[erlang-patches] SNMP/VACM: bugfix for vacmViewTreeFamilyMask

Stefan Zegenhagen <>
Mon Jun 10 11:07:00 CEST 2013

Dear all,

it's almost a year since I sent the patch attached to this e-mail, and I
just found out that I have not yet gotten a response to it.

I would consider this patch important because it fixes an issue with the
interpretation of data that might be critical for SNMPv3 operation. I
confirmed at that time that erlangs interpretation of
vacmViewTreeFamilyMask is indeed not interoperable with other SNMP

Kind regards,

> > > the implementation of SNMP-VIEW-BASED-ACM.mib assumes that the input for
> > > vacmViewTreeFamilyMask is an OID consisting of 1's and 0's only to form
> > > the mask. However, the MIB states that the input should be a bitstring.
> > > 
> > > The OID representation of the mask is useful in the code as it speeds up
> > > time-critical code paths when checking access permissions for EACH SNMP
> > > access. Reading/writing the view mask objects is less time-critical.
> > > 
> > > Therefore, to fix the issue, convert between OID representation and
> > > bitstring when the vacmViewTreeFamilyMask objects are accessed. This is
> > > done by the patch attached to this e-mail.
> I'm very sorry for the troubles that I am causing but it seems that the
> previous version of the patch did more than it should: the OID-bitstring
> conversion was also applied to other tables in the same MIB on
> get/get-next requests.
> The version of the patch that is attached to this e-mail restricts the
> OID-bitstring conversion to vacmViewTreeFamilyMask alone.

Dr. Stefan Zegenhagen

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