gosnmp

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// Copyright 2023 The GoSNMP Authors. All rights reserved.  Use of this
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// source code is governed by a BSD-style license that can be found in the
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// LICENSE file.
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/*
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The developer of the trapserver code (https://github.com/jda) says "I'm working
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on the best level of abstraction but I'm able to receive traps from a Cisco
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switch and Net-SNMP".
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Pull requests welcome.
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*/
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package main
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import (
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	"flag"
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	"fmt"
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	"log"
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	"net"
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	"os"
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	"path/filepath"
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	g "github.com/gosnmp/gosnmp"
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)
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var secParamsList = []*g.UsmSecurityParameters{
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	{
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		UserName:                 "myuser",
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		AuthenticationProtocol:   g.MD5,
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		AuthenticationPassphrase: "mypassword",
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		PrivacyProtocol:          g.AES,
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		PrivacyPassphrase:        "myprivacy",
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	},
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	{
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		UserName:                 "myuser2",
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		AuthenticationProtocol:   g.SHA,
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		AuthenticationPassphrase: "mypassword2",
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		PrivacyProtocol:          g.DES,
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		PrivacyPassphrase:        "myprivacy2",
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	},
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	{
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		UserName:                 "myuser2",
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		AuthenticationProtocol:   g.MD5,
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		AuthenticationPassphrase: "mypassword2",
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		PrivacyProtocol:          g.AES,
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		PrivacyPassphrase:        "myprivacy2",
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	},
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}
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func main() {
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	flag.Usage = func() {
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		fmt.Printf("Usage:\n")
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		fmt.Printf("   %s\n", filepath.Base(os.Args[0]))
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		flag.PrintDefaults()
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	}
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	tl := g.NewTrapListener()
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	tl.OnNewTrap = myTrapHandler
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	usmTable := g.NewSnmpV3SecurityParametersTable(g.NewLogger(log.New(os.Stdout, "", 0)))
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	for _, sp := range secParamsList {
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		err := usmTable.Add(sp.UserName, sp)
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		if err != nil {
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			usmTable.Logger.Print(err)
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		}
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	}
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	gs := &g.GoSNMP{
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		Port:                        161,
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		Transport:                   "udp",
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		Version:                     g.Version3, // Always using version3 for traps, only option that works with all SNMP versions simultaneously
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		SecurityModel:               g.UserSecurityModel,
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		SecurityParameters:          &g.UsmSecurityParameters{AuthoritativeEngineID: "12345"}, // Use for server's engine ID
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		TrapSecurityParametersTable: usmTable,
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	}
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	tl.Params = gs
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	tl.Params.Logger = g.NewLogger(log.New(os.Stdout, "", 0))
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	err := tl.Listen("0.0.0.0:9162")
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	if err != nil {
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		log.Panicf("error in listen: %s", err)
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	}
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}
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func myTrapHandler(packet *g.SnmpPacket, addr *net.UDPAddr) {
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	log.Printf("got trapdata from %s\n", addr.IP)
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	for _, v := range packet.Variables {
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		switch v.Type {
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		case g.OctetString:
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			b := v.Value.([]byte)
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			fmt.Printf("OID: %s, string: %x\n", v.Name, b)
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		default:
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			log.Printf("trap: %+v\n", v)
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		}
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	}
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}
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