# -*- ruby encoding: utf-8 -*-
module Net # :nodoc:
##
# == Basic Encoding Rules (BER) Support Module
#
# Much of the text below is cribbed from Wikipedia:
# http://en.wikipedia.org/wiki/Basic_Encoding_Rules
#
# The ITU Specification is also worthwhile reading:
# http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
#
# The Basic Encoding Rules were the original rules laid out by the ASN.1
# standard for encoding abstract information into a concrete data stream.
# The rules, collectively referred to as a transfer syntax in ASN.1
# parlance, specify the exact octet sequences which are used to encode a
# given data item. The syntax defines such elements as: the
# representations for basic data types, the structure of length
# information, and the means for defining complex or compound types based
# on more primitive types. The BER syntax, along with two subsets of BER
# (the Canonical Encoding Rules and the Distinguished Encoding Rules), are
# defined by the ITU-T's X.690 standards document, which is part of the
# ASN.1 document series.
#
# == Encoding
# The BER format specifies a self-describing and self-delimiting format
# for encoding ASN.1 data structures. Each data element is encoded as a
# type identifier, a length description, the actual data elements, and
# where necessary, an end-of-content marker. This format allows a receiver
# to decode the ASN.1 information from an incomplete stream, without
# requiring any pre-knowledge of the size, content, or semantic meaning of
# the data.
#
# <Type | Length | Value [| End-of-Content]>
#
# == Protocol Data Units (PDU)
# Protocols are defined with schema represented in BER, such that a PDU
# consists of cascaded type-length-value encodings.
#
# === Type Tags
# BER type tags are represented as single octets (bytes). The lower five
# bits of the octet are tag identifier numbers and the upper three bits of
# the octet are used to distinguish the type as native to ASN.1,
# application-specific, context-specific, or private. See
# Net::BER::TAG_CLASS and Net::BER::ENCODING_TYPE for more information.
#
# If Class is set to Universal (0b00______), the value is of a type native
# to ASN.1 (e.g. INTEGER). The Application class (0b01______) is only
# valid for one specific application. Context_specific (0b10______)
# depends on the context and private (0b11_______) can be defined in
# private specifications
#
# If the primitive/constructed bit is zero (0b__0_____), it specifies that
# the value is primitive like an INTEGER. If it is one (0b__1_____), the
# value is a constructed value that contains type-length-value encoded
# types like a SET or a SEQUENCE.
#
# === Defined Universal (ASN.1 Native) Types
# There are a number of pre-defined universal (native) types.
#
# <table>
# <tr><th>Name</th><th>Primitive<br />Constructed</th><th>Number</th></tr>
# <tr><th>EOC (End-of-Content)</th><th>P</th><td>0: 0 (0x0, 0b00000000)</td></tr>
# <tr><th>BOOLEAN</th><th>P</th><td>1: 1 (0x01, 0b00000001)</td></tr>
# <tr><th>INTEGER</th><th>P</th><td>2: 2 (0x02, 0b00000010)</td></tr>
# <tr><th>BIT STRING</th><th>P</th><td>3: 3 (0x03, 0b00000011)</td></tr>
# <tr><th>BIT STRING</th><th>C</th><td>3: 35 (0x23, 0b00100011)</td></tr>
# <tr><th>OCTET STRING</th><th>P</th><td>4: 4 (0x04, 0b00000100)</td></tr>
# <tr><th>OCTET STRING</th><th>C</th><td>4: 36 (0x24, 0b00100100)</td></tr>
# <tr><th>NULL</th><th>P</th><td>5: 5 (0x05, 0b00000101)</td></tr>
# <tr><th>OBJECT IDENTIFIER</th><th>P</th><td>6: 6 (0x06, 0b00000110)</td></tr>
# <tr><th>Object Descriptor</th><th>P</th><td>7: 7 (0x07, 0b00000111)</td></tr>
# <tr><th>EXTERNAL</th><th>C</th><td>8: 40 (0x28, 0b00101000)</td></tr>
# <tr><th>REAL (float)</th><th>P</th><td>9: 9 (0x09, 0b00001001)</td></tr>
# <tr><th>ENUMERATED</th><th>P</th><td>10: 10 (0x0a, 0b00001010)</td></tr>
# <tr><th>EMBEDDED PDV</th><th>C</th><td>11: 43 (0x2b, 0b00101011)</td></tr>
# <tr><th>UTF8String</th><th>P</th><td>12: 12 (0x0c, 0b00001100)</td></tr>
# <tr><th>UTF8String</th><th>C</th><td>12: 44 (0x2c, 0b00101100)</td></tr>
# <tr><th>RELATIVE-OID</th><th>P</th><td>13: 13 (0x0d, 0b00001101)</td></tr>
# <tr><th>SEQUENCE and SEQUENCE OF</th><th>C</th><td>16: 48 (0x30, 0b00110000)</td></tr>
# <tr><th>SET and SET OF</th><th>C</th><td>17: 49 (0x31, 0b00110001)</td></tr>
# <tr><th>NumericString</th><th>P</th><td>18: 18 (0x12, 0b00010010)</td></tr>
# <tr><th>NumericString</th><th>C</th><td>18: 50 (0x32, 0b00110010)</td></tr>
# <tr><th>PrintableString</th><th>P</th><td>19: 19 (0x13, 0b00010011)</td></tr>
# <tr><th>PrintableString</th><th>C</th><td>19: 51 (0x33, 0b00110011)</td></tr>
# <tr><th>T61String</th><th>P</th><td>20: 20 (0x14, 0b00010100)</td></tr>
# <tr><th>T61String</th><th>C</th><td>20: 52 (0x34, 0b00110100)</td></tr>
# <tr><th>VideotexString</th><th>P</th><td>21: 21 (0x15, 0b00010101)</td></tr>
# <tr><th>VideotexString</th><th>C</th><td>21: 53 (0x35, 0b00110101)</td></tr>
# <tr><th>IA5String</th><th>P</th><td>22: 22 (0x16, 0b00010110)</td></tr>
# <tr><th>IA5String</th><th>C</th><td>22: 54 (0x36, 0b00110110)</td></tr>
# <tr><th>UTCTime</th><th>P</th><td>23: 23 (0x17, 0b00010111)</td></tr>
# <tr><th>UTCTime</th><th>C</th><td>23: 55 (0x37, 0b00110111)</td></tr>
# <tr><th>GeneralizedTime</th><th>P</th><td>24: 24 (0x18, 0b00011000)</td></tr>
# <tr><th>GeneralizedTime</th><th>C</th><td>24: 56 (0x38, 0b00111000)</td></tr>
# <tr><th>GraphicString</th><th>P</th><td>25: 25 (0x19, 0b00011001)</td></tr>
# <tr><th>GraphicString</th><th>C</th><td>25: 57 (0x39, 0b00111001)</td></tr>
# <tr><th>VisibleString</th><th>P</th><td>26: 26 (0x1a, 0b00011010)</td></tr>
# <tr><th>VisibleString</th><th>C</th><td>26: 58 (0x3a, 0b00111010)</td></tr>
# <tr><th>GeneralString</th><th>P</th><td>27: 27 (0x1b, 0b00011011)</td></tr>
# <tr><th>GeneralString</th><th>C</th><td>27: 59 (0x3b, 0b00111011)</td></tr>
# <tr><th>UniversalString</th><th>P</th><td>28: 28 (0x1c, 0b00011100)</td></tr>
# <tr><th>UniversalString</th><th>C</th><td>28: 60 (0x3c, 0b00111100)</td></tr>
# <tr><th>CHARACTER STRING</th><th>P</th><td>29: 29 (0x1d, 0b00011101)</td></tr>
# <tr><th>CHARACTER STRING</th><th>C</th><td>29: 61 (0x3d, 0b00111101)</td></tr>
# <tr><th>BMPString</th><th>P</th><td>30: 30 (0x1e, 0b00011110)</td></tr>
# <tr><th>BMPString</th><th>C</th><td>30: 62 (0x3e, 0b00111110)</td></tr>
# </table>
module BER
VERSION = '0.3.0'
##
# Used for BER-encoding the length and content bytes of a Fixnum integer
# values.
MAX_FIXNUM_SIZE = 0.size
##
# BER tag classes are kept in bits seven and eight of the tag type
# octet.
#
# <table>
# <tr><th>Bitmask</th><th>Definition</th></tr>
# <tr><th><tt>0b00______</tt></th><td>Universal (ASN.1 Native) Types</td></tr>
# <tr><th><tt>0b01______</tt></th><td>Application Types</td></tr>
# <tr><th><tt>0b10______</tt></th><td>Context-Specific Types</td></tr>
# <tr><th><tt>0b11______</tt></th><td>Private Types</td></tr>
# </table>
TAG_CLASS = {
:universal => 0b00000000, # 0
:application => 0b01000000, # 64
:context_specific => 0b10000000, # 128
:private => 0b11000000, # 192
}
##
# BER encoding type is kept in bit 6 of the tag type octet.
#
# <table>
# <tr><th>Bitmask</th><th>Definition</th></tr>
# <tr><th><tt>0b__0_____</tt></th><td>Primitive</td></tr>
# <tr><th><tt>0b__1_____</tt></th><td>Constructed</td></tr>
# </table>
ENCODING_TYPE = {
:primitive => 0b00000000, # 0
:constructed => 0b00100000, # 32
}
##
# Accepts a hash of hashes describing a BER syntax and converts it into
# a byte-keyed object for fast BER conversion lookup. The resulting
# "compiled" syntax is used by Net::BER::BERParser.
#
# This method should be called only by client classes of Net::BER (e.g.,
# Net::LDAP and Net::SNMP) and not by clients of those classes.
#
# The hash-based syntax uses TAG_CLASS keys that contain hashes of
# ENCODING_TYPE keys that contain tag numbers with object type markers.
#
# :<TAG_CLASS> => {
# :<ENCODING_TYPE> => {
# <number> => <object-type>
# },
# },
#
# === Permitted Object Types
# <tt>:string</tt>:: A string value, represented as BerIdentifiedString.
# <tt>:integer</tt>:: An integer value, represented with Fixnum.
# <tt>:oid</tt>:: An Object Identifier value; see X.690 section
# 8.19. Currently represented with a standard array,
# but may be better represented as a
# BerIdentifiedOID object.
# <tt>:array</tt>:: A sequence, represented as BerIdentifiedArray.
# <tt>:boolean</tt>:: A boolean value, represented as +true+ or +false+.
# <tt>:null</tt>:: A null value, represented as BerIdentifiedNull.
#
# === Example
# Net::LDAP defines its ASN.1 BER syntax something like this:
#
# class Net::LDAP
# AsnSyntax = Net::BER.compile_syntax({
# :application => {
# :primitive => {
# 2 => :null,
# },
# :constructed => {
# 0 => :array,
# # ...
# },
# },
# :context_specific => {
# :primitive => {
# 0 => :string,
# # ...
# },
# :constructed => {
# 0 => :array,
# # ...
# },
# }
# })
# end
#
# NOTE:: For readability and formatting purposes, Net::LDAP and its
# siblings actually construct their syntaxes more deliberately,
# as shown below. Since a hash is passed in the end in any case,
# the format does not matter.
#
# primitive = { 2 => :null }
# constructed = {
# 0 => :array,
# # ...
# }
# application = {
# :primitive => primitive,
# :constructed => constructed
# }
#
# primitive = {
# 0 => :string,
# # ...
# }
# constructed = {
# 0 => :array,
# # ...
# }
# context_specific = {
# :primitive => primitive,
# :constructed => constructed
# }
# AsnSyntax = Net::BER.compile_syntax(:application => application,
# :context_specific => context_specific)
def self.compile_syntax(syntax)
# TODO 20100327 AZ: Should we be allocating an array of 256 values
# that will either be +nil+ or an object type symbol, or should we
# allocate an empty Hash since unknown values return +nil+ anyway?
out = [ nil ] * 256
syntax.each do |tag_class_id, encodings|
tag_class = TAG_CLASS[tag_class_id]
encodings.each do |encoding_id, classes|
encoding = ENCODING_TYPE[encoding_id]
object_class = tag_class + encoding
classes.each do |number, object_type|
out[object_class + number] = object_type
end
end
end
out
end
end
end
class Net::BER::BerError < RuntimeError; end
##
# An Array object with a BER identifier attached.
class Net::BER::BerIdentifiedArray < Array
attr_accessor :ber_identifier
def initialize(*args)
super
end
end
##
# A BER object identifier.
class Net::BER::BerIdentifiedOid
attr_accessor :ber_identifier
def initialize(oid)
if oid.is_a?(String)
oid = oid.split(/\./).map {|s| s.to_i }
end
@value = oid
end
def to_ber
to_ber_oid
end
def to_ber_oid
@value.to_ber_oid
end
def to_s
@value.join(".")
end
def to_arr
@value.dup
end
end
##
# A String object with a BER identifier attached.
class Net::BER::BerIdentifiedString < String
attr_accessor :ber_identifier
def initialize args
super args
# LDAP uses UTF-8 encoded strings
force_encoding('UTF-8') if respond_to?(:encoding)
end
end
module Net::BER
##
# A BER null object.
class BerIdentifiedNull
attr_accessor :ber_identifier
def to_ber
"\005\000"
end
end
##
# The default BerIdentifiedNull object.
Null = Net::BER::BerIdentifiedNull.new
end
require 'net/ber/core_ext'