dynamic_auth.rb

#!/usr/bin/ruby
# -*- coding: utf-8 -*-

require 'rexml/document'
require '../lab1/static_auth.rb'

# Used for inteprete tags from card and decrypt cert and static auth
class CardReader
  attr_accessor :dynamic_tags, :card_dynamic_info, :dynamic_auth

  def initialize(static_tags, dynamic_tags, ca_keys)
    @static_tags = static_tags
    @dynamic_tags = dynamic_tags

    # Load all keys
    ca = CA.new(ca_keys)

    # Find us key
    rid = @static_tags['4f - Application identifier (AID)'].unpack('a10')[0]
    caKeyIndex = @static_tags['8f - Certification Authority Public Key Index']
    @ca_key = ca.getKey(rid, caKeyIndex)

    # Do main work
    decrypt_static_cert()
    decrypt_static_auth()

    decrypt_dynamic_cert()
    decrypt_dynamic_auth()
  end

  def decrypt_dynamic_cert()
    mod =  @card_static_info['mod_em']
    if @static_tags['92 - Issuer Public Key Remainder'] != nil
      mod = mod + @static_tags['92 - Issuer Public Key Remainder']
    end

    # card_info = cert^e mod n
    card_info_raw = @dynamic_tags['9F46 - Integrated Circuit Card (ICC) Public Key Certificate'].hex.
            mod_pow(@static_tags['9f32 - Issuer Public Key Exponent'].hex, mod.hex)

    mod_len_with_padding = (@dynamic_tags['9F46 - Integrated Circuit Card (ICC) Public Key Certificate'].size/2 - 42)
    @card_dynamic_info =
      Hash.create(['prefix',         # 1 byte
                   'format',         # 1 byte
                   'card_number',    # 10 byte
                   'expire_date',    # 2 byte
                   'serial',         # 3 byte
                   'alg_hash',       # 1 byte
                   'alg_sign',       # 1 byte
                   'mod_len',        # 1 byte
                   'exp_len',        # 1 byte
                   'mod_em',         # L(CA) - 42
                   'cert_hash',      # 20 byte
                   'suffix'          # 1 byte
                  ], card_info_raw.to_s(16).unpack("a2a2a20a4a6a2a2a2a2a" + (mod_len_with_padding * 2).to_s  + "a40a2"))
    check_bounds(@card_dynamic_info)
    # Remove padding if exists
    # XXX: hm, we may notify about that?
    padding_len = mod_len_with_padding - @card_dynamic_info['mod_len'].hex
    if padding_len > 0
      @card_dynamic_info['mod_em'] = @card_dynamic_info['mod_em'].chomp("bb" * padding_len)
    end

  end

  def decrypt_dynamic_auth()
    mod = @card_dynamic_info['mod_em']
    if  @dynamic_tags['9F48 - Integrated Circuit Card (ICC) Public Key Remainder'] != nil
      mod = mod + @dynamic_tags['9F48 - Integrated Circuit Card (ICC) Public Key Remainder']
    end

    dynamic_auth_raw = @dynamic_tags['9F4B - Signed Dynamic Application Data'].hex.
      mod_pow(@dynamic_tags['9F47 - Integrated Circuit Card (ICC) Public Key Exponent'].hex, mod.hex)

    # XXX: 9 is len of dynamic data. Static? Where we find it?
    padding_len = (@dynamic_tags['9F4B - Signed Dynamic Application Data'].size/2 - 25 - 9)
    @dynamic_auth =
      Hash.create(['prefix',         # 1 byte
                   'format',         # 1 byte
                   'alg_hash',       # 1 byte
                   'len_data',       # 1 byte
                   'dyn_data',       # 9 byte
                   'padding',        # L(ICC) - L(DD) - 25
                   'card_hash',      # 20 byte
                   'suffix'          # 1 byte
                  ], dynamic_auth_raw.to_s(16).unpack("a2a2a2a2a18a" + (padding_len * 2).to_s  + "a40a2"))

    check_bounds(@dynamic_auth)
  end

  def check_bounds(data)
    unless data['prefix'] == "6a" and data['suffix'] == "bc"
      raise "Bad card info, prefix = #{data['prefix']} and suffix = #{data['suffix']}"
    end
  end

    private :check_bounds
end

# It is my task
$card_dynamic_var2 = {
  '9F37 - Unpredictable number'                                 => 'BABABABA',
  '9F46 - Integrated Circuit Card (ICC) Public Key Certificate' => '06A4B80EBD734270ADAE007C0DE8B173' +
                                                                   'D3411FB297084B1415578201DB71A738' +
                                                                   '8EE5109463DE286398DBFAB5797B04DF' +
                                                                   'DD355D0152BD6ABF7AB7B65AC4D375F3' +
                                                                   '4F3B8B945158E0CE581A5A90F494589B' +
                                                                   '1A07B7559C24E39006EC501B68AC1CEA' +
                                                                   'F05E22636E3E840A6E8F77ECAADC9E3F' +
                                                                   '79D47C0E8B5B65731C27E030B59DBE46',
  '9F47 - Integrated Circuit Card (ICC) Public Key Exponent'    => '03',
  '9F48 - Integrated Circuit Card (ICC) Public Key Remainder'   => nil,
  '9F49 - Dynamic Data Authentication Data Object List (DDOL)'  => '9F3704',
  '9F4B - Signed Dynamic Application Data'                      => '33085A1397B566C317690A1A68DA5073' +
                                                                   '8677DB80D5F32A20F64D38669DF41F3E' +
                                                                   'F54C7E2CAB8B32230FFE146C8B330ADB' +
                                                                   '56015533076C4A23A3FBB2B3F8CDCFD1'
}

# XXX: We use static tags from 1 lab.
if __FILE__ == $PROGRAM_NAME
  cr = CardReader.new($card_static_var2, $card_dynamic_var2, '../ca_keys.xml')

  print_hash("Dynamic tag", $card_dynamic_var2)
  print_hash("Ca key", cr.ca_key)
  print_hash("Dynamic info", cr.card_dynamic_info)
  print_hash("Dynamic auth", cr.dynamic_auth)
end