Robustness fix in mbedtls_ssl_derive_keys

In mbedtls_ssl_derive_keys, don't call mbedtls_md_hmac_starts in
ciphersuites that don't use HMAC. This doesn't change the behavior of
the code, but avoids relying on an uncaught error when attempting to
start an HMAC operation that hadn't been initialized.
This commit is contained in:
Gilles Peskine 2018-03-19 19:06:08 +01:00
parent 6013004fa9
commit 21701305ce

View file

@ -855,8 +855,13 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
defined(MBEDTLS_SSL_PROTO_TLS1_2)
if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 )
{
mbedtls_md_hmac_starts( &transform->md_ctx_enc, mac_enc, mac_key_len );
mbedtls_md_hmac_starts( &transform->md_ctx_dec, mac_dec, mac_key_len );
/* For HMAC-based ciphersuites, initialize the HMAC transforms.
For AEAD-based ciphersuites, there is nothing to do here. */
if( mac_key_len != 0 )
{
mbedtls_md_hmac_starts( &transform->md_ctx_enc, mac_enc, mac_key_len );
mbedtls_md_hmac_starts( &transform->md_ctx_dec, mac_dec, mac_key_len );
}
}
else
#endif