lib/jwt/x5c_key_finder.rb
# frozen_string_literal: true
module JWT
# If the x5c header certificate chain can be validated by trusted root
# certificates, and none of the certificates are revoked, returns the public
# key from the first certificate.
# See https://tools.ietf.org/html/rfc7515#section-4.1.6
class X5cKeyFinder
def initialize(root_certificates, crls = nil)
raise(ArgumentError, 'Root certificates must be specified') unless root_certificates
@store = build_store(root_certificates, crls)
end
def from(x5c_header_or_certificates)
signing_certificate, *certificate_chain = parse_certificates(x5c_header_or_certificates)
store_context = OpenSSL::X509::StoreContext.new(@store, signing_certificate, certificate_chain)
if store_context.verify
signing_certificate.public_key
else
error = "Certificate verification failed: #{store_context.error_string}."
if (current_cert = store_context.current_cert)
error = "#{error} Certificate subject: #{current_cert.subject}."
end
raise(JWT::VerificationError, error)
end
end
private
def build_store(root_certificates, crls)
store = OpenSSL::X509::Store.new
store.purpose = OpenSSL::X509::PURPOSE_ANY
store.flags = OpenSSL::X509::V_FLAG_CRL_CHECK | OpenSSL::X509::V_FLAG_CRL_CHECK_ALL
root_certificates.each { |certificate| store.add_cert(certificate) }
crls&.each { |crl| store.add_crl(crl) }
store
end
def parse_certificates(x5c_header_or_certificates)
if x5c_header_or_certificates.all? { |obj| obj.is_a?(OpenSSL::X509::Certificate) }
x5c_header_or_certificates
else
x5c_header_or_certificates.map do |encoded|
OpenSSL::X509::Certificate.new(::JWT::Base64.url_decode(encoded))
end
end
end
end
end