Eric,
Looks good. I've suggested a few minor changes below, mostly to soften the notion that this is an official response, as opposed to some comments to jump start Friday's discussion.
David
On Wed, 2013-10-30 at 16:25 +0000, Eric Goodman wrote:
Morning AD-DS-AM folks!
Here’s my draft of a response to the comments below. Does this sufficiently capture our discussion and responses? Comments? Corrections? Additions? Wordsmithing?
--- Eric
AD DS workgroup's response to the comments by Scott Koranda and Tom Barton,
AD Silver Cookbook workgroup's thoughts on the comments by Scott Koranda and Tom Barton
We are responding to the following comments noted in the thread below:
1) That administrative accounts that exist in an AD DS store are in scope of 4.2.3.6.1, 4.2.3.4 and 4.2.8(.2). (In response to our interpretation of 4.2.3.6.1)
2) That calling out the "change my password page" is potentially confusing and unintentionally scope-limiting. (In response to our interpretation of 4.2.3.6.2)
3) That our restriction/categorization of the requirements of various Authentication Secrets is not in line with the IAP (Also in response to our interpretation of 4.2.3.6.2)
We are largely in agreement with comments (1) and (2). Our intent in each of these was to limit the scope of the AD configuration requirements to only address accounts which can be used to generate IdP assertions. Note that there is a minor but significant error in our text, in that the reference to the "change my password page" should
...is a small but significant...
have been headed with "e.g.", not "i.e." In this way, we meant the statement to broadly include your comment #2 as well. We are happy to remove the specific example, and will work on language to clarify that any system or account that can undermine IdP assertion generation is in scope.
The one further clarification that we would add is this:
If AD is NOT the IdP verifier, but only has provisioned copies of the password used by the IdP, then the security of the administrative accounts in the AD DS are still out of scope of IAP in this section. That is, only those admin accounts, etc. that are capable of changing the password copies used by the IdP are relevant.
I think it's a little broader than just changing passwords. How about "...that are capable of affecting assertions issued by the IdP are relevant."
On comment number (3), we believe our original interpretation sufficiently addresses the concerns subsequently raised in the discussion below.
With the configuration we have specified, username and password are the only Authentication Secrets that can be used to generate authentication assertions from the IdP. Therefore, Kerberos traffic (which does not directly transmit username/password) and NTLM traffic (which does not directly transmit username/password) while containing Authentication Secrets (encrypted tickets, challenges and responses) does not contain Authentication Secrets that are used by the IdP. Again, our interpretation is that Authentication Secrets used by the IdP are in scope of the IAP, regardless of whether the use of those secrets are by IdP or “some non-IdP application to a verifier”. Authentication Secrets that are NOT used by the IdP are the only secrets we are declaring out of scope.
We will note that if Kerberos and in particular NTLM traffic is considered in scope, then we believe either AD systems will not be able to be used to house InCommon Silver-compliant credentials in any realistic deployment and we will therefore submit an Alternate Means proposal allowing the use of these protocols. The arguments for the Alternative Means statement would be largely identical to the arguments we’ve given in the interpretation and in the above paragraph, we’d just be changing from arguing that our configuration “meets the requirements” to it “is an acceptable alternate means to meet the requirement”.
The use of the word "realistic" seems to argue against an alternative means that would be comparable. How about, "...then we believe that, in a literal reading of the IAP, AD systems cannot be used to house Silver-compliant credentials, because AD does not use Approved Algorithms." We would, therefore, propose an Alternative Means statement allowing the use of other algorithms in specific situations."
--- Eric
-----Original Message-----
From: [mailto:] On Behalf Of Dunker, Mary
Sent: Wednesday, October 23, 2013 12:39 PM
To: ''
Subject: [AD-Assurance] FW: [aac] AD Assurance Cookbook: Interpretation Sections
AD Assurance Cookbook Working Group members,
On behalf of the InCommon Assurance Advisory Committee (AAC), I am forwarding (below) comments by Scott Koranda and Tom Barton regarding specific sections of the AD Assurance Cookbook. We look forward to further discussion with you during your conference call at noon on Friday, November 1, 2013.
Best regards,
Mary Dunker
Chair, InCommon Assurance Advisory Committee
-----------------------------------------------------------------
Mary Dunker
Director, Secure Enterprise Technology Initiatives Virginia Tech Information Technology
1700 Pratt Drive
Blacksburg, VA 24060
540-231-9327
--------------------------------------------------------------------
-----Original Message-----
From: [mailto:] On Behalf Of Tom Barton
Sent: Monday, October 14, 2013 12:30 PM
To:
Subject: Re: [aac] AD Assurance Cookbook: Interpretation Sections
Some responses to the issues Scott raised are below. -Tom
On 10/13/2013 11:04 AM, Scott Koranda wrote:
> Hi,
>
>> Hi All,
>>
>> As I mentioned on yesterday's AAC call, the AD Assurance Cookbook has
>> been released for open review, and the working group is looking for
>> our guidance on their interpretations of the specific sections. I've
>> included the link to the entire cookbook below as well as the specific wording they would like reviewed.
>>
>> LINK: https://spaces.internet2.edu/display/InCAssurance/
>> InCommon+Silver+with+Active+Directory+Domain+Services+Cookbook+-+DRAFT+20131002
>> #
>> InCommonSilverwithActiveDirectoryDomainServicesCookbook-DRAFT20131002
>> -SecuringAuthenticationTraffic
>>
>> Thoughts?
>>
>> Ann
>>
>>
>> 4.2.2. Interpretation of IAP requirement, Section 4.2.3.6.1 - Strong
>> Protection of Authentication Secrets (Second Sentence)
>>
>> Note, this IAP requirement addresses both storage and transmission of
>> passwords, so is addressed under both the "Encrypting Passwords"
>> topic and the "Securing Authentication Traffic" sections.
>>
>> This requirement applies when IdP Verifier passwords are provisioned
>> into an AD DS store, whether or not the AD DS store being provisioned
>> to is the actual IdP Verifier. Note that this requirement only
>> applies to passwords for accounts that are actually authenticated by
>> the IdP (non-IdP accounts that are "co located" in the AD DS have no such requirements).
> I think the statement "this requirement only applies to passwords for
> accounts that are actually authenticated by the IdP (non-IdP accounts
> that are "co-located" in the AD DS have no such requirements)" is too
> strong.
>
> I would agree that non-administrative non-IdP co-located accounts have
> no such requirements, but any administrative account in the AD must be
> covered and subject to operational constraints in 4.2.3.4 and 4.2.8,
> since any compromise of an AD privileged account immediately escalates
> to compromising AD accounts that are authenticated by the IdP.
Right, although this section of the cookbook addresses 4.2.3.6.1 perhaps it should also account for 4.2.8.2, which it currently does not mention.
>> For example, if an MIT Kerberos system is used as the IdP Verifier,
>> but the passwords used by that Kerberos system are also provisioned
>> into an AD DS, the AD DS provisioning process is in scope and
>> therefore must use Protected Channels, even though it is not being
>> used as the IdP's Verifier. (Again, this only applies to passwords
>> for accounts that are actually authenticated by the
>> IdP)
> See above. It should apply to passwords for accounts that are actually
> authenticated by the IdP AND all administrative or privileged accounts
> that can be used to make any administrative changes to accounts that
> are authenticated by the IdP.
>
>> 4.2.3. Interpretation of IAP Requirement, Section 4.2.3.6.2
>> - Strong Protection of Authentication Secrets
>>
>> Authentication Secrets[1] in the context of this requirement is
>> interpreted to mean those secrets (passwords, Kerberos session keys,
>> NTLM challenge responses, etc.) that can be used to directly
>> authenticate to the IdP or to directly modify authentication
>> credentials (i.e., can be submitted directly to a change my password
>> page).
>>
>> Another way of stating this is that the intent of 4.2.3.6.2 is only
>> to protect against risks that can attack the IdP’s direct
>> authentication to its Verifier; protection of non-IdP Authentication
>> Secrets that incidentally use the same Verifier as the IdP, such as
>> Windows/Kerberos Tickets used to authenticate a user to a domain (a
>> la ctrl-alt-del)[2], are not in scope of 4.2.3.6.2. These non-IdP
>> Authentication Secrets are addressed elsewhere in the spec, such as
>> in 4.2.3.6.3.
> I disagree.
>
> 4.2.3.6.2 is clear:
>
> "...for example, an IdP to a Verifier, or some non-IdP application to
> a Verifier".
>
> The phrase "non-IdP application to a Verifier" clearly puts "non-IdP
> Authentication Secrets that incidentally use the same Verifier as the
> IdP" in scope for 4.2.3.6.2.
>
> I understand that by making this statement and arguing that
> 4.2.3.6.2 keeps in scope the AD traffic between MS Windows deployments
> and the AD server there are serious issues, but I see no other way to
> interpret 4.2.3.6.2 in version 1.2 of the spec.
>
> I would appreciate hearing other input on this before I proceed
> further with the items below, since I believe the construction the AD
> Cookbook team is using to "thread the needle" here falls apart here if
> my interpretation stands.
When I read this section I understand "non-IdP authentication secrets" to mean those of credentials that are not in scope for the IAP (for which a definition is offered in the first paragraph of this cookbook section). I don't see any statement in cookbook section 4.2.3 that implies that a non-IdP app using AD as a verifier is exempt from 4.2.3.6.2 when handling an in-scope secret. Also the cookbook's recommendations in section 5.3.1 explicitly apply to non-IdP apps equally.
I read cookbook section 4.2.3's use of a "change my password" app to be a literal broadening of what it means to be in scope for the IAP, though a logical one. But I suppose it might also mislead a reader to think that no other non-IdP app is covered by 4.2.3.6.2. Perhaps a specific statement should be included explaining that non-IdP apps which handle in-scope secrets are also subject to 4.2.3.6.2 and those that use AD as a verifier are addressed in cookbook section 5.3.2.
Further, use of a "change my password" app in connection with in-scope secrets is covered under IAP 4.2.4.3. When IAP 4.2.4.3.1 is used for password changing, the password changing app is subject to 4.2.3.6.2. So I'm not sure that singling it out here is really helpful.
Back to defining what's in scope, the definition in this cookbook section appears to be: if it's used to authenticate to the IdP, or if it's used to authenticate to a change my password app. I think the definition of in-scope authentication secrets is not related solely to specific technologies. They are in scope if they meet a whole variety of criteria that underpin the design of the overall Silver implementation.
We might suggest editorial changes be made in cookbook section 4.2 to help ensure that readers understand what I think the authors intended.
> Thanks,
>
> Scott
>
>> [1] The term “Authentication Secret” is assumed here to include the
>> information in an authentication packet; e.g., in addition to actual
>> authentication credentials (username/password), the information
>> negotiating the initial exchange of a session key or the response to
>> an authentication challenge is an “Authentication Secret”.
>>
>> [2] This assumes that the local Windows/Kerberos tickets cannot be
>> leveraged to authenticate the user to the IdP, such as a standard
>> webpage that prompts for entry of user credentials. If the IdP
>> supports mechanisms that allow the user to generate authentication
>> assertions based directly on the possession of local Windows/Kerberos
>> tickets (e.g., SPNEGO, GSSAPI), then the Windows/Kerberos tickets used in that interaction WOULD be in scope of this requirement.
>>
>> 4.2.4. Interpretation of IAP Requirement, Section 4.2.3.6.3
>> - Strong Protection of Authentication Secrets
>>
>> This section addresses all handling of IdP Verifier authentication
>> secrets, even if those authentication secrets are not used to
>> authenticate anyone to the IdP. Note that authentication secrets that
>> could be replayed to authenticate directly to the IdP are also
>> covered by section 4.2.3.6.2, which has stricter requirements around
>> transport encryption.
>>
>> That is, assuming an IdP that requires manual entry of a
>> username/password:
>>
>> • applications (including non-IdP applications) that
>> handle the username/ password would be covered by both
>> sections 4.2.3.6.2 and 4.2.3.6.3. • applications
>> (including non-IdP applications) that handle non-IdP
>> authentication secrets based on IdP passwords (e.g., LM,
>> NTLMv1, NTLMv2 or MIT Kerberos authentication packets for
>> Silver IAQ users) would be covered only by section
>> 4.2.3.6.3
>>
>> This section requires that policies and procedures are in place to
>> minimize the risk of this traffic being attacked in a way that would
>> subvert the security of IdP authentication events. While traffic
>> covered in this section may use Protected Channels to secure
>> authentication communications, an institution could also use other
>> mechanisms that are generally considered secure, even if they are not
>> Protected Channels.
>>
>> For completeness, we note that protection of the password while it is
>> being locally processed within any application is also required, not
>> just protection while in transit to or from said application.
>> However, security of the information while being handled in a
>> transient fashion within a web application is beyond the scope of AD
>> DS configuration, so is not covered here.
>>
>> 4.2.5. Interpretation of IAP Requirement, Section 4.2.5.1 - Resist
>> Replay Attack
>>
>> This section refers specifically to traffic between the Subject and
>> the IdP, the IdP's Verifier, and/or a relying party as part of an IdP
>> authentication/ assertion event. All other traffic between the
>> Subject and the AD DS is beyond the scope of 4.2.5.2. Replay of
>> non-IdP authentication/assertion traffic is covered by sections
>> 4.2.3.6.2 and 4.2.3.6.3.
>>
>> 4.2.6. Interpretation of IAP Requirement, Section 4.2.5.2 - Resist
>> Eavesdropper Attack
>>
>> This section refers specifically to traffic between the Subject and
>> the IdP, the IdP's Verifier, and/or a relying party as part of an IdP
>> authentication/ assertion event. All other traffic between the
>> Subject and the AD DS is beyond the scope of 4.2.5.2. Eavesdropping
>> on non-IdP authentication/assertion traffic is covered by sections
>> 4.2.3.6.2 and 4.2.3.6.3.
>>
>> 4.2.7. Interpretation of IAP Requirement, Section 4.2.8.2.1
>> - Network Security
>>
>> "Network communications supporting IdMS operations" is interpreted to
>> mean communications between the actual software elements of the IDMS
>> operation or administrative traffic to the IDMS.
>>
>> So the only AD DS-specific communications that would be in scope of
>> this requirement is intra-domain controller password replication.
>> (Note that provisioning of passwords into AD-DS is covered by
>> 4.2.3.6.1)
>>
>>
>> Ann West Assistant Director, InCommon Assurance and Community
>> Internet2 based at Michigan Tech office:
>> +1.906.487.1726
|
