Class: LDAP::Server::Filter

Inherits:
Object
  • Object
show all
Defined in:
lib/ldap/server/filter.rb

Overview

LDAP filters are parsed into a LISP-like internal representation: 

  [:true]
  [:false]
  [:undef]
  [:and, ..., ..., ...]
  [:or, ..., ..., ...]
  [:not, ...]
  [:present, attr]
  [:eq, attr, MO, val]
  [:approx, attr, MO, val]
  [:substrings, attr, MO, initial=nil, {any, any...}, final=nil]
  [:ge, attr, MO, val]
  [:le, attr, MO, val]

This is done rather than a more object-oriented approach, in the hope that it will make it easier to match certain filter structures when converting them into something else. e.g. certain LDAP filter constructs can be mapped to some fixed SQL queries.

See RFC 2251 4.5.1 for the three-state(!) boolean logic from LDAP

If no schema is provided: ‘attr’ is the raw attribute name as provided by the client. If a schema is provided: attr is converted to its normalized name as listed in the schema, e.g. ‘commonname’ becomes ‘cn’, ‘objectclass’ becomes ‘objectClass’ etc. If a schema is provided, MO is a matching object which can be used to perform the match. If no schema is provided, this is ‘nil’. In that case you could use LDAP::Server::MatchingRule::DefaultMatch.

Class Method Summary (collapse)

Class Method Details

+ (Object) parse(asn1, schema = nil)

Parse a filter in OpenSSL::ASN1 format into our own format.

There are some trivial optimisations we make: e.g. 

  (&(objectClass=*)(cn=foo)) -> (&(cn=foo)) -> (cn=foo)


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# File 'lib/ldap/server/filter.rb', line 44

def self.parse(asn1, schema=nil)
  case asn1.tag
  when 0 # and
    conds = asn1.value.collect { |a| parse(a) }
    conds.delete([:true])
    return [:true] if conds.size == 0
    return conds.first if conds.size == 1
    return [:false] if conds.include?([:false])
    return conds.unshift(:and)

  when 1 # or
    conds = asn1.value.collect { |a| parse(a) }
    conds.delete([:false])
    return [:false] if conds.size == 0
    return conds.first if conds.size == 1
    return [:true] if conds.include?([:true])
    return conds.unshift(:or)

  when 2 # not
    cond = parse(asn1.value[0])
    case cond
    when [:false];	return [:true]
	when [:true];	return [:false]
	when [:undef];	return [:undef]
	end
	return [:not, cond]

  when 3 # equalityMatch
    attr = asn1.value[0].value
    val = asn1.value[1].value
    return [:true] if attr =~ /\AobjectClass\z/i and val =~ /\Atop\z/i
    if schema
      a = schema.find_attrtype(attr)
      return [:undef] unless a.equality
      return [:eq, a.to_s, a.equality, val]
    end
    return [:eq, attr, nil, val]

  when 4 # substrings
    attr = asn1.value[0].value
    if schema
      a = schema.find_attrtype(attr)
      return [:undef] unless a.substr
      res = [:substrings, a.to_s, a.substr, nil]
    else
      res = [:substrings, attr, nil, nil]
    end
    final_val = nil

    asn1.value[1].value.each do |ss|
      case ss.tag
      when 0
        res[3] = ss.value
      when 1
        res << ss.value
      when 2
        final_val = ss.value
      else
        raise LDAP::ResultError::ProtocolError,
          "Unrecognised substring tag #{ss.tag.inspect}"
      end
    end
    res << final_val
    return res

  when 5 # greaterOrEqual
    attr = asn1.value[0].value
    val = asn1.value[1].value
    if schema
      a = schema.find_attrtype(attr)
      return [:undef] unless a.ordering
      return [:ge, a.to_s, a.ordering, val]
    end
    return [:ge, attr, nil, val]

  when 6 # lessOrEqual
    attr = asn1.value[0].value
    val = asn1.value[1].value
    if schema
      a = schema.find_attrtype(attr)
      return [:undef] unless a.ordering
      return [:le, a.to_s, a.ordering, val]
    end
    return [:le, attr, nil, val]

  when 7 # present
    attr = asn1.value
    return [:true] if attr =~ /\AobjectClass\z/i
    if schema
      begin
        a = schema.find_attrtype(attr)
        return [:present, a.to_s]
      rescue LDAP::ResultError::UndefinedAttributeType
        return [:false]
      end
    end
    return [:present, attr]

  when 8 # approxMatch
    attr = asn1.value[0].value
    val = asn1.value[1].value
    if schema
      a = schema.find_attrtype(attr)
      # I don't know how properly to deal with approxMatch. I'm assuming
      # that the object will have an equality MatchingRule, and we
      # can defer to that.
      return [:undef] unless a.equality
      return [:approx, a.to_s, a.equality, val]
    end
    return [:approx, attr, nil, val]

  #when 9 # extensibleMatch
  #  FIXME

  else
    raise LDAP::ResultError::ProtocolError,
      "Unrecognised Filter tag #{asn1.tag}"
  end

# Unknown attribute type
rescue LDAP::ResultError::UndefinedAttributeType
  return [:undef]
end

+ (Object) run(filter, av)

Run a parsed filter against an attr=>[val] hash.

Returns true, false or nil.

Raises:



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# File 'lib/ldap/server/filter.rb', line 172

def self.run(filter, av)
  case filter[0]
  when :and
    res = true
    filter[1..-1].each do |elem|
      r = run(elem, av)
      return false if r == false
      res = nil if r.nil?
    end
    return res

  when :or
    res = false
    filter[1..-1].each do |elem|
      r = run(elem, av)
      return true if r == true
      res = nil if r.nil?
    end
    return res

  when :not
    case run(filter[1], av)
    when true; 	return false
    when false;	return true
    else		return nil
    end

  when :present
    return av.has_key?(filter[1])

  when :eq, :approx, :le, :ge, :substrings
    # the filter now includes a suitable matching object
    return (filter[2] || LDAP::Server::MatchingRule::DefaultMatch).send(
            filter.first, av[filter[1].to_s], *filter[3..-1])

  when :true
    return true

  when :false
    return false

  when :undef
    return nil
  end

  raise LDAP::ResultError::OperationsError,
    "Unimplemented filter #{filter.first.inspect}"
end