Merge branch 'mk-normalize-ldap-user-dns' into 'master'

Normalize LDAP user DNs (downcase and remove excess spaces)

See merge request gitlab-org/gitlab-ce!14697

changelogs/unreleased/mk-normalize-ldap-user-dns.yml

+---
+title: Search or compare LDAP DNs case-insensitively and ignore excess whitespace
+merge_request: 14697
+author:
+type: fixed

db/post_migrate/20170921101004_normalize_ldap_extern_uids.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class NormalizeLdapExternUids < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  MIGRATION = 'NormalizeLdapExternUidsRange'.freeze
+  DELAY_INTERVAL = 10.seconds
+
+  disable_ddl_transaction!
+
+  class Identity < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'identities'
+  end
+
+  def up
+    ldap_identities = Identity.where("provider like 'ldap%'")
+
+    if ldap_identities.any?
+      queue_background_migration_jobs_by_range_at_intervals(Identity, MIGRATION, DELAY_INTERVAL)
+    end
+  end
+
+  def down
+  end
+end

lib/gitlab/ldap/auth_hash.rb

@@ -3,6 +3,10 @@
 module Gitlab
   module LDAP
     class AuthHash < Gitlab::OAuth::AuthHash
+      def uid
+        Gitlab::LDAP::Person.normalize_dn(super)
+      end
+
       private
 
       def get_info(key)

lib/gitlab/ldap/person.rb

@@ -36,6 +36,26 @@ module Gitlab
         ]
       end
 
+      def self.normalize_dn(dn)
+        ::Gitlab::LDAP::DN.new(dn).to_normalized_s
+      rescue ::Gitlab::LDAP::DN::FormatError => e
+        Rails.logger.info("Returning original DN \"#{dn}\" due to error during normalization attempt: #{e.message}")
+
+        dn
+      end
+
+      # Returns the UID in a normalized form.
+      #
+      # 1. Excess spaces are stripped
+      # 2. The string is downcased (for case-insensitivity)
+      def self.normalize_uid(uid)
+        ::Gitlab::LDAP::DN.normalize_value(uid)
+      rescue ::Gitlab::LDAP::DN::FormatError => e
+        Rails.logger.info("Returning original UID \"#{uid}\" due to error during normalization attempt: #{e.message}")
+
+        uid
+      end
+
       def initialize(entry, provider)
         Rails.logger.debug { "Instantiating #{self.class.name} with LDIF:\n#{entry.to_ldif}" }
         @entry = entry
@@ -58,7 +78,9 @@ module Gitlab
         attribute_value(:email)
       end
 
-      delegate :dn, to: :entry
+      def dn
+        self.class.normalize_dn(entry.dn)
+      end
 
       private
 

spec/lib/gitlab/background_migration/normalize_ldap_extern_uids_range_spec.rb

+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration::NormalizeLdapExternUidsRange, :migration, schema: 20170921101004 do
+  let!(:identities) { table(:identities) }
+
+  before do
+    # LDAP identities
+    (1..4).each do |i|
+      identities.create!(id: i, provider: 'ldapmain', extern_uid: " uid = foo #{i}, ou = People, dc = example, dc = com ", user_id: i)
+    end
+
+    # Non-LDAP identity
+    identities.create!(id: 5, provider: 'foo', extern_uid: " uid = foo 5, ou = People, dc = example, dc = com ", user_id: 5)
+
+    # Another LDAP identity
+    identities.create!(id: 6, provider: 'ldapmain', extern_uid: " uid = foo 6, ou = People, dc = example, dc = com ", user_id: 6)
+  end
+
+  it 'normalizes the LDAP identities in the range' do
+    described_class.new.perform(1, 3)
+    expect(identities.find(1).extern_uid).to eq("uid=foo 1,ou=people,dc=example,dc=com")
+    expect(identities.find(2).extern_uid).to eq("uid=foo 2,ou=people,dc=example,dc=com")
+    expect(identities.find(3).extern_uid).to eq("uid=foo 3,ou=people,dc=example,dc=com")
+    expect(identities.find(4).extern_uid).to eq(" uid = foo 4, ou = People, dc = example, dc = com ")
+    expect(identities.find(5).extern_uid).to eq(" uid = foo 5, ou = People, dc = example, dc = com ")
+    expect(identities.find(6).extern_uid).to eq(" uid = foo 6, ou = People, dc = example, dc = com ")
+
+    described_class.new.perform(4, 6)
+    expect(identities.find(1).extern_uid).to eq("uid=foo 1,ou=people,dc=example,dc=com")
+    expect(identities.find(2).extern_uid).to eq("uid=foo 2,ou=people,dc=example,dc=com")
+    expect(identities.find(3).extern_uid).to eq("uid=foo 3,ou=people,dc=example,dc=com")
+    expect(identities.find(4).extern_uid).to eq("uid=foo 4,ou=people,dc=example,dc=com")
+    expect(identities.find(5).extern_uid).to eq(" uid = foo 5, ou = People, dc = example, dc = com ")
+    expect(identities.find(6).extern_uid).to eq("uid=foo 6,ou=people,dc=example,dc=com")
+  end
+end

spec/lib/gitlab/ldap/auth_hash_spec.rb

@@ -4,7 +4,7 @@ describe Gitlab::LDAP::AuthHash do
   let(:auth_hash) do
     described_class.new(
       OmniAuth::AuthHash.new(
-        uid: '123456',
+        uid: given_uid,
         provider: 'ldapmain',
         info: info,
         extra: {
@@ -32,6 +32,8 @@ describe Gitlab::LDAP::AuthHash do
   end
 
   context "without overridden attributes" do
+    let(:given_uid) { 'uid=John Smith,ou=People,dc=example,dc=com' }
+
     it "has the correct username" do
       expect(auth_hash.username).to eq("123456")
     end
@@ -42,6 +44,8 @@ describe Gitlab::LDAP::AuthHash do
   end
 
   context "with overridden attributes" do
+    let(:given_uid) { 'uid=John Smith,ou=People,dc=example,dc=com' }
+
     let(:attributes) do
       {
         'username'  => %w(mail email),
@@ -61,4 +65,22 @@ describe Gitlab::LDAP::AuthHash do
       expect(auth_hash.name).to eq("John Smith")
     end
   end
+
+  describe '#uid' do
+    context 'when there is extraneous (but valid) whitespace' do
+      let(:given_uid) { 'uid     =john smith ,  ou = people, dc=  example,dc =com' }
+
+      it 'removes the extraneous whitespace' do
+        expect(auth_hash.uid).to eq('uid=john smith,ou=people,dc=example,dc=com')
+      end
+    end
+
+    context 'when there are upper case characters' do
+      let(:given_uid) { 'UID=John Smith,ou=People,dc=example,dc=com' }
+
+      it 'downcases' do
+        expect(auth_hash.uid).to eq('uid=john smith,ou=people,dc=example,dc=com')
+      end
+    end
+  end
 end

spec/lib/gitlab/ldap/dn_spec.rb

+require 'spec_helper'
+
+describe Gitlab::LDAP::DN do
+  using RSpec::Parameterized::TableSyntax
+
+  describe '#normalize_value' do
+    subject { described_class.normalize_value(given) }
+
+    it_behaves_like 'normalizes a DN attribute value'
+
+    context 'when the given DN is malformed' do
+      context 'when ending with a comma' do
+        let(:given) { 'John Smith,' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+
+      context 'when given a BER encoded attribute value with a space in it' do
+        let(:given) { '#aa aa' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the end of an attribute value, but got \"a\"")
+        end
+      end
+
+      context 'when given a BER encoded attribute value with a non-hex character in it' do
+        let(:given) { '#aaXaaa' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the first character of a hex pair, but got \"X\"")
+        end
+      end
+
+      context 'when given a BER encoded attribute value with a non-hex character in it' do
+        let(:given) { '#aaaYaa' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the second character of a hex pair, but got \"Y\"")
+        end
+      end
+
+      context 'when given a hex pair with a non-hex character in it, inside double quotes' do
+        let(:given) { '"Sebasti\\cX\\a1n"' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the second character of a hex pair inside a double quoted value, but got \"X\"")
+        end
+      end
+
+      context 'with an open (as opposed to closed) double quote' do
+        let(:given) { '"James' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+
+      context 'with an invalid escaped hex code' do
+        let(:given) { 'J\ames' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'Invalid escaped hex code "\am"')
+        end
+      end
+
+      context 'with a value ending with the escape character' do
+        let(:given) { 'foo\\' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+    end
+  end
+
+  describe '#to_normalized_s' do
+    subject { described_class.new(given).to_normalized_s }
+
+    it_behaves_like 'normalizes a DN'
+
+    context 'when we do not support the given DN format' do
+      context 'multivalued RDNs' do
+        context 'without extraneous whitespace' do
+          let(:given) { 'uid=john smith+telephonenumber=+1 555-555-5555,ou=people,dc=example,dc=com' }
+
+          it 'raises UnsupportedError' do
+            expect { subject }.to raise_error(Gitlab::LDAP::DN::UnsupportedError)
+          end
+        end
+
+        context 'with extraneous whitespace' do
+          context 'around the phone number plus sign' do
+            let(:given) { 'uid = John Smith  + telephoneNumber  = + 1 555-555-5555 , ou = People,dc=example,dc=com' }
+
+            it 'raises UnsupportedError' do
+              expect { subject }.to raise_error(Gitlab::LDAP::DN::UnsupportedError)
+            end
+          end
+
+          context 'not around the phone number plus sign' do
+            let(:given) { 'uid = John Smith  + telephoneNumber  = +1 555-555-5555 , ou = People,dc=example,dc=com' }
+
+            it 'raises UnsupportedError' do
+              expect { subject }.to raise_error(Gitlab::LDAP::DN::UnsupportedError)
+            end
+          end
+        end
+      end
+    end
+
+    context 'when the given DN is malformed' do
+      context 'when ending with a comma' do
+        let(:given) { 'uid=John Smith,' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+
+      context 'when given a BER encoded attribute value with a space in it' do
+        let(:given) { '0.9.2342.19200300.100.1.25=#aa aa' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the end of an attribute value, but got \"a\"")
+        end
+      end
+
+      context 'when given a BER encoded attribute value with a non-hex character in it' do
+        let(:given) { '0.9.2342.19200300.100.1.25=#aaXaaa' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the first character of a hex pair, but got \"X\"")
+        end
+      end
+
+      context 'when given a BER encoded attribute value with a non-hex character in it' do
+        let(:given) { '0.9.2342.19200300.100.1.25=#aaaYaa' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the second character of a hex pair, but got \"Y\"")
+        end
+      end
+
+      context 'when given a hex pair with a non-hex character in it, inside double quotes' do
+        let(:given) { 'uid="Sebasti\\cX\\a1n"' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, "Expected the second character of a hex pair inside a double quoted value, but got \"X\"")
+        end
+      end
+
+      context 'without a name value pair' do
+        let(:given) { 'John' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+
+      context 'with an open (as opposed to closed) double quote' do
+        let(:given) { 'cn="James' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+
+      context 'with an invalid escaped hex code' do
+        let(:given) { 'cn=J\ames' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'Invalid escaped hex code "\am"')
+        end
+      end
+
+      context 'with a value ending with the escape character' do
+        let(:given) { 'cn=\\' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'DN string ended unexpectedly')
+        end
+      end
+
+      context 'with an invalid OID attribute type name' do
+        let(:given) { '1.2.d=Value' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'Unrecognized RDN OID attribute type name character "d"')
+        end
+      end
+
+      context 'with a period in a non-OID attribute type name' do
+        let(:given) { 'd1.2=Value' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'Unrecognized RDN attribute type name character "."')
+        end
+      end
+
+      context 'when starting with non-space, non-alphanumeric character' do
+        let(:given) { ' -uid=John Smith' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'Unrecognized first character of an RDN attribute type name "-"')
+        end
+      end
+
+      context 'when given a UID with an escaped equal sign' do
+        let(:given) { 'uid\\=john' }
+
+        it 'raises MalformedError' do
+          expect { subject }.to raise_error(Gitlab::LDAP::DN::MalformedError, 'Unrecognized RDN attribute type name character "\\"')
+        end
+      end
+    end
+  end
+
+  def assert_generic_test(test_description, got, expected)
+    test_failure_message = "Failed test description: '#{test_description}'\n\n    expected: \"#{expected}\"\n         got: \"#{got}\""
+    expect(got).to eq(expected), test_failure_message
+  end
+end

spec/lib/gitlab/ldap/person_spec.rb

@@ -16,6 +16,34 @@ describe Gitlab::LDAP::Person do
     )
   end
 
+  describe '.normalize_dn' do
+    subject { described_class.normalize_dn(given) }
+
+    it_behaves_like 'normalizes a DN'
+
+    context 'with an exception during normalization' do
+      let(:given) { 'John "Smith,' } # just something that will cause an exception
+
+      it 'returns the given DN unmodified' do
+        expect(subject).to eq(given)
+      end
+    end
+  end
+
+  describe '.normalize_uid' do
+    subject { described_class.normalize_uid(given) }
+
+    it_behaves_like 'normalizes a DN attribute value'
+
+    context 'with an exception during normalization' do
+      let(:given) { 'John "Smith,' } # just something that will cause an exception
+
+      it 'returns the given UID unmodified' do
+        expect(subject).to eq(given)
+      end
+    end
+  end
+
   describe '#name' do
     it 'uses the configured name attribute and handles values as an array' do
       name = 'John Doe'
@@ -43,4 +71,9 @@ describe Gitlab::LDAP::Person do
       expect(person.email).to eq([user_principal_name])
     end
   end
+
+  def assert_generic_test(test_description, got, expected)
+    test_failure_message = "Failed test description: '#{test_description}'\n\n    expected: #{expected}\n         got: #{got}"
+    expect(got).to eq(expected), test_failure_message
+  end
 end

spec/lib/gitlab/ldap/user_spec.rb

@@ -11,7 +11,7 @@ describe Gitlab::LDAP::User do
     }
   end
   let(:auth_hash) do
-    OmniAuth::AuthHash.new(uid: 'my-uid', provider: 'ldapmain', info: info)
+    OmniAuth::AuthHash.new(uid: 'uid=John Smith,ou=People,dc=example,dc=com', provider: 'ldapmain', info: info)
   end
   let(:ldap_user_upper_case) { described_class.new(auth_hash_upper_case) }
   let(:info_upper_case) do
@@ -22,12 +22,12 @@ describe Gitlab::LDAP::User do
     }
   end
   let(:auth_hash_upper_case) do
-    OmniAuth::AuthHash.new(uid: 'my-uid', provider: 'ldapmain', info: info_upper_case)
+    OmniAuth::AuthHash.new(uid: 'uid=John Smith,ou=People,dc=example,dc=com', provider: 'ldapmain', info: info_upper_case)
   end
 
   describe '#changed?' do
     it "marks existing ldap user as changed" do
-      create(:omniauth_user, extern_uid: 'my-uid', provider: 'ldapmain')
+      create(:omniauth_user, extern_uid: 'uid=John Smith,ou=People,dc=example,dc=com', provider: 'ldapmain')
       expect(ldap_user.changed?).to be_truthy
     end
 
@@ -37,7 +37,7 @@ describe Gitlab::LDAP::User do
     end
 
     it "does not mark existing ldap user as changed" do
-      create(:omniauth_user, email: 'john@example.com', extern_uid: 'my-uid', provider: 'ldapmain')
+      create(:omniauth_user, email: 'john@example.com', extern_uid: 'uid=john smith,ou=people,dc=example,dc=com', provider: 'ldapmain')
       ldap_user.gl_user.user_synced_attributes_metadata(provider: 'ldapmain', email: true)
       expect(ldap_user.changed?).to be_falsey
     end
@@ -60,7 +60,7 @@ describe Gitlab::LDAP::User do
 
   describe 'find or create' do
     it "finds the user if already existing" do
-      create(:omniauth_user, extern_uid: 'my-uid', provider: 'ldapmain')
+      create(:omniauth_user, extern_uid: 'uid=John Smith,ou=People,dc=example,dc=com', provider: 'ldapmain')
 
       expect { ldap_user.save }.not_to change { User.count }
     end
@@ -70,7 +70,7 @@ describe Gitlab::LDAP::User do
       expect { ldap_user.save }.not_to change { User.count }
 
       existing_user.reload
-      expect(existing_user.ldap_identity.extern_uid).to eql 'my-uid'
+      expect(existing_user.ldap_identity.extern_uid).to eql 'uid=john smith,ou=people,dc=example,dc=com'
       expect(existing_user.ldap_identity.provider).to eql 'ldapmain'
     end
 
@@ -79,7 +79,7 @@ describe Gitlab::LDAP::User do
       expect { ldap_user.save }.not_to change { User.count }
 
       existing_user.reload
-      expect(existing_user.ldap_identity.extern_uid).to eql 'my-uid'
+      expect(existing_user.ldap_identity.extern_uid).to eql 'uid=john smith,ou=people,dc=example,dc=com'
       expect(existing_user.ldap_identity.provider).to eql 'ldapmain'
       expect(existing_user.id).to eql ldap_user.gl_user.id
     end
@@ -89,7 +89,7 @@ describe Gitlab::LDAP::User do
       expect { ldap_user_upper_case.save }.not_to change { User.count }
 
       existing_user.reload
-      expect(existing_user.ldap_identity.extern_uid).to eql 'my-uid'
+      expect(existing_user.ldap_identity.extern_uid).to eql 'uid=john smith,ou=people,dc=example,dc=com'
       expect(existing_user.ldap_identity.provider).to eql 'ldapmain'
       expect(existing_user.id).to eql ldap_user.gl_user.id
     end

spec/migrations/normalize_ldap_extern_uids_spec.rb

+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20170921101004_normalize_ldap_extern_uids')
+
+describe NormalizeLdapExternUids, :migration, :sidekiq do
+  let!(:identities) { table(:identities) }
+
+  around do |example|
+    Timecop.freeze { example.run }
+  end
+
+  before do
+    stub_const("Gitlab::Database::MigrationHelpers::BACKGROUND_MIGRATION_BATCH_SIZE", 2)
+    stub_const("Gitlab::Database::MigrationHelpers::BACKGROUND_MIGRATION_JOB_BUFFER_SIZE", 2)
+
+    # LDAP identities
+    (1..4).each do |i|
+      identities.create!(id: i, provider: 'ldapmain', extern_uid: " uid = foo #{i}, ou = People, dc = example, dc = com ", user_id: i)
+    end
+
+    # Non-LDAP identity
+    identities.create!(id: 5, provider: 'foo', extern_uid: " uid = foo 5, ou = People, dc = example, dc = com ", user_id: 5)
+  end
+
+  it 'correctly schedules background migrations' do
+    Sidekiq::Testing.fake! do
+      Timecop.freeze do
+        migrate!
+
+        expect(BackgroundMigrationWorker.jobs[0]['args']).to eq([described_class::MIGRATION, [1, 2]])
+        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(10.seconds.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[1]['args']).to eq([described_class::MIGRATION, [3, 4]])
+        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(20.seconds.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[2]['args']).to eq([described_class::MIGRATION, [5, 5]])
+        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(30.seconds.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs.size).to eq 3
+      end
+    end
+  end
+
+  it 'migrates the LDAP identities' do
+    Sidekiq::Testing.inline! do
+      migrate!
+      identities.where(id: 1..4).each do |identity|
+        expect(identity.extern_uid).to eq("uid=foo #{identity.id},ou=people,dc=example,dc=com")
+      end
+    end
+  end
+
+  it 'does not modify non-LDAP identities' do
+    Sidekiq::Testing.inline! do
+      migrate!
+      identity = identities.last
+      expect(identity.extern_uid).to eq(" uid = foo 5, ou = People, dc = example, dc = com ")
+    end
+  end
+end

spec/support/ldap_shared_examples.rb

+shared_examples_for 'normalizes a DN' do
+  using RSpec::Parameterized::TableSyntax
+
+  where(:test_description, :given, :expected) do
+    'strips extraneous whitespace'                                                                 | 'uid     =John Smith ,  ou = People, dc=  example,dc =com'                                            | 'uid=john smith,ou=people,dc=example,dc=com'
+    'strips extraneous whitespace for a DN with a single RDN'                                      | 'uid  =  John Smith'                                                                                  | 'uid=john smith'
+    'unescapes non-reserved, non-special Unicode characters'                                       | 'uid   =  Sebasti\\c3\\a1n\\ C.\\20Smith,   ou=People (aka. \\22humans\\")  ,dc=example, dc=com'      | 'uid=sebastián c. smith,ou=people (aka. \\"humans\\"),dc=example,dc=com'
+    'downcases the whole string'                                                                   | 'UID=John Smith,ou=People,dc=example,dc=com'                                                          | 'uid=john smith,ou=people,dc=example,dc=com'
+    'for a null DN (empty string), returns empty string and does not error'                        | ''                                                                                                    | ''
+    'does not strip an escaped leading space in an attribute value'                                | 'uid=\\ John Smith,ou=People,dc=example,dc=com'                                                       | 'uid=\\ john smith,ou=people,dc=example,dc=com'
+    'does not strip an escaped leading space in the last attribute value'                          | 'uid=\\ John Smith'                                                                                   | 'uid=\\ john smith'
+    'does not strip an escaped trailing space in an attribute value'                               | 'uid=John Smith\\ ,ou=People,dc=example,dc=com'                                                       | 'uid=john smith\\ ,ou=people,dc=example,dc=com'
+    'strips extraneous spaces after an escaped trailing space'                                     | 'uid=John Smith\\   ,ou=People,dc=example,dc=com'                                                     | 'uid=john smith\\ ,ou=people,dc=example,dc=com'
+    'strips extraneous spaces after an escaped trailing space at the end of the DN'                | 'uid=John Smith,ou=People,dc=example,dc=com\\   '                                                     | 'uid=john smith,ou=people,dc=example,dc=com\\ '
+    'properly preserves escaped trailing space after unescaped trailing spaces'                    | 'uid=John Smith  \\  ,ou=People,dc=example,dc=com'                                                    | 'uid=john smith  \\ ,ou=people,dc=example,dc=com'
+    'preserves multiple inner spaces in an attribute value'                                        | 'uid=John   Smith,ou=People,dc=example,dc=com'                                                        | 'uid=john   smith,ou=people,dc=example,dc=com'
+    'preserves inner spaces after an escaped space'                                                | 'uid=John\\   Smith,ou=People,dc=example,dc=com'                                                      | 'uid=john   smith,ou=people,dc=example,dc=com'
+    'hex-escapes an escaped leading newline in an attribute value'                                 | "uid=\\\nJohn Smith,ou=People,dc=example,dc=com"                                                      | "uid=\\0ajohn smith,ou=people,dc=example,dc=com"
+    'hex-escapes and does not strip an escaped trailing newline in an attribute value'             | "uid=John Smith\\\n,ou=People,dc=example,dc=com"                                                      | "uid=john smith\\0a,ou=people,dc=example,dc=com"
+    'hex-escapes an unescaped leading newline (actually an invalid DN?)'                           | "uid=\nJohn Smith,ou=People,dc=example,dc=com"                                                        | "uid=\\0ajohn smith,ou=people,dc=example,dc=com"
+    'strips an unescaped trailing newline (actually an invalid DN?)'                               | "uid=John Smith\n,ou=People,dc=example,dc=com"                                                        | "uid=john smith,ou=people,dc=example,dc=com"
+    'does not strip if no extraneous whitespace'                                                   | 'uid=John Smith,ou=People,dc=example,dc=com'                                                          | 'uid=john smith,ou=people,dc=example,dc=com'
+    'does not modify an escaped equal sign in an attribute value'                                  | 'uid= foo  \\=  bar'                                                                                  | 'uid=foo  \\=  bar'
+    'converts an escaped hex equal sign to an escaped equal sign in an attribute value'            | 'uid= foo  \\3D  bar'                                                                                 | 'uid=foo  \\=  bar'
+    'does not modify an escaped comma in an attribute value'                                       | 'uid= John C. Smith, ou=San Francisco\\, CA'                                                          | 'uid=john c. smith,ou=san francisco\\, ca'
+    'converts an escaped hex comma to an escaped comma in an attribute value'                      | 'uid= John C. Smith, ou=San Francisco\\2C CA'                                                         | 'uid=john c. smith,ou=san francisco\\, ca'
+    'does not modify an escaped hex carriage return character in an attribute value'               | 'uid= John C. Smith, ou=San Francisco\\,\\0DCA'                                                       | 'uid=john c. smith,ou=san francisco\\,\\0dca'
+    'does not modify an escaped hex line feed character in an attribute value'                     | 'uid= John C. Smith, ou=San Francisco\\,\\0ACA'                                                       | 'uid=john c. smith,ou=san francisco\\,\\0aca'
+    'does not modify an escaped hex CRLF in an attribute value'                                    | 'uid= John C. Smith, ou=San Francisco\\,\\0D\\0ACA'                                                   | 'uid=john c. smith,ou=san francisco\\,\\0d\\0aca'
+    'allows attribute type name OIDs'                                                              | '0.9.2342.19200300.100.1.25=Example,0.9.2342.19200300.100.1.25=Com'                                   | '0.9.2342.19200300.100.1.25=example,0.9.2342.19200300.100.1.25=com'
+    'strips extraneous whitespace from attribute type name OIDs'                                   | '0.9.2342.19200300.100.1.25 = Example, 0.9.2342.19200300.100.1.25 = Com'                              | '0.9.2342.19200300.100.1.25=example,0.9.2342.19200300.100.1.25=com'
+  end
+
+  with_them do
+    it 'normalizes the DN' do
+      assert_generic_test(test_description, subject, expected)
+    end
+  end
+end
+
+shared_examples_for 'normalizes a DN attribute value' do
+  using RSpec::Parameterized::TableSyntax
+
+  where(:test_description, :given, :expected) do
+    'strips extraneous whitespace'                                                      | '   John Smith   '                 | 'john smith'
+    'unescapes non-reserved, non-special Unicode characters'                            | 'Sebasti\\c3\\a1n\\ C.\\20Smith'   | 'sebastián c. smith'
+    'downcases the whole string'                                                        | 'JoHn C. Smith'                    | 'john c. smith'
+    'does not strip an escaped leading space in an attribute value'                     | '\\ John Smith'                    | '\\ john smith'
+    'does not strip an escaped trailing space in an attribute value'                    | 'John Smith\\ '                    | 'john smith\\ '
+    'hex-escapes an escaped leading newline in an attribute value'                      | "\\\nJohn Smith"                   | "\\0ajohn smith"
+    'hex-escapes and does not strip an escaped trailing newline in an attribute value'  | "John Smith\\\n"                   | "john smith\\0a"
+    'hex-escapes an unescaped leading newline (actually an invalid DN value?)'          | "\nJohn Smith"                     | "\\0ajohn smith"
+    'strips an unescaped trailing newline (actually an invalid DN value?)'              | "John Smith\n"                     | "john smith"
+    'does not strip if no extraneous whitespace'                                        | 'John Smith'                       | 'john smith'
+    'does not modify an escaped equal sign in an attribute value'                       | ' foo  \\=  bar'                   | 'foo  \\=  bar'
+    'converts an escaped hex equal sign to an escaped equal sign in an attribute value' | ' foo  \\3D  bar'                  | 'foo  \\=  bar'
+    'does not modify an escaped comma in an attribute value'                            | 'San Francisco\\, CA'              | 'san francisco\\, ca'
+    'converts an escaped hex comma to an escaped comma in an attribute value'           | 'San Francisco\\2C CA'             | 'san francisco\\, ca'
+    'does not modify an escaped hex carriage return character in an attribute value'    | 'San Francisco\\,\\0DCA'           | 'san francisco\\,\\0dca'
+    'does not modify an escaped hex line feed character in an attribute value'          | 'San Francisco\\,\\0ACA'           | 'san francisco\\,\\0aca'
+    'does not modify an escaped hex CRLF in an attribute value'                         | 'San Francisco\\,\\0D\\0ACA'       | 'san francisco\\,\\0d\\0aca'
+  end
+
+  with_them do
+    it 'normalizes the DN attribute value' do
+      assert_generic_test(test_description, subject, expected)
+    end
+  end
+end