Verification flaw in Solid identity-token-verifier

Summary

### Impact #### Severity Any Pod on a Solid server using a vulnerable version of the identity-token-verifier library is at risk of a spoofed Demonstration of Proof-of-Possession (DPoP) token binding. This vulnerability could give total and complete access to a targeted Pod.

#### Summary A verification flaw in the implementation of the identity token verifier library (https://github.com/solid/identity-token-verifier) allows DPoP proofs to be spoofed.

DPoP proofs are used to bind access tokens to a private key meant to be in sole possession of a specific user. Instead of verifying against the hash of an embedded public key, the library instead verifies against a field that an attacker can modify to spoof another user’s DPoP.

A stolen DPoP proof, when used in the right context, therefore allows the rebinding of a DPoP-bound access token. Any attacker in possession of a targeted access token could build an attack environment to replay it on any Pod service with this vulnerability.

### Patches A new version 0.5.2 of identity-token-verifier fixes the verification: https://github.com/solid/identity-token-verifier/blob/7e18d86d65ee681e8ae912b6a032a1bae3cae570/src/lib/DPoP.ts#L25-L35

### Workarounds None

### References _Are there any links users can visit to find out more?_

### For more information If you have any questions or comments about this advisory: * Open an issue in the [identity-token-verifier](https://github.com/solid/identity-token-verifier/) repository. * Email: info@solidproject.org