lib/rex/proto/kerberos/model/enc_ap_rep_part.rb
# -*- coding: binary -*-
module Rex
module Proto
module Kerberos
module Model
# This class provides a representation of an EncAPRepPart, sent as the
# encrypted part of an AP-REP message
class EncApRepPart < Element
# @!attribute ctime
# @return [Time] The current time of the client's host
attr_accessor :ctime
# @!attribute cusec
# @return [Integer] The microsecond part of the client's timestamp
attr_accessor :cusec
# @!attribute subkey
# @return [Rex::Proto::Kerberos::Model::EncryptionKey] the client's choice for an encryption
# key which is to be used to protect this specific application session
attr_accessor :subkey
# @!attribute sequence_number
# @return [Integer] The initial sequence number to be used for future communications
attr_accessor :sequence_number
# @!attribute enc_key_usage
# @return [Rex::Proto::Kerberos::Crypto::KeyUsage,Integer] The enc key usage number for this object
attr_accessor :enc_key_usage
# Decodes the Rex::Proto::Kerberos::Model::EncApRepPart from an input
#
# @param input [String, OpenSSL::ASN1::ASN1Data] the input to decode from
# @return [self] if decoding succeeds
# @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if decoding doesn't succeed
def decode(input)
case input
when String
decode_string(input)
when OpenSSL::ASN1::ASN1Data
decode_asn1(input)
else
raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, 'Failed to decode EncApRepPart, invalid input'
end
self
end
# Encodes the Rex::Proto::Kerberos::Model::EncApReqPart into an ASN.1 String
#
# @return [String]
def encode
elems = []
elems << OpenSSL::ASN1::ASN1Data.new([encode_ctime], 0, :CONTEXT_SPECIFIC)
elems << OpenSSL::ASN1::ASN1Data.new([encode_cusec], 1, :CONTEXT_SPECIFIC)
elems << OpenSSL::ASN1::ASN1Data.new([encode_subkey], 2, :CONTEXT_SPECIFIC) if subkey
elems << OpenSSL::ASN1::ASN1Data.new([encode_sequence_number], 3, :CONTEXT_SPECIFIC) if sequence_number
seq = OpenSSL::ASN1::Sequence.new(elems)
seq_asn1 = OpenSSL::ASN1::ASN1Data.new([seq], ENC_AP_REP_PART, :APPLICATION)
seq_asn1.to_der
end
# Encrypts the Rex::Proto::Kerberos::Model::EncApRepPart
#
# @param etype [Integer] the crypto schema to encrypt
# @param key [String] the key to encrypt
# @return [String] the encrypted result
# @raise [NotImplementedError] if the encryption schema isn't supported
def encrypt(etype, key)
raise ::Rex::Proto::Kerberos::Model::Error::KerberosError, 'Missing enc_key_usage' unless enc_key_usage
data = self.encode
encryptor = Rex::Proto::Kerberos::Crypto::Encryption::from_etype(etype)
encryptor.encrypt(data, key, enc_key_usage)
end
private
# Encodes the cusec field
#
# @return [OpenSSL::ASN1::Integer]
def encode_cusec
bn = OpenSSL::BN.new(cusec.to_s)
int = OpenSSL::ASN1::Integer.new(bn)
int
end
# Encodes the ctime field
#
# @return [OpenSSL::ASN1::GeneralizedTime]
def encode_ctime
OpenSSL::ASN1::GeneralizedTime.new(ctime)
end
# Encodes the subkey field
#
# @return [String]
def encode_subkey
subkey.encode
end
# Encodes the sequence_number field
#
# @return [OpenSSL::ASN1::Integer]
def encode_sequence_number
bn = OpenSSL::BN.new(sequence_number.to_s)
int = OpenSSL::ASN1::Integer.new(bn)
int
end
# Decodes a Rex::Proto::Kerberos::Model::EncApRepPart from an String
#
# @param input [String] the input to decode from
def decode_string(input)
asn1 = OpenSSL::ASN1.decode(input)
decode_asn1(asn1)
end
# Decodes a Rex::Proto::Kerberos::Model::EncApRepPart
#
# @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
# @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if decoding doesn't succeed
def decode_asn1(input)
input.value[0].value.each do |val|
case val.tag
when 0
self.ctime = decode_ctime(val)
when 1
self.cusec = decode_cusec(val)
when 2
self.subkey = decode_subkey(val)
when 3
self.sequence_number = decode_sequence_number(val)
else
raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, "Failed to decode EncApRepPart SEQUENCE (#{val.tag})"
end
end
end
# Decodes the ctime field
#
# @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
# @return [Time]
def decode_ctime(input)
input.value[0].value
end
# Decodes the cusec field
#
# @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
# @return [Integer]
def decode_cusec(input)
input.value[0].value
end
# Decodes the sequence_number field
#
# @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
# @return [Integer]
def decode_sequence_number(input)
input.value[0].value.to_i
end
# Decodes the subkey field
#
# @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
# @return [Integer]
def decode_subkey(input)
Rex::Proto::Kerberos::Model::EncryptionKey::decode(input.value[0])
end
end
end
end
end
end