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"""
Discover SNMPv3 SecurityEngineId
++++++++++++++++++++++++++++++++
Send SNMP GET request using the following scenario and options:
* try to communicate with a SNMPv3 Engine using:
* a non-existing user
* over IPv4/UDP
* to an Agent at demo.snmplabs.com:161
* if remote SNMP Engine ID is discovered, send SNMP GET request:
* with SNMPv3, user 'usr-md5-none', MD5 authentication, no privacy
at discovered securityEngineId
* to the same SNMP Engine ID
* for an OID in text form
"""#
from pysnmp.entity.rfc3413.oneliner.cmdgen import *
snmpEngine = SnmpEngine()
transportTarget = UdpTransportTarget(('demo.snmplabs.com', 161))
#
# To discover remote SNMP EngineID we will tap on SNMP engine inner workings
# by setting up execution point observer setup on INTERNAL class PDU processing
#
observerContext = {}
# Register a callback to be invoked at specified execution point of
# SNMP Engine and passed local variables at execution point's local scope
snmpEngine.observer.registerObserver(
lambda e,p,v,c: c.update(securityEngineId=v['securityEngineId']),
'rfc3412.prepareDataElements:internal',
cbCtx=observerContext
)
# Send probe SNMP request with invalid credentials
authData = UsmUserData('non-existing-user')
errorIndication, errorStatus, errorIndex, varBinds = next(
getCmd(snmpEngine, authData, transportTarget, ContextData(),
ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0)))
)
# See if our SNMP engine received REPORT PDU containing securityEngineId
if 'securityEngineId' not in observerContext:
print("Can't discover peer EngineID, errorIndication: %s" % errorIndication)
raise Exception()
securityEngineId = observerContext.pop('securityEngineId')
print('Remote securityEngineId = %s' % securityEngineId.prettyPrint())
#
# Query remote SNMP Engine using usmUserTable entry configured for it
#
authData = UsmUserData('usr-md5-none', 'authkey1',
securityEngineId=securityEngineId)
errorIndication, errorStatus, errorIndex, varBinds = next(
getCmd(snmpEngine,
authData,
transportTarget,
ContextData(),
ObjectType(ObjectIdentity('1.3.6.1.2.1.1.1.0')))
)
if errorIndication:
print(errorIndication)
elif errorStatus:
print('%s at %s' % (
errorStatus.prettyPrint(),
errorIndex and varBinds[int(errorIndex)-1][0] or '?'
)
)
else:
for name, val in varBinds:
print('%s = %s' % (name.prettyPrint(), val.prettyPrint()))
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