[erlang-questions] SNMP v3 usmStatsNotInTimeWindows error

Devangana Tarafdar <>
Mon Sep 19 15:46:28 CEST 2016


Sorry about the late reply Daniel, I missed the email.

Yes the engine id was correct in the wireshark trace.   That was the first
thing I had to correct. I had to convert the engine id string to an
explicit list of decimals for the id.

On Sep 15, 2016 10:52 AM, "Daniel Goertzen" <>
wrote:

> Check that the engine ids are what you expect them to be.  You've redacted
> all the engine ids from the trace, so I can't check them.
>
> The SNMP config files have trouble storing non-ascii engine ids; not sure
> if this affect you.  This should be fixed agent-side for 19.1, not sure
> about manager-side.
>
> On Wed, Sep 14, 2016 at 1:42 PM Devangana Tarafdar <>
> wrote:
>
>> Hi Dominik,
>>
>> So I was able look at the wireshark stream decoded after entering snmp
>> credentials  (that was very helpful, thanks !) and compared the 2 streams :
>> One from the snmp get tool and the other from the erlang script.
>>
>> Wireshark is not able to decode the encrypted pdu  in the erlang stream
>> but it can decode the snmpget stream.
>>
>> The message is clear enough I suppose but I don't know what I am doing
>> wrong with the key.
>>
>> I changed my local key generation to :
>>
>>  %Priv_key_local = snmp:passwd2localized_key(sha, Priv_key ,
>> Agent_engine_id),
>>
>>  % since auth protocol is SHA
>>   Priv_key_local = lists:sublist(snmp:passwd2localized_key(sha, Priv_key
>> , Agent_engine_id),16),
>>
>> but it did not help.
>>
>>
>> msgData: encryptedPDU (1)
>>         encryptedPDU: 8a3e7fc633c531d2747782a6fc8d89187c452929426e4b6e...
>>             Decrypted data not formatted as expected, wrong key?
>>                 [Expert Info (Warn/Malformed): Decrypted data not
>> formatted as expected]
>>                     [Message: Decrypted data not formatted as expected]
>>                     [Severity level: Warn]
>>                     [Group: Malformed]
>>
>>
>> Attaching  good wireshark trace from snmpget and a bad one from erlang.
>>
>> Also tried putting a context name but did not work but snmpget does not
>> put one and it works.
>>
>> Thanks,
>> Devangana
>>
>>
>>
>> On Sun, Sep 11, 2016 at 4:09 PM, Devangana Tarafdar <>
>> wrote:
>>
>>> Hi Dominik,
>>>
>>> I have not looked into the context. Will check all the items that you
>>> mention.  I have been able to connect to the agent using snmpwalk and
>>> snmpget though I have not studied the wireshark output of those in detail.
>>> Thanks again for all these tips and I will get back to you .
>>>
>>> Devangana
>>>
>>> On Sep 11, 2016 3:08 PM, "Dominik Pawlak" <>
>>> wrote:
>>>
>>>> Hello Devangana,
>>>> Hard to tell, but I see that you haven't specified any context in your
>>>> sync_get. Are you sure it is not needed? I would also double check the
>>>> engine id and security configuration.
>>>> Have you managed to connect to that agent from something other than OTP
>>>> (say snmpb, snmpget)?
>>>> If so, you can compare in Wireshark, the snmp requests from erlang and
>>>> from that tool. You can even enter your snmp credentials in Wireshark and
>>>> it will decode encrypted messages.
>>>> I hope any of this helps.
>>>>
>>>> Best
>>>> Dominik
>>>>
>>>> On 11.09.2016 16:46, Devangana Tarafdar wrote:
>>>>
>>>> Hello Dominik,
>>>>
>>>> Thanks you for the reply.
>>>>
>>>> I  sent another sync_get after the first as you suggested. The
>>>> wireshark trace shows the manager has updated the 'msgAuthoritativeEngineBoots'
>>>> and 'msgAuthoritativeEngineTime' to the values sent by the Agent as you
>>>> pointed out. But now the agent does not respond at all and the sync_get
>>>> fails with a timeout. I tried adding a second's sleep between the 2 gets as
>>>> well. I don't have access currently to the agent's logs or configuration
>>>> but have you seen this before ?
>>>>
>>>> Thanks !
>>>> Devangana
>>>>
>>>>
>>>> On Sat, Sep 10, 2016 at 6:09 PM, Dominik Pawlak <
>>>> > wrote:
>>>>
>>>>> Hello Devangana,
>>>>> Basically, you just have to perform the sync_get once more. I observed
>>>>> similar behavior in OTP 17.1 (snmp 4.25.1). The first request will always
>>>>> fail because the manager is not fully configured to communicate with the
>>>>> agent (more on that below).
>>>>>
>>>>> A longer explanation:
>>>>>
>>>>> In snmp v3 there is a process called 'discovery', which should be
>>>>> performed before secure communication with the agent can be established. It
>>>>> is described here:
>>>>>
>>>>> https://tools.ietf.org/html/rfc3414#section-4
>>>>>
>>>>> The snmp library in OTP does not implement that process (at least not
>>>>> as described in the RFC).
>>>>> This process has two steps: 'snmpEngineID discovery' and 'time
>>>>> synchronization'.
>>>>> The first step is skipped altogether in OTP - you have to provide
>>>>> engine id upfront.
>>>>> The second step is performed by the first request - it will always
>>>>> fail with the 'usmStatsNotInTimeWindows' error report message, but it will
>>>>> set the required 'msgAuthoritativeEngineBoots' and
>>>>> 'msgAuthoritativeEngineTime' in the manager.
>>>>>
>>>>> Best,
>>>>> Dominik
>>>>>
>>>>>
>>>>> On 10.09.2016 06:48, Devangana Tarafdar wrote:
>>>>>
>>>>> Hello,
>>>>>
>>>>> I am trying to connect to a third party SNMP agent, using snmp manager
>>>>> (snmp v3) ( in the erlang 19 release snmp 5.2.3) and I am running into a
>>>>> problem where the agent is returning this error on the manager calling
>>>>> sync_get:
>>>>>
>>>>>
>>>>> *** [2016:09:08 21:26:00 830] SNMP M-SERVER TRACE ***
>>>>>    handle_snmp_report -> entry with
>>>>>    Domain:  snmpUDPDomain
>>>>>    Addr:    {{xx,xxx,xxx,xxx},161}
>>>>>    ReqId:   37078226
>>>>>    Rep:     {invalid_sec_info,[{sec_level,3,1},
>>>>>                                {request_id,37078226,2147483647}]}
>>>>>    Pdu:     {pdu,report,2147483647,noError,0,
>>>>>                  [{varbind,[1,3,6,1,6,3,15,1,
>>>>> 1,2,0],'Counter32',33,1}]}
>>>>> *** [2016:09:08 21:26:00 830] SNMP M-SERVER DEBUG ***
>>>>>    handle_snmp_report -> found corresponding request:
>>>>>    reply to sync request
>>>>>    Ref:    #Ref<0.0.4.210>
>>>>>    ModRef: #Ref<0.0.4.211>
>>>>>    From:   {<0.3.0>,#Ref<0.0.4.202>}
>>>>> *** [2016:09:08 21:26:00 830] SNMP M-SERVER TRACE ***
>>>>>    handle_snmp_pdu(get-response) -> Remaining: 4979
>>>>> *** [2016:09:08 21:26:00 830] SNMP M-SERVER TRACE ***
>>>>>    handle_snmp_report -> deliver reply
>>>>>
>>>>> {error,{invalid_sec_info,[{sec_level,3,1},{request_id,37078226,
>>>>> 2147483647}],{noError,0,[{varbind,[1,3,6,1,
>>>>> 6,3,15,1,1,2,0],'Counter32',33,1}]}}}
>>>>>
>>>>> *** [2016:09:08 21:26:00 831]
>>>>>
>>>>> Where [1,3,6,1,6,3,15,1,1,2,0]  maps to "usmStatsNotInTimeWindows"
>>>>> (from http://www.oid-info.com/)
>>>>>
>>>>> I have attached a  wireshark trace for the snmp part of this exchange.
>>>>>
>>>>> I am invoking the snmpm module functions through a basic script as
>>>>> follows (using tips from the tutorial at
>>>>> https://erlangcentral.org/wiki/index.php?title=SNMP_Quick_Start )
>>>>> .........
>>>>> ..........
>>>>>
>>>>>   ok = application:start(crypto),
>>>>>   ok = application:start(snmp),
>>>>>
>>>>>   Userid = "snmp3user",
>>>>>   Agent_target = "testagent",
>>>>>   Agent_engine_id = [128,0,0,8,2,0,0,26,84,40,108,176],
>>>>>   Agent_ip = {xx,xxx,xxx,xxx},
>>>>>   Agent_port = 161 ,
>>>>>   Secure_name= Userid,
>>>>>
>>>>>   Security_level = 'authPriv',
>>>>>   Security_model = 'usm',
>>>>>   Agent_version = 'v3',
>>>>>   Auth_protocol = 'usmHMACSHAAuthProtocol',
>>>>>   Priv_protocol = 'usmAesCfb128Protocol',
>>>>>
>>>>>   % this is 16 in length
>>>>>   Priv_key_local = snmp:passwd2localized_key(md5, Priv_key , Agent_engine_id),
>>>>>
>>>>>   % this is 20 in length
>>>>>   Auth_key_local = snmp:passwd2localized_key(sha, Auth_key , Agent_engine_id),
>>>>>
>>>>>   ok = snmpm:register_user(Userid,snmpm_user_default,[]),
>>>>>
>>>>>   ok = snmpm:register_usm_user(Agent_engine_id, Userid, [
>>>>>                               {auth, Auth_protocol},
>>>>>                               {auth_key,Auth_key_local},
>>>>>                               {priv, Priv_protocol},
>>>>>                               {priv_key,Priv_key_local },
>>>>>                               {sec_name, Secure_name}
>>>>>                         ]),
>>>>>   ok = snmpm:register_agent(Userid, Agent_target ,[
>>>>>                                                    {engine_id,Agent_engine_id},
>>>>>                                                    {address, Agent_ip},
>>>>>                                                    {port, Agent_port},
>>>>>                                                    {version,Agent_version},
>>>>>                                                    {sec_model,Security_model},
>>>>>                                                    {sec_name,Secure_name},
>>>>>                                                    {sec_level, Security_level}
>>>>>
>>>>>                                ]),
>>>>>   Res0 = snmpm:sync_get(Userid, Agent_target, [[1,3,6,1,4,1,9,10,19,1,1,9,1,3,7,2]]),   ........................
>>>>>
>>>>>   ........................
>>>>>
>>>>> Can anyone please tell me what I am doing wrong here ? Any tips would be appreciated !
>>>>>
>>>>> Thanks, Devangana
>>>>>
>>>>> _______________________________________________
>>>>> erlang-questions mailing ://erlang.org/mailman/listinfo/erlang-questions
>>>>>
>>>>>
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>> 
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>>
>
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