353 lines
10 KiB
Ruby
353 lines
10 KiB
Ruby
#
|
|
# Copyright (c) 2004 David R. Halliday
|
|
# All rights reserved.
|
|
#
|
|
# This SNMP library is free software. Redistribution is permitted under the
|
|
# same terms and conditions as the standard Ruby distribution. See the
|
|
# COPYING file in the Ruby distribution for details.
|
|
#
|
|
|
|
#
|
|
# Add ord method to Integer for forward compatibility with Ruby 1.9
|
|
#
|
|
if "a"[0].kind_of? Integer
|
|
unless Integer.methods.include? :ord
|
|
class Integer
|
|
def ord; self; end
|
|
end
|
|
end
|
|
end
|
|
|
|
#
|
|
# This module implements methods for encoding and decoding SNMP packets
|
|
# using the ASN.1 BER (Basic Encoding Rules).
|
|
#
|
|
module SNMP
|
|
module BER #:nodoc:all
|
|
|
|
# SNMP version codes
|
|
SNMP_V1 = 0
|
|
SNMP_V2C = 1
|
|
SNMP_V3 = 3 # not supported
|
|
|
|
# SNMP context-specific data types
|
|
# See RFC 1157 for SNMPv1
|
|
# See RFC 1905 for SNMPv2c
|
|
GetRequest_PDU_TAG = 0xa0
|
|
GetNextRequest_PDU_TAG = 0xa1
|
|
Response_PDU_TAG = 0xa2
|
|
SetRequest_PDU_TAG = 0xa3
|
|
SNMPv1_Trap_PDU_TAG = 0xa4 # Note: valid for SNMPv1 only
|
|
GetBulkRequest_PDU_TAG = 0xa5
|
|
InformRequest_PDU_TAG = 0xa6
|
|
SNMPv2_Trap_PDU_TAG = 0xa7
|
|
Report_PDU_TAG = 0xa8 # Note: Usage not defined - not supported
|
|
|
|
# Primitive ASN.1 data types
|
|
INTEGER_TAG = 0x02
|
|
OCTET_STRING_TAG = 0x04
|
|
NULL_TAG = 0x05
|
|
OBJECT_IDENTIFIER_TAG = 0x06
|
|
|
|
# Constructed ASN.1 data type
|
|
SEQUENCE_TAG = 0x30
|
|
|
|
# SNMP application data types
|
|
# See RFC 1155 for SNMPv1
|
|
# See RFC 1902 for SNMPv2c
|
|
IpAddress_TAG = 0x40
|
|
Counter32_TAG = 0x41 # Counter in SNMPv1
|
|
Gauge32_TAG = 0x42 # Gauge in SNMPv1
|
|
Unsigned32_TAG = 0x42 # Note: same as Gauge32
|
|
TimeTicks_TAG = 0x43
|
|
Opaque_TAG = 0x44
|
|
Counter64_TAG = 0x46
|
|
|
|
# VarBind response exceptions
|
|
NoSuchObject_TAG = 0x80
|
|
NoSuchInstance_TAG = 0x81
|
|
EndOfMibView_TAG = 0x82
|
|
|
|
# Exceptions thrown in this module
|
|
class OutOfData < RuntimeError; end
|
|
class InvalidLength < RuntimeError; end
|
|
class InvalidTag < RuntimeError; end
|
|
class InvalidObjectId < RuntimeError; end
|
|
|
|
def assert_no_remainder(remainder)
|
|
raise ParseError, remainder.inspect if (remainder and remainder != "")
|
|
end
|
|
|
|
#
|
|
# Decode tag-length-value data. The data is assumed to be a string of
|
|
# bytes in network byte order. This format is returned by Socket#recv.
|
|
#
|
|
# Returns a tuple containing the tag, the value, and any remaining
|
|
# unprocessed data.
|
|
#
|
|
# The data is not interpreted by this method. Use one of the other
|
|
# decoding methods to interpret the data.
|
|
#
|
|
# Note that ASN.1 supports an indefinite length format where the end of
|
|
# content is marked by a pair of 0 octets. SNMP does not support this
|
|
# format, so only the two definite forms are implemented (single byte and
|
|
# multi-byte).
|
|
#
|
|
def decode_tlv(data)
|
|
raise OutOfData if (data.length == 2 && data[1].ord != 0) || data.length < 2
|
|
tag = data[0].ord
|
|
length = data[1].ord
|
|
if length < 0x80
|
|
value = data[2, length]
|
|
remainder = data[length+2..-1]
|
|
else
|
|
# ASN.1 says this octet can't be 0xff
|
|
raise InvalidLength, length.to_s if length == 0xff
|
|
num_octets = length & 0x7f
|
|
length = build_integer(data, 2, num_octets)
|
|
value = data[num_octets+2, length]
|
|
remainder = data[num_octets+2+length..-1]
|
|
end
|
|
return tag, value, remainder
|
|
end
|
|
|
|
#
|
|
# Decode TLV data for an ASN.1 integer.
|
|
#
|
|
# Throws an InvalidTag exception if the tag is incorrect.
|
|
#
|
|
# Returns a tuple containing an integer and any remaining unprocessed data.
|
|
#
|
|
def decode_integer(data)
|
|
tag, value, remainder = decode_tlv(data)
|
|
raise InvalidTag, tag.to_s if tag != INTEGER_TAG
|
|
return decode_integer_value(value), remainder
|
|
end
|
|
|
|
def decode_timeticks(data)
|
|
tag, value, remainder = decode_tlv(data)
|
|
raise InvalidTag, tag.to_s if tag != TimeTicks_TAG
|
|
return decode_uinteger_value(value), remainder
|
|
end
|
|
|
|
def decode_integer_value(value)
|
|
result = build_integer(value, 0, value.length)
|
|
if value[0].ord[7] == 1
|
|
result -= (1 << (8 * value.length))
|
|
end
|
|
result
|
|
end
|
|
|
|
##
|
|
# Decode an integer, ignoring the sign bit. Some agents insist on
|
|
# encoding 32 bit unsigned integers with four bytes even though it
|
|
# should be 5 bytes (at least the way I read it).
|
|
#
|
|
def decode_uinteger_value(value)
|
|
build_integer(value, 0, value.length)
|
|
end
|
|
|
|
def build_integer(data, start, num_octets)
|
|
number = 0
|
|
num_octets.times { |i| number = number<<8 | data[start+i].ord }
|
|
return number
|
|
end
|
|
|
|
#
|
|
# Decode TLV data for an ASN.1 octet string.
|
|
#
|
|
# Throws an InvalidTag exception if the tag is incorrect.
|
|
#
|
|
# Returns a tuple containing a string and any remaining unprocessed data.
|
|
#
|
|
def decode_octet_string(data)
|
|
tag, value, remainder = decode_tlv(data)
|
|
raise InvalidTag, tag.to_s if tag != OCTET_STRING_TAG
|
|
return value, remainder
|
|
end
|
|
|
|
def decode_ip_address(data)
|
|
tag, value, remainder = decode_tlv(data)
|
|
raise InvalidTag, tag.to_s if tag != IpAddress_TAG
|
|
raise InvalidLength, tag.to_s if value.length != 4
|
|
return value, remainder
|
|
end
|
|
|
|
#
|
|
# Decode TLV data for an ASN.1 sequence.
|
|
#
|
|
# Throws an InvalidTag exception if the tag is incorrect.
|
|
#
|
|
# Returns a tuple containing the sequence data and any remaining
|
|
# unprocessed data that follows the sequence.
|
|
#
|
|
def decode_sequence(data)
|
|
tag, value, remainder = decode_tlv(data)
|
|
raise InvalidTag, tag.to_s if tag != SEQUENCE_TAG
|
|
return value, remainder
|
|
end
|
|
|
|
#
|
|
# Unwrap TLV data for an ASN.1 object identifier. This method extracts
|
|
# the OID value as a character string but does not decode it further.
|
|
#
|
|
# Throws an InvalidTag exception if the tag is incorrect.
|
|
#
|
|
# Returns a tuple containing the object identifier (OID) and any
|
|
# remaining unprocessed data. The OID is represented as an array
|
|
# of integers.
|
|
#
|
|
def decode_object_id(data)
|
|
tag, value, remainder = decode_tlv(data)
|
|
raise InvalidTag, tag.to_s if tag != OBJECT_IDENTIFIER_TAG
|
|
return decode_object_id_value(value), remainder
|
|
end
|
|
|
|
def decode_object_id_value(value)
|
|
if value.length == 0
|
|
object_id = []
|
|
else
|
|
value0 = value[0].ord
|
|
if value0 == 0x2b
|
|
object_id = [1,3]
|
|
else
|
|
second = value0 % 40
|
|
first = (value0 - second) / 40
|
|
raise InvalidObjectId, value.to_s if first > 2
|
|
object_id = [first, second]
|
|
end
|
|
n = 0
|
|
for i in 1...value.length
|
|
n = (n<<7) + (value[i].ord & 0x7f)
|
|
if value[i].ord < 0x80
|
|
object_id << n
|
|
n = 0
|
|
end
|
|
end
|
|
end
|
|
return object_id
|
|
end
|
|
|
|
#
|
|
# Encode the length field for TLV data. Returns the length octets
|
|
# as a string.
|
|
#
|
|
def encode_length(length)
|
|
raise InvalidLength, length.to_s if length < 0
|
|
if length < 0x80
|
|
length.chr
|
|
else
|
|
data = integer_to_octets(length)
|
|
(data.size | 0x80).chr << data
|
|
end
|
|
end
|
|
|
|
#
|
|
# Encode integer
|
|
#
|
|
def encode_integer(value)
|
|
encode_tagged_integer(INTEGER_TAG, value)
|
|
end
|
|
|
|
def encode_tagged_integer(tag, value)
|
|
if value > 0 && value < 0x80
|
|
data = value.chr
|
|
else
|
|
data = integer_to_octets(value)
|
|
if value > 0 && data[0].ord > 0x7f
|
|
data = "\000" << data
|
|
elsif value < 0 && data[0].ord < 0x80
|
|
data = "\377" << data
|
|
end
|
|
end
|
|
encode_tlv(tag, data)
|
|
end
|
|
|
|
#
|
|
# Helper method for encoding integer-like things.
|
|
#
|
|
def integer_to_octets(i)
|
|
if i >= 0
|
|
done = 0
|
|
else
|
|
done = -1
|
|
end
|
|
octets = ""
|
|
begin
|
|
octets = (i & 0xff).chr << octets
|
|
i = i >> 8
|
|
end until i == done
|
|
octets
|
|
end
|
|
|
|
def encode_null
|
|
NULL_TAG.chr << "\000"
|
|
end
|
|
|
|
#
|
|
# Encode an exception. The encoding is simply the exception tag with
|
|
# no data, similar to NULL.
|
|
#
|
|
def encode_exception(tag)
|
|
tag.chr << "\000"
|
|
end
|
|
|
|
#
|
|
# Wraps value in a tag and length. This method expects an
|
|
# integer tag and a string value.
|
|
#
|
|
def encode_tlv(tag, value)
|
|
data = tag.chr << encode_length(value.length)
|
|
data = data << value if value.length > 0
|
|
data
|
|
end
|
|
|
|
#
|
|
# Wrap string in a octet string tag and length.
|
|
#
|
|
def encode_octet_string(value)
|
|
encode_tlv(OCTET_STRING_TAG, value)
|
|
end
|
|
|
|
#
|
|
# Wrap value in a sequence tag and length.
|
|
#
|
|
def encode_sequence(value)
|
|
encode_tlv(SEQUENCE_TAG, value)
|
|
end
|
|
|
|
#
|
|
# Encode an object id. The input is assumed to be an array of integers
|
|
# representing the object id.
|
|
#
|
|
def encode_object_id(value)
|
|
raise InvalidObjectId, value.to_s if value.length < 1
|
|
raise InvalidObjectId, value.to_s if value[0] > 2
|
|
data = ""
|
|
if (value.length > 1)
|
|
raise InvalidObjectId if value[0] < 2 && value[1] > 40
|
|
data << (40 * value[0] + value[1]).chr
|
|
for i in 2...value.length
|
|
if value[i] < 0x80
|
|
data << value[i].chr
|
|
else
|
|
octets = ""
|
|
n = value[i]
|
|
begin
|
|
octets = (n & 0x7f | 0x80).chr << octets
|
|
n = n >> 7
|
|
end until n == 0
|
|
octets[-1] = (octets[-1].ord & 0x7f).chr
|
|
data << octets
|
|
end
|
|
end
|
|
elsif (value.length == 1)
|
|
data << (40 * value[0]).chr
|
|
end
|
|
encode_tlv(OBJECT_IDENTIFIER_TAG, data)
|
|
end
|
|
|
|
end
|
|
end
|
|
|