epa4all-client has a VAU Signature bypass

Impact

In SignedPublicKeysTrustValidatorImpl.isTrusted(), the ECDSA signature verification at line 45 discards the boolean return value of Signature.verify(). The method performs certificate chain validation, OCSP check, and signature algorithm setup, but never checks whether the signature actually matches. For any structurally valid signature, it returns true.

Patches

Patched in #34.

Workarounds

None.

Resources

• MS-OVIVA-EPA4ALL-d76aec

Credits

Machine Spirits (contact@machinespirits.de)

• Dr. rer. nat. Simon Weber
• Dipl.-Inf. Volker Schönefeld
• Chiara Fliegner