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5  Extended Components Definition 
This section describes Extended Components Definition. 
5.1  Restricted forwarding of data to external interfaces (FPT_FDI_EXP) 
Family behaviour 
This family defines requirements for the TSF to restrict direct forwarding of information from one external 
interface to another external interface. 
 
Many products receive information on specific external interfaces and are intended to transform and process 
this information before it is transmitted on another external interface. However, some products may provide 
the capability for attackers to misuse external interfaces to violate the security of the TOE or devices that are 
connected to the TOE's external interfaces. Therefore, direct forwarding of unprocessed data between 
different external interfaces is forbidden unless explicitly allowed by an authorized administrative role. The 
family FPT_FDI_EXP has been defined to specify this kind of functionality. 
 
Component levelling: 
FPT_FDI_EXP: Restricted forwarding of data to external interfaces  1 
 
FPT_FDI_EXP.1 Restricted forwarding of data to external interfaces provides for the functionality to require 
TSF controlled processing of data received over defined external interfaces before these data are sent out on 
another external interface. Direct forwarding of data from one external interface to another one requires 
explicit allowance by an authorized administrative role. 
 
Management: FPT_FDI_EXP.1 
The following actions could be considered for the management functions in FMT: 
a)  Definition of the role(s) that are allowed to perform the management activities 
b)  Management of the conditions under which direct forwarding can be allowed by an administrative role 
c)  Revocation of such an allowance 
 
Audit: FPT_FDI_EXP.1 
There are no auditable events foreseen. 
 
Rationale: 
Quite often, a TOE is supposed to perform specific checks and process data received on one external 
interface before such (processed) data are allowed to be transferred to another external interface. Examples