Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Thanks, Ludwig. Note that last paragraph of the new Operational Considerations section at https://tools.ietf.org/html/draft-ietf-ace-cwt-proof-of-possession-03#section-6 addresses this issue. In particular, the last sentence of the section talks about the need to keep keys used in different contexts separate if there is otherwise any chance of confusion. I'll also note that for the constrained environments that ACE is addressing, I expect that deployments with exactly one PoP key to be predominant use case. In this use case, such confusion is impossible in the first place. -- Mike -Original Message- From: Ace On Behalf Of Ludwig Seitz Sent: Tuesday, July 3, 2018 2:33 AM To: 'ace' Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 On 2018-07-03 11:31, Ludwig Seitz wrote: > > 6. Client B gets 2 from AS bound via the cnf claim to KID="A" > This should of course read: Client B gets T2 from AS ... /Ludwig -- Ludwig Seitz, PhD Security Lab, RISE SICS Phone +46(0)70-349 92 51 ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
On 2018-07-03 11:31, Ludwig Seitz wrote: 6. Client B gets 2 from AS bound via the cnf claim to KID="A" This should of course read: Client B gets T2 from AS ... /Ludwig -- Ludwig Seitz, PhD Security Lab, RISE SICS Phone +46(0)70-349 92 51 ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
I've finally had the time to think about that Key ID issue for ACE. Here is what I got: The case Jim is worried about is the following: * Client A has key K1 with KID = "A" * RS also has key K1 with KID = "A" * Client A has the right to token T1 on RS * Client B has the right to token T2 on RS 1. Client A gets T1 from AS bound via the cnf claim to KID="A" 2. Client A transfers T1 to RS 3. Client A performs the proof-of-possession with key K1 and gets access to RS according to T1 4. Malicious Client B learns of the KID = "A" for T1 (but not of K1). 5. Client B chooses K2 and assigns it KID = "A" 6. Client B gets 2 from AS bound via the cnf claim to KID="A" 7. Client B transfers T2 to RS 8. ? 9. Client B performs the proof-of-possession for K2 and gets access to both T1 and T2 Now I'm claiming there is no step 8 that makes step 9 work, unless B can get RS to accept a new key (K2) with a duplicate KID. Thus I'd say, we need to Security Considerations about handling key Ids at the recipient of a CWT containing a cnf claim. Something along the lines of: "If a recipient receives a CWT with the a confirmation claim, the recipient MUST make sure that keys that may be contained in that claim do not have a key identifier that duplicates one of a different key that the recipient already recognizes." Or shorter: "Recipients MUST make sure that they do not accept identical key identifiers for different keys" /Ludwig -- Ludwig Seitz, PhD Security Lab, RISE SICS Phone +46(0)70-349 92 51 ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
see inline On Fri, Jun 29, 2018 at 7:57 AM, Jim Schaad wrote: > > > > > *From:* Samuel Erdtman > *Sent:* Thursday, June 28, 2018 5:40 PM > *To:* Jim Schaad > *Cc:* Samuel Erdtman ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org; Mike Jones ; Hannes > Tschofenig ; Benjamin Kaduk ; > ace > *Subject:* Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > > > Thanks for the clarifying comments here comes a few replies since I will > not be able to join the IETF meeting :-( > > > > see inline > > > > On Wed, Jun 27, 2018 at 9:19 AM, Jim Schaad > wrote: > > > > > > *From:* Samuel Erdtman > *Sent:* Wednesday, June 27, 2018 8:18 AM > *To:* Jim Schaad > *Cc:* Hannes Tschofenig ; Benjamin Kaduk < > ka...@mit.edu>; Mike Jones ; > draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org > *Subject:* Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > > > Jim, are you saying that if the client can pick the key identifier and if > it has seen a key identifier of another client it could request a PoP token > with the observed key-id and the observed subject but with an new key. > I guess this is a potential scenario that could be worth mentioning in > security considerations. > > [JLS] No I am not assuming that the observed subject is also chosen by the > attacker, just the observed key-id. > > OK, see comments below on why I think the attacker would have to know the > subject too. > > > > > If we look at ACE-OAuth there are as far as I can tell a few things that > makes this a hard attack to do. > > When the client makes the token request it is authenticated. > > [JLS] Unclear why this is relevant. I am asking for this new token as > myself. > > In my opinion authentication of the client will significantly lessen the > number of attackers since they need to have some initial access. i.e. no > absolute protection but one layer. > > > > [JLS] I am already in the system and have full credentials. I am trying > to get the same permissions that you have. Not all attackers are external > to the system. > I agree, but the number of such attackers are fewer and you could revoke access to such users. It is not perfect but it is better than nothing. > > > > And with the subject being the authenticated client cannot control what > goes into the cwt as subject > > [JLS] You are making an assumption that a) the subject is actually going > to be populated rather than be left empty and thus be anonymous and 2) that > the resource server is going to make any enforcement based on the subject.. > I expect it to be done based on audience and scope only. > > My assumption is that RS will uniquely identify the key with Issuer, > Subject and Key-ID. If subject is omitted for an anonymous token I assume > that the AS (Issuer) makes sure the key-id is unique during the lifetime of > the token. If issuer is left out I assume it is identified by the CWT > signing key or that the RS only accept tokens from one AS. > > When the key is found and has been used to authenticate the user of the > token I too expect that the RS does the authorization based on audience and > scope. > > > > [JLS] I am not sure how this is going to work. As the CS I do a DTLS > connect to the RS and put the Key-ID into the PSK identifier field. The RS > now has the Key-ID, but does not have the Issuer or Subject information. > Are you using this triple value binding someplace else? > I would not send the key-id in the PSK identifier I would send the full token as described in draft-ietf-ace-dtls-authorize (4.1. DTLS Channel Setup Between C and RS). > > > > Since the cwt with the PoP key is signed there is no way for the attacking > client to retro-fit the token to suit its needs e.g. change subject or > key-id. > > [JLS] I am asking for a new token not trying to modify an existing token > so this is not especially relevant. > > Based on my previous statement you should not be able to impersonate the > observed key with a token issued for you. > > > > [JLS] Given two anonymous subject fields, the subject would not be a > differentiator > I agree so the AS (issuer) MUST keep key-id unique for the lifetime of the token. > > Finally I think it is preferable if the server selects key identifier. > > [JLS] I would agree, however if you have two AS that are operating in the > same authorization range and are not tightly linked then this is not easy > for doing an additional privilege token where the POP is identified by the > KID. This is even harder if an RS is going to allow two different AS from &
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Samuel, Jim, We have two cases in ACE-OAuth: 1) Client provides a key (or a reference to a key) to the AS. It wants the AS to include that key into the PoP token. The key is the long version of the key id*. 2) Client asks the AS to get a token. In this case the AS creates a key and places that key or key id in the PoP token. We seem to be worried that these keys / key ids are not unique over the lifetime of the tokens. The ACE-OAuth document should say that the AS has to make sure that keys and key ids are not re-used over the lifetime of a PoP token, unless this is a desired behaviour. I don’t think that the CWT PoP token is the right place to discuss this topic. Ciao Hannes *: Here is what the draft says: “ The proof-of-possession key can also be identified by the use of a Key ID instead of communicating the actual key, provided the recipient is able to obtain the identified key using the Key ID. “ From: Samuel Erdtman [mailto:erdt...@spotify.com] Sent: 27 June 2018 08:18 To: Jim Schaad Cc: Hannes Tschofenig; Benjamin Kaduk; Mike Jones; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 Jim, are you saying that if the client can pick the key identifier and if it has seen a key identifier of another client it could request a PoP token with the observed key-id and the observed subject but with an new key. I guess this is a potential scenario that could be worth mentioning in security considerations. If we look at ACE-OAuth there are as far as I can tell a few things that makes this a hard attack to do. When the client makes the token request it is authenticated. And with the subject being the authenticated client cannot control what goes into the cwt as subject Since the cwt with the PoP key is signed there is no way for the attacking client to retro-fit the token to suit its needs e.g. change subject or key-id. Finally I think it is preferable if the server selects key identifier. Best regards //Samuel On Tue, 26 Jun 2018 at 18:57, Jim Schaad mailto:i...@augustcellars.com>> wrote: Hannes, My worry is not about implementers getting this correct and picking random key ids. My worry is about an attacker seeing the key id of somebody and trying to use it either with the same or a different AS and getting a key and then getting permissions associated with the initial key that they should not be doing. This is about an attack not about getting things to generally work right. Jim > -Original Message- > From: Hannes Tschofenig > mailto:hannes.tschofe...@arm.com>> > Sent: Tuesday, June 26, 2018 6:09 PM > To: Jim Schaad mailto:i...@augustcellars.com>>; > 'Benjamin Kaduk' > mailto:ka...@mit.edu>>; 'Mike Jones' > mailto:michael.jo...@microsoft.com>> > Cc: > draft-ietf-ace-cwt-proof-of-possess...@ietf.org<mailto:draft-ietf-ace-cwt-proof-of-possess...@ietf.org>; > ace@ietf.org<mailto:ace@ietf.org> > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Hi Jim, > > you are essentially proposing that we should not directly use the key id that > is in the CWT-PoP but rather use it as input in a key derivation function. The > details of that key derivation function are specified outside the CWT-POP > document and most likely in the context of the various profiles. > Your proposals below suggest to use, among other things, the session key as > input to that function. That sounds pretty straight forward but raises the > question why we fail to trust the implementer to create random key ids but > then still trust them to create random keys. > > That's fine for me nevertheless. > > Ciao > Hannes > > -Original Message- > From: Jim Schaad > [mailto:i...@augustcellars.com<mailto:i...@augustcellars.com>] > Sent: 24 June 2018 10:15 > To: 'Benjamin Kaduk'; 'Mike Jones' > Cc: Hannes Tschofenig; > draft-ietf-ace-cwt-proof-of-possess...@ietf.org<mailto:draft-ietf-ace-cwt-proof-of-possess...@ietf.org>; > ace@ietf.org<mailto:ace@ietf.org> > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Thinking things through, I would be more comfortable with something like > the > following: > > 1. Create a confirmation called 'computed key id'. This has two basic > values: What is the computation method? What is the proof value? You can > optionally have an unprotected KID value used to filter the set of keys on the > RS down to a reasonable set to enumerate (hopefully one). > > 2. For RPK and TLS: Define a method called hash of SPKI which has a hash > method as a parameter. Given that this can be computed independently by > all entities based on a Public Key value and it
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Hi Jim, It sounds like we need some high bandwidth face-to-face time on this issue in Montreal. This is an interesting issue and IMHO reaches outside the CWT PoP document. Ciao Hannes -Original Message- From: Jim Schaad [mailto:i...@augustcellars.com] Sent: 26 June 2018 18:57 To: Hannes Tschofenig; 'Benjamin Kaduk'; 'Mike Jones' Cc: draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 Hannes, My worry is not about implementers getting this correct and picking random key ids. My worry is about an attacker seeing the key id of somebody and trying to use it either with the same or a different AS and getting a key and then getting permissions associated with the initial key that they should not be doing. This is about an attack not about getting things to generally work right. Jim > -Original Message- > From: Hannes Tschofenig > Sent: Tuesday, June 26, 2018 6:09 PM > To: Jim Schaad ; 'Benjamin Kaduk' > ; 'Mike Jones' > Cc: draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Hi Jim, > > you are essentially proposing that we should not directly use the key id that > is in the CWT-PoP but rather use it as input in a key derivation function. The > details of that key derivation function are specified outside the CWT-POP > document and most likely in the context of the various profiles. > Your proposals below suggest to use, among other things, the session key as > input to that function. That sounds pretty straight forward but raises the > question why we fail to trust the implementer to create random key ids but > then still trust them to create random keys. > > That's fine for me nevertheless. > > Ciao > Hannes > > -Original Message- > From: Jim Schaad [mailto:i...@augustcellars.com] > Sent: 24 June 2018 10:15 > To: 'Benjamin Kaduk'; 'Mike Jones' > Cc: Hannes Tschofenig; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > ace@ietf.org > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Thinking things through, I would be more comfortable with something like > the > following: > > 1. Create a confirmation called 'computed key id'. This has two basic > values: What is the computation method? What is the proof value? You can > optionally have an unprotected KID value used to filter the set of keys on the > RS down to a reasonable set to enumerate (hopefully one). > > 2. For RPK and TLS: Define a method called hash of SPKI which has a hash > method as a parameter. Given that this can be computed independently by > all entities based on a Public Key value and it will be unique then you have a > key identifier that will not have collisions independent of who issues the > CWT. > > 3. For PSK and TLS: Define a method which takes some parameters including > the key value, the CWT issuer identity and perhaps some random string and > compute a proof of possession value on the PSK. > > 4. For PSK and OSCORE: Define a similar method the question would be what > the key value is to be used but that can be defined as part of OSCORE > > When using the keys for TLS > > For RPK the key is carried in the handshake and the server/client can > generate the computed key id and compare it to what the AS distributed. > The server can identify which CWTs are applicable by either comparison of > the RPKs or the computed key id. This means you have a high probability > that you will not make a mistake and match to the wrong key. > > For PSK the identifier is carried in the handshake which is used to look up a > key value and the handshake is performed. By matching computed key ids > with the secret value one can ensure to a high probably that only CWTs that > reference the same secret are going to be used for permissions even if they > come from different AS entities. > > For OSCORE it is similar, the identifier is used to look up a key value and by > decrypting the CWT the key value is proofed. You then match computed key > ids in the same manner. > > If you really want to have something that is not cryptographically computed > and point to something else, then it makes more sense to me to reference a > CWT issued by the same entity and say "use the same conformation method > as this CWT does". > > jim > > > -----Original Message----- > > From: Benjamin Kaduk > > Sent: Saturday, June 23, 2018 11:30 PM > > To: Mike Jones > > Cc: Hannes Tschofenig ; Jim Schaad > > ; > > draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > > ace@ietf.org
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
From: Samuel Erdtman Sent: Wednesday, June 27, 2018 8:18 AM To: Jim Schaad Cc: Hannes Tschofenig ; Benjamin Kaduk ; Mike Jones ; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 Jim, are you saying that if the client can pick the key identifier and if it has seen a key identifier of another client it could request a PoP token with the observed key-id and the observed subject but with an new key. I guess this is a potential scenario that could be worth mentioning in security considerations. [JLS] No I am not assuming that the observed subject is also chosen by the attacker, just the observed key-id. If we look at ACE-OAuth there are as far as I can tell a few things that makes this a hard attack to do. When the client makes the token request it is authenticated. [JLS] Unclear why this is relevant. I am asking for this new token as myself. And with the subject being the authenticated client cannot control what goes into the cwt as subject [JLS] You are making an assumption that a) the subject is actually going to be populated rather than be left empty and thus be anonymous and 2) that the resource server is going to make any enforcement based on the subject. I expect it to be done based on audience and scope only. Since the cwt with the PoP key is signed there is no way for the attacking client to retro-fit the token to suit its needs e.g. change subject or key-id. [JLS] I am asking for a new token not trying to modify an existing token so this is not especially relevant. Finally I think it is preferable if the server selects key identifier. [JLS] I would agree, however if you have two AS that are operating in the same authorization range and are not tightly linked then this is not easy for doing an additional privilege token where the POP is identified by the KID. This is even harder if an RS is going to allow two different AS from different scopes to be authoritative as they would never coordinate together. Best regards //Samuel On Tue, 26 Jun 2018 at 18:57, Jim Schaad mailto:i...@augustcellars.com> > wrote: Hannes, My worry is not about implementers getting this correct and picking random key ids. My worry is about an attacker seeing the key id of somebody and trying to use it either with the same or a different AS and getting a key and then getting permissions associated with the initial key that they should not be doing. This is about an attack not about getting things to generally work right. Jim > -Original Message- > From: Hannes Tschofenig <mailto:hannes.tschofe...@arm.com> > > Sent: Tuesday, June 26, 2018 6:09 PM > To: Jim Schaad mailto:i...@augustcellars.com> >; > 'Benjamin Kaduk' > mailto:ka...@mit.edu> >; 'Mike Jones' > mailto:michael.jo...@microsoft.com> > > Cc: draft-ietf-ace-cwt-proof-of-possess...@ietf.org > <mailto:draft-ietf-ace-cwt-proof-of-possess...@ietf.org> ; ace@ietf.org > <mailto:ace@ietf.org> > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Hi Jim, > > you are essentially proposing that we should not directly use the key id that > is in the CWT-PoP but rather use it as input in a key derivation function. The > details of that key derivation function are specified outside the CWT-POP > document and most likely in the context of the various profiles. > Your proposals below suggest to use, among other things, the session key as > input to that function. That sounds pretty straight forward but raises the > question why we fail to trust the implementer to create random key ids but > then still trust them to create random keys. > > That's fine for me nevertheless. > > Ciao > Hannes > > -Original Message- > From: Jim Schaad [mailto:i...@augustcellars.com > <mailto:i...@augustcellars.com> ] > Sent: 24 June 2018 10:15 > To: 'Benjamin Kaduk'; 'Mike Jones' > Cc: Hannes Tschofenig; draft-ietf-ace-cwt-proof-of-possess...@ietf.org > <mailto:draft-ietf-ace-cwt-proof-of-possess...@ietf.org> ; > ace@ietf.org <mailto:ace@ietf.org> > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Thinking things through, I would be more comfortable with something like > the > following: > > 1. Create a confirmation called 'computed key id'. This has two basic > values: What is the computation method? What is the proof value? You can > optionally have an unprotected KID value used to filter the set of keys on the > RS down to a reasonable set to enumerate (hopefully one). > > 2. For RPK and TLS: Define a method called hash of SPKI which has a hash > method as a parameter. Given that this can be computed independently
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Jim, are you saying that if the client can pick the key identifier and if it has seen a key identifier of another client it could request a PoP token with the observed key-id and the observed subject but with an new key. I guess this is a potential scenario that could be worth mentioning in security considerations. If we look at ACE-OAuth there are as far as I can tell a few things that makes this a hard attack to do. When the client makes the token request it is authenticated. And with the subject being the authenticated client cannot control what goes into the cwt as subject Since the cwt with the PoP key is signed there is no way for the attacking client to retro-fit the token to suit its needs e.g. change subject or key-id. Finally I think it is preferable if the server selects key identifier. Best regards //Samuel On Tue, 26 Jun 2018 at 18:57, Jim Schaad wrote: > Hannes, > > My worry is not about implementers getting this correct and picking random > key ids. My worry is about an attacker seeing the key id of somebody and > trying to use it either with the same or a different AS and getting a key > and then getting permissions associated with the initial key that they > should not be doing. > > This is about an attack not about getting things to generally work right. > > Jim > > > > -Original Message- > > From: Hannes Tschofenig > > Sent: Tuesday, June 26, 2018 6:09 PM > > To: Jim Schaad ; 'Benjamin Kaduk' > > ; 'Mike Jones' > > Cc: draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org > > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > > possession-02 > > > > Hi Jim, > > > > you are essentially proposing that we should not directly use the key id > that > > is in the CWT-PoP but rather use it as input in a key derivation > function. > The > > details of that key derivation function are specified outside the CWT-POP > > document and most likely in the context of the various profiles. > > Your proposals below suggest to use, among other things, the session key > as > > input to that function. That sounds pretty straight forward but raises > the > > question why we fail to trust the implementer to create random key ids > but > > then still trust them to create random keys. > > > > That's fine for me nevertheless. > > > > Ciao > > Hannes > > > > -Original Message- > > From: Jim Schaad [mailto:i...@augustcellars.com] > > Sent: 24 June 2018 10:15 > > To: 'Benjamin Kaduk'; 'Mike Jones' > > Cc: Hannes Tschofenig; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > > ace@ietf.org > > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > > possession-02 > > > > Thinking things through, I would be more comfortable with something like > > the > > following: > > > > 1. Create a confirmation called 'computed key id'. This has two basic > > values: What is the computation method? What is the proof value? You > can > > optionally have an unprotected KID value used to filter the set of keys > on > the > > RS down to a reasonable set to enumerate (hopefully one). > > > > 2. For RPK and TLS: Define a method called hash of SPKI which has a > hash > > method as a parameter. Given that this can be computed independently by > > all entities based on a Public Key value and it will be unique then you > have a > > key identifier that will not have collisions independent of who issues > the > > CWT. > > > > 3. For PSK and TLS: Define a method which takes some parameters > including > > the key value, the CWT issuer identity and perhaps some random string and > > compute a proof of possession value on the PSK. > > > > 4. For PSK and OSCORE: Define a similar method the question would be > what > > the key value is to be used but that can be defined as part of OSCORE > > > > When using the keys for TLS > > > > For RPK the key is carried in the handshake and the server/client can > > generate the computed key id and compare it to what the AS distributed. > > The server can identify which CWTs are applicable by either comparison of > > the RPKs or the computed key id. This means you have a high probability > > that you will not make a mistake and match to the wrong key. > > > > For PSK the identifier is carried in the handshake which is used to look > up a > > key value and the handshake is performed. By matching computed key ids > > with the secret value one can ensure to a high probably that only CWTs > that > > reference the same secret are going t
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Hannes, My worry is not about implementers getting this correct and picking random key ids. My worry is about an attacker seeing the key id of somebody and trying to use it either with the same or a different AS and getting a key and then getting permissions associated with the initial key that they should not be doing. This is about an attack not about getting things to generally work right. Jim > -Original Message- > From: Hannes Tschofenig > Sent: Tuesday, June 26, 2018 6:09 PM > To: Jim Schaad ; 'Benjamin Kaduk' > ; 'Mike Jones' > Cc: draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Hi Jim, > > you are essentially proposing that we should not directly use the key id that > is in the CWT-PoP but rather use it as input in a key derivation function. The > details of that key derivation function are specified outside the CWT-POP > document and most likely in the context of the various profiles. > Your proposals below suggest to use, among other things, the session key as > input to that function. That sounds pretty straight forward but raises the > question why we fail to trust the implementer to create random key ids but > then still trust them to create random keys. > > That's fine for me nevertheless. > > Ciao > Hannes > > -Original Message- > From: Jim Schaad [mailto:i...@augustcellars.com] > Sent: 24 June 2018 10:15 > To: 'Benjamin Kaduk'; 'Mike Jones' > Cc: Hannes Tschofenig; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > ace@ietf.org > Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Thinking things through, I would be more comfortable with something like > the > following: > > 1. Create a confirmation called 'computed key id'. This has two basic > values: What is the computation method? What is the proof value? You can > optionally have an unprotected KID value used to filter the set of keys on the > RS down to a reasonable set to enumerate (hopefully one). > > 2. For RPK and TLS: Define a method called hash of SPKI which has a hash > method as a parameter. Given that this can be computed independently by > all entities based on a Public Key value and it will be unique then you have a > key identifier that will not have collisions independent of who issues the > CWT. > > 3. For PSK and TLS: Define a method which takes some parameters including > the key value, the CWT issuer identity and perhaps some random string and > compute a proof of possession value on the PSK. > > 4. For PSK and OSCORE: Define a similar method the question would be what > the key value is to be used but that can be defined as part of OSCORE > > When using the keys for TLS > > For RPK the key is carried in the handshake and the server/client can > generate the computed key id and compare it to what the AS distributed. > The server can identify which CWTs are applicable by either comparison of > the RPKs or the computed key id. This means you have a high probability > that you will not make a mistake and match to the wrong key. > > For PSK the identifier is carried in the handshake which is used to look up a > key value and the handshake is performed. By matching computed key ids > with the secret value one can ensure to a high probably that only CWTs that > reference the same secret are going to be used for permissions even if they > come from different AS entities. > > For OSCORE it is similar, the identifier is used to look up a key value and by > decrypting the CWT the key value is proofed. You then match computed key > ids in the same manner. > > If you really want to have something that is not cryptographically computed > and point to something else, then it makes more sense to me to reference a > CWT issued by the same entity and say "use the same conformation method > as this CWT does". > > jim > > > -----Original Message----- > > From: Benjamin Kaduk > > Sent: Saturday, June 23, 2018 11:30 PM > > To: Mike Jones > > Cc: Hannes Tschofenig ; Jim Schaad > > ; > > draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > > ace@ietf.org > > Subject: Re: [Ace] Key IDs ... RE: WGLC on > > draft-ietf-ace-cwt-proof-of- > > possession-02 > > > > On Fri, Jun 22, 2018 at 08:48:35PM +, Mike Jones wrote: > > > See my note just now proposing this text to Jim: > > > > > > "Likewise, if PoP keys are used for multiple different kinds of CWTs > > > in > an > > application and the PoP keys are identified by Key IDs, care must be > > taken > to &g
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
No Ben, you are 100% correct. This is about identifiers and not session keys. > -Original Message- > From: Benjamin Kaduk > Sent: Tuesday, June 26, 2018 5:14 PM > To: Hannes Tschofenig > Cc: Mike Jones ; Jim Schaad > ; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > ace@ietf.org > Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > I thought we were worried about collision of key *identifiers*, which were > not necessarily raw keys or hashes thereof. But it's possible I was not paying > enough attention and got confused. > > -Ben > > On Tue, Jun 26, 2018 at 03:12:52PM +, Hannes Tschofenig wrote: > > It does answer my question, Ben. > > > > This begs the question why the collision of session keys is suddenly a > problem in the ACE context when it wasn't a problem so far. Something must > have changed. > > > > Ciao > > Hannes > > > > > > -Original Message- > > From: Benjamin Kaduk [mailto:ka...@mit.edu] > > Sent: 26 June 2018 17:00 > > To: Hannes Tschofenig > > Cc: Mike Jones; Jim Schaad; > > draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org > > Subject: Re: [Ace] Key IDs ... RE: WGLC on > > draft-ietf-ace-cwt-proof-of-possession-02 > > > > On Tue, Jun 26, 2018 at 08:53:57AM +, Hannes Tschofenig wrote: > > > Ben, > > > > > > I was wondering whether the situation is any different in Kerberos. If the > KDC creates tickets with a session key included then it needs to make sure > that it does not create the same symmetric key for different usages. > > > The key in the Kerberos ticket is similar to the PoP key in our discussion. > > > > > > Are we aware of key collision in Kerberos? > > > > I don't believe key collision is an issue in Kerberos. Long-term keys > > (which are not what we're talking about here) are identified by a > > principal name, encryption type, and version number. Session keys > > that are contained within tickets (and returned to the client in the > > KDC-REP) are random, so even if we are only using the birthday bound > > we're still in pretty good shape. The modern enctypes tend to use > > subsession keys generated by the client and/or server as well as the > > KDC-generated session key, which provides further binding to the current > session. > > > > Does that answer your question? > > > > -Ben > > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended recipient, > please notify the sender immediately and do not disclose the contents to any > other person, use it for any purpose, or store or copy the information in any > medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Hi Ben, You are right. We were talking about the key identifiers. Let me still stick with the Kerberos example. In that context this would mean that the KDC stores multiple accounts in the database that point to the same principal name. Have you seen that happening? Re-using the same principle name over time as identifier get recycle when users get retired or otherwise leave the system might be an option. Is this a more likely? As you see I am trying to find some examples of vulnerabilities in existing systems and I am having a hard time. Ciao Hannes -Original Message- From: Benjamin Kaduk [mailto:ka...@mit.edu] Sent: 26 June 2018 17:14 To: Hannes Tschofenig Cc: Mike Jones; Jim Schaad; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 I thought we were worried about collision of key *identifiers*, which were not necessarily raw keys or hashes thereof. But it's possible I was not paying enough attention and got confused. -Ben On Tue, Jun 26, 2018 at 03:12:52PM +, Hannes Tschofenig wrote: > It does answer my question, Ben. > > This begs the question why the collision of session keys is suddenly a > problem in the ACE context when it wasn't a problem so far. Something must > have changed. > > Ciao > Hannes > > > -Original Message- > From: Benjamin Kaduk [mailto:ka...@mit.edu] > Sent: 26 June 2018 17:00 > To: Hannes Tschofenig > Cc: Mike Jones; Jim Schaad; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > ace@ietf.org > Subject: Re: [Ace] Key IDs ... RE: WGLC on > draft-ietf-ace-cwt-proof-of-possession-02 > > On Tue, Jun 26, 2018 at 08:53:57AM +, Hannes Tschofenig wrote: > > Ben, > > > > I was wondering whether the situation is any different in Kerberos. If the > > KDC creates tickets with a session key included then it needs to make sure > > that it does not create the same symmetric key for different usages. > > The key in the Kerberos ticket is similar to the PoP key in our discussion. > > > > Are we aware of key collision in Kerberos? > > I don't believe key collision is an issue in Kerberos. Long-term keys > (which are not what we're talking about here) are identified by a principal > name, encryption type, and version number. Session keys that are contained > within tickets (and returned to the client in the KDC-REP) are random, so > even if we are only using the birthday bound we're still in pretty good > shape. The modern enctypes tend to use subsession keys generated by the > client and/or server as well as the KDC-generated session key, which > provides further binding to the current session. > > Does that answer your question? > > -Ben > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Hi Jim, you are essentially proposing that we should not directly use the key id that is in the CWT-PoP but rather use it as input in a key derivation function. The details of that key derivation function are specified outside the CWT-POP document and most likely in the context of the various profiles. Your proposals below suggest to use, among other things, the session key as input to that function. That sounds pretty straight forward but raises the question why we fail to trust the implementer to create random key ids but then still trust them to create random keys. That's fine for me nevertheless. Ciao Hannes -Original Message- From: Jim Schaad [mailto:i...@augustcellars.com] Sent: 24 June 2018 10:15 To: 'Benjamin Kaduk'; 'Mike Jones' Cc: Hannes Tschofenig; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: RE: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 Thinking things through, I would be more comfortable with something like the following: 1. Create a confirmation called 'computed key id'. This has two basic values: What is the computation method? What is the proof value? You can optionally have an unprotected KID value used to filter the set of keys on the RS down to a reasonable set to enumerate (hopefully one). 2. For RPK and TLS: Define a method called hash of SPKI which has a hash method as a parameter. Given that this can be computed independently by all entities based on a Public Key value and it will be unique then you have a key identifier that will not have collisions independent of who issues the CWT. 3. For PSK and TLS: Define a method which takes some parameters including the key value, the CWT issuer identity and perhaps some random string and compute a proof of possession value on the PSK. 4. For PSK and OSCORE: Define a similar method the question would be what the key value is to be used but that can be defined as part of OSCORE When using the keys for TLS For RPK the key is carried in the handshake and the server/client can generate the computed key id and compare it to what the AS distributed. The server can identify which CWTs are applicable by either comparison of the RPKs or the computed key id. This means you have a high probability that you will not make a mistake and match to the wrong key. For PSK the identifier is carried in the handshake which is used to look up a key value and the handshake is performed. By matching computed key ids with the secret value one can ensure to a high probably that only CWTs that reference the same secret are going to be used for permissions even if they come from different AS entities. For OSCORE it is similar, the identifier is used to look up a key value and by decrypting the CWT the key value is proofed. You then match computed key ids in the same manner. If you really want to have something that is not cryptographically computed and point to something else, then it makes more sense to me to reference a CWT issued by the same entity and say "use the same conformation method as this CWT does". jim > -Original Message- > From: Benjamin Kaduk > Sent: Saturday, June 23, 2018 11:30 PM > To: Mike Jones > Cc: Hannes Tschofenig ; Jim Schaad > ; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > ace@ietf.org > Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > On Fri, Jun 22, 2018 at 08:48:35PM +, Mike Jones wrote: > > See my note just now proposing this text to Jim: > > > > "Likewise, if PoP keys are used for multiple different kinds of CWTs in an > application and the PoP keys are identified by Key IDs, care must be taken to > keep the keys for the different kinds of CWTs segregated so that an attacker > cannot cause the wrong PoP key to be used by using a valid Key ID for the > wrong kind of CWT." > > > > As long as the PoP keys for different contexts are kept segregated, Key ID > collisions or reuse cause no problems. > > If we trust everyone to implement things properly. We should probably only > take that risk if we get some other benefit from it, though. Jim mentioned > (off-list?) a scenario involving giving the same client additional privileges, and > of course we can gain some simplicity savings if we don't need to enforce > global key-id uniqueness (for appropriate values of "global"). So this may > well be the right thing to do; I just don't think it's without tradeoffs as your > text seems to imply. > > -Ben IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
I thought we were worried about collision of key *identifiers*, which were not necessarily raw keys or hashes thereof. But it's possible I was not paying enough attention and got confused. -Ben On Tue, Jun 26, 2018 at 03:12:52PM +, Hannes Tschofenig wrote: > It does answer my question, Ben. > > This begs the question why the collision of session keys is suddenly a > problem in the ACE context when it wasn't a problem so far. Something must > have changed. > > Ciao > Hannes > > > -Original Message- > From: Benjamin Kaduk [mailto:ka...@mit.edu] > Sent: 26 June 2018 17:00 > To: Hannes Tschofenig > Cc: Mike Jones; Jim Schaad; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; > ace@ietf.org > Subject: Re: [Ace] Key IDs ... RE: WGLC on > draft-ietf-ace-cwt-proof-of-possession-02 > > On Tue, Jun 26, 2018 at 08:53:57AM +, Hannes Tschofenig wrote: > > Ben, > > > > I was wondering whether the situation is any different in Kerberos. If the > > KDC creates tickets with a session key included then it needs to make sure > > that it does not create the same symmetric key for different usages. > > The key in the Kerberos ticket is similar to the PoP key in our discussion. > > > > Are we aware of key collision in Kerberos? > > I don't believe key collision is an issue in Kerberos. Long-term keys > (which are not what we're talking about here) are identified by a principal > name, encryption type, and version number. Session keys that are contained > within tickets (and returned to the client in the KDC-REP) are random, so > even if we are only using the birthday bound we're still in pretty good > shape. The modern enctypes tend to use subsession keys generated by the > client and/or server as well as the KDC-generated session key, which > provides further binding to the current session. > > Does that answer your question? > > -Ben > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
It does answer my question, Ben. This begs the question why the collision of session keys is suddenly a problem in the ACE context when it wasn't a problem so far. Something must have changed. Ciao Hannes -Original Message- From: Benjamin Kaduk [mailto:ka...@mit.edu] Sent: 26 June 2018 17:00 To: Hannes Tschofenig Cc: Mike Jones; Jim Schaad; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 On Tue, Jun 26, 2018 at 08:53:57AM +, Hannes Tschofenig wrote: > Ben, > > I was wondering whether the situation is any different in Kerberos. If the > KDC creates tickets with a session key included then it needs to make sure > that it does not create the same symmetric key for different usages. > The key in the Kerberos ticket is similar to the PoP key in our discussion. > > Are we aware of key collision in Kerberos? I don't believe key collision is an issue in Kerberos. Long-term keys (which are not what we're talking about here) are identified by a principal name, encryption type, and version number. Session keys that are contained within tickets (and returned to the client in the KDC-REP) are random, so even if we are only using the birthday bound we're still in pretty good shape. The modern enctypes tend to use subsession keys generated by the client and/or server as well as the KDC-generated session key, which provides further binding to the current session. Does that answer your question? -Ben IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
On Tue, Jun 26, 2018 at 08:53:57AM +, Hannes Tschofenig wrote: > Ben, > > I was wondering whether the situation is any different in Kerberos. If the > KDC creates tickets with a session key included then it needs to make sure > that it does not create the same symmetric key for different usages. > The key in the Kerberos ticket is similar to the PoP key in our discussion. > > Are we aware of key collision in Kerberos? I don't believe key collision is an issue in Kerberos. Long-term keys (which are not what we're talking about here) are identified by a principal name, encryption type, and version number. Session keys that are contained within tickets (and returned to the client in the KDC-REP) are random, so even if we are only using the birthday bound we're still in pretty good shape. The modern enctypes tend to use subsession keys generated by the client and/or server as well as the KDC-generated session key, which provides further binding to the current session. Does that answer your question? -Ben ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
Ben, I was wondering whether the situation is any different in Kerberos. If the KDC creates tickets with a session key included then it needs to make sure that it does not create the same symmetric key for different usages. The key in the Kerberos ticket is similar to the PoP key in our discussion. Are we aware of key collision in Kerberos? Ciao Hannes -Original Message- From: Benjamin Kaduk [mailto:ka...@mit.edu] Sent: 23 June 2018 23:30 To: Mike Jones Cc: Hannes Tschofenig; Jim Schaad; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 On Fri, Jun 22, 2018 at 08:48:35PM +, Mike Jones wrote: > See my note just now proposing this text to Jim: > > "Likewise, if PoP keys are used for multiple different kinds of CWTs in an > application and the PoP keys are identified by Key IDs, care must be taken to > keep the keys for the different kinds of CWTs segregated so that an attacker > cannot cause the wrong PoP key to be used by using a valid Key ID for the > wrong kind of CWT." > > As long as the PoP keys for different contexts are kept segregated, Key ID > collisions or reuse cause no problems. If we trust everyone to implement things properly. We should probably only take that risk if we get some other benefit from it, though. Jim mentioned (off-list?) a scenario involving giving the same client additional privileges, and of course we can gain some simplicity savings if we don't need to enforce global key-id uniqueness (for appropriate values of "global"). So this may well be the right thing to do; I just don't think it's without tradeoffs as your text seems to imply. -Ben IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
On 2018-06-22 15:36, Hannes Tschofenig wrote: Hi Jim, I would like to comment on this issue. - 14. I have real problems w/ the use of a KID for POP identification. It may identify the wrong key or, if used for granting access, may have problems w/ identity collisions. These need to be spelt out someplace to help people tracking down questions of why can't I verify w/ this CWT, I know it's right. I just wanted to note that we inherited that issue from RFC 7800, does someone recall what the security considerations were in that case? Perhaps a variant of Hannes' text comes closer to what Jim is looking for: " - Operational Considerations When an issuer creates a CWT containing a key id claim, it is not acceptable to issue another CWT containing the same key id, unless they both are for the same subject and for the same audience (e.g. providing additional privileges for the subject). " /Ludwig -- Ludwig Seitz, PhD Security Lab, RISE SICS Phone +46(0)70-349 92 51 ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
On Fri, Jun 22, 2018 at 08:48:35PM +, Mike Jones wrote: > See my note just now proposing this text to Jim: > > "Likewise, if PoP keys are used for multiple different kinds of CWTs in an > application and the PoP keys are identified by Key IDs, care must be taken to > keep the keys for the different kinds of CWTs segregated so that an attacker > cannot cause the wrong PoP key to be used by using a valid Key ID for the > wrong kind of CWT." > > As long as the PoP keys for different contexts are kept segregated, Key ID > collisions or reuse cause no problems. If we trust everyone to implement things properly. We should probably only take that risk if we get some other benefit from it, though. Jim mentioned (off-list?) a scenario involving giving the same client additional privileges, and of course we can gain some simplicity savings if we don't need to enforce global key-id uniqueness (for appropriate values of "global"). So this may well be the right thing to do; I just don't think it's without tradeoffs as your text seems to imply. -Ben ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
The sentence I sent was in addition to Hannes language to address the multiple CWT case discussed in the thread - not a replacement for it. -- Mike -Original Message- From: Jim Schaad Sent: Saturday, June 23, 2018 9:05 AM To: Mike Jones ; Hannes Tschofenig ; draft-ietf-ace-cwt-proof-of-possess...@ietf.org Cc: ace@ietf.org Subject: RE: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of-possession-02 No not really, Hannes's language is much closer to what I am looking for. I don't care if they are different kinds of CWTs. I care about impersonation. > -Original Message- > From: Mike Jones > Sent: Friday, June 22, 2018 10:44 PM > To: Jim Schaad ; Hannes Tschofenig > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org > Cc: ace@ietf.org > Subject: RE: Key IDs ... RE: [Ace] WGLC on > draft-ietf-ace-cwt-proof-of- > possession-02 > > I think you're looking for language something along these lines, right Jim? > > "Likewise, if PoP keys are used for multiple different kinds of CWTs > in an application and the PoP keys are identified by Key IDs, care > must be taken to > keep the keys for the different kinds of CWTs segregated so that an attacker > cannot cause the wrong PoP key to be used by using a valid Key ID for > the wrong kind of CWT." > > -- Mike > > -Original Message- > From: Jim Schaad > Sent: Friday, June 22, 2018 7:59 AM > To: Hannes Tschofenig ; Mike Jones > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org > Cc: ace@ietf.org > Subject: RE: Key IDs ... RE: [Ace] WGLC on > draft-ietf-ace-cwt-proof-of- > possession-02 > > That language works if you assume that there is only one CWT that an > RS will > look to. If there are multiple CWTs then one needs coordination > language between them. > > > -Original Message- > > From: Hannes Tschofenig > > Sent: Friday, June 22, 2018 6:36 AM > > To: Jim Schaad ; 'Mike Jones' > > ; draft-ietf-ace-cwt-proof-of- > > possess...@ietf.org > > Cc: ace@ietf.org > > Subject: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of- > > possession-02 > > > > Hi Jim, > > > > I would like to comment on this issue. > > > > - > > > > 14. I have real problems w/ the use of a KID for POP > > > > identification. It > > may > > > identify the wrong key or, if used for granting access, may have > > > problems > > w/ > > > identity collisions. These need to be spelt out someplace to help > > > people tracking down questions of why can't I verify w/ this CWT, > > > I know it's > > right. > > > > > > The Key ID is a hint to help identify which PoP key to use. Yes, > > > if a Key > > ID is > > > sent that doesn't correspond to the right PoP key, failures may occur. > > > I > > view > > > that as usage bug - not a protocol problem. If keys aren't > > > consistently > > known > > > and identified by both parties, there are lots of things that can > > > go > > wrong, and > > > this is only one such instance. That said, I can try to say > > > something > > about the > > > need for keys to be consistently and known by both parties, if you > > > think > > that > > > would help. > > > > > My problem is that if there are two different people with the same > > > Key ID, > > either intentionally or unintentionally, then using the key ID to > > identify > the > > key may allow the other person to masquerade as the first person. I > > am unworried about the instance of a failure to get a key based on a > > key id. > > That is not the problem you are proposing to address. > > > > - > > > > I think we should document this issue. Here is some text proposal > > that > could > > go into a separate operational consideration section (or into the > > security consideration section instead). > > > > " > > - Operational Considerations > > > > The use of CWTs with proof-of-possession keys requires additional > > information to be shared between the involved parties in order to > > ensure correct processing. The recipient needs to be able to use > > credentials to > verify > > the authenticity, integrity and potentially the confidentiality of > > the CWT > and > > its content. This requires the recipient to know information about > > the > issuer. > > Like-wise there needs to be an upfron
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
No not really, Hannes's language is much closer to what I am looking for. I don't care if they are different kinds of CWTs. I care about impersonation. > -Original Message- > From: Mike Jones > Sent: Friday, June 22, 2018 10:44 PM > To: Jim Schaad ; Hannes Tschofenig > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org > Cc: ace@ietf.org > Subject: RE: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > I think you're looking for language something along these lines, right Jim? > > "Likewise, if PoP keys are used for multiple different kinds of CWTs in an > application and the PoP keys are identified by Key IDs, care must be taken to > keep the keys for the different kinds of CWTs segregated so that an attacker > cannot cause the wrong PoP key to be used by using a valid Key ID for the > wrong kind of CWT." > > -- Mike > > -Original Message- > From: Jim Schaad > Sent: Friday, June 22, 2018 7:59 AM > To: Hannes Tschofenig ; Mike Jones > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org > Cc: ace@ietf.org > Subject: RE: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > That language works if you assume that there is only one CWT that an RS will > look to. If there are multiple CWTs then one needs coordination language > between them. > > > -Original Message- > > From: Hannes Tschofenig > > Sent: Friday, June 22, 2018 6:36 AM > > To: Jim Schaad ; 'Mike Jones' > > ; draft-ietf-ace-cwt-proof-of- > > possess...@ietf.org > > Cc: ace@ietf.org > > Subject: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of- > > possession-02 > > > > Hi Jim, > > > > I would like to comment on this issue. > > > > - > > > > 14. I have real problems w/ the use of a KID for POP > > > > identification. It > > may > > > identify the wrong key or, if used for granting access, may have > > > problems > > w/ > > > identity collisions. These need to be spelt out someplace to help > > > people tracking down questions of why can't I verify w/ this CWT, I > > > know it's > > right. > > > > > > The Key ID is a hint to help identify which PoP key to use. Yes, if > > > a Key > > ID is > > > sent that doesn't correspond to the right PoP key, failures may occur. > > > I > > view > > > that as usage bug - not a protocol problem. If keys aren't > > > consistently > > known > > > and identified by both parties, there are lots of things that can go > > wrong, and > > > this is only one such instance. That said, I can try to say > > > something > > about the > > > need for keys to be consistently and known by both parties, if you > > > think > > that > > > would help. > > > > > My problem is that if there are two different people with the same > > > Key ID, > > either intentionally or unintentionally, then using the key ID to > > identify > the > > key may allow the other person to masquerade as the first person. I > > am unworried about the instance of a failure to get a key based on a key id. > > That is not the problem you are proposing to address. > > > > - > > > > I think we should document this issue. Here is some text proposal that > could > > go into a separate operational consideration section (or into the > > security consideration section instead). > > > > " > > - Operational Considerations > > > > The use of CWTs with proof-of-possession keys requires additional > > information to be shared between the involved parties in order to > > ensure correct processing. The recipient needs to be able to use > > credentials to > verify > > the authenticity, integrity and potentially the confidentiality of the > > CWT > and > > its content. This requires the recipient to know information about the > issuer. > > Like-wise there needs to be an upfront agreement between the issuer > > and the recipient about the claims that need to be present and what > > degree of trust can be put into those. > > > > When an issuer creates a CWT containing a key id claim, it needs to > > make sure that it does not issue another CWT containing the same key > > id with a different content, or for a different subject, within the > > lifetime of the > CWTs, > > unless intentionally desired. Failure to do so may allow one party to > > impersonate another party with the potential to gain additional > privileges. > > " > > > > > > Ciao > > Hannes > > > > IMPORTANT NOTICE: The contents of this email and any attachments are > > confidential and may also be privileged. If you are not the intended > recipient, > > please notify the sender immediately and do not disclose the contents > > to > any > > other person, use it for any purpose, or store or copy the information > > in > any > > medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
> -Original Message- > From: Benjamin Kaduk > Sent: Friday, June 22, 2018 10:44 PM > To: Hannes Tschofenig > Cc: Jim Schaad ; 'Mike Jones' > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org; ace@ietf.org > Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > On Fri, Jun 22, 2018 at 01:36:16PM +, Hannes Tschofenig wrote: > > Hi Jim, > > > > > > > My problem is that if there are two different people with the same > > > Key ID, > > either intentionally or unintentionally, then using the key ID to > > identify the key may allow the other person to masquerade as the first > > person. I am unworried about the instance of a failure to get a key based > on a key id. > > That is not the problem you are proposing to address. > > > > - > > > > I think we should document this issue. Here is some text proposal that > > could go into a separate operational consideration section (or into the > security consideration section instead). > > > > " > > - Operational Considerations > > > > The use of CWTs with proof-of-possession keys requires additional > > information to be shared between the involved parties in order to > > ensure correct processing. The recipient needs to be able to use > > credentials to verify the authenticity, integrity and potentially the > confidentiality of the CWT and its content. This requires the recipient to > know information about the issuer. > > Like-wise there needs to be an upfront agreement between the issuer > > and the recipient about the claims that need to be present and what > degree of trust can be put into those. > > > > When an issuer creates a CWT containing a key id claim, it needs to > > make sure that it does not issue another CWT containing the same key > > id with a different content, or for a different subject, within the > > lifetime of the CWTs, unless intentionally desired. Failure to do so may > allow one party to impersonate another party with the potential to gain > additional privileges. > > " > > When would this be "intentionally desired"? It seems like there would be > better ways to share authorization between parties than to issue such > duplicate CWTs. One case where this is desired is if you issue a second CWT with additional permissions for a client and you want to tie it to the same key. You could either duplicate the key or just reference it by ID. Jim > > -Ben ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
See my note just now proposing this text to Jim: "Likewise, if PoP keys are used for multiple different kinds of CWTs in an application and the PoP keys are identified by Key IDs, care must be taken to keep the keys for the different kinds of CWTs segregated so that an attacker cannot cause the wrong PoP key to be used by using a valid Key ID for the wrong kind of CWT." As long as the PoP keys for different contexts are kept segregated, Key ID collisions or reuse cause no problems. -- Mike -Original Message- From: Benjamin Kaduk Sent: Friday, June 22, 2018 1:44 PM To: Hannes Tschofenig Cc: Jim Schaad ; Mike Jones ; draft-ietf-ace-cwt-proof-of-possess...@ietf.org; ace@ietf.org Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02 On Fri, Jun 22, 2018 at 01:36:16PM +, Hannes Tschofenig wrote: > Hi Jim, > > > > My problem is that if there are two different people with the same > > Key ID, > either intentionally or unintentionally, then using the key ID to > identify the key may allow the other person to masquerade as the first > person. I am unworried about the instance of a failure to get a key based on > a key id. > That is not the problem you are proposing to address. > > - > > I think we should document this issue. Here is some text proposal that > could go into a separate operational consideration section (or into the > security consideration section instead). > > " > - Operational Considerations > > The use of CWTs with proof-of-possession keys requires additional > information to be shared between the involved parties in order to > ensure correct processing. The recipient needs to be able to use > credentials to verify the authenticity, integrity and potentially the > confidentiality of the CWT and its content. This requires the recipient to > know information about the issuer. > Like-wise there needs to be an upfront agreement between the issuer > and the recipient about the claims that need to be present and what degree of > trust can be put into those. > > When an issuer creates a CWT containing a key id claim, it needs to > make sure that it does not issue another CWT containing the same key > id with a different content, or for a different subject, within the > lifetime of the CWTs, unless intentionally desired. Failure to do so may > allow one party to impersonate another party with the potential to gain > additional privileges. > " When would this be "intentionally desired"? It seems like there would be better ways to share authorization between parties than to issue such duplicate CWTs. -Ben ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
I think you're looking for language something along these lines, right Jim? "Likewise, if PoP keys are used for multiple different kinds of CWTs in an application and the PoP keys are identified by Key IDs, care must be taken to keep the keys for the different kinds of CWTs segregated so that an attacker cannot cause the wrong PoP key to be used by using a valid Key ID for the wrong kind of CWT." -- Mike -Original Message- From: Jim Schaad Sent: Friday, June 22, 2018 7:59 AM To: Hannes Tschofenig ; Mike Jones ; draft-ietf-ace-cwt-proof-of-possess...@ietf.org Cc: ace@ietf.org Subject: RE: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of-possession-02 That language works if you assume that there is only one CWT that an RS will look to. If there are multiple CWTs then one needs coordination language between them. > -Original Message- > From: Hannes Tschofenig > Sent: Friday, June 22, 2018 6:36 AM > To: Jim Schaad ; 'Mike Jones' > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org > Cc: ace@ietf.org > Subject: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Hi Jim, > > I would like to comment on this issue. > > - > > > 14. I have real problems w/ the use of a KID for POP > > > identification. It > may > > identify the wrong key or, if used for granting access, may have > > problems > w/ > > identity collisions. These need to be spelt out someplace to help > > people tracking down questions of why can't I verify w/ this CWT, I > > know it's > right. > > > > The Key ID is a hint to help identify which PoP key to use. Yes, if > > a Key > ID is > > sent that doesn't correspond to the right PoP key, failures may occur. > > I > view > > that as usage bug - not a protocol problem. If keys aren't > > consistently > known > > and identified by both parties, there are lots of things that can go > wrong, and > > this is only one such instance. That said, I can try to say > > something > about the > > need for keys to be consistently and known by both parties, if you > > think > that > > would help. > > > My problem is that if there are two different people with the same > > Key ID, > either intentionally or unintentionally, then using the key ID to > identify the > key may allow the other person to masquerade as the first person. I > am unworried about the instance of a failure to get a key based on a key id. > That is not the problem you are proposing to address. > > - > > I think we should document this issue. Here is some text proposal that could > go into a separate operational consideration section (or into the > security consideration section instead). > > " > - Operational Considerations > > The use of CWTs with proof-of-possession keys requires additional > information to be shared between the involved parties in order to > ensure correct processing. The recipient needs to be able to use > credentials to verify > the authenticity, integrity and potentially the confidentiality of the > CWT and > its content. This requires the recipient to know information about the issuer. > Like-wise there needs to be an upfront agreement between the issuer > and the recipient about the claims that need to be present and what > degree of trust can be put into those. > > When an issuer creates a CWT containing a key id claim, it needs to > make sure that it does not issue another CWT containing the same key > id with a different content, or for a different subject, within the > lifetime of the CWTs, > unless intentionally desired. Failure to do so may allow one party to > impersonate another party with the potential to gain additional privileges. > " > > > Ciao > Hannes > > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended recipient, > please notify the sender immediately and do not disclose the contents > to any > other person, use it for any purpose, or store or copy the information > in any > medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
On Fri, Jun 22, 2018 at 01:36:16PM +, Hannes Tschofenig wrote: > Hi Jim, > > > > My problem is that if there are two different people with the same Key ID, > either intentionally or unintentionally, then using the key ID to identify > the key may allow the other person to masquerade as the first person. I am > unworried about the instance of a failure to get a key based on a key id. > That is not the problem you are proposing to address. > > - > > I think we should document this issue. Here is some text proposal that could > go into a > separate operational consideration section (or into the security > consideration section instead). > > " > - Operational Considerations > > The use of CWTs with proof-of-possession keys requires additional information > to be shared > between the involved parties in order to ensure correct processing. The > recipient needs to be > able to use credentials to verify the authenticity, integrity and potentially > the confidentiality of > the CWT and its content. This requires the recipient to know information > about the issuer. > Like-wise there needs to be an upfront agreement between the issuer and the > recipient about > the claims that need to be present and what degree of trust can be put into > those. > > When an issuer creates a CWT containing a key id claim, it needs to make sure > that it does not > issue another CWT containing the same key id with a different content, or for > a different subject, > within the lifetime of the CWTs, unless intentionally desired. Failure to do > so may allow one party > to impersonate another party with the potential to gain additional privileges. > " When would this be "intentionally desired"? It seems like there would be better ways to share authorization between parties than to issue such duplicate CWTs. -Ben ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
That language works if you assume that there is only one CWT that an RS will look to. If there are multiple CWTs then one needs coordination language between them. > -Original Message- > From: Hannes Tschofenig > Sent: Friday, June 22, 2018 6:36 AM > To: Jim Schaad ; 'Mike Jones' > ; draft-ietf-ace-cwt-proof-of- > possess...@ietf.org > Cc: ace@ietf.org > Subject: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of- > possession-02 > > Hi Jim, > > I would like to comment on this issue. > > - > > > 14. I have real problems w/ the use of a KID for POP > > > identification. It > may > > identify the wrong key or, if used for granting access, may have > > problems > w/ > > identity collisions. These need to be spelt out someplace to help > > people tracking down questions of why can't I verify w/ this CWT, I > > know it's > right. > > > > The Key ID is a hint to help identify which PoP key to use. Yes, if a > > Key > ID is > > sent that doesn't correspond to the right PoP key, failures may occur. > > I > view > > that as usage bug - not a protocol problem. If keys aren't > > consistently > known > > and identified by both parties, there are lots of things that can go > wrong, and > > this is only one such instance. That said, I can try to say something > about the > > need for keys to be consistently and known by both parties, if you > > think > that > > would help. > > > My problem is that if there are two different people with the same Key > > ID, > either intentionally or unintentionally, then using the key ID to identify the > key may allow the other person to masquerade as the first person. I am > unworried about the instance of a failure to get a key based on a key id. > That is not the problem you are proposing to address. > > - > > I think we should document this issue. Here is some text proposal that could > go into a separate operational consideration section (or into the security > consideration section instead). > > " > - Operational Considerations > > The use of CWTs with proof-of-possession keys requires additional > information to be shared between the involved parties in order to ensure > correct processing. The recipient needs to be able to use credentials to verify > the authenticity, integrity and potentially the confidentiality of the CWT and > its content. This requires the recipient to know information about the issuer. > Like-wise there needs to be an upfront agreement between the issuer and > the recipient about the claims that need to be present and what degree of > trust can be put into those. > > When an issuer creates a CWT containing a key id claim, it needs to make > sure that it does not issue another CWT containing the same key id with a > different content, or for a different subject, within the lifetime of the CWTs, > unless intentionally desired. Failure to do so may allow one party to > impersonate another party with the potential to gain additional privileges. > " > > > Ciao > Hannes > > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended recipient, > please notify the sender immediately and do not disclose the contents to any > other person, use it for any purpose, or store or copy the information in any > medium. Thank you. ___ Ace mailing list Ace@ietf.org https://www.ietf.org/mailman/listinfo/ace
