service_matcher-go/snmp/v2/snmpv2.go

package v2

import (
	"encoding/asn1"
	"math/rand"

	osm "git.loafle.net/overflow/service_matcher-go"
)

type snmpv2 struct {
	Version   int
	Community []byte
	Data      struct {
		RequestID   int32
		ErrorStatus int
		ErrorIndex  int
		Bindings    []binding
	} `asn1:"tag:0"`
}

type response struct {
	ID          int32
	ErrorStatus int
	ErrorIndex  int
	Bindings    []binding
}

type binding struct {
	Name  asn1.ObjectIdentifier
	Value asn1.RawValue
}

var (
	null           = asn1.RawValue{Class: 0, Tag: 5}
	noSuchObject   = asn1.RawValue{Class: 2, Tag: 0}
	noSuchInstance = asn1.RawValue{Class: 2, Tag: 1}
	endOfMibView   = asn1.RawValue{Class: 2, Tag: 2}
)

type SNMPMatcher struct {
	osm.Matchers

	requestID int32
}

func (s *SNMPMatcher) Key() string {
	return "SNMP"
}

func (s *SNMPMatcher) Name(matchCtx *osm.MatchCtx) string {
	return "SNMP"
}

func (s *SNMPMatcher) IsPrePacket(matchCtx *osm.MatchCtx) bool {
	return false
}

func (s *SNMPMatcher) HasResponse(matchCtx *osm.MatchCtx, index int) bool {
	return true
}

func (s *SNMPMatcher) Match(matchCtx *osm.MatchCtx, index int, packet *osm.Packet) error {

	if packet == nil || !packet.Valid() {
		return osm.NoPacketReceivedError()
	}

	var p struct {
		Version   int
		Community []byte
		Data      struct {
			RequestID   int32
			ErrorStatus int
			ErrorIndex  int
			Bindings    []binding
		} `asn1:"tag:2"`
	}

	if _, err := asn1.Unmarshal(packet.Buffer, &p); err != nil {
		return err
	}

	resp := &response{p.Data.RequestID, p.Data.ErrorStatus, p.Data.ErrorIndex, p.Data.Bindings}

	if s.requestID != resp.ID {
		return osm.NotMatchedError()
	}

	if len(resp.Bindings) == 0 {
		return osm.NotMatchedError()
	}

	for _, binding := range resp.Bindings {
		if len(binding.Value.Bytes) <= 0 {
			continue
		}
		// if binding.Name.String() == "1.3.6.1.2.1.1.5.0" {
		matchCtx.SetAttribute(binding.Name.String(), string(binding.Value.Bytes))
		// }

	}

	return nil

}

func (s *SNMPMatcher) IsSend(port int) bool {
	if 161 == port {
		return true
	}
	return false
}

func NewMatcher() osm.UDPMatcher {

	m := &SNMPMatcher{}
	m.requestID = rand.Int31()

	p := snmpv2{}
	p.Version = 0
	p.Community = []byte("test1252serc")
	p.Data.RequestID = m.requestID
	p.Data.Bindings = []binding{
		binding{
			Name:  []int{1, 3, 6, 1, 2, 1, 1, 5, 0},
			Value: null,
		},
		binding{
			Name:  []int{1, 3, 6, 1, 2, 1, 1, 1, 0},
			Value: null,
		},
	}
	buf, _ := asn1.Marshal(p)

	m.AddPacket(osm.NewPacket(buf, len(buf)))

	return m
}