SNMPv3: Remote snmptrap engineID not found

Question

I'm having trouble getting snmptrapd to accept remote SNMPv3 TRAP messages.

Here's my simple snmptrapd.conf:

root@snmptrapper:~# cat /tmp/testsnmptrapd.conf
createUser -e 0x80001f8880013da3af54da7882 skohrs MD5 PaSSWoRD DES
createUser -e 0x80001f888047483cc654cfeee8 skohrs MD5 PaSSWoRD DES
authUser log skohrs

When I start the service, I can see it creates both users. However, when the remote message comes in, it can't match the remote engineID:

root@snmptrapper:~# snmptrapd -f -C -c /tmp/testsnmptrapd.conf -Le -Dusm,usmUser,snmptrapd
registered debug token usm, 1
registered debug token usmUser, 1
registered debug token snmptrapd, 1
netsnmp_assert !"registration != duplicate" failed agent_registry.c:535 netsnmp_subtree_load()
netsnmp_assert !"registration != duplicate" failed agent_registry.c:535 netsnmp_subtree_load()
netsnmp_assert !"registration != duplicate" failed agent_registry.c:535 netsnmp_subtree_load()
usmUser: created a new user skohrs at 80 00 1F 88 80 01 3D A3 AF 54 DA 78 82
usmUser: created a new user skohrs at 80 00 1F 88 80 47 48 3C C6 54 CF EE E8
NET-SNMP version 5.4.1


usm: USM processing begun...
usm: match on user skohrs
usm: no match on engineID (80 00 1F 88 80 47 48 3C C6 54 CF EE E8 )
usm: match on user skohrs
usm: Verification succeeded.
usm: USM processing completed.
snmptrapd: input: a7
snmptrapd: Trap OID: DISMAN-EVENT-MIB::sysUpTimeInstance
snmptrapd: Running auth trap handlers
snmptrapd:auth: Comparing auth types: result=8, request=0, result=1
snmptrapd:auth: Calling VACM for checking phase 0:read
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 1:write
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 2:notify
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 3:log
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 4:execute
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 5:net
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 6:(null)
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 7:(null)
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Final bitmask auth: 0
snmptrapd:auth: Dropping unauthorized message

If I send an SNMPv3 TRAP from the localhost, the message is logged:

usm: USM processing begun...
usm: match on user skohrs
usm: Verification succeeded.
usm: USM processing completed.
snmptrapd: input: a7
snmptrapd: Trap OID: DISMAN-EVENT-MIB::sysUpTimeInstance
snmptrapd: Running auth trap handlers
snmptrapd:auth: Comparing auth types: result=0, request=0, result=1
snmptrapd:auth: Calling VACM for checking phase 0:read
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 1:write
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 2:notify
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 3:log
snmptrapd:auth:   result: authorized
snmptrapd:auth: Calling VACM for checking phase 4:execute
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 5:net
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 6:(null)
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Calling VACM for checking phase 7:(null)
snmptrapd:auth:   result: not authorized
snmptrapd:auth: Final bitmask auth: 8
snmptrapd: Running pre-global trap handlers
snmptrapd:auth: Comparing auth types: result=8, request=8, result=1
snmptrapd: print_handler
snmptrapd: v2/3 format
2015-02-11 09:40:51 localhost [UDP: [127.0.0.1]:48403]:
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (55) 0:00:00.55        SNMPv2-MIB::snmpTrapOID.0 = OID: DISMAN-EVENT-MIB::sysUpTimeInstance
snmptrapd: Running trap specific handlers
snmptrapd: get_traphandler default (0)
snmptrapd: Running global handlers
snmptrapd:auth: Comparing auth types: result=8, request=8, result=1
snmptrapd: notification_handler

Here is the snmptrap command I'm using, in case that's the problem:

root@client:~# snmptrap -v3 -a MD5 -A PaSSWoRD -x DES -X PaSSWoRD -u skohrs -mALL -l authPriv -Dusm snmptrapper 55 sysUpTime.0

The net-snmp Wiki and man pages aren't much help. I'm hoping someone here can offer some guidance.

score 1 · Answer 1 · answered Feb 12 '15 at 20:43

I discovered the problem by enabling all debug options for snmptrapd with -Dall:

root@snmptrapper:~# snmptrapd -f -C -c /root/testsnmptrapd.conf -Le -Dall

The issue turned out to be a bad context set in ~/.snmp/snmp.conf. I had created this file, early in the initial SNMPv3 setup.

root@client:~# cat ~/.snmp/snmp.conf
defContext none
defVersion 3
defSecurityName skohrs
defAuthType MD5
defAuthPassphrase PaSSWoRD
defPrivType DES
defPrivPassphrase PaSSWoRD
defSecurityLevel authPriv

I misunderstood that defContext none is not the same as setting the context to"". When I deleted that token, the remote SNMPv3 TRAP messages were logged correctly.

SNMPv3: Remote snmptrap engineID not found

1 Answers1