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Fix potential buffer overread with USE_PSA

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Using opaque keys for static ECDH is not supported in this branch (will
be introduced in 3.2). In case we reach that point, error out cleanly
instead of miscasting a pointer. Since opaque keys were introduced,
mbedtls_pk_can_do() was no longer a precise enough check.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard
2022-06-10 09:25:01 +02:00
committed by Manuel Pégourié-Gonnard
parent bb54fce91e
commit 37e5999ac3
2 changed files with 11 additions and 2 deletions
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6
ChangeLog.d/buf-overread-use-psa-static-ecdh.txt Normal file
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@ -0,0 +1,6 @@
Security
* Fix a potential heap buffer overread in TLS 1.2 server-side when
MBEDTLS_USE_PSA_CRYPTO is enabled, an opaque key (created with
mbedtls_pk_setup_opaque()) is provisioned, and a static ECDH ciphersuite
is selected. This may result in an application crash. No path to
information leak has been identified.

7
library/ssl_srv.c
View File

@ -3239,15 +3239,18 @@ static int ssl_write_certificate_request( mbedtls_ssl_context *ssl )
static int ssl_get_ecdh_params_from_cert( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_pk_context *own_key = mbedtls_ssl_own_key( ssl );
if( ! mbedtls_pk_can_do( mbedtls_ssl_own_key( ssl ), MBEDTLS_PK_ECKEY ) )
/* We want to call mbedtls_pk_ec(), which only works on those types. */
if( mbedtls_pk_get_type( own_key ) != MBEDTLS_PK_ECKEY &&
mbedtls_pk_get_type( own_key ) != MBEDTLS_PK_ECKEY_DH )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "server key not ECDH capable" ) );
return( MBEDTLS_ERR_SSL_PK_TYPE_MISMATCH );
}
if( ( ret = mbedtls_ecdh_get_params( &ssl->handshake->ecdh_ctx,
mbedtls_pk_ec( *mbedtls_ssl_own_key( ssl ) ),
mbedtls_pk_ec( *own_key ),
MBEDTLS_ECDH_OURS ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ecdh_get_params" ), ret );