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Introduce helper function to determine whether suite uses server CRT

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This commit introduces a static helper function

   `mbedtls_ssl_ciphersuite_uses_srv_cert()`

which determines whether a ciphersuite may make use of server-side CRTs.

This function is in turn uses in `mbedtls_ssl_parse_certificate()` to
skip certificate parsing for ciphersuites which don't involve CRTs.

Note: Ciphersuites not using server-side CRTs don't allow client-side CRTs
either, so it is safe to guard `mbedtls_ssl_{parse/write}_certificate()`
this way.

Note: Previously, the code uses a positive check over the suites

- MBEDTLS_KEY_EXCHANGE_PSK
- MBEDTLS_KEY_EXCHANGE_DHE_PSK
- MBEDTLS_KEY_EXCHANGE_ECDHE_PSK
- MBEDTLS_KEY_EXCHANGE_ECJPAKE,

while now, it uses a negative check over `mbedtls_ssl_ciphersuite_uses_srv_cert()`,
which checks for the suites

- MBEDTLS_KEY_EXCHANGE_RSA
- MBEDTLS_KEY_EXCHANGE_RSA_PSK
- MBEDTLS_KEY_EXCHANGE_DHE_RSA
- MBEDTLS_KEY_EXCHANGE_ECDH_RSA
- MBEDTLS_KEY_EXCHANGE_ECDHE_RSA
- MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA
- MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA

This is equivalent since, together, those are all ciphersuites.
Quoting ssl_ciphersuites.h:

```
typedef enum {
    MBEDTLS_KEY_EXCHANGE_NONE = 0,
    MBEDTLS_KEY_EXCHANGE_RSA,
    MBEDTLS_KEY_EXCHANGE_DHE_RSA,
    MBEDTLS_KEY_EXCHANGE_ECDHE_RSA,
    MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA,
    MBEDTLS_KEY_EXCHANGE_PSK,
    MBEDTLS_KEY_EXCHANGE_DHE_PSK,
    MBEDTLS_KEY_EXCHANGE_RSA_PSK,
    MBEDTLS_KEY_EXCHANGE_ECDHE_PSK,
    MBEDTLS_KEY_EXCHANGE_ECDH_RSA,
    MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA,
    MBEDTLS_KEY_EXCHANGE_ECJPAKE,
} mbedtls_key_exchange_type_t;
```
This commit is contained in:
Hanno Becker 2019-02-05 13:36:46 +00:00
parent 2148993900
commit 7177a88a36
2 changed files with 22 additions and 17 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
include/mbedtls/ssl_ciphersuites.h
View file

@ -486,6 +486,24 @@ static inline int mbedtls_ssl_ciphersuite_cert_req_allowed( const mbedtls_ssl_ci
}
}
static inline int mbedtls_ssl_ciphersuite_uses_srv_cert( const mbedtls_ssl_ciphersuite_t *info )
{
switch( info->key_exchange )
{
case MBEDTLS_KEY_EXCHANGE_RSA:
case MBEDTLS_KEY_EXCHANGE_RSA_PSK:
case MBEDTLS_KEY_EXCHANGE_DHE_RSA:
case MBEDTLS_KEY_EXCHANGE_ECDH_RSA:
case MBEDTLS_KEY_EXCHANGE_ECDHE_RSA:
case MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA:
case MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA:
return( 1 );
default:
return( 0 );
}
}
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__DHE_ENABLED)
static inline int mbedtls_ssl_ciphersuite_uses_dhe( const mbedtls_ssl_ciphersuite_t *info )
{

21
library/ssl_tls.c
View file

@ -5565,10 +5565,7 @@ int mbedtls_ssl_write_certificate( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write certificate" ) );
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
if( !mbedtls_ssl_ciphersuite_uses_srv_cert( ciphersuite_info ) )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip write certificate" ) );
ssl->state++;
@ -5585,10 +5582,7 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate" ) );
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
if( !mbedtls_ssl_ciphersuite_uses_srv_cert( ciphersuite_info ) )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
ssl->state++;
@ -5611,10 +5605,7 @@ int mbedtls_ssl_write_certificate( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write certificate" ) );
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
if( !mbedtls_ssl_ciphersuite_uses_srv_cert( ciphersuite_info ) )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip write certificate" ) );
ssl->state++;
@ -5755,7 +5746,6 @@ static int ssl_parse_certificate_chain( mbedtls_ssl_context *ssl )
size_t i, n;
uint8_t alert;
if( ssl->in_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate message" ) );
@ -5970,10 +5960,7 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate" ) );
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
if( !mbedtls_ssl_ciphersuite_uses_srv_cert( ciphersuite_info ) )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
goto exit;