- caops-wg - lists.ogf.org

RE: Name Constraints, was Re: [caops-wg] Re: ca signing policy file
by Cowles, Robert D. 16 Oct '05

16 Oct '05

> -----Original Message----- > From: David Chadwick [mailto:d.w.chadwick@kent.ac.uk] > Sent: Thursday, October 13, 2005 2:39 AM ... > > Robert > > perhaps the real question is, do you change your authorisation rights > more or less frequently than your identifier. If more > frequently, then > it does not really matter if your identifier changes every > year or two > since you can change your authorisation rights to match the new > identifier when it comes active. But if your authorisation rights are > much longer lived than your identifier, then it becomes a > pain to have > to change these as well. However, in this case I would > suggest that your > authorisation rights are wrapped into the PKC, say in the > subjectDirectoryAttributes extension, then they would carry > over to the > new identifier. > > regards > > David In teresting point .. and that is precisely a problem we have with Attribute Certificates and Proxy Certificate renewal. I have been wondering if we can extend the allowed lifetime of proxy certificates so long as we can revoke their authorizaton to do anything. BC

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RE: [caops-wg] Name Constraints - attempt at framing issues
by Cowles, Robert D. 16 Oct '05

16 Oct '05

> the issue is about global naming. You used a globally unique email > address in the certificate when you posed the question, so I > said yes. > If on the other hand you had just put Brett in the cert then > of course I > would not expect this to always name the same person. > But how can you believe that brett(a)isp.com is globally unique over time when companies like Verisign will resell "isp.com" almost immediately when it becomes available? BC

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RE: [caops-wg] Name Constraints - attempt at framing issues
by Cowles, Robert D. 16 Oct '05

16 Oct '05

> > As I have said before, the purpose of a CA is to authenticate > a user's > right to use a claimed name, and then bind that to his public > key ie. to > certify the key to name binding. ie., a certification > authority. It is > not, I repeat not, to be a naming authority. > > regards > David As I have said before, the purpose of a CA it to be sure that if it is issuing a certificate either the DN has not been used before by that CA or it can verify that it is issuing the Cert to the same person as used the DN before. Unfortunately, this means storing Personally Identifiable Information so you can have something to check at time of renewal / re-issue ... and we are being required to have more and more protection associated with any PII we retain. Bob Cowles

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RE: Name Constraints, was Re: [caops-wg] Re: ca signing policy file
by Cowles, Robert D. 16 Oct '05

16 Oct '05

> -----Original Message----- > From: David Chadwick [mailto:d.w.chadwick@kent.ac.uk] > Sent: Friday, October 14, 2005 9:48 AM ... > Cowles, Robert D. wrote: > > > > The gridmapfile gives no clue as to CA or to VO. > > > > Why do PKI *users* care about 2)? > > They dont (except to know which CA to go to). Name constraints is a > trust issue between CAs, they set the policies, and then the > RPs enforce > them when giving access to their resources. Of course an RP > can ignore a > CA's policy, and trust any cert it wanted to, but then it would be > entirely responsible for any losses incurred. > > regards > David Precisely .. it's between CA's. When I brought up the issue of signing policy several year ago it was in the context that we weren't telling the relying parties that the authentication mechanism relied on the signing policy file and in keeping the DN's for the CA's to be disjoint sets. A site could easily believe that another CA was entirely trustworthy in authenticating users (e. g. Verisign rather than Thawte) and not realize that if the set of DN's you could get Versign to issue overlapped with one of the other CA's then you no longer had viable authentication, eventhough all the Ca's were doing their job and you correctly described the certificates that could be trusted in the signing policy file. My point is that we always say it's up to the RP to put any CA in the list of trusted CA's but we weren't saying that the DN's MUST NOT overlap those from any other trusted CA.

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RE: Name Constraints, was Re: [caops-wg] Re: ca signing policy file
by Cowles, Robert D. 16 Oct '05

16 Oct '05

> -----Original Message----- > From: David Chadwick [mailto:d.w.chadwick@kent.ac.uk] > Sent: Friday, October 14, 2005 9:50 AM ... > > Cowles, Robert D. wrote: > > > > The gridmapfile gives no clue as to CA or to VO. > > Also to the time of day, or user location, or request parameters, or > hundreds of other things that might place conditions on what > the user is > allowed to do. So gridmap files were a nice first shortcut to get > something working fast (a bit like the GridShib mapping file > today)but > they cannot realistically be expected to provide a long term solution > > regards > > David No .. but they seem very "sticky" and difficult to get rid of. I am also aware of sites adding CA's to the trusted list without understanding the implications of having a "trusted CA" that had no signing policy constraints .... I could be wrong -- if a CA doesn't appear in the signing policy file, is it unconstrained or competely constrained? (if couse, if the latter, the site is likely to add an unconstrained entry to get things working rather than try to figure out the proper constraints.) BC

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RE: Name Constraints, was Re: [caops-wg] Re: ca signing policy file
by Cowles, Robert D. 14 Oct '05

14 Oct '05

The name constraints are important because the gridmapfile doesn't contain the CA that issued the DN, only the DN. Therefore, name collisions can occur and cannot be detected. If we make sure that the middleware includes a check of the CA when it compares on DN, then what you say is correct. > -----Original Message----- > From: owner-caops-wg(a)ggf.org [mailto:owner-caops-wg@ggf.org] > On Behalf Of David Chadwick > Sent: Wednesday, October 12, 2005 10:57 AM > To: helm(a)fionn.es.net > Cc: Von Welch; Tony J. Genovese; 'Frank Siebenlist'; > 'CAOPS-WG'; 'Olle Mulmo'; 'Joni Hahkala'; 'Jules Wolfrat'; > 'Ron Trompert' > Subject: Re: Name Constraints, was Re: [caops-wg] Re: ca > signing policy file > > Mike > > this is a very interesting viewpoint. What you are saying, if > I put it > another way, is that everyone can have a completely random name, its > irrelevant what it actually is, as long as the user can > authenticate to > that name (via signing something whose signature validates with the > certificate containing that name) and then as long as the > authorisation > infrastructure can reliably get the set of attributes that > are bound to > the same name, then correct authorisation can be performed, > regardless > of the name of the user. In which case name constraints are > irrelevant. > I would agree with that > > regards > > David > > Mike Helm wrote: > > Von Welch writes: > > > >>I meant to say that unless NameConstraints are adopted by CAs in > >>general (which probably means both "Grid CAs" as well as all the > >>various software packages our communities use to generate > >>certificates), we still need something like current ca signing > >>policies (i.e. relying party-specified name constraints). > > > > > > I don't think name constraints, in general, no matter who does them, > > are worth the slitest amount of our attention. They don't solve > > any problem that anyone actually has. (I think this is one reason > > rfc 2459 name constraints took so long to get any support.) > > > > This is particularly true in grid environments where the > authentication > > and authorization has been separated. > > > > What we do need, just like in any other pki, is some way of stating > > whether or not a CA is trusted, and for what purposes (cert types). > > If "purposes" includes naming, fine, but I don't think that > > should be its primary or only method. One purpose might > > be "any" or "none": A scheme like that would > > be very useful to the middleware: you can distribute a large > > number of CA signing certs and make it easy for the > > relying party to configure the CA trust list. (Most of our > > current CAs are grid-only.) > > > > The current signing policy file is useful, in that it puts a brake > > on what is going to be trusted, but the only decision it allows > > is based on naming, which I contend is useless, and forces people > > to deal with an inherently clumsy syntax that has been > dis-optimized. > > > > A side effect is that it places a huge emphasis on naming in Grids, > > which is a waste of everyone's time. We should be free to use > > whatever naming is appropriate and not jam ourselves into narrow > > naming rules so that we don't disturb the delicate naming policy > > rule distributed everywhere. Since names in grids have no inherent > > meaning and we have authorization schemes to enroll and control > > privileges on successful authentication, the name > constraint in Grids > > doesn't add anything. I also think this is functioning as a > > market inhibitor, in that CAs that don't fit this pattern such > > as commercial CAs or other schemes are kept out of the business. > > > > > > -- > > ***************************************************************** > David W. Chadwick, BSc PhD > Professor of Information Systems Security > The Computing Laboratory, University of Kent, Canterbury, CT2 7NF > Tel: +44 1227 82 3221 > Fax +44 1227 762 811 > Mobile: +44 77 96 44 7184 > Email: D.W.Chadwick(a)kent.ac.uk > Home Page: http://www.cs.kent.ac.uk/people/staff/dwc8/index.html > Research Web site: http://sec.cs.kent.ac.uk > Entrust key validation string: MLJ9-DU5T-HV8J > PGP Key ID is 0xBC238DE5 > > ***************************************************************** > >

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RE: Name Constraints, was Re: [caops-wg] Re: ca signing policy file
by Cowles, Robert D. 14 Oct '05

14 Oct '05

The gridmapfile gives no clue as to CA or to VO. Why do PKI *users* care about 2)? Unless you consider the CA's to be "PKI users*. BC > Bob > > I think 2) is the main reason used by PKI users in general. > What are the design flaws in 1)? > > thanks > > David > > > Cowles, Robert D. wrote: > > My impression of why we had the constraints were: > > > > (1) gridmapfile design flaw > > > > (2) the CA's wanted some limitations so as to help > > divide up the people coming to them ... so that > > one CA didn't have to issue certs for the whole > > world (since it's being done on pretty limited > > budgets). > > > > BC > > > > > >>-----Original Message----- > >>From: Frank Siebenlist [mailto:franks@mcs.anl.gov] > >>Sent: Wednesday, October 12, 2005 12:09 PM > >>To: helm(a)fionn.es.net > >>Cc: Cowles, Robert D.; David Chadwick; Von Welch; Tony J. > >>Genovese; CAOPS-WG; Olle Mulmo; Joni Hahkala; Jules Wolfrat; > >>Ron Trompert > >>Subject: Re: Name Constraints, was Re: [caops-wg] Re: ca > >>signing policy file > >> > >>Sorry, but I have to disagree strongly. > >> > >>Having no name constraints and letting any CA issue any name > >>it wants, > >>puts all your trusted CAs on equal footing concerning the > names they > >>issue: any CA can overstep its policy boundaries concerning > >>the issued > >>names and you have no way to find out. > >> > >>Some form of enforced name constraining policy or localizing the > >>name-issuing to a CA is the only safeguard you have against > >>any rogue CA > >>among the zillions that may be present in your trusted CA-directory. > >> > >>Wasn't that the main reason that we have our current ca > >>signing policy > >>files in the first place? > >>Did I miss anything? > >> > >>-Frank. > >> > >> > >>Mike Helm wrote: > >> > >>>"Cowles, Robert D." writes: > >>> > >>> > >>>>that the middleware includes a check of the CA when it compares > >>>>on DN, then what you say is correct. > >>>> > >>> > >>>This is one of the essential problems with this service that > >>>has never been addressed as far as I know. name constraints > >>>"be" an incomplete barrier. > >>> > >>>BTW, we have found this omission _useful_ in our past. > >>> > >>>We switched from a test, development lab CA (DOE Science > >> > >>Grid) to a production > >> > >>>quality CA (doegrids), and we used this property to ease > >> > >>subscribers' > >> > >>>transition to the new CA. Lesson? Overlapping name spaces > >>>might be useful! > >>> > >>> > >> > >>-- > >>Frank Siebenlist franks(a)mcs.anl.gov > >>The Globus Alliance - Argonne National Laboratory > >> > >> > > > > > > -- > > ***************************************************************** > David W. Chadwick, BSc PhD > Professor of Information Systems Security > The Computing Laboratory, University of Kent, Canterbury, CT2 7NF > Tel: +44 1227 82 3221 > Fax +44 1227 762 811 > Mobile: +44 77 96 44 7184 > Email: D.W.Chadwick(a)kent.ac.uk > Home Page: http://www.cs.kent.ac.uk/people/staff/dwc8/index.html > Research Web site: http://sec.cs.kent.ac.uk > Entrust key validation string: MLJ9-DU5T-HV8J > PGP Key ID is 0xBC238DE5 > > ***************************************************************** >

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RE: [caops-wg] Name Constraints - attempt at framing issues
by Cowles, Robert D. 14 Oct '05

14 Oct '05

> Trusted third parties that cannot be trusted!! Why are we > bothering with > them? Building a whole trust infrastructure on untrusted TTPs is a > pointless exercise in futility. > Yes ... well, it was pointed out at the last EUgridPMA meeting that the VO's go thru almost the exact same process to register people ... so what value did the CA's provide? BC

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RE: [caops-wg] Name Constraints - attempt at framing issues
by Cowles, Robert D. 14 Oct '05

14 Oct '05

> 1) What CAs do we wish to consider as potential issuers for our > community? Is it just "Grid CAs" (by that I mean CA we can > reasonably > except to adhere to best practices as specified by GGF WGs) or do we > want to also consider CAs that we have no reasonable expectation of > being able to impact their policies or procedures (e.g. commercial > CAs) as potential issuers for our community as well? I think that if we are successful, all this will be used in ways we can't now imagine or, in the future, control. To me, the idea of depending on CA's to issue certificates for DNs that are globally unique is just asking for trouble. Administrative controls to keep the namespaces separate are clearly not good enough. The signing policy file is a technical control but it still seems pretty weak. To me, the thing that is unique is (DN + CA) and the function of the CA is to try it's best to not issue a cert with the same DN to different people. I would be happy if they can do just that and I think it unreasonable to believe that the DN is unique in the universe (or even a small section thereof). The signing policy files basically allow us to say - given this DN, it should have been issued by that CA - and as far as I can see, it's because the CA is't stored in the gridmapfile (and maybe it's not there because the DN was suppoed to be unique - but that was8-10 years ago, and we know better now). > > 2) Do we believe that during normal operation the CAs indicated in > the response to the first question have policy that will result in > their issuing globally unique names and will reliably follow that > policy? I think it's not true in "normal operation" and that any moderately talented attacker would be able to generate a condition outside of "normal operations" and get *someone* to issue a certificate with any DN they chose. > > 3) If a CA is compromised, given currently implementations, > this will (my comments here were in an earlier email).

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RE: [caops-wg] Name Constraints - attempt at framing issues
by Cowles, Robert D. 14 Oct '05

14 Oct '05

No ... we already have a "sort of" structure for that ... it's called DNS. > > Bob > > dont you think it is a little optimistic to assume that a TTP that > cannot be trusted to issue unique names to its clients, can > be trusted to get a unique name for itself? > > regards > > David

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