Merge pull request #31 from healthify/PP-696/encrypted-assertion-v2

Introduce option for encrypting SAML assertions

Author: samudary

Diff for: README.md

@@ -99,7 +99,7 @@ end
 
 ### Generating a SAML Response
 
-The gem provides a `SamlResponse` class used to generate a custom signed unencrypted XML SAML response. The SAML response is currently generated by the `ruby-saml-idp` gem and that functionality will be replaced with this class in a later update.
+The gem provides a `SamlResponse` class used to generate a custom signed XML SAML response with an assertion that can be encrypted by setting `encryption_enabled` to `true`.
 
 **Usage**
 
@@ -109,7 +109,6 @@ saml_response = FakeIdp::SamlResponse.new(
   saml_acs_url: "http://localhost.dev:3000/auth/saml/devidp/callback",
   saml_request_id: "_#{SecureRandom.uuid}",
   name_id: "[email protected]",
-  audience_uri: "http://localhost.dev:3000",
   issuer_uri: "http://publichost.dev:3000",
   algorithm_name: :sha256,
   certificate: "YOUR IDP CERTIFICATE HERE",
@@ -124,8 +123,6 @@ saml_response = FakeIdp::SamlResponse.new(
   },
 )
 
-# Returns a signed unencrypted XML SAML response document
+# Returns a signed XML SAML response document
 saml_response.build
 ```
-
-**Note**: Encrypted assertions will be supported in a future update.

Diff for: lib/fake_idp/application.rb

@@ -1,18 +1,16 @@
+# frozen_string_literal: true
+
+require_relative "./saml_response"
+require "ruby-saml"
+
 module FakeIdp
   class Application < Sinatra::Base
     include SamlIdp::Controller
 
-    get '/saml/auth' do
+    get "/saml/auth" do
       begin
-        decode_SAMLRequest(mock_saml_request)
-        @saml_acs_url = callback_url
-
-        configure_cert_and_keys
-
-        @saml_response = encode_SAMLResponse(
-            name_id,
-            attributes_provider: attributes_statement(user_attrs),
-        )
+        decode_SAMLRequest(generate_saml_request)
+        @saml_response = Base64.encode64(build_xml_saml_response).delete("\r\n")
 
         erb :auth
       rescue => e
@@ -26,60 +24,44 @@ def configuration
       FakeIdp.configuration
     end
 
-    def callback_url
-      configuration.callback_url
-    end
-
-    def configure_cert_and_keys
-      self.x509_certificate = idp_certificate
-      self.secret_key = configuration.idp_secret_key
-      self.algorithm = configuration.algorithm
-    end
-
-    def certificate
-      Base64.encode64(configuration.certificate).delete("\n")
-    end
-
-    def idp_certificate
-      Base64.encode64(configuration.idp_certificate).delete("\n")
-    end
-
-    def user_attrs
-      signed_in_user_attrs.merge(configuration.additional_attributes)
+    def build_xml_saml_response
+      FakeIdp::SamlResponse.new(
+        name_id: configuration.name_id,
+        issuer_uri: configuration.issuer,
+        saml_acs_url: @saml_acs_url, # Defined in #decode_SAMLRequest in ruby-saml-idp gem
+        saml_request_id: @saml_request_id, # Defined in #decode_SAMLRequest in ruby-saml-idp gem
+        user_attributes: user_attributes,
+        algorithm_name: configuration.algorithm,
+        certificate: configuration.idp_certificate,
+        secret_key: configuration.idp_secret_key,
+        encryption_enabled: configuration.encryption_enabled,
+      ).build
     end
 
-    def signed_in_user_attrs
+    def user_attributes
       {
         uuid: configuration.sso_uid,
         username: configuration.username,
         first_name: configuration.first_name,
         last_name: configuration.last_name,
-        email: configuration.email
-      }
-    end
-
-    def name_id
-      configuration.name_id
+        email: configuration.email,
+      }.merge(configuration.additional_attributes)
     end
 
-    def mock_saml_request
-      current_gem_dir = File.dirname(__FILE__)
-      sample_file_name = "#{current_gem_dir}/sample_init_request.txt"
-      File.write(sample_file_name, params[:SAMLRequest]) if params[:SAMLRequest]
-      File.read(sample_file_name).strip
+    # An AuthRequest is required by the ruby-saml-idp gem to begin the process of returning
+    # a SAMLResponse. We will likely remove the ruby-saml-idp dependency in a future update
+    def generate_saml_request
+      auth_request = OneLogin::RubySaml::Authrequest.new
+      auth_url = auth_request.create(saml_settings)
+      CGI.unescape(auth_url.split("=").last)
     end
 
-    def attributes_statement(attributes)
-      attributes_xml = attributes_xml(attributes).join
-
-      %[<saml:AttributeStatement>#{attributes_xml}</saml:AttributeStatement>]
-    end
-
-    def attributes_xml(attributes)
-      attributes.map do |name, value|
-        attribute_value = %[<saml:AttributeValue>#{value}</saml:AttributeValue>]
-
-        %[<saml:Attribute Name="#{name}">#{attribute_value}</saml:Attribute>]
+    def saml_settings
+      OneLogin::RubySaml::Settings.new.tap do |setting|
+        setting.assertion_consumer_service_url = configuration.callback_url
+        setting.issuer = configuration.issuer
+        setting.idp_sso_target_url = configuration.idp_sso_target_url
+        setting.name_identifier_format = FakeIdp::SamlResponse::EMAIL_ADDRESS_FORMAT
       end
     end
   end

Diff for: lib/fake_idp/configuration.rb

@@ -11,6 +11,8 @@ class Configuration
       :certificate,
       :idp_certificate,
       :idp_secret_key,
+      :idp_sso_target_url,
+      :issuer,
       :algorithm,
       :additional_attributes,
       :encryption_enabled,
@@ -27,6 +29,8 @@ def initialize
       @certificate = default_certificate
       @idp_certificate = default_idp_certificate
       @idp_secret_key = default_idp_secret_key
+      @idp_sso_target_url = idp_sso_target_url
+      @issuer = issuer
       @algorithm = default_algorithm
       @additional_attributes = {}
       @encryption_enabled = default_encryption

Diff for: lib/fake_idp/encryptor.rb

@@ -1,4 +1,5 @@
 require "xmlenc"
+require "builder"
 
 module FakeIdp
   class Encryptor
@@ -35,7 +36,7 @@ def encrypt
 
     def openssl_cert
       @_openssl_cert ||= if certificate.is_a?(String)
-                           OpenSSL::X509::Certificate.new(Base64.decode64(certificate))
+                           OpenSSL::X509::Certificate.new(certificate)
                          else
                            certificate
                          end

Diff for: lib/fake_idp/saml_response.rb

@@ -3,12 +3,13 @@
 require "securerandom"
 require "nokogiri"
 require "openssl"
+require_relative "./encryptor"
 
 module FakeIdp
   class SamlResponse
     DSIG = "http://www.w3.org/2000/09/xmldsig#"
     SAML_VERSION = "2.0"
-    ISSUER_VALUE = "urn:oasis:names:tc:SAML:2.0:assertion"
+    ASSERTION_NAMESPACE = "urn:oasis:names:tc:SAML:2.0:assertion"
     ENTITY_FORMAT = "urn:oasis:names:SAML:2.0:nameid-format:entity"
     BEARER_FORMAT = "urn:oasis:names:tc:SAML:2.0:cm:bearer"
     ENVELOPE_SCHEMA = "http://www.w3.org/2000/09/xmldsig#enveloped-signature"
@@ -23,18 +24,16 @@ class SamlResponse
 
     def initialize(
       name_id:,
-      audience_uri:,
       issuer_uri:,
       saml_acs_url:,
       saml_request_id:,
       user_attributes:,
       algorithm_name:,
       certificate:,
       secret_key:,
-      encryption_enabled:
+      encryption_enabled: false
     )
       @name_id = name_id
-      @audience_uri = audience_uri
       @issuer_uri = issuer_uri
       @saml_acs_url = saml_acs_url
       @saml_request_id = saml_request_id
@@ -55,11 +54,33 @@ def build
       end
 
       document_with_digest = replace_digest_value(@builder.to_xml)
-      replace_signature_value(document_with_digest)
+      document = replace_signature_value(document_with_digest)
+      encrypt_assertion!(document)
     end
 
     private
 
+    def encrypt_assertion!(document)
+      return document unless @encryption_enabled
+
+      document_copy = document.dup
+      working_document = Nokogiri::XML(document)
+      assertion = working_document.at_xpath("//saml:Assertion", "saml" => ASSERTION_NAMESPACE)
+      encrypted_assertion_xml = FakeIdp::Encryptor.new(
+        assertion.to_xml,
+        @certificate,
+      ).encrypt
+
+      document_copy = Nokogiri::XML(document_copy)
+      target_assertion_node = document_copy.at_xpath(
+        "//saml:Assertion",
+        "saml" => ASSERTION_NAMESPACE,
+      )
+      # Replace Assertion node with encrypted assertion
+      target_assertion_node.replace(encrypted_assertion_xml)
+      document_copy.to_xml
+    end
+
     def replace_digest_value(document)
       document_copy = document.dup
       working_document = Nokogiri::XML(document)
@@ -76,7 +97,7 @@ def replace_digest_value(document)
 
       # Replace digest node with the generated value
       document_copy = Nokogiri::XML(document_copy)
-      target_digest_node = document_copy.at_xpath("//ds:DigestValue")
+      target_digest_node = document_copy.at_xpath("//ds:DigestValue", "ds" => DSIG)
       target_digest_node.content = digest_value
       document_copy
     end
@@ -91,13 +112,13 @@ def replace_signature_value(document)
 
       signature_value = sign(canon_string)
 
-      target_signature_node = document_copy.at_xpath("//ds:SignatureValue")
+      target_signature_node = document_copy.at_xpath("//ds:SignatureValue", "ds" => DSIG)
       target_signature_node.content = signature_value
       document_copy.to_xml
     end
 
     def build_issuer_segment(parent_attribute)
-      parent_attribute[:saml].Issuer("xmlns:saml" => ISSUER_VALUE) do |issuer|
+      parent_attribute[:saml].Issuer("xmlns:saml" => ASSERTION_NAMESPACE) do |issuer|
         issuer << @issuer_uri
       end
     end
@@ -166,15 +187,15 @@ def build_assertion_signature(parent_attribute)
 
             # The digest_value is set and derived from creating a digest of the Assertion element
             # without the signature element after the document is generated
-            reference[:ds].DigestValue { |d| d << "" }
+            reference[:ds].DigestValue("xmlns:ds" => DSIG) { |d| d << "" }
           end
         end
 
         # The signature_value is set and derived from signing the SignedInfo element after the
         # document is generated
         signature[:ds].SignatureValue { |signature_value| signature_value << "" }
 
-        signature.KeyInfo("xmlns" => DSIG) do |key_info|
+        signature.KeyInfo("xmlns:ds" => DSIG) do |key_info|
           key_info[:ds].X509Data do |x509_data|
             x509_data[:ds].X509Certificate do |x509_certificate|
               x509_certificate << Base64.encode64(@certificate)
@@ -222,13 +243,12 @@ def root_namespace_attributes
         "InResponseTo" => @saml_request_id,
         "IssueInstant" => @timestamp.strftime("%Y-%m-%dT%H:%M:%S"),
         "Version" => SAML_VERSION,
-        "xmlns:ds" => DSIG,
       }
     end
 
     def assertion_namespace_attributes
       {
-        "xmlns:saml" => ISSUER_VALUE,
+        "xmlns:saml" => ASSERTION_NAMESPACE,
         "ID" => assertion_reference_response_id,
         "IssueInstant" => @timestamp.strftime("%Y-%m-%dT%H:%M:%S"),
         "Version" => SAML_VERSION,

Diff for: lib/fake_idp/sample_init_request.txt

@@ -5,7 +5,7 @@
 describe FakeIdp::Encryptor do
   it "encrypts and decrypts XML" do
     raw_xml = "<foo>bar</foo>"
-    encryptor = described_class.new(raw_xml, Base64.encode64(fake_certificate).delete("\n"))
+    encryptor = described_class.new(raw_xml, fake_certificate)
     encrypted_xml = encryptor.encrypt
 
     expect(encrypted_xml).to_not match raw_xml