Re: [MIB-DOCTORS] Fix of Security Guidelines for IETF MIB Modules

Glenn Mansfield Keeni <glenn@cysols.com> Sun, 30 September 2018 13:00 UTC

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To: Randy Presuhn <randy_presuhn@alumni.stanford.edu>, mib-doctors@ietf.org, warren@kumari.net, ibagdona@gmail.com
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From: Glenn Mansfield Keeni <glenn@cysols.com>
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Date: Sun, 30 Sep 2018 21:59:05 +0900
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Subject: Re: [MIB-DOCTORS] Fix of Security Guidelines for IETF MIB Modules
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Hi,
 >         What
 >         is the point of limiting read access and then sending the
 >         information in the clear?
Total agreement. Sending info in the clear is by default NG and must
be strongly discouraged.
It will help to have some proposed replacement text for
 > OLD:  It is thus important to control even GET and/or NOTIFY access to
 >        these objects and possibly to even encrypt the values of these
 >        objects when sending them over the network via SNMP.
 >

Glenn


On 2018/09/30 2:56, Randy Presuhn wrote:
> Hi -
> 
> On 9/28/2018 11:52 PM, Glenn Mansfield Keeni wrote:
>> Warren,Ignas,
>>         Hi. The Security Guidelines for IETF MIB Modules
>> needs a fix in the text that is generally used verbatim
>> in MIB documents.
>> The proposed fix is
>>
>> OLD: Some of the readable objects in this MIB module
>>       (i.e., objects with a MAX-ACCESS other than
>>        not-accessible)
>> NEW: Some of the readable objects in this MIB module
>>       (e.g., objects with a MAX-ACCESS other than
>>        not-accessible)
>>
>> The above is a significant nit. It appears in the
>> Security Considerations sections section of every
>> MIB document.
>>
>> There has been some discussion on the IETF MIB-DOCTORS
>> mailing list on this matter. There is no disagreement
>> on the proposed fix.
> 
> In the scope of the document under consideration at the
> time, I think that fix was ok, but in the context of a
> boilerplate update I think we'd need to do better.
> 
> For those who missed the original discussion, the issue is
> that the values of "not-accessible" objects can
>     (1) be sensitive
>     (2) be revealed as index values
> 
> Consider, as a trivial, made-up example, a table indexed
> by user name.
> 
> OLD:  Some of the readable objects in this MIB module (i.e., objects
>        with a MAX-ACCESS other than not-accessible) may be considered
>        sensitive or vulnerable in some network environments.
> 
> NEW:  Some of the objects in this MIB module may be considered sensitive
>        or vulnerable in some network environments.  This includes INDEX
>        objects with a MAX-ACCESS of not-accessible, and any indices from
>        other modules exposed via AUGMENTS.
> 
> But, if we are going to touch the boilerplate, I wouldn't stop there.
> I think the next sentence brings its own related problems.
> 
> OLD:  It is thus important to control even GET and/or NOTIFY access to
>        these objects and possibly to even encrypt the values of these
>        objects when sending them over the network via SNMP.
> 
> The issues I see with this are:
> 
>     (1) in the case of objects used as indexes, controlling access to
>         them via VACM is *not* just a matter of controlling access to
>         the objects themselves, but of controlling access to all
>         objects using them as indexes, including usage via AUGMENTS.
> 
>     (2) index values may be leaked by "pointer" objects of type
>         OBJECT IDENTIFIER.  If VACM is being used for access control,
>         the rules have to be formulated in terms of the pointer, not
>         the set of things it might point to.  That problem is outside
>         the scope of the module whose objects are being pointed to,
>         but it's still a problem that needs to be addressed in any
>         module defining such pointers.
> 
>     (3) even without considering the case of indexes, I would argue that
>         if something is sensitive enough to merit limiting read access,
>         in any sane security regime it will also merit encryption.  What
>         is the point of limiting read access and then sending the
>         information in the clear?
> 
> I'll concede that there are cases where limiting *write* access does not
> imply a need for encryption, but this paragraph conflates sensitive and
> vulnerable information.  It might make sense to split the paragraph into
> two, one identifying the information for which disclosure is an issue,
> and another identifying the information for which creation / deletion /
> modification is an issue.
> 
> Randy