core: Vagrant::Util::Keypair for generating keypairs

lib/vagrant/util/keypair.rb

@@ -0,0 +1,46 @@
+require "base64"
+require "openssl"
+
+module Vagrant
+  module Util
+    class Keypair
+      # Creates an SSH keypair and returns it.
+      #
+      # @param [String] password Password for the key, or nil for no password.
+      # @return [Array<String, String, String>] PEM-encoded public and private key,
+      #   respectively. The final element is the OpenSSH encoded public
+      #   key.
+      def self.create(password=nil)
+        rsa_key     = OpenSSL::PKey::RSA.new(2048)
+        public_key  = rsa_key.public_key
+        private_key = rsa_key.to_pem
+
+        if password
+          cipher      = OpenSSL::Cipher::Cipher.new('des3')
+          private_key = rsa_key.to_pem(cipher, password)
+        end
+
+        # Generate the binary necessary for the OpenSSH public key.
+        binary = [7].pack("N")
+        binary += "ssh-rsa"
+        ["e", "n"].each do |m|
+          val  = public_key.send(m)
+          data = val.to_s(2)
+
+          first_byte = data[0,1].unpack("c").first
+          if val < 0
+            data[0] = [0x80 & first_byte].pack("c")
+          elsif first_byte < 0
+            data = 0.chr + data
+          end
+
+          binary += [data.length].pack("N") + data
+        end
+
+        openssh_key = "ssh-rsa #{Base64.encode64(binary).gsub("\n", "")} vagrant"
+        public_key  = public_key.to_pem
+        return [public_key, private_key, openssh_key]
+      end
+    end
+  end
+end

test/unit/vagrant/util/keypair_test.rb

@@ -0,0 +1,34 @@
+require "openssl"
+
+require File.expand_path("../../../base", __FILE__)
+
+require "vagrant/util/keypair"
+
+describe Vagrant::Util::Keypair do
+  describe ".create" do
+    it "generates a usable keypair with no password" do
+      # I don't know how to validate the final return value yet...
+      pubkey, privkey, _ = described_class.create
+
+      pubkey  = OpenSSL::PKey::RSA.new(pubkey)
+      privkey = OpenSSL::PKey::RSA.new(privkey)
+
+      encrypted = pubkey.public_encrypt("foo")
+      decrypted = privkey.private_decrypt(encrypted)
+
+      expect(decrypted).to eq("foo")
+    end
+
+    it "generates a keypair that requires a password" do
+      pubkey, privkey, _ = described_class.create("password")
+
+      pubkey  = OpenSSL::PKey::RSA.new(pubkey)
+      privkey = OpenSSL::PKey::RSA.new(privkey, "password")
+
+      encrypted = pubkey.public_encrypt("foo")
+      decrypted = privkey.private_decrypt(encrypted)
+
+      expect(decrypted).to eq("foo")
+    end
+  end
+end