"""
Multiple SNMP USM users
+++++++++++++++++++++++

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with
the following options:

* SNMPv3
* with USM user:
    - 'usr-md5-des', auth: MD5, priv DES or
    - 'usr-sha-none', auth: SHA, no privacy
    - 'usr-sha-aes128', auth: SHA, priv AES
* allow access to SNMPv2-MIB objects (1.3.6.1.2.1)
* over IPv4/UDP, listening at 127.0.0.1:161
* using asyncio network transport (available since Python 3.4)

Either of the following Net-SNMP commands will walk this Agent:

| $ snmpwalk -v3 -u usr-md5-des -l authPriv -A authkey1 -X privkey1 localhost .1.3.6
| $ snmpwalk -v3 -u usr-sha-none -l authNoPriv -a SHA -A authkey1 localhost .1.3.6
| $ snmpwalk -v3 -u usr-sha-aes128 -l authPriv -a SHA -A authkey1 -x AES -X privkey1 localhost .1.3.6

Requires Python 3.4 and later!

"""  #

import asyncio

from pysnmp.carrier.asyncio.dgram import udp
from pysnmp.entity import config, engine
from pysnmp.entity.rfc3413 import cmdrsp, context

# Create a new event loop
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

# Create SNMP engine with autogenernated engineID and pre-bound
# to socket transport dispatcher
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine, udp.domainName, udp.UdpTransport().openServerMode(("127.0.0.1", 161))
)

# SNMPv3/USM setup

# user: usr-md5-des, auth: MD5, priv DES
config.addV3User(
    snmpEngine,
    "usr-md5-des",
    config.usmHMACMD5AuthProtocol,
    "authkey1",
    config.usmDESPrivProtocol,
    "privkey1",
)
# user: usr-sha-none, auth: SHA, priv NONE
config.addV3User(snmpEngine, "usr-sha-none", config.usmHMACSHAAuthProtocol, "authkey1")
# user: usr-sha-none, auth: SHA, priv AES
config.addV3User(
    snmpEngine,
    "usr-sha-aes128",
    config.usmHMACSHAAuthProtocol,
    "authkey1",
    config.usmAesCfb128Protocol,
    "privkey1",
)

# Allow full MIB access for each user at VACM
config.addVacmUser(
    snmpEngine, 3, "usr-md5-des", "authPriv", (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1)
)
config.addVacmUser(
    snmpEngine, 3, "usr-sha-none", "authNoPriv", (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1)
)
config.addVacmUser(
    snmpEngine, 3, "usr-sha-aes128", "authPriv", (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1)
)

# Get default SNMP context this SNMP engine serves
snmpContext = context.SnmpContext(snmpEngine)

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

# Run asyncio main loop
loop.run_forever()