Class: OpenID::SimpleSign

Inherits:
Object
  • Object
show all
Defined in:
lib/gapps_openid.rb

Overview

Basic implementation of the XML Simple Sign algorithm. Currently only supports RSA-SHA1

Constant Summary collapse

C14N_RAW_OCTETS = 
'http://docs.oasis-open.org/xri/xrd/2009/01#canonicalize-raw-octets'
SIGN_RSA_SHA1 = 
'http://www.w3.org/2000/09/xmldsig#rsa-sha1'
NAMESPACES = 
{
  'ds' => 'http://www.w3.org/2000/09/xmldsig#',
  'xrds' => 'xri://xrds'
}
@@store = 
nil

Class Method Summary collapse

Class Method Details

.parse_certificates(doc) ⇒ Object

Extracts the signer’s certificates from the XML



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# File 'lib/gapps_openid.rb', line 264

def self.parse_certificates(doc) 
  certs = []
  REXML::XPath.each(doc, "//ds:Signature/ds:KeyInfo/ds:X509Data/ds:X509Certificate", NAMESPACES ) { | encoded |
    encoded = encoded.text.strip.scan(/.{1,64}/).join("\n")
    encoded = "-----BEGIN CERTIFICATE-----\n#{encoded}\n-----END CERTIFICATE-----\n"
    cert = OpenSSL::X509::Certificate.new(encoded)
    certs << cert
  }
  return certs
end

.store ⇒ Object

Initialize the store



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# File 'lib/gapps_openid.rb', line 252

def self.store
  if @@store.nil?
    OpenID.logger.info("Initializing CA bundle") unless OpenID.logger.nil?        
    ca_bundle_path = File.join(File.dirname(__FILE__), 'ca-bundle.crt')
    @@store = OpenSSL::X509::Store.new
    @@store.set_default_paths
    @@store.add_file(ca_bundle_path)        
  end
  return @@store
end

.valid_chain?(chain) ⇒ Boolean

Verifies the chain of trust for the signing certificates

Returns:

  • (Boolean) 


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# File 'lib/gapps_openid.rb', line 276

def self.valid_chain?(chain)
  if chain.nil? or chain.empty?
    return false
  end
  cert = chain.shift
  if self.store.verify(cert)
    return true
  end
  if chain.empty? or not cert.verify(chain.first.public_key)
    return false
  end
  return self.valid_chain?(chain)
end

.verify(xml, signature_value) ⇒ Object

Verifies the signature of the doc, returning the CN of the signer if valid



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# File 'lib/gapps_openid.rb', line 291

def self.verify(xml, signature_value) 
  doc = REXML::Document.new(xml)

  return nil if REXML::XPath.first(doc, "//ds:Signature").nil? and signature_value.nil?    

  decoded_sig = Base64.decode64(signature_value)
  certs = self.parse_certificates(doc)
  raise "No signature in document" if certs.nil? or certs.empty?
  raise "Missing signature value" if signature_value.nil?


  signing_certificate = certs.first
  raise "Invalid signature" if !signing_certificate.public_key.verify(OpenSSL::Digest::SHA1.new, decoded_sig, xml)
  raise "Certificate chain not valid" if !self.valid_chain?(certs)

  # Signature is valid, return CN of the subject
  subject = signing_certificate.subject.to_a
  signed_by = subject.last[1]
  return signed_by
end