Aleksey:
I'll have to check the spec also -- but it simply *can't* work this way. If
I sign e-mail today and it can't be verified tomorrow even though nothing has
changed, that's *wrong*. I do know that signing of certs works this way but
that's handled by ensuring that the root cert is valid as of the expiration of
the child cert. While you are likely correct about CRLs .. none of the other
signing schemes other than certs behave this way (i.e., code signing (JAVA and
Authenticode) and S/Mime e-mail don't behave this way).
Depending on what the spec says about this and whether it's MUST, SHOULD or MAY,
will determine how to proceed here. If it's SHOULD or MAY and you feel strongly
that the current behavior is correct, what about an option for applications
where the data must be proved authentic essentially forever and the only desired
restriction is that the cert must have been valid when the data was
signed?
One way to look at this is that I'm giving my customers a perpetual license to
my application -- if it suddenly stops working in 9 months when my cert expires,
they aren't going to be happy. The commercial CA's won't even give you a cert
greater than 12 (maybe 24 if you press hard) months. There's no way to validate
code and other application meta-data (the XML issue at hand) for a greater
period of time if your assumption is correct. That just won't work
...
Please check on this and reconsider if it's at all an optional behavior (which I
strongly believe it is).
Thanks!
Ferrell
-----Original Message-----I believe you are wrong here. The certificate must be valid when signature is verified.
From: Aleksey Sanin [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, October 09, 2002 11:48 AM
To: Moultrie, Ferrell (ISSAtlanta)
Cc: Roman Bouchner; [EMAIL PROTECTED]
Subject: Re: [xmlsec] Verify signature after certificate expired
Where "valid" includes:
1) certificate is signed by another "valid" cert or trusted root cert
2) certificate is not in the CRL
3) the certificate purpose matches the action you are going to do (sign, verify, etc.)
4) the certificate is not expired
All 4 items are important. I do not have an X509 spec around so I could not prove my point.
However, RFC 2560 (http://rfc.sunsite.dk/rfc/rfc2560.html):An OCSP responder MAY choose to retain revocation information beyond a certificate's expiration. The date obtained by subtracting this retention interval value from the producedAt time in a response is defined as the certificate's "archive cutoff" date.Please note that when certificate is expired the OSCP may remove the CRL from memory!
Aleksey
Moultrie, Ferrell (ISSAtlanta) wrote:
Aleksey: Very important question here -- I want to make sure I understand your reply. In general, it is not permitted to *sign* data after the signing certificate has expired but it is allowed to *verify* data after expiration. An example: I sign my code today allowing the user to verify that it is uncorrupted when he installs/runs it. My certificate expires in three months. If you don't honor the signature any more at that point, then his code stops working -- a very bad thing. Another example: I sign an e-mail to you today. Three months later my cert expires. Six months later you try to read my e-mail and you're told the signature is invalid. A bad thing. As these two examples illustrate, it is *not* standard practice to invalidate signatures because the signer's cert has expired. The only date restrictions should be: 1) Signers cert *must* be valid as of the date the data was signed; 2) Root cert(s) *must* be valid as of the date they signed the subsidiary cert (in fact, I believe proper practice is that CA's shouldn't sign certs that extend beyond their own validity date). The key concept is that user signing's *don't*, *shouldn't*, *mustn't* expire just because the user's cert has expired. At that point, he can't sign anything else until he renews his cert but everything he signed still remains valid forever because it was valid when he signed it and it hasn't changed. Is there a problem here or did I just misunderstand something? Thanks! Ferrell -----Original Message----- From: Aleksey Sanin [mailto:[EMAIL PROTECTED]] Sent: Wednesday, October 09, 2002 11:05 AM To: Roman Bouchner Cc: [EMAIL PROTECTED] Subject: Re: [xmlsec] Verify signature after certificate expired From the general security point of view the data are *not valid* if the cert is expired. If you really want to do this then you should take a look at the OpenSSL cert verification function and remove date check. However, this is DANGEROUSE! Aleksey. Roman Bouchner wrote:Hello I would like to verify signed data however signer's certificate has already expired. I want only verify data integrity. If I use function xmlSecDSigValidate, it returns negative value, so I cannot determine if data was changed or not. If I change local date it does work, however it is not right way I think.. How I can solve this problems? Thanks:) Roman Bouchner _______________________________________________ xmlsec mailing list [EMAIL PROTECTED] http://www.aleksey.com/mailman/listinfo/xmlsec_______________________________________________ xmlsec mailing list [EMAIL PROTECTED] http://www.aleksey.com/mailman/listinfo/xmlsec
