Class: SamlIdp::XMLSecurity::SignedDocument

Inherits:
REXML::Document
  • Object
show all
Defined in:
lib/saml_idp/xml_security.rb

Constant Summary collapse

ValidationError = 
Class.new(StandardError)
C14N = 
"http://www.w3.org/2001/10/xml-exc-c14n#"
DSIG = 
"http://www.w3.org/2000/09/xmldsig#"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(response) ⇒ SignedDocument

Returns a new instance of SignedDocument.



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# File 'lib/saml_idp/xml_security.rb', line 41

def initialize(response)
  super(response)
  extract_signed_element_id
end

Instance Attribute Details

#signed_element_id ⇒ Object

Returns the value of attribute signed_element_id.



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# File 'lib/saml_idp/xml_security.rb', line 39

def signed_element_id
  @signed_element_id
end

Instance Method Details

#fingerprint_cert(cert) ⇒ Object 



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# File 'lib/saml_idp/xml_security.rb', line 66

def fingerprint_cert(cert)
  # pick algorithm based on the doc's digest algorithm
  ref_elem = REXML::XPath.first(self, "//ds:Reference", {"ds"=>DSIG})
  digest_algorithm = algorithm(REXML::XPath.first(ref_elem, "//ds:DigestMethod"))
  digest_algorithm.hexdigest(cert.to_der)
end

#fingerprint_cert_sha1(cert) ⇒ Object 



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# File 'lib/saml_idp/xml_security.rb', line 73

def fingerprint_cert_sha1(cert)
  OpenSSL::Digest::SHA1.hexdigest(cert.to_der)
end

#validate(idp_cert_fingerprint, soft = true) ⇒ Object

Raises:



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# File 'lib/saml_idp/xml_security.rb', line 46

def validate(idp_cert_fingerprint, soft = true)
  # get cert from response
  cert_element = REXML::XPath.first(self, "//ds:X509Certificate", { "ds"=>DSIG })
  raise ValidationError.new("Certificate element missing in response (ds:X509Certificate)") unless cert_element
  base64_cert  = cert_element.text
  cert_text    = Base64.decode64(base64_cert)
  cert         = OpenSSL::X509::Certificate.new(cert_text)

  # check cert matches registered idp cert
  fingerprint = fingerprint_cert(cert)
  sha1_fingerprint = fingerprint_cert_sha1(cert)
  plain_idp_cert_fingerprint = idp_cert_fingerprint.gsub(/[^a-zA-Z0-9]/,"").downcase

  if fingerprint != plain_idp_cert_fingerprint && sha1_fingerprint != plain_idp_cert_fingerprint
    return soft ? false : (raise ValidationError.new("Fingerprint mismatch"))
  end

  validate_doc(base64_cert, soft)
end

#validate_doc(base64_cert, soft = true) ⇒ Object 



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# File 'lib/saml_idp/xml_security.rb', line 77

def validate_doc(base64_cert, soft = true)
  # validate references

  # check for inclusive namespaces
  inclusive_namespaces = extract_inclusive_namespaces

  document = Nokogiri.parse(self.to_s)

  # create a working copy so we don't modify the original
  @working_copy ||= REXML::Document.new(self.to_s).root

  # store and remove signature node
  @sig_element ||= begin
                     element = REXML::XPath.first(@working_copy, "//ds:Signature", {"ds"=>DSIG})
                     element.remove
                   end


  # verify signature
  signed_info_element     = REXML::XPath.first(@sig_element, "//ds:SignedInfo", {"ds"=>DSIG})
  noko_sig_element = document.at_xpath('//ds:Signature', 'ds' => DSIG)
  noko_signed_info_element = noko_sig_element.at_xpath('./ds:SignedInfo', 'ds' => DSIG)
  canon_algorithm = canon_algorithm REXML::XPath.first(@sig_element, '//ds:CanonicalizationMethod', 'ds' => DSIG)
  canon_string = noko_signed_info_element.canonicalize(canon_algorithm)
  noko_sig_element.remove

  # check digests
  REXML::XPath.each(@sig_element, "//ds:Reference", {"ds"=>DSIG}) do |ref|
    uri                           = ref.attributes.get_attribute("URI").value

    hashed_element                = document.at_xpath("//*[@ID='#{uri[1..-1]}']")
    canon_algorithm               = canon_algorithm REXML::XPath.first(ref, '//ds:CanonicalizationMethod', 'ds' => DSIG)
    canon_hashed_element          = hashed_element.canonicalize(canon_algorithm, inclusive_namespaces)

    digest_algorithm              = algorithm(REXML::XPath.first(ref, "//ds:DigestMethod"))

    hash                          = digest_algorithm.digest(canon_hashed_element)
    digest_value                  = Base64.decode64(REXML::XPath.first(ref, "//ds:DigestValue", {"ds"=>DSIG}).text)

    unless digests_match?(hash, digest_value)
      return soft ? false : (raise ValidationError.new("Digest mismatch"))
    end
  end

  base64_signature        = REXML::XPath.first(@sig_element, "//ds:SignatureValue", {"ds"=>DSIG}).text
  signature               = Base64.decode64(base64_signature)

  # get certificate object
  cert_text               = Base64.decode64(base64_cert)
  cert                    = OpenSSL::X509::Certificate.new(cert_text)

  # signature method
  signature_algorithm     = algorithm(REXML::XPath.first(signed_info_element, "//ds:SignatureMethod", {"ds"=>DSIG}))

  unless cert.public_key.verify(signature_algorithm.new, signature, canon_string)
    return soft ? false : (raise ValidationError.new("Key validation error"))
  end

  return true
end