Class: OmniAuth::Strategies::Pfas::SignedDocument

Inherits:
REXML::Document
  • Object
show all
Defined in:
lib/omniauth/strategies/pfas/signed_document.rb

Constant Summary collapse

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/omniauth/strategies/pfas/signed_document.rb', line 33

def initialize(response)
  super(response)
  extract_signed_element_id
  extract_expires
end

Instance Attribute Details

#expires_on ⇒ Object

Returns the value of attribute expires_on.



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# File 'lib/omniauth/strategies/pfas/signed_document.rb', line 31

def expires_on
  @expires_on
end

#signed_element_id ⇒ Object

Returns the value of attribute signed_element_id.



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# File 'lib/omniauth/strategies/pfas/signed_document.rb', line 31

def signed_element_id
  @signed_element_id
end

Instance Method Details

#extract_expires ⇒ Object 



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# File 'lib/omniauth/strategies/pfas/signed_document.rb', line 94

def extract_expires
  self.expires_on  = Time.parse(REXML::XPath.first(self, "//trust:Lifetime/wsu:Expires").text)
end

#extract_signed_element_id ⇒ Object 



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# File 'lib/omniauth/strategies/pfas/signed_document.rb', line 89

def extract_signed_element_id
  reference_element       = REXML::XPath.first(self, "//ds:Signature/ds:SignedInfo/ds:Reference", { "ds" => DSIG })
  self.signed_element_id  = reference_element.attribute("URI").value unless reference_element.nil?
end

#validate!(idp_cert_fingerprint) ⇒ Object 



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# File 'lib/omniauth/strategies/pfas/signed_document.rb', line 39

def validate!(idp_cert_fingerprint)
  # get cert from response
  base64_cert = self.elements["//ds:X509Certificate"].text
  cert_text   = Base64.decode64(base64_cert)
  cert        = OpenSSL::X509::Certificate.new(cert_text)

  # check cert matches registered idp cert
  fingerprint = Digest::SHA1.hexdigest(cert.to_der)

  if fingerprint != idp_cert_fingerprint.gsub(/[^a-zA-Z0-9]/,"").downcase
    raise ValidationError.new("Fingerprint mismatch")
  end

  # remove signature node
  sig_element = REXML::XPath.first(self, "//ds:Signature", { "ds" => DSIG })
  sig_element.remove

  # check digests
  REXML::XPath.each(sig_element, "//ds:Reference", {"ds"=>"http://www.w3.org/2000/09/xmldsig#"}) do |ref|
    uri                           = ref.attributes.get_attribute("URI").value
    hashed_element                = REXML::XPath.first(self, "//[@AssertionID='#{uri[1,uri.size]}']")
    canoner                       = XML::Util::XmlCanonicalizer.new(false, true)
    canon_hashed_element          = canoner.canonicalize(hashed_element)
    hash                          = Base64.encode64(Digest::SHA1.digest(canon_hashed_element)).chomp
    digest_value                  = REXML::XPath.first(ref, "//ds:DigestValue", { "ds" => DSIG }).text

    if hash != digest_value
      raise ValidationError.new("Digest mismatch")
    end
  end

  # verify signature
  canoner                 = XML::Util::XmlCanonicalizer.new(false, true)
  signed_info_element     = REXML::XPath.first(sig_element, "//ds:SignedInfo", { "ds" => DSIG })
  canon_string            = canoner.canonicalize(signed_info_element)

  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)

  if !cert.public_key.verify(OpenSSL::Digest::SHA1.new, signature, canon_string)
    raise ValidationError.new("Key validation error")
  end

  true
end