gistfile1.txt

ssh_keypair { '/tmp/foo':
  ensure   => present,
  key_type => 'dsa',
}

# /etc/puppet/modules/<module_name>lib/puppet/type/ssh_keypair.rb

Puppet::Type.newtype(:ssh_keypair) do

  newparam(:name, :namevar => true) do
    validate do |x|
      unless x =~ /^\//
        fail("Invalid filename #{x}, must be absolute path")
      end
    end
  end

  ensurable

  newproperty(:key_type) do
    newvalues('rsa', 'dsa')
  end

#  validate do

#  end
end

# /etc/puppet/modules/<module_name>lib/puppet/provider/ssh_keypair/default.rb

Puppet::Type.type(:ssh_keypair).provide(
  :default,
) do

  def create
    File.open(resource[:name], 'w') do |fh|
      fh.puts(resource[:key_type])
    end
  end

  # def destroy

  # def exists?

  def exists?
    File.exists?(resource[:name])
  end

  def key_type
    File.read(resource[:name])
  end

  def key_type=(value)
    File.open(resource[:name], 'w') do |fh|
      fh.write(resource[:key_type])
    end
  end

end