List of known `Mdm::Cred#ptypes` in the values in this hash https://github.com/rapid7/metasploit_data_models/blob/master/app/models/mdm/cred.rb#L6:

```ruby
PTYPES = {
      'read/write password' => 'password_rw',
      'read-only password' => 'password_ro',
      'SMB hash' => 'smb_hash',
      'SSH private key' => 'ssh_key',
      'SSH public key' => 'ssh_pubkey'
  }
```