--- -- SNMP functions. -- -- @args snmpcommunity The community string to use. If not given, it is -- "public", or whatever is passed to buildPacket. -- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html module(... or "snmp",package.seeall) require("bit") require("asn1") -- SNMP ASN.1 Encoders local tagEncoder = {} -- Override the boolean encoder tagEncoder['boolean'] = function(self, val) return bin.pack('H', '05 00') end -- Complex tag encoders tagEncoder['table'] = function(self, val) if val._snmp == '06' then -- OID local oidStr = string.char(val[1]*40 + val[2]) for i = 3, #val do oidStr = oidStr .. self.encode_oid_component(val[i]) end return bin.pack("HAA", '06', self.encodeLength(#oidStr), oidStr) elseif (val._snmp == '40') then -- ipAddress return bin.pack("HC4", '40 04', unpack(val)) -- counter or gauge or timeticks or opaque elseif (val._snmp == '41' or val._snmp == '42' or val._snmp == '43' or val._snmp == '44') then local val = self:encodeInt(val[1]) return bin.pack("HAA", val._snmp, self.encodeLength(string.len(val)), val) end local encVal = "" for _, v in ipairs(val) do encVal = encVal .. self:encode(v) -- todo: buffer? end local tableType = bin.pack("H", "30") if (val["_snmp"]) then tableType = bin.pack("H", val["_snmp"]) end return bin.pack('AAA', tableType, self.encodeLength(string.len(encVal)), encVal) end --- -- Encodes a given value according to ASN.1 basic encoding rules for SNMP -- packet creation. -- @param val Value to be encoded. -- @return Encoded value. function encode(val) local vtype = type(val) local encoder = asn1.ASN1Encoder:new() encoder:registerTagEncoders( tagEncoder ) local encVal = encoder:encode(val) if encVal then return encVal end return '' end -- SNMP ASN.1 Decoders local tagDecoder = {} -- Application specific tags -- -- IP Address tagDecoder["40"] = function( self, encStr, elen, pos ) local ip = {} pos, ip[1], ip[2], ip[3], ip[4] = bin.unpack("C4", encStr, pos) ip._snmp = '40' return pos, ip end -- Counter tagDecoder["41"] = function( self, encStr, elen, pos ) local tbl = {} pos, tbl[1] = self.decodeInt(encStr, elen, pos) tbl._snmp = '41' return pos, tbl end -- Gauge tagDecoder["42"] = function( self, encStr, elen, pos ) local tbl = {} pos, tbl[1] = self.decodeInt(encStr, elen, pos) tbl._snmp = '41' return pos, tbl end -- TimeTicks tagDecoder["43"] = function( self, encStr, elen, pos ) local tbl = {} pos, tbl[1] = self.decodeInt(encStr, elen, pos) tbl._snmp = '41' return pos, tbl end -- Opaque tagDecoder["44"] = function( self, encStr, elen, pos ) local tbl = {} pos, tbl[1] = self.decodeInt(encStr, elen, pos) tbl._snmp = '41' return pos, tbl end -- Context specific tags -- tagDecoder["A0"] = function( self, encStr, elen, pos ) local seq pos, seq = self:decodeSeq(encStr, elen, pos) seq._snmp = "A0" return pos, seq end tagDecoder["A1"] = function( self, encStr, elen, pos ) local seq pos, seq = self:decodeSeq(encStr, elen, pos) seq._snmp = "A1" return pos, seq end tagDecoder["A2"] = function( self, encStr, elen, pos ) local seq pos, seq = self:decodeSeq(encStr, elen, pos) seq._snmp = "A2" return pos, seq end tagDecoder["A3"] = function( self, encStr, elen, pos ) local seq pos, seq = self:decodeSeq(encStr, elen, pos) seq._snmp = "A3" return pos, seq end tagDecoder["A4"] = function( self, encStr, elen, pos ) local seq pos, seq = self:decodeSeq(encStr, elen, pos) seq._snmp = "A4" return pos, seq end --- -- Decodes an SNMP packet or a part of it according to ASN.1 basic encoding -- rules. -- @param encStr Encoded string. -- @param pos Current position in the string. -- @return The position after decoding -- @return The decoded value(s). function decode(encStr, pos) local decoder = asn1.ASN1Decoder:new() decoder:registerTagDecoders( tagDecoder ) return decoder:decode( encStr, pos ) end --- -- Decodes an SNMP packet or a part of it according to ASN.1 basic encoding -- rules. -- @param encStr Encoded string. -- @param pos Current position in the string. -- @return The decoded value(s). function dec(encStr, pos) local result local _ _, result = decode(encStr, pos) return result end --- -- Create an SNMP packet. -- @param PDU SNMP Protocol Data Unit to be encapsulated in the packet. -- @param version SNMP version, default 0 (SNMP V1). -- @param commStr community string, if not already supplied in registry or as -- the snmpcommunity script argument. function buildPacket(PDU, version, commStr) local comm = nmap.registry.args.snmpcommunity if (not comm) then comm = nmap.registry.snmpcommunity end if (not comm) then comm = commStr end if (not comm) then comm = "public" end if (not version) then version = 0 end local packet = {} packet[1] = version packet[2] = comm packet[3] = PDU return packet end --- -- Create an SNMP Get Request PDU. -- @param options A table containing the following fields: -- * "reqId": Request ID. -- * "err": Error. -- * "errIdx": Error index. -- @param ... Object identifiers to be queried. -- @return Table representing PDU. function buildGetRequest(options, ...) if not options then options = {} end if not options.reqId then options.reqId = math.mod(nmap.clock_ms(), 65000) end if not options.err then options.err = 0 end if not options.errIdx then options.errIdx = 0 end local req = {} req._snmp = 'A0' req[1] = options.reqId req[2] = options.err req[3] = options.errIdx local payload = {} for i=1, select('#', ...) do payload[i] = {} payload[i][1] = select(i, ...) if type(payload[i][1]) == "string" then payload[i][1] = str2oid(payload[i][1]) end payload[i][2] = false end req[4] = payload return req end --- -- Create an SNMP Get Next Request PDU. -- @param options A table containing the following fields: -- * "reqId": Request ID. -- * "err": Error. -- * "errIdx": Error index. -- @param ... Object identifiers to be queried. -- @return Table representing PDU. function buildGetNextRequest(options, ...) if not options then options = {} end if not options.reqId then options.reqId = math.mod(nmap.clock_ms(), 65000) end if not options.err then options.err = 0 end if not options.errIdx then options.errIdx = 0 end local req = {} req._snmp = 'A1' req[1] = options.reqId req[2] = options.err req[3] = options.errIdx local payload = {} for i=1, select('#', ...) do payload[i] = {} payload[i][1] = select(i, ...) if type(payload[i][1]) == "string" then payload[i][1] = str2oid(payload[i][1]) end payload[i][2] = false end req[4] = payload return req end --- -- Create an SNMP Set Request PDU. -- -- Takes one OID/value pair or an already prepared table. -- @param options A table containing the following keys and values: -- * "reqId": Request ID. -- * "err": Error. -- * "errIdx": Error index. -- @param oid Object identifiers of object to be set. -- @param value To which value object should be set. If given a table, use the -- table instead of OID/value pair. -- @return Table representing PDU. function buildSetRequest(options, oid, value) if not options then options = {} end if not options.reqId then options.reqId = math.mod(nmap.clock_ms(), 65000) end if not options.err then options.err = 0 end if not options.errIdx then options.errIdx = 0 end local req = {} req._snmp = 'A3' req[1] = options.reqId req[2] = options.err req[3] = options.errIdx if (type(value) == "table") then req[4] = value else local payload = {} if (type(oid) == "string") then payload[1] = str2oid(oid) else payload[1] = oid end payload[2] = value req[4] = {} req[4][1] = payload end return req end --- -- Create an SNMP Trap PDU. -- @return Table representing PDU function buildTrap(enterpriseOid, agentIp, genTrap, specTrap, timeStamp) local req = {} req._snmp = 'A4' if (type(enterpriseOid) == "string") then req[1] = str2oid(enterpriseOid) else req[1] = enterpriseOid end req[2] = {} req[2]._snmp = '40' for n in string.gmatch(agentIp, "%d+") do table.insert(req[2], tonumber(n)) end req[3] = genTrap req[4] = specTrap req[5] = {} req[5]._snmp = '43' req[5][1] = timeStamp req[6] = {} return req end --- -- Create an SNMP Get Response PDU. -- -- Takes one OID/value pair or an already prepared table. -- @param options A table containing the following keys and values: -- * "reqId": Request ID. -- * "err": Error. -- * "errIdx": Error index. -- @param oid Object identifiers of object to be sent back. -- @param value If given a table, use the table instead of OID/value pair. -- @return Table representing PDU. function buildGetResponse(options, oid, value) if not options then options = {} end -- if really a response, should use reqId of request! if not options.reqId then options.reqId = math.mod(nmap.clock_ms(), 65000) end if not options.err then options.err = 0 end if not options.errIdx then options.errIdx = 0 end local resp = {} resp._snmp = 'A2' resp[1] = options.reqId resp[2] = options.err resp[3] = options.errIdx if (type(value) == "table") then resp[4] = value else local payload = {} if (type(oid) == "string") then payload[1] = str2oid(oid) else payload[1] = oid end payload[2] = value resp[4] = {} resp[4][1] = payload end return resp end --- -- Transforms a string into an object identifier table. -- @param oidStr Object identifier as string, for example -- "1.3.6.1.2.1.1.1.0". -- @return Table representing OID. function str2oid(oidStr) local oid = {} for n in string.gmatch(oidStr, "%d+") do table.insert(oid, tonumber(n)) end oid._snmp = '06' return oid end --- -- Transforms a table representing an object identifier to a string. -- @param oid Object identifier table. -- @return OID string. function oid2str(oid) if (type(oid) ~= "table") then return 'invalid oid' end return table.concat(oid, '.') end --- -- Transforms a table representing an IP to a string. -- @param ip IP table. -- @return IP string. function ip2str(ip) if (type(ip) ~= "table") then return 'invalid ip' end return table.concat(ip, '.') end --- -- Transforms a string into an IP table. -- @param ipStr IP as string. -- @return Table representing IP. function str2ip(ipStr) local ip = {} for n in string.gmatch(ipStr, "%d+") do table.insert(ip, tonumber(n)) end ip._snmp = '40' return ip end --- -- Fetches values from a SNMP response. -- @param resp SNMP Response (will be decoded if necessary). -- @return Table with all decoded responses and their OIDs. function fetchResponseValues(resp) if (type(resp) == "string") then local _ _, resp = decode(resp) end if (type(resp) ~= "table") then return {} end local varBind if (resp._snmp and resp._snmp == 'A2') then varBind = resp[4] elseif (resp[3]._snmp and resp[3]._snmp == 'A2') then varBind = resp[3][4] end if (varBind and type(varBind) == "table") then local result = {} for k, v in ipairs(varBind) do local val = v[2] if (type(v[2]) == "table") then if (v[2]._snmp == '40') then val = v[2][1] .. '.' .. v[2][2] .. '.' .. v[2][3] .. '.' .. v[2][4] elseif (v[2]._snmp == '41') then val = v[2][1] elseif (v[2]._snmp == '42') then val = v[2][1] elseif (v[2]._snmp == '43') then val = v[2][1] elseif (v[2]._snmp == '44') then val = v[2][1] end end table.insert(result, {val, oid2str(v[1]), v[1]}) end return result end return {} end --- -- Fetches the first value from a SNMP response. -- @param response SNMP Response (will be decoded if necessary). -- @return First decoded value of the response. function fetchFirst(response) local result = fetchResponseValues(response) if type(result) == "table" and result[1] and result[1][1] then return result[1][1] else return nil end end --- Walks the MIB Tree -- -- @param socket socket already connected to the server -- @param base_oid string containing the base object ID to walk -- @return status true on success, false on failure -- @return table containing oid and value function snmpWalk( socket, base_oid ) local snmp_table = {} local oid = base_oid local status, err, payload while ( true ) do local value, response, snmpdata, options, item = nil, nil, nil, {}, {} options.reqId = 28428 -- unnecessary? payload = snmp.encode( snmp.buildPacket( snmp.buildGetNextRequest(options, oid) ) ) status, err = socket:send(payload) if ( not( status ) ) then stdnse.print_debug("snmp.snmpWalk: Send failed") return false, err end status, response = socket:receive_bytes(1) if ( not( status ) ) then -- Unless we don't have a usefull error message, don't report it if ( response ~= "ERROR" ) then stdnse.print_debug("snmp.snmpWalk: Received no answer (%s)", response) return false, response end return false, nil end snmpdata = snmp.fetchResponseValues( response ) value = snmpdata[1][1] oid = snmpdata[1][2] if not oid:match( base_oid ) or base_oid == oid then break end item.oid = oid item.value = value table.insert( snmp_table, item ) end snmp_table.baseoid = base_oid return true, snmp_table end