(PUP-2995) Proposal for processing an external OID mapping file for

resolving custom trusted OIDs

This patch is a proposal that allows custom OIDs used in trusted facts to be resolved into user-friendly names that can be used in puppet manifests.

For instance a mapping file such as

```
---
oid_mapping:
  - ['1.3.6.1.4.1.34380.1.2.1.1', 'shortname', 'Long name']
  - ['1.3.6.1.4.1.34380.1.2.1.2', 'othershortname', 'Other Long name']
```

could be used to obtain `$trusted[extensions][shortname]`.

Before deciding to submit this proposal, we had written a custom puppet
function that does quite the same (`$mapped_trusted =
oid_to_name($trusted, '/etc/puppet/trusted_oid_mapping.yaml')`) but we
realize that other sites could need this feature.

_Note_: I couldn't achieve to add a configuration option for this as the
`puppet/ssl/oids` library seems to be loaded very early and I don't have
more time to dig deeper.

lib/puppet/ssl/oids.rb

@@ -25,6 +25,8 @@
 # @api private
 module Puppet::SSL::Oids
 
+  EXTERNAL_OID_DEFINITION_FILE = '/etc/puppet/ssl_trusted_oid_mapping.yaml'
+
   PUPPET_OIDS = [
     ["1.3.6.1.4.1.34380", 'puppetlabs', 'Puppet Labs'],
     ["1.3.6.1.4.1.34380.1", 'ppCertExt', 'Puppet Certificate Extension'],
@@ -43,6 +45,18 @@ module Puppet::SSL::Oids
     OpenSSL::ASN1::ObjectId.register(*oid_defn)
   end
 
+  # Process external oid definition file if present
+  if File.exists?(EXTERNAL_OID_DEFINITION_FILE)
+    begin
+      mapping = YAML.load_file(EXTERNAL_OID_DEFINITION_FILE)['oid_mapping']
+      mapping.each do |oid_defn|
+        OpenSSL::ASN1::ObjectId.register(*oid_defn)
+      end
+    rescue
+      # Do nothing
+    end
+  end
+
   # Determine if the first OID contains the second OID
   #
   # @param first [String] The containing OID, in dotted form or as the short name