Using DTLS
SNMP over DTLS over UDP is supported in Net-SNMP 5.5 and beyond. This page describes what is necessary to configure the software to use it.
Generating X.509 Certificates
Configuring Servers
Configuring Certificates
The tokens for specifying which X.509 certificates are configured in the snmp.conf file. Note: NOT the snmpd.conf file. The tokens are specific to all applications and thus belong in the snmp.conf file (without the "d"). If you wish to put them in the snmpd.conf file you can do so by prefixing the lines with [snmp], as described in the snmp_config manual page.
Setting the Server's Certificate
The server needs to be configured with both it's private and public keys. To do this, use the following two snmp.conf tokens to configure the server:
defX509ServerPub /path/to/servercert.cert defX509ServerPriv /path/to/servercert.priv
Recognizing Client Certificates
Additionally, the client's incoming certificates need to be cryptographically checked and verified. To define the root CA certificates, or self-signed certificates, they all need to be put together in a single file containing a concatenated set of acceptable certificates:
defX509ClientCerts /path/to/for-users.cert
Setting up Access Control
SNMP over DTLS is a mode of SNMPv3, so access control settings are done using the standard VACM configuration tokens. The security model used should normally be TSM (further discussed below in the example usage section). Here are some example snmpd.conf configuration settings for incoming users with a X.509 CommonName field of "Wes Hardaker":
rwuser -s tsm "Wes Hardaker"
Opening and Listening on a Port for DTLS traffic
snmpd and snmptrapd can both be configured to accept and process connections sent over DTLS. This is done on the command line using the dtls: addressing specifier. E.G. this:
snmpd dtls:9161
tells snmpd to open port 9161 and listen for incoming SNMP over DTLS connections on it.
Configuring the Applications
Tools like snmpget, snmpwalk or anything that uses the core session structures within the main Net-Snmp library like the perl and python modules can make use of DTLS using the procedures described below.
Setting the Clients's Certificate
The client needs to be configured with both it's private and public keys. To do this, use the following two snmp.conf tokens to configure the client:
defX509ClientPub /path/to/user-cert.cert defX509ClientPriv /path/to/user-cert.priv
Recognizing Client Certificates
Additionally, the certificates for the servers that the client should connect to need to be cryptographically checked and verified. To define the server's root CA certificates, or self-signed certificates, they all need to be put together in a single file containing a concatenated set of acceptable certificates:
defX509ServerCerts /path/to/servers.cert
