PD 0152: Internal Inconsistency within the IDS System PP regarding FPT_STM

["Observation Decisions Review Board" <faigin@aero.org>]

The following PD (PD-0152) was developed by the ODRB during its April/
May meeting.  Comments on this PD are welcome and will be considered at
the next ODRB meeting.


TITLE	

Internal Inconsistency within the IDS System PP regarding FPT_STM

ISSUE

There is an apparent inconsistency in the U.S. Government Protection
Profile Intrusion Detection System - System For Medium Robustness
Environments.  This inconsistency relates to FPT_STM.  FPT_STM levies
the reliable timestamp requirement on the TOE, whereas the mapped
objective (OE.TIME) states that the timestamps shall be provided by the
IT environment. 

A recent evaluation addressed this inconsistency by noting the following
in the rationale for the work unit ASE_TSS.1-1, it states: 

	Although, no description is present in the TSS that describes
	how the TOE meets FPT_STM.1, there is an application note in ST
	section 6.1.4.2 which justifies its omission from the TSS. The
	application note states: 

	"Application Note: FPT_STM.1 is included in the IDS System PP;
	however, this contradicts OE.TIME: "The IT Environment will
	provide reliable timestamps to the TOE.", which is also part of
	the IDS System PP. This ST will treat FPT_STM.1 as an IT
	Environment SFR." 

The evaluator has determined this is an expectable solution due the
conflicting justification in the PP that includes FPT_STM.1 as a TOE
SFR, yet maps the function to an Objective for the Environment
(OE.TIME).  
 
RESOLUTION

The U.S. Government Protection Profile Intrusion Detection System -
System For Medium Robustness Environments states in "OE.TIME" that the
IT Environment will provide reliable timestamps to the TOE. Therefore,
CCEVS agrees that FPT_STM.1 Reliable time stamps should be designated to
the IT environment.  The PP will be updated to reflect this decision in
the next version.  In the interim, CCEVS accepts the above application
note as an acceptable justification to be placed in a product ST
claiming conformance to the U.S. Government Protection Profile Intrusion
Detection System - System For Medium Robustness Environments.  

RATIONALE

A product can comply with the IDS PP and be distinct from an underlying
OS. Therefore, the TOE getting the timestamps from the environment was
intended to be acceptable, as stated in the objective OE.TIME.  The PP
shall be updated to remedy the identified inconsistency. 


--
Daniel Faigin, CISSP, Coordinator for the CCEVS ODRB
Please send any comments or questions on this post to faigin@aero.org, and 
indicate it is an ODRB issue.