config_asymmetric_key: process aborts on assert() when diff references a removed keystore entry

[awesomenode]

Hi!

When trying to remove certs from the server, libnetconf2 assertion killed the process. The RPC:

<ks:keystore>
  <ks:asymmetric-keys>
    <ks:asymmetric-key nc:operation="remove">
      <ks:name>server_key</ks:name>
    </ks:asymmetric-key>
  </ks:asymmetric-keys>
</ks:keystore>
<ts:truststore>
  <ts:certificate-bags nc:operation="remove">
    <ts:certificate-bag>
      <ts:name>ca_cert</ts:name>
    </ts:certificate-bag>
  </ts:certificate-bags>
</ts:truststore>
<ncs:netconf-server>
  <ncs:listen>
    <ncs:endpoints>
      <ncs:endpoint nc:operation="remove">
        <ncs:name>main_tls</ncs:name>
      </ncs:endpoint>
    </ncs:endpoints>
  </ncs:listen>
</ncs:netconf-server>

Apparently, it was because in config_asymmetric_key the assertion fails when a diff walks an asymmetric-key list entry (as a parent traversal with operation="none" or "delete") that is no longer present in the internal keystore->entries array.

I've attached a simple reproduction code that kind of simulates what is happening.

It seems that internally, libnetconf2's diff walker visits the asymmetric-key as a parent traversal after it's already removed from keystore->entries, and the assertion kills the server.

Maybe it'd be better if config_asymmetric_key would not assert() in this case and on "entry not found" during NC_OP_DELETE / NC_OP_NONE, it would return a error (or no-op for NC_OP_NONE) instead?

I'm using libnetconf2 version 4.2.14.

Thanks!

libnetconf2_bug_repro.zip