Adding an option to only perform CRL checks for leaf nodes

Maxim Dounin mdounin at
Thu Apr 27 16:43:01 UTC 2017


On Thu, Apr 27, 2017 at 04:18:30PM +0100, Nicholas Humfrey wrote:

> I was having trouble getting CRL checks working for client certificates 
> and it turns out that the problem is because nginx checks CRLs for all 
> levels of the certificate hierarchy, but the CA I am using does not 
> publish CRLs for intermediate certificates.
> It is not uncommon for the private key of the root CA certificate to be 
> locked-away offline in a safe, to prevent any other intermediate 
> certificates from being issued. However this means that CRLs cannot be 
> generated for the intermediate certificates, only the leaf certificates. 
> Hence only the leaf certificates can be CRL checked.

How do you revoke intermediate certificates if compromised then?

> The solution to this is very simple; just set X509_V_FLAG_CRL_CHECK in 
> OpenSSL without the X509_V_FLAG_CRL_CHECK_ALL flag.
> Would you accept a patch that adds a new configuration option to nginx 
> to control this?

Unlikely, this was already discussed on this list several weeks 

Maxim Dounin

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