metasploit-framework/lib/rex/encoder/xdr.rb

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module Rex
module Encoder
###
#
# This class implements basic XDR encoding.
#
###
module XDR
MAX_ARG = 0xffffffff
# Also: unsigned int, bool, enum
def XDR.encode_int(int)
return [int].pack('N')
end
def XDR.decode_int!(data)
return data.slice!(0..3).unpack('N')[0]
end
def XDR.encode_lchar(char)
char |= 0xffffff00 if char & 0x80 != 0
return encode_int(char)
end
def XDR.decode_lchar!(data)
return (decode_int!(data) & 0xff).chr
end
# Also: Variable length opaque
def XDR.encode_string(str, max=MAX_ARG)
raise ArgumentError, 'XDR: String too long' if str.length > max
len = str.length
str += "\x00" * ((4 - (len & 3)) & 3)
return encode_int(len) + str
end
def XDR.decode_string!(data)
real_len = decode_int!(data)
return "" if real_len == 0
align_len = (real_len + 3) & ~3
return data.slice!(0..align_len-1).slice(0..real_len-1)
end
def XDR.encode_varray(arr, max=MAX_ARG, &block)
raise ArgumentError, 'XDR: Too many array elements' if arr.length > max
return encode_int(arr.length) + arr.collect(&block).join(nil)
end
def XDR.decode_varray!(data)
buf = []
1.upto(decode_int!(data)) { buf.push(yield(data)) }
return buf
end
# encode(0, [0, 1], "foo", ["bar", 4]) does:
# encode_int(0) +
# encode_varray([0, 1]) { |i| XDR.encode_int(i) } +
# encode_string("foo") +
# encode_string("bar", 4)
def XDR.encode(*data)
data.collect do |var|
if var.kind_of?(String)
encode_string(var)
elsif var.kind_of?(Integer)
encode_int(var)
elsif var.kind_of?(Array) && var[0].kind_of?(String)
raise ArgumentError, 'XDR: Incorrect string array arguments' if var.length != 2
encode_string(var[0], var[1])
elsif var.kind_of?(Array) && var[0].kind_of?(Integer)
encode_varray(var) { |i| XDR.encode_int(i) }
# 0 means an empty array index in the case of Integer and an empty string in
# the case of String so we get the best of both worlds
elsif var.kind_of?(Array) && var[0].nil?
encode_int(0)
else
type = var.class
type = var[0].class if var.kind_of?(Array)
raise TypeError, "XDR: encode does not support #{type}"
end
end.join(nil)
end
# decode(buf, Integer, String, [Integer], [String]) does:
# [decode_int!(buf), decode_string!(buf),
# decode_varray!(buf) { |i| XDR.decode_int!(i) },
# decode_varray!(buf) { |s| XDR.decode_string(s) }]
def XDR.decode!(buf, *data)
return *data.collect do |var|
if data.length == 0
elsif var.kind_of?(Array) && var[0] == String
decode_varray!(buf) { |s| XDR.decode_string!(s) }
elsif var.kind_of?(Array) && var[0] == Integer
decode_varray!(buf) { |i| XDR.decode_int!(i) }
elsif var == String
decode_string!(buf)
elsif var == Integer
decode_int!(buf)
end
end
end
end
end
end