CVE-2024-41948 in biscuit-java
Summary
by MITRE • 08/02/2024
biscuit-java is the java implementation of Biscuit, an authentication and authorization token for microservices architectures. 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, which includes the public key of the previous block (used in the signature) and 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. This vulnerability is fixed in 4.0.0.
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Analysis
by VulDB Data Team • 08/09/2024
The vulnerability identified as CVE-2024-41948 affects biscuit-java, a java implementation of the Biscuit authentication and authorization framework designed for microservices architectures. This system enables secure token-based authentication by allowing third-party blocks to be generated without requiring the complete token to be transmitted to external authorities. The framework operates by enabling third-party authorities to generate blocks containing datalog expressions that can trust specific public keys, using a mechanism where only necessary information is shared rather than the entire token. The security model relies on proper key management and signature validation to maintain trust relationships within the token structure.
The technical flaw stems from insufficient validation of third-party block requests that can be forged by malicious actors. When a third-party authority processes a ThirdPartyBlock request, it should verify that the public key information provided in the request correctly corresponds to the expected keypair that should be trusted in the datalog expressions. However, the vulnerability allows attackers to manipulate the request data in such a way that the third-party authority generates a block that incorrectly associates trust relationships with the wrong keypair. This occurs because the system fails to properly validate the consistency between the public key information included in the request and the cryptographic context required for proper signature verification.
The operational impact of this vulnerability is significant for systems relying on biscuit-java for authentication and authorization. An attacker who successfully exploits this flaw can cause the third-party authority to generate malicious blocks that establish incorrect trust relationships within the token. This could allow unauthorized entities to gain elevated privileges or bypass access controls by manipulating the datalog expressions that govern authorization decisions. The vulnerability essentially undermines the cryptographic integrity of the token system, as it enables attackers to inject malicious trust relationships that may go undetected by the token validation mechanisms. This represents a critical failure in the token's security model and could compromise the entire authorization infrastructure built on top of the Biscuit framework.
The vulnerability aligns with CWE-295 which addresses improper certificate validation and improper key validation in cryptographic systems. It also maps to ATT&CK technique T1550.002 which covers use of valid accounts through abuse of credentials and T1078.004 which involves valid accounts used for lateral movement. The fix implemented in version 4.0.0 addresses this by strengthening the validation mechanisms for third-party block requests, ensuring that the cryptographic context and key information provided in these requests are properly verified against the expected security parameters. Organizations should immediately upgrade to version 4.0.0 or later to remediate this vulnerability and ensure that their authentication and authorization systems maintain proper cryptographic integrity. The fix likely involves implementing more rigorous validation checks on the public key information and signature contexts to prevent the injection of malicious trust relationships into the token structure.