Normalize existing persisted DNs

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
+
+  class Identity < ActiveRecord::Base
+    self.table_name = 'identities'
+  end
+
+  # Copied this class to make this migration resilient to future code changes.
+  # And if the normalize behavior is changed in the future, it must be
+  # accompanied by another migration.
+  module Gitlab
+    module LDAP
+      MalformedDnError = Class.new(StandardError)
+      UnsupportedDnFormatError = Class.new(StandardError)
+
+      class DN
+        ##
+        # Initialize a DN, escaping as required. Pass in attributes in name/value
+        # pairs. If there is a left over argument, it will be appended to the dn
+        # without escaping (useful for a base string).
+        #
+        # Most uses of this class will be to escape a DN, rather than to parse it,
+        # so storing the dn as an escaped String and parsing parts as required
+        # with a state machine seems sensible.
+        def initialize(*args)
+          buffer = StringIO.new
+
+          args.each_index do |index|
+            buffer << "=" if index.odd?
+            buffer << "," if index.even? && index != 0
+
+            arg = args[index].downcase
+
+            buffer << if index < args.length - 1 || index.odd?
+                        self.class.escape(arg)
+                      else
+                        arg
+                      end
+          end
+
+          @dn = buffer.string
+        end
+
+        ##
+        # Parse a DN into key value pairs using ASN from
+        # http://tools.ietf.org/html/rfc2253 section 3.
+        # rubocop:disable Metrics/AbcSize
+        # rubocop:disable Metrics/CyclomaticComplexity
+        # rubocop:disable Metrics/PerceivedComplexity
+        def each_pair
+          state = :key
+          key = StringIO.new
+          value = StringIO.new
+          hex_buffer = ""
+
+          @dn.each_char do |char|
+            case state
+            when :key then
+              case char
+              when 'a'..'z' then
+                state = :key_normal
+                key << char
+              when '0'..'9' then
+                state = :key_oid
+                key << char
+              when ' ' then state = :key
+              else raise(MalformedDnError, "Unrecognized first character of an RDN attribute type name \"#{char}\"")
+              end
+            when :key_normal then
+              case char
+              when '=' then state = :value
+              when 'a'..'z', '0'..'9', '-', ' ' then key << char
+              else raise(MalformedDnError, "Unrecognized RDN attribute type name character \"#{char}\"")
+              end
+            when :key_oid then
+              case char
+              when '=' then state = :value
+              when '0'..'9', '.', ' ' then key << char
+              else raise(MalformedDnError, "Unrecognized RDN OID attribute type name character \"#{char}\"")
+              end
+            when :value then
+              case char
+              when '\\' then state = :value_normal_escape
+              when '"' then state = :value_quoted
+              when ' ' then state = :value
+              when '#' then
+                state = :value_hexstring
+                value << char
+              when ',' then
+                state = :key
+                yield key.string.strip, value.string.rstrip
+                key = StringIO.new
+                value = StringIO.new
+              else
+                state = :value_normal
+                value << char
+              end
+            when :value_normal then
+              case char
+              when '\\' then state = :value_normal_escape
+              when ',' then
+                state = :key
+                yield key.string.strip, value.string.rstrip
+                key = StringIO.new
+                value = StringIO.new
+              when '+' then raise(UnsupportedDnFormatError, "Multivalued RDNs are not supported")
+              else value << char
+              end
+            when :value_normal_escape then
+              case char
+              when '0'..'9', 'a'..'f' then
+                state = :value_normal_escape_hex
+                hex_buffer = char
+              when /\s/ then
+                state = :value_normal_escape_whitespace
+                value << char
+              else
+                state = :value_normal
+                value << char
+              end
+            when :value_normal_escape_hex then
+              case char
+              when '0'..'9', 'a'..'f' then
+                state = :value_normal
+                value << "#{hex_buffer}#{char}".to_i(16).chr
+              else raise(MalformedDnError, "Invalid escaped hex code \"\\#{hex_buffer}#{char}\"")
+              end
+            when :value_normal_escape_whitespace then
+              case char
+              when '\\' then state = :value_normal_escape
+              when ',' then
+                state = :key
+                yield key.string.strip, value.string # Don't strip trailing escaped space!
+                key = StringIO.new
+                value = StringIO.new
+              when '+' then raise(UnsupportedDnFormatError, "Multivalued RDNs are not supported")
+              else value << char
+              end
+            when :value_quoted then
+              case char
+              when '\\' then state = :value_quoted_escape
+              when '"' then state = :value_end
+              else value << char
+              end
+            when :value_quoted_escape then
+              case char
+              when '0'..'9', 'a'..'f' then
+                state = :value_quoted_escape_hex
+                hex_buffer = char
+              else
+                state = :value_quoted
+                value << char
+              end
+            when :value_quoted_escape_hex then
+              case char
+              when '0'..'9', 'a'..'f' then
+                state = :value_quoted
+                value << "#{hex_buffer}#{char}".to_i(16).chr
+              else raise(MalformedDnError, "Expected the second character of a hex pair inside a double quoted value, but got \"#{char}\"")
+              end
+            when :value_hexstring then
+              case char
+              when '0'..'9', 'a'..'f' then
+                state = :value_hexstring_hex
+                value << char
+              when ' ' then state = :value_end
+              when ',' then
+                state = :key
+                yield key.string.strip, value.string.rstrip
+                key = StringIO.new
+                value = StringIO.new
+              else raise(MalformedDnError, "Expected the first character of a hex pair, but got \"#{char}\"")
+              end
+            when :value_hexstring_hex then
+              case char
+              when '0'..'9', 'a'..'f' then
+                state = :value_hexstring
+                value << char
+              else raise(MalformedDnError, "Expected the second character of a hex pair, but got \"#{char}\"")
+              end
+            when :value_end then
+              case char
+              when ' ' then state = :value_end
+              when ',' then
+                state = :key
+                yield key.string.strip, value.string.rstrip
+                key = StringIO.new
+                value = StringIO.new
+              else raise(MalformedDnError, "Expected the end of an attribute value, but got \"#{char}\"")
+              end
+            else raise "Fell out of state machine"
+            end
+          end
+
+          # Last pair
+          raise(MalformedDnError, 'DN string ended unexpectedly') unless
+            [:value, :value_normal, :value_hexstring, :value_end].include? state
+
+          yield key.string.strip, value.string.rstrip
+        end
+
+        ##
+        # Returns the DN as an array in the form expected by the constructor.
+        def to_a
+          a = []
+          self.each_pair { |key, value| a << key << value } unless @dn.empty?
+          a
+        end
+
+        ##
+        # Return the DN as an escaped string.
+        def to_s
+          @dn
+        end
+
+        ##
+        # Return the DN as an escaped and normalized string.
+        def to_s_normalized
+          self.class.new(*to_a).to_s
+        end
+
+        # https://tools.ietf.org/html/rfc4514 section 2.4 lists these exceptions
+        # for DN values. All of the following must be escaped in any normal string
+        # using a single backslash ('\') as escape. The space character is left
+        # out here because in a "normalized" string, spaces should only be escaped
+        # if necessary (i.e. leading or trailing space).
+        NORMAL_ESCAPES = [',', '+', '"', '\\', '<', '>', ';', '='].freeze
+
+        # The following must be represented as escaped hex
+        HEX_ESCAPES = {
+          "\n" => '\0a',
+          "\r" => '\0d'
+        }.freeze
+
+        # Compiled character class regexp using the keys from the above hash, and
+        # checking for a space or # at the start, or space at the end, of the
+        # string.
+        ESCAPE_RE = Regexp.new("(^ |^#| $|[" +
+                               NORMAL_ESCAPES.map { |e| Regexp.escape(e) }.join +
+                               "])")
+
+        HEX_ESCAPE_RE = Regexp.new("([" +
+                               HEX_ESCAPES.keys.map { |e| Regexp.escape(e) }.join +
+                               "])")
+
+        ##
+        # Escape a string for use in a DN value
+        def self.escape(string)
+          escaped = string.gsub(ESCAPE_RE) { |char| "\\" + char }
+          escaped.gsub(HEX_ESCAPE_RE) { |char| HEX_ESCAPES[char] }
+        end
+
+        ##
+        # Proxy all other requests to the string object, because a DN is mainly
+        # used within the library as a string
+        # rubocop:disable GitlabSecurity/PublicSend
+        def method_missing(method, *args, &block)
+          @dn.send(method, *args, &block)
+        end
+      end
+    end
+  end
+
+  def up
+    ldap_identities = Identity.where("provider like 'ldap%'")
+    ldap_identities.find_each do |identity|
+      begin
+        identity.extern_uid = Gitlab::LDAP::DN.new(identity.extern_uid).to_s_normalized
+        unless identity.save
+          say "Unable to normalize \"#{identity.extern_uid}\". Skipping."
+        end
+      rescue Gitlab::LDAP::MalformedDnError, Gitlab::LDAP::UnsupportedDnFormatError => e
+        say "Unable to normalize \"#{identity.extern_uid}\" due to \"#{e.message}\". Skipping."
+      end
+    end
+  end
+
+  def down
+  end
+end