MAAS IPMI k_g validation error

[Andy Wu]

Configure k_g value of at MAAS->security->IPMI->k_g may results in error ""Ensure this value has at most 20 characters (it has 40)"

This can occur if the input k_g value is 40 bytes long and in hex-encoded format , as it is quite common settings in Dell idrac. The hex value needs to be converted to ascii before compare to the length which is 20 byte maxmium.

See impi implemetaion here : https://github.com/ipmitool/ipmitool/blob/be11d948f89b10be094e28d8a0a5e8fb532c7b60/lib/ipmi_main.c#L515

the code for ipmi_parse_hex is here:
https://github.com/ipmitool/ipmitool/blob/be11d948f89b10be094e28d8a0a5e8fb532c7b60/lib/helper.c#L158

The erorr "Ensure this value has at most 20 characters (it has 40)" is probably caused by MAAS skipping the hex conversion process.

If I configure the k_g under machine -> configuration -> power settings, the same long hex value is taken, but in order to make the power check work, the input value needs to be prefixed with '0x', for example, if k_g value in idrac is 1234, the k_g value in MAAS should be 0x1234

MAAS version 3.4/stable

[Jerzy Husakowski (jhusakowski)]

MAAS explicitly checks if the passed k_g sting is 20 characters here: https://git.launchpad.net/maas/tree/src/maasserver/forms/settings.py#n931

Since the ipmitool allows hex-encoded input which will be longer than 20 characters and still resolve to 20 bytes, this validation needs to be fixed (either removed or made equivalent to what the ipmitool does).