Module

OpenSSL::OCSP implements Online Certificate Status Protocol requests and responses.

Creating and sending an OCSP request requires a subject certificate that contains an OCSP URL in an authorityInfoAccess extension and the issuer certificate for the subject certificate. First, load the issuer and subject certificates:

subject = OpenSSL::X509::Certificate.new subject_pem
issuer  = OpenSSL::X509::Certificate.new issuer_pem

To create the request we need to create a certificate ID for the subject certificate so the CA knows which certificate we are asking about:

digest = OpenSSL::Digest::SHA1.new
certificate_id =
  OpenSSL::OCSP::CertificateId.new subject, issuer, digest

Then create a request and add the certificate ID to it:

request = OpenSSL::OCSP::Request.new
request.add_certid certificate_id

Adding a nonce to the request protects against replay attacks but not all CA process the nonce.

request.add_nonce

To submit the request to the CA for verification we need to extract the OCSP URI from the subject certificate:

authority_info_access = subject.extensions.find do |extension|
  extension.oid == 'authorityInfoAccess'
end

descriptions = authority_info_access.value.split "\n"
ocsp = descriptions.find do |description|
  description.start_with? 'OCSP'
end

require 'uri'

ocsp_uri = URI ocsp[/URI:(.*)/, 1]

To submit the request we’ll POST the request to the OCSP URI (per RFC 2560). Note that we only handle HTTP requests and don’t handle any redirects in this example, so this is insufficient for serious use.

require 'net/http'

http_response =
  Net::HTTP.start ocsp_uri.hostname, ocsp.port do |http|
    http.post ocsp_uri.path, request.to_der,
              'content-type' => 'application/ocsp-request'
end

response = OpenSSL::OCSP::Response.new http_response.body
response_basic = response.basic

First we check if the response has a valid signature. Without a valid signature we cannot trust it. If you get a failure here you may be missing a system certificate store or may be missing the intermediate certificates.

store = OpenSSL::X509::Store.new
store.set_default_paths

unless response_basic.verify [], store then
  raise 'response is not signed by a trusted certificate'
end

The response contains the status information (success/fail). We can display the status as a string:

puts response.status_string #=> successful

Next we need to know the response details to determine if the response matches our request. First we check the nonce. Again, not all CAs support a nonce. See Request#check_nonce for the meanings of the return values.

p request.check_nonce basic_response #=> value from -1 to 3

Then extract the status information for the certificate from the basic response.

single_response = basic_response.find_response(certificate_id)

unless single_response
  raise 'basic_response does not have the status for the certificiate'
end

Then check the validity. A status issued in the future must be rejected.

unless single_response.check_validity
  raise 'this_update is in the future or next_update time has passed'
end

case single_response.cert_status
when OpenSSL::OCSP::V_CERTSTATUS_GOOD
  puts 'certificate is still valid'
when OpenSSL::OCSP::V_CERTSTATUS_REVOKED
  puts "certificate has been revoked at #{single_response.revocation_time}"
when OpenSSL::OCSP::V_CERTSTATUS_UNKNOWN
  puts 'responder doesn't know about the certificate'
end
Constants

Internal error in issuer

Illegal confirmation request

The certificate was revoked for an unknown reason

You must sign the request and resubmit

Response has valid confirmations

Try again later

The certificate subject’s name or other information changed

This CA certificate was revoked due to a key compromise

The certificate is on hold

The certificate is no longer needed

The certificate was revoked due to a key compromise

The certificate was previously on hold and should now be removed from the CRL

The certificate was superseded by a new certificate

Your request is unauthorized.

The certificate was revoked for an unspecified reason

Do not include certificates in the response

Do not search certificates contained in the response for a signer

Do not check the signature on the response

Do not verify the certificate chain on the response

Do not verify the response at all

Do not check trust

(This flag is not used by OpenSSL 1.0.1g)

(This flag is not used by OpenSSL 1.0.1g)

Do not make additional signing certificate checks

Do not verify additional certificates

Identify the response by signing the certificate key ID

Do not include producedAt time in response

Indicates the certificate is not revoked but does not necessarily mean the certificate was issued or that this response is within the certificate’s validity interval

Indicates the certificate has been revoked either permanently or temporarily (on hold).

Indicates the responder does not know about the certificate being requested.

The responder ID is based on the key name.

The responder ID is based on the public key.