On Mar 28, 2022, at 1:04 PM, Steinar Noem <stei...@udelt.no> wrote:
Interesting, but won't two collaborating clients just pass any
data they want to each other? Why would these collaborating
clients go through the trouble of exchanging private keys, dpop
proofs or tokens? Could you elaborate some more on the scenario?
S
man. 28. mar. 2022 kl. 16:29 skrev Denis <denis.i...@free.fr>:
Rifaat & Hannes,
Hereafter are my comments:
The introduction states :
Recipients of such tokens are then able to verify the binding
of the token to the key pair thatthe client has demonstrated
that it holds via the DPoP header, thereby providing
some assurance that the client presenting the token also
possesses the private key.
In other words, the legitimate presenter of the token
is constrained to be the sender that holds and can prove
possession of the private part of the key pair.
The client presenting the token *does not necessarily possess
the private key*. The client presenting the token has been
able to use
the results of some cryptographic functions using the private
part of the key pair.
These results may be communicated by one client to another
client, if the two clients agree to collaborate. This
statement will be added later on.
Proposed rewording:
Recipients of such tokens are then able to verify the
binding of the token to the key pair thatthe client has
demonstrated
that it holds via the DPoP header, thereby providing
some assurance that the client presenting the token *either
*also possesses
the private key *or* has been able to use the result of
cryptographic computations from another client that possesses
the private key.
In other words, the presenter of the token can prove
that it has been able to use the results of cryptographic
computations performed
by using the private part of the key pair.
The objectives states
The primary aim of DPoP is to prevent unauthorized or
illegitimate parties from using leaked or stolen access tokens,
by binding a token to a public key upon issuance and
requiring that the client proves possession of the corresponding
private key when using the token.
DPoP does not prevent unauthorized or illegitimate parties
from using access tokens, as soon as two clients agree to
collaborate.
Proposed rewording:
The primary aim of DPoP is to bind a token to a public
key upon issuance and requiring that the client proves possession
of the corresponding private key when using the
token.This does not demonstrate that the client presenting the
token is
necessarily the legitimate client. In the case of
non-collaborating clients, DPoP prevents unauthorized or
illegitimate parties
from using leaked or stolen access tokens. In the case
of collaborating clients, the security of DPoP is ineffective
(see section 11.X).
Section 11 is about "Security Considerations" and addresses
the following topics:
11.1.DPoP Proof Replay
11.2.DPoP Proof Pre-Generation
11.3.DPoP Nonce Downgrade
11.4.Untrusted Code in the Client Context
11.5.Signed JWT Swapping
11.6.Signature Algorithms
11.7.Message Integrity
11.8.Access Token and Public Key Binding
11.9.Authorization Code and Public Key Binding
The case of collaborative clients should be addressed within
section 11.
Text proposal.
11.X. Collaborative clients
DPoP demonstrates that the client presenting the
token has been able to use the results of some cryptographic
functions
using the private part of the key pair.
If a client agrees to collaborate with another client, the
security of DPoP is no longer effective.When two clients agree
to collaborate,
these results of the cryptographic computations performed by
one client may be communicated to another client.
Even if the private key used for DPoP is stored in such a way
that it cannot be exported, e.g., in a hardware or software
security module,
the client can perform all the cryptographic computations
needed by the other client to create DPoP proofs.
The client can easily create new DPoP proofs as long as the
other client is online.
Note: There exist other techniques able to limit, in some
cases, the use of a token transmitted voluntarily by a
legitimate client
to an illegitimate client.
Denis
All,
As discussed during the IETF meeting in *Vienna* last week,
this is a *WG Last Call *for the *DPoP* document:
https://datatracker.ietf.org/doc/draft-ietf-oauth-dpop/
Please, provide your feedback on the mailing list by April 11th.
Regards,
Rifaat & Hannes
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--
Vennlig hilsen
Steinar Noem
Partner Udelt AS
Systemutvikler
| stei...@udelt.no <mailto:stei...@udelt.no> | h...@udelt.no | +47
955 21 620 | www.udelt.no <http://www.udelt.no/> |
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