New SSL features for Nginx.

[Igor Sysoev]

On Wed, Jul 22, 2009 at 07:20:39PM +0200, Brice Figureau wrote:

> On 22/07/09 14:16, Igor Sysoev wrote:
> >On Wed, Jul 22, 2009 at 12:21:23PM +0200, Brice Figureau wrote:
> >
> >>Hi Igor,
> >>
> >>On Wed, 2009-07-22 at 12:44 +0400, Igor Sysoev wrote:
> >>>On Tue, Jul 21, 2009 at 08:02:05PM +0200, Brice Figureau wrote:
> >>>
> >>>>Hi,
> >>>>
> >>>>For Puppet[1] Nginx deployement (that is using Nginx as a front-end 
> >>>>load-balancers to puppetmasters[2]), I had to create the following two 
> >>>>patches, to match Apache behaviour:
> >>>>
> >>>> * The first patch allows:
> >>>>  + a new variant of ssl_client_verify: optional. In this mode, if the 
> >>>>client sends a certificate it is verified, but if the client doesn't 
> >>>>send a certificate, the connection is authorized too.
> >>>>
> >>>>  + a new variable: $ssl_client_verify which contains, either NONE, 
> >>>>SUCCESS or FAILURE depending on the verification status. It can be used 
> >>>>to send information to the upstream about the client verification.
> >>>>
> >>>> * The second patch adds CRL support to the client certificate 
> >>>>verification:
> >>>>
> >>>>  ssl_crl /path/to/crl.pem;
> >>>>
> >>>> Nginx then verifies the client certificate hasn't been revoked in the 
> >>>>given CRL before allowing the connection to proceed.
> >>>>
> >>>>For access to the patches, please see my last blog article:
> >>>>http://www.masterzen.fr/2009/07/21/new-ssl-features-for-nginx/
> >>>>
> >>>>It would be great if those patches could be merged in the official 
> >>>>Nginx source tree.
> >>>Thank you, I have looked the patches, it was really surpise for me that
> >>>OpenSSL 0.9.7 supports CRL. I read in old enough book "Network Security
> >>>with OpenSSL" written when 0.9.7 was being developed, that OpenSSL has
> >>>no built-in CRL support. 
> >>Ah, ok. I based all my development on OpenSSL 0.9.8, since that's what
> >>I'm building Nginx againt. And definitely there is CRL support.
> >>Is OpenSSL 0.9.7 a strict dependency for Nginx?
> >
> >No. I think this code should be just "#ifdef'ed X509_V_FLAG_CRL_CHECK".
> 
> I'm OK with this. BTW, I checked and CRL support was added in 0.9.7.
> 
> >>>Then I have looked in Apache's mod_ssl sources and
> >>>its CRL support seemed to me very heavy: mod_ssl does a lot of useless
> >>>operations.
> >>Which ones?
> >>What I don't get is why they're doing the CRL verification themselves.
> >
> >Because mod_ssl were developed before 0.9.7.
> 
> Yes, I do think so. But it's error-prone and certainly less efficient.
> 
> >>I found this comment in the code:
> >>     * OpenSSL provides the general mechanism to deal with CRLs but does
> >>not
> >>     * use them automatically when verifying certificates, so we do it
> >>     * explicitly here. We will check the CRL for the currently checked
> >>     * certificate, if there is such a CRL in the store.
> >>
> >>This seems wrong to me, as I already tested, and it works fine at least
> >>in version 0.9.8.
> >
> >Yes, this implementation. However, I made mistake: it's not too heavy as
> >it seemed to me first time I have looked.
> >
> >>>I think that it's enough to store hash of only public key of
> >>>all CRL certificates (including intermediate ones). 
> >>Why reinvent the wheel?
> >>The CRL is a standard thing (see RFC 3280), and basically this is a DER
> >>encoded ASN1 structure containing the list of the revoked certificates
> >>serial number, signed by the CA cert.
> >>
> >>>Have you looked
> >>>how CRL is implemented in OpenSSL ?
> >>Yes, I did. It is pretty extensive, and matches RFC3280.
> >>
> >>I'll fetch OpenSSL 0.9.7 to see if it supports or not CRL, but I'd be
> >>suprised it wouldn't.
> 
> 0.9.7 definitely supports CRL verification.

Yes. When I mentioned the book, I meant that CRL were not supported
at least in 0.9.6.

> >>Thanks for reviewing the patch (at least the first one could be merged,
> >>isn't it?).
> >
> >Probabaly, I will commit the patches in next 0.8.7.
> 
> Will you merge the CRL one (feel free to rewrite it if you prefer), too ?

Yes, the single issue is name of directive: ssl_crl. Should it be longer and
more expressive ? Apache has SSLCARevocationFile.


-- 
Igor Sysoev
http://sysoev.ru/en/