ASN.1 definitions for basic SNMP exchanges

Question

What online resource is the authority for the complete set of ASN.1 definitions for the SNMP data structures used to request and respond with information? I am interested in versions 2c and version 3.

In RFC 3416 Section 3, I have found most of the definitions needed to use version 2c. However, the document has no mention of something that I have found on other resources referred to as the "snmpv2 message". For example, this shows up in the SNMP Programmers Reference Wiki and in the blog post Simple? Network Management Protocol. It's the data structure that contains the community string, so it's role is essential, but I cannot find where the authoritative source (probably an RFC) with an ASN.1 definition.

Similarly, I cannot find any authoritative ASN.1 definitions of SNMPv3 data structures. I found an ASN file in a github repo's test suite, but I cannot find where this information was taken from.

I would appreciate any help locating these. I'm usually a pretty good Googler, but my usual strategies are not turning anything up beyond what I've already linked to.

Answer 1

You might want to dig ASN.1 documents out of SNMP RFCs:

• Base data types, RFC2578
• SNMP v2c message, RFC3416
• SNMP v3 message, RFC3412
• SNMP v3 USM, RFC3414

Answer 2

SNMP v3 message format is defined in RFC3412 page 19 as section 6 as ASN.1.

SNMP v2c reuses most of v1 message format, except defining new message body (PDU). I think that's why in RFC 3416 you don't see all details, because it only mentions the new PDU definitions for simplicity.