Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH06/17] PKCS#7: Verify internal certificate chain | Date | Thu, 10 Jul 2014 21:37:37 +0100 |
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Valdis.Kletnieks@vt.edu wrote:
> > Verify certificate chain in the X.509 certificates contained within the > > PKCS#7 message as far as possible. If any signature that we should be > > able to verify fails, we reject the whole lot. > > What happens if we see a signature that we shouldn't be able to verify? Or > should that changelog entry be reduced to "If any signature fails", period?
No.
When I say "any signature that we should be able to verify" I mean that a signature for which we have an appropriate public key.
If we don't have a public key for a signature, we prune the trust chain at that point.
What I mean is that the PKCS#7 message can have several signatures applied to it. We can form a chain from each signature going back through the X.509 certificates included in the PKCS#7 message:
PKCS#7 ---> X.509 ---> X.509 ---> X.509 ---> X.509
where the PKCS#7 message and each X.509 cert has a signature that the next X.509 cert in the chain can be used to verify with the public key contained therein.
Any of the signatures in any of the chains can form an intersection point with the keyring of public keys provided. If there's a verified match on one or more of them, we permit the message.
If any "Y ---> X.509" verification is rejected, we reject the whole message because there's something wrong. If an intersection point verification is rejected, again we reject the whole message.
If there are no intersection points, we also reject the message, but with ENOKEY rather than EKEYREJECTED.
David
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