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  • openssl/ossl.c

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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::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.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 OpenSSL::OCSP::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 from the basic response. (You can check multiple certificates in a request, but for this example we only submitted one.)

response_certificate_id, status, reason, revocation_time,
  this_update, next_update, extensions = basic_response.status

Then check the various fields.

unless response_certificate_id == certificate_id then
  raise 'certificate id mismatch'
end

now = Time.now

if this_update > now then
  raise 'update date is in the future'
end

if now > next_update then
  raise 'next update time has passed'
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.