedtls_md_info_from_type( md_type );
size_t const md_size = mbedtls_md_get_size( md_info );
#if !defined(MBEDTLS_DEBUG_C)
ssl = NULL; /* make sure we don't use it except for debug */
((void) ssl);
#endif
/* 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
* v
*/
ret = mbedtls_ssl_tls13_evolve_secret( md_type,
NULL, /* Old secret */
psk, psk_len, /* Input */
early_secret );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_evolve_secret", ret );
goto exit;
}
if( psk_type == MBEDTLS_SSL_TLS1_3_PSK_RESUMPTION )
{
ret = mbedtls_ssl_tls13_derive_secret( md_type,
early_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( res_binder ),
NULL, 0, MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED,
binder_key, md_size );
MBEDTLS_SSL_DEBUG_MSG( 4, ( "Derive Early Secret with 'res binder'" ) );
}
else
{
ret = mbedtls_ssl_tls13_derive_secret( md_type,
early_secret, md_size,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( ext_binder ),
NULL, 0, MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED,
binder_key, md_size );
MBEDTLS_SSL_DEBUG_MSG( 4, ( "Derive Early Secret with 'ext binder'" ) );
}
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_derive_secret", ret );
goto exit;
}
/*
* The binding_value is computed in the same way as the Finished message
* but with the BaseKey being the binder_key.
*/
ret = ssl_tls13_calc_finished_core( md_type, binder_key, transcript, result );
if( ret != 0 )
goto exit;
MBEDTLS_SSL_DEBUG_BUF( 3, "psk binder", result, md_size );
exit:
mbedtls_platform_zeroize( early_secret, sizeof( early_secret ) );
mbedtls_platform_zeroize( binder_key, sizeof( binder_key ) );
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 );
if( ciphersuite_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "ciphersuite info for %d not found",
ciphersuite ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
cipher_info = mbedtls_cipher_info_from_type( ciphersuite_info->cipher );
if( cipher_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "cipher info for %u not found",
ciphersuite_info->cipher ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
/*
* 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->minor_ver = MBEDTLS_SSL_MINOR_VERSION_4;
/* We add the true record content type (1 Byte) to the plaintext and
* then pad to the configured granularity. The mimimum length of the
* type-extended and padded plaintext is therefore the padding
* granularity. */
transform->minlen =
transform->taglen + MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY;
return( 0 );
}
int mbedtls_ssl_tls13_key_schedule_stage_early( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_md_type_t md_type;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
if( handshake->ciphersuite_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "cipher suite info not found" ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
md_type = handshake->ciphersuite_info->mac;
ret = mbedtls_ssl_tls13_evolve_secret( md_type, NULL, NULL, 0,
handshake->tls13_master_secrets.early );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_evolve_secret", ret );
return( ret );
}
return( 0 );
}
/* mbedtls_ssl_tls13_generate_handshake_keys() generates keys necessary for
* protecting the handshake messages, as described in Section 7 of TLS 1.3. */
int mbedtls_ssl_tls13_generate_handshake_keys( mbedtls_ssl_context *ssl,
mbedtls_ssl_key_set *traffic_keys )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_md_type_t md_type;
mbedtls_md_info_t const *md_info;
size_t md_size;
unsigned char transcript[MBEDTLS_TLS1_3_MD_MAX_SIZE];
size_t transcript_len;
mbedtls_cipher_info_t const *cipher_info;
size_t key_len, iv_len;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info = handshake->ciphersuite_info;
mbedtls_ssl_tls13_handshake_secrets *tls13_hs_secrets = &handshake->tls13_hs_secrets;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_tls13_generate_handshake_keys" ) );
cipher_info = mbedtls_cipher_info_from_type( ciphersuite_info->cipher );
key_len = cipher_info->key_bitlen >> 3;
iv_len = cipher_info->iv_size;
md_type = ciphersuite_info->mac;
md_info = mbedtls_md_info_from_type( md_type );
md_size = mbedtls_md_get_size( md_info );
ret = mbedtls_ssl_get_handshake_transcript( ssl, md_type,
transcript,
sizeof( transcript ),
&transcript_len );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1,
"mbedtls_ssl_get_handshake_transcript",
ret );
return( ret );
}
ret = mbedtls_ssl_tls13_derive_handshake_secrets( md_type,
handshake->tls13_master_secrets.handshake,
transcript, transcript_len, tls13_hs_secrets );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_derive_handshake_secrets",
ret );
return( ret );
}
MBEDTLS_SSL_DEBUG_BUF( 4, "Client handshake traffic secret",
tls13_hs_secrets->client_handshake_traffic_secret,
md_size );
MBEDTLS_SSL_DEBUG_BUF( 4, "Server handshake traffic secret",
tls13_hs_secrets->server_handshake_traffic_secret,
md_size );
/*
* Export client handshake traffic secret
*/
if( ssl->f_export_keys != NULL )
{
ssl->f_export_keys( ssl->p_export_keys,
MBEDTLS_SSL_KEY_EXPORT_TLS1_3_CLIENT_HANDSHAKE_TRAFFIC_SECRET,
tls13_hs_secrets->client_handshake_traffic_secret,
md_size,
handshake->randbytes + 32,
handshake->randbytes,
MBEDTLS_SSL_TLS_PRF_NONE /* TODO: FIX! */ );
ssl->f_export_keys( ssl->p_export_keys,
MBEDTLS_SSL_KEY_EXPORT_TLS1_3_SERVER_HANDSHAKE_TRAFFIC_SECRET,
tls13_hs_secrets->server_handshake_traffic_secret,
md_size,
handshake->randbytes + 32,
handshake->randbytes,
MBEDTLS_SSL_TLS_PRF_NONE /* TODO: FIX! */ );
}
ret = mbedtls_ssl_tls13_make_traffic_keys( md_type,
tls13_hs_secrets->client_handshake_traffic_secret,
tls13_hs_secrets->server_handshake_traffic_secret,
md_size, key_len, iv_len, traffic_keys );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_make_traffic_keys", ret );
goto exit;
}
MBEDTLS_SSL_DEBUG_BUF( 4, "client_handshake write_key",
traffic_keys->client_write_key,
traffic_keys->key_len);
MBEDTLS_SSL_DEBUG_BUF( 4, "server_handshake write_key",
traffic_keys->server_write_key,
traffic_keys->key_len);
MBEDTLS_SSL_DEBUG_BUF( 4, "client_handshake write_iv",
traffic_keys->client_write_iv,
traffic_keys->iv_len);
MBEDTLS_SSL_DEBUG_BUF( 4, "server_handshake write_iv",
traffic_keys->server_write_iv,
traffic_keys->iv_len);
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_tls13_generate_handshake_keys" ) );
exit:
return( ret );
}
int mbedtls_ssl_tls13_key_schedule_stage_handshake( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
mbedtls_md_type_t const md_type = handshake->ciphersuite_info->mac;
size_t ephemeral_len = 0;
unsigned char ecdhe[MBEDTLS_ECP_MAX_BYTES];
#if defined(MBEDTLS_DEBUG_C)
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 );
#endif /* MBEDTLS_DEBUG_C */
#if defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDHE_ENABLED)
/*
* Compute ECDHE secret used to compute the handshake secret from which
* client_handshake_traffic_secret and server_handshake_traffic_secret
* are derived in the handshake secret derivation stage.
*/
if( mbedtls_ssl_tls13_ephemeral_enabled( ssl ) )
{
if( mbedtls_ssl_tls13_named_group_is_ecdhe( handshake->offered_group_id ) )
{
#if defined(MBEDTLS_ECDH_C)
ret = mbedtls_ecdh_calc_secret( &handshake->ecdh_ctx,
&ephemeral_len, ecdhe, sizeof( ecdhe ),
ssl->conf->f_rng,
ssl->conf->p_rng );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_calc_secret", ret );
return( ret );
}
#endif /* MBEDTLS_ECDH_C */
}
else if( mbedtls_ssl_tls13_named_group_is_dhe( handshake->offered_group_id ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "DHE not supported." ) );
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
}
}
#else
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
#endif /* MBEDTLS_KEY_EXCHANGE_SOME_ECDHE_ENABLED */
/*
* Compute the Handshake Secret
*/
ret = mbedtls_ssl_tls13_evolve_secret( md_type,
handshake->tls13_master_secrets.early,
ecdhe, ephemeral_len,
handshake->tls13_master_secrets.handshake );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_evolve_secret", ret );
return( ret );
}
MBEDTLS_SSL_DEBUG_BUF( 4, "Handshake secret",
handshake->tls13_master_secrets.handshake, md_size );
#if defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDHE_ENABLED)
mbedtls_platform_zeroize( ecdhe, sizeof( ecdhe ) );
#endif /* MBEDTLS_KEY_EXCHANGE_SOME_ECDHE_ENABLED */
return( 0 );
}
/* Generate application traffic keys since any records following a 1-RTT Finished message
* MUST be encrypted under the application traffic key.
*/
int mbedtls_ssl_tls13_generate_application_keys(
mbedtls_ssl_context *ssl,
mbedtls_ssl_key_set *traffic_keys )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
/* Address at which to store the application secrets */
mbedtls_ssl_tls13_application_secrets * const app_secrets =
&ssl->session_negotiate->app_secrets;
/* Holding the transcript up to and including the ServerFinished */
unsigned char transcript[MBEDTLS_TLS1_3_MD_MAX_SIZE];
size_t transcript_len;
/* Variables relating to the hash for the chosen ciphersuite. */
mbedtls_md_type_t md_type;
mbedtls_md_info_t const *md_info;
size_t md_size;
/* Variables relating to the cipher for the chosen ciphersuite. */
mbedtls_cipher_info_t const *cipher_info;
size_t key_len, iv_len;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> derive application traffic keys" ) );
/* Extract basic information about hash and ciphersuite */
cipher_info = mbedtls_cipher_info_from_type(
handshake->ciphersuite_info->cipher );
key_len = cipher_info->key_bitlen / 8;
iv_len = cipher_info->iv_size;
md_type = handshake->ciphersuite_info->mac;
md_info = mbedtls_md_info_from_type( md_type );
md_size = mbedtls_md_get_size( md_info );
/* Compute current handshake transcript. It's the caller's responsiblity
* to call this at the right time, that is, after the ServerFinished. */
ret = mbedtls_ssl_get_handshake_transcript( ssl, md_type,
transcript, sizeof( transcript ),
&transcript_len );
if( ret != 0 )
goto cleanup;
/* Compute application secrets from master secret and transcript hash. */
ret = mbedtls_ssl_tls13_derive_application_secrets( md_type,
handshake->tls13_master_secrets.app,
transcript, transcript_len,
app_secrets );
/* Erase master secrets */
mbedtls_platform_zeroize( &ssl->handshake->tls13_master_secrets,
sizeof( ssl->handshake->tls13_master_secrets ) );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1,
"mbedtls_ssl_tls13_derive_application_secrets", ret );
goto cleanup;
}
/* Derive first epoch of IV + Key for application traffic. */
ret = mbedtls_ssl_tls13_make_traffic_keys( md_type,
app_secrets->client_application_traffic_secret_N,
app_secrets->server_application_traffic_secret_N,
md_size, key_len, iv_len, traffic_keys );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_make_traffic_keys", ret );
goto cleanup;
}
MBEDTLS_SSL_DEBUG_BUF( 4, "Client application traffic secret",
app_secrets->client_application_traffic_secret_N,
md_size );
MBEDTLS_SSL_DEBUG_BUF( 4, "Server application traffic secret",
app_secrets->server_application_traffic_secret_N,
md_size );
/*
* Export client/server application traffic secret 0
*/
if( ssl->f_export_keys != NULL )
{
ssl->f_export_keys( ssl->p_export_keys,
MBEDTLS_SSL_KEY_EXPORT_TLS1_3_CLIENT_APPLICATION_TRAFFIC_SECRET,
app_secrets->client_application_traffic_secret_N, md_size,
handshake->randbytes + 32,
handshake->randbytes,
MBEDTLS_SSL_TLS_PRF_NONE /* TODO: this should be replaced by
a new constant for TLS 1.3! */ );
ssl->f_export_keys( ssl->p_export_keys,
MBEDTLS_SSL_KEY_EXPORT_TLS1_3_SERVER_APPLICATION_TRAFFIC_SECRET,
app_secrets->server_application_traffic_secret_N, md_size,
handshake->randbytes + 32,
handshake->randbytes,
MBEDTLS_SSL_TLS_PRF_NONE /* TODO: this should be replaced by
a new constant for TLS 1.3! */ );
}
MBEDTLS_SSL_DEBUG_BUF( 4, "client application_write_key:",
traffic_keys->client_write_key, key_len );
MBEDTLS_SSL_DEBUG_BUF( 4, "server application write key",
traffic_keys->server_write_key, key_len );
MBEDTLS_SSL_DEBUG_BUF( 4, "client application write IV",
traffic_keys->client_write_iv, iv_len );
MBEDTLS_SSL_DEBUG_BUF( 4, "server application write IV",
traffic_keys->server_write_iv, iv_len );
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= derive application traffic keys" ) );
cleanup:
/* randbytes is not used again */
mbedtls_platform_zeroize( ssl->handshake->randbytes,
sizeof( ssl->handshake->randbytes ) );
mbedtls_platform_zeroize( transcript, sizeof( transcript ) );
return( ret );
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
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