# module OpenSSL::OCSP

`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.new('SHA1')
    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:

    ocsp_uris = subject.ocsp_uris

    require 'uri'

    ocsp_uri = URI ocsp_uris[0]

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_uri.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 certificate'
    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

NOCASIGN

  (This flag is not used by `OpenSSL` 1.0.1g)

NOCERTS

  Do not include certificates in the response

NOCHAIN

  Do not verify the certificate chain on the response

NOCHECKS

  Do not make additional signing certificate checks

NODELEGATED

  (This flag is not used by `OpenSSL` 1.0.1g)

NOEXPLICIT

  Do not check trust

NOINTERN

  Do not search certificates contained in the response for a signer

NOSIGS

  Do not check the signature on the response

NOTIME

  Do not include producedAt time in response

NOVERIFY

  Do not verify the response at all

RESPID_KEY

  Identify the response by signing the certificate key ID

RESPONSE_STATUS_INTERNALERROR

  Internal error in issuer

RESPONSE_STATUS_MALFORMEDREQUEST

  Illegal confirmation request

RESPONSE_STATUS_SIGREQUIRED

  You must sign the request and resubmit

RESPONSE_STATUS_SUCCESSFUL

  `Response` has valid confirmations

RESPONSE_STATUS_TRYLATER

  Try again later

RESPONSE_STATUS_UNAUTHORIZED

  Your request is unauthorized.

REVOKED_STATUS_AFFILIATIONCHANGED

  The certificate subject’s name or other information changed

REVOKED_STATUS_CACOMPROMISE

  This CA certificate was revoked due to a key compromise

REVOKED_STATUS_CERTIFICATEHOLD

  The certificate is on hold

REVOKED_STATUS_CESSATIONOFOPERATION

  The certificate is no longer needed

REVOKED_STATUS_KEYCOMPROMISE

  The certificate was revoked due to a key compromise

REVOKED_STATUS_NOSTATUS

  The certificate was revoked for an unknown reason

REVOKED_STATUS_REMOVEFROMCRL

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

REVOKED_STATUS_SUPERSEDED

  The certificate was superseded by a new certificate

REVOKED_STATUS_UNSPECIFIED

  The certificate was revoked for an unspecified reason

TRUSTOTHER

  Do not verify additional certificates

V_CERTSTATUS_GOOD

  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

V_CERTSTATUS_REVOKED

  Indicates the certificate has been revoked either permanently or temporarily (on hold).

V_CERTSTATUS_UNKNOWN

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

V_RESPID_KEY

  The responder ID is based on the public key.

V_RESPID_NAME

  The responder ID is based on the key name.