Nginx – How to check multiple CRL lists with nginx client authentication

crlnginxopenssl

I have a custom easyrsa setup with a root and three CAs signed by the root. (Three different sub-cas depending on the user type), like this:

RootCA
  +----- AdminUserCA
  +----- EmployeeCA
  +----- ClientCA

I have authentication working with the following config:

server {
  listen               127.0.0.1:443;
  server_name          www.acme.corp;
  ssl                  on;
  ssl_certificate      /data/src/easy-rsa/bundles/www.acme.corp_bundle.crt;
  ssl_certificate_key  /data/src/easy-rsa/whfWebCA/pki/private/www.acme.corp.key;
  add_header           Strict-Transport-Security "max-age=315360000; includeSubdomains";
  ssl_protocols        SSLv3 TLSv1;
  ssl_ciphers ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-RC4-SHA:ECDHE-RSA-RC4-SHA:ECDH-ECDSA-RC4-SHA:ECDH-RSA-RC4-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:RC4-SHA;
  ssl_prefer_server_ciphers on;
  ssl_verify_client optional;
  ssl_client_certificate /data/src/easy-rsa/bundles/client_auth_ca_chain.crt;
  ssl_verify_depth 2;
  ssl_crl /data/src/easy-rsa/bundles/crls/all.pem;

  ...
}

The problem is with the CRL checking. CRLs are signed by the issuing CA therefore they can not be appened together like intermediate certificate+root certificates.

So a user's certificate will be issued by the given intermediate CA depending on their user type. The problem is I really need to check four CRL lists to be effective. The nginx ssl_crl only supports a single file.

So my question is: Is it possible to have nginx correctly check for a client certificate revokation in this setup without having to do the check in my application?

Best Answer

Yes, it is possible. Just concatenate multiple PEM-encoded CRLs into a single file specified in the ssl_crl directive.

(A question in nginx mailing list referenced this question. Posting the answer here as well.)

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