GHSA-5hcj-rwm6-xmw4 biscuit-java vulnerable to public key confusion in third party block

• Maven org.biscuitsec:biscuit: >= 3.0.0, < 4.0.0 → fixed in 4.0.0

Impact Tokens with third-party blocks containing trusted annotations generated through a third party block request. Due to implementation issues in biscuit-java, third party block support in published versions is inoperating. Nevertheless, to synchronize with other implementations, we publish this advisory and the related fix. Description Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a `ThirdPartyBlock` request can be sent, providing only the necessary info to generate a third-party block and to sign it: the public key of the previous block (used in the signature) the public keys part of the token symbol table (for public key interning in datalog expressions) A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. Consider the following example (nominal case) • Authority A emits the following token: `check if thirdparty("b") trusting ${pubkeyB}` • The well-behaving holder then generates a third-party block request based on the token and sends it to third-party authority B • Third-party B generates the following third-party block `thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}` • The token holder now must obtain a third-party block from third party C to be able to use the token Now, with a malicious user: • Authority A emits the following token: `check if thirdparty("b") trusting ${pubkeyB}` • The holder then attenuates the token with the following third party block `thirdparty("c")`, signed with a keypair pubkeyD, privkeyD) they generate • The holder then generates a third-party block request based on this token, but alter the `ThirdPartyBlockRequest` publicKeys field and replace pubkeyD with pubkeyC • Third-party B generates the following third-party block `thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}` • Due to the altered symbol table, the actual meaning of the block is `thirdparty("b"); check if thirdparty("c") trusting ${pubkeyD}` • The attacker can now use the token without obtaining a third-party block from C. Patches _Has the problem been patched? What versions should users upgrade to?_ Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ References _Are there any links users can visit to find out more?_