README

SNMP packet parser and renderer (encoder/decoder).

Implemented Standards and vendor-specific extensions

There are quite some RFCs and Drafts involved, I'm trying to give some overview.

SNMPv1

While being very old, SNMPv1 is still relevant, and therefore supported.

A Simple Network Management Protocol (SNMP)

SNMPv1, the initial implementation of the SNMP protocol, has been defined in the 1980s. However, it is still relevant, and therefore supported:

SNMPv2c

TODO

SNMPv3

We implemented and tested all official and (well-known) vendor-specific authentication and privacy (encryption) methods.

Authentication Methods

The User-based Security Model (USM) hast been implemented according to RFC 3414 (User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)). All authentication mechanisms from that RFC and from RFC7860 (HMAC-SHA-2 Authentication Protocols in User-Based Security Model (USM) for SNMPv3) have been implemented.

MD5: required in RFC 3414
SHA (SHA1): optional in RFC 3414
SHA-224: optional in RFC 7860 with 128bit HMAC
SHA-256: required in RFC 7860 with 192bit HMAC
SHA-384: optional in RFC 7860 with 256bit HMAC
SHA-512: suggested in RFC 7860 with 384bit HMAC

Privacy / Encryption Methods

DES: in CBC mode, defined in RFC 3414
3-DES: Triple-DES EDE in "Outside" CBC mode, mostly used by Cisco, defined in draft-reeder-snmpv3-usm-3desede-00
AES-128: in CFB mode, required in RFC 3826 with "Blumenthal" Key localization
AES-192: in CFB mode, as of draft-blumenthal-aes-usm-04 with "Blumenthal" Key localization
AES-192: in CFB mode, "Cisco variant", therefore named AES-192-C, as of draft-reeder-snmpv3-usm-3desede-00 with "Reeder" Key localization
AES-256: in CFB mode, as of draft-blumenthal-aes-usm-04 with "Blumenthal" Key localization
AES-256: in CFB mode, "Cisco variant", therefore named AES-256-C, as of draft-reeder-snmpv3-usm-3desede-00 with "Reeder" Key localization

Crypto implementation

We're using system-provided MD5/SHA hashing methods, and encryption as provided by OpenSSL. Everything related to (pre-IV), Key generation and Salt exchange have been implemented from scratch.

SNMPv3 standardization history

January 1998 two sets of related RFCs have been published in parallel:

RFC 2261–2270 (SNMPv3 "Standard")
RFC 2271–2275 (SNMPv3 "Experimental")

The reason for this have been two irreconcilable factions in the IETF by the end of 1997:

SNMPv3 Working Group (RFC 2261–2270): official approach, based on SNMPv2u (User-based Security). Main goal: faster standardization with minimal changes to SNMPv2
Secure SNMPv3 Ad-Hoc Group (RFC 2271–2275): alternative approach, USM (User-based Security Model), focussed on higher security. This "rebel" draft has been pushed by Cisco, IBM and others, who considered the official draft too weak.

The "experimental" party eventually won, the official "Standard" suffered a silent death, has never been widely adopted, and has only historic relevance es of today. In 1999 the experimental RFCs have been updated (RFC 2571–2575), became a Draft Standard, and replaced all the former RFCs from both parties. Finally, in Dezember 2002, RFC 3410-3418 became an Internet Standard.

Other related RFCs