Pass persist bug

[majorostamas]

Hello,
I experienced the following issue. When I send this command:

snmpset -t 5 -v 3 -m NTCIP1218-v01 -l authPriv -u snmpPrivateTestUser -a SHA1 -A passWord2024Priv -x AES128 -X passWord2024Priv udp:192.168.11.97:161 rsuXmitMsgFwdingPsid.1 x 0020 rsuXmitMsgFwdingDestIpAddr.1 s "192.168.9.178" rsuXmitMsgFwdingDestPort.1 i 60001 rsuXmitMsgFwdingProtocol.1 i 2 rsuXmitMsgFwdingDeliveryStart.1 x 07E5031916010000 rsuXmitMsgFwdingDeliveryStop.1 x 07EE031916010000 rsuXmitMsgFwdingSecure.1 i 0 rsuXmitMsgFwdingStatus.1 i 4

Everything works fine, the following lines are received by my pass persist script:
set
.1.3.6.1.4.1.1206.4.2.18.20.2.1.2.1
octet "00 20"

But when I use 20 instead of 0020:

snmpset -t 5 -v 3 -m NTCIP1218-v01 -l authPriv -u snmpPrivateTestUser -a SHA1 -A passWord2024Priv -x AES128 -X passWord2024Priv udp:192.168.11.97:161 rsuXmitMsgFwdingPsid.1 x 20 rsuXmitMsgFwdingDestIpAddr.1 s "192.168.9.178" rsuXmitMsgFwdingDestPort.1 i 60001 rsuXmitMsgFwdingProtocol.1 i 2 rsuXmitMsgFwdingDeliveryStart.1 x 07E5031916010000 rsuXmitMsgFwdingDeliveryStop.1 x 07EE031916010000 rsuXmitMsgFwdingSecure.1 i 0 rsuXmitMsgFwdingStatus.1 i 4

Something goes wrong, the following lines are received by my pass persist script.
set
.1.3.6.1.4.1.1206.4.2.18.20.2.1.2.1
string " "

The root cause is that 20 is considered hexadecimal and it is converted to ASCII by net-snmp. ASCII 32 is the space character.

[fenner]

The pass infrastructure does not read the MIB to know the types of objects; it just passes along what was received on the wire. As you identified, there's ambiguity when the underlying type is an OCTET STRING, and so, net-snmp applies a heuristic: if the input is composed of all printable characters, then it uses string, otherwise it uses octet, to pass the data to the subprocess.

A pass-persist script should be prepared to receive either representation.