ECP: Add mbedtls_ecp_tls_read_group_id()
`mbedtls_ecp_tls_read_group()` both parses the group ID and loads the
group into the structure provided. We want to support alternative
implementations of ECDH in the future and for that we need to parse the
group ID without populating an `mbedtls_ecp_group` structure (because
alternative implementations might not use that).
This commit moves the part that parses the group ID to a new function.
There is no need to test the new function directly, because the tests
for `mbedtls_ecp_tls_read_group()` are already implicitly testing it.
There is no intended change in behaviour in this commit.
diff --git a/library/ecp.c b/library/ecp.c
index de5725c..49255b1 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -833,7 +833,24 @@
/*
* Set a group from an ECParameters record (RFC 4492)
*/
-int mbedtls_ecp_tls_read_group( mbedtls_ecp_group *grp, const unsigned char **buf, size_t len )
+int mbedtls_ecp_tls_read_group( mbedtls_ecp_group *grp,
+ const unsigned char **buf, size_t len )
+{
+ int ret;
+ mbedtls_ecp_group_id grp_id;
+
+ if( ( ret = mbedtls_ecp_tls_read_group_id( &grp_id, buf, len ) ) != 0 )
+ return( ret );
+
+ return mbedtls_ecp_group_load( grp, grp_id );
+}
+
+/*
+ * Read a group id from an ECParameters record (RFC 4492) and convert it to
+ * mbedtls_ecp_group_id.
+ */
+int mbedtls_ecp_tls_read_group_id( mbedtls_ecp_group_id *grp,
+ const unsigned char **buf, size_t len )
{
uint16_t tls_id;
const mbedtls_ecp_curve_info *curve_info;
@@ -860,7 +877,9 @@
if( ( curve_info = mbedtls_ecp_curve_info_from_tls_id( tls_id ) ) == NULL )
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
- return mbedtls_ecp_group_load( grp, curve_info->grp_id );
+ *grp = curve_info->grp_id;
+
+ return( 0 );
}
/*