Re:EFail – Vulnerabilities in end-to-end encryption technolo...
by rocqua on Monday May 14, 2018 @01:16PM
(#17067300)
This isn't undefined behavior. This is malleability. Attackers get to change some parts of the plain text without needing to know the encryption key.
This is very much an issue with the S/MIME standard, which has no defence against this kind of attack. For PGP it is slightly different, as there is a defense against it (the 'MDC', a sha-1 hash of the plaintext) but it has a soft-fail if the MDC is not present.
Both are issues with the standard. For S/MIME it is a total failure, whilst for PGP the failure is mitigated slightly by an obscure and non-urgent error message. But, it is unreasonable to expect users to act on this kind of error message. Really, what you want here is a hard fail, but that would break backwards compatibility.
This is very much an issue with the S/MIME standard, which has no defence against this kind of attack. For PGP it is slightly different, as there is a defense against it (the 'MDC', a sha-1 hash of the plaintext) but it has a soft-fail if the MDC is not present.
Both are issues with the standard. For S/MIME it is a total failure, whilst for PGP the failure is mitigated slightly by an obscure and non-urgent error message. But, it is unreasonable to expect users to act on this kind of error message. Really, what you want here is a hard fail, but that would break backwards compatibility.