1 files changed, 41 insertions, 0 deletions
diff --git a/spec/support/helpers/key_generator_helper.rb b/spec/support/helpers/key_generator_helper.rb
new file mode 100644
index 00000000000..b1c289ffef7
--- /dev/null
+++ b/spec/support/helpers/key_generator_helper.rb
@@ -0,0 +1,41 @@
+module Spec
+  module Support
+    module Helpers
+      class KeyGeneratorHelper
+        # The components in a openssh .pub / known_host RSA public key.
+        RSA_COMPONENTS = ['ssh-rsa', :e, :n].freeze
+
+        attr_reader :size
+
+        def initialize(size = 2048)
+          @size = size
+        end
+
+        def generate
+          key = OpenSSL::PKey::RSA.generate(size)
+          components = RSA_COMPONENTS.map do |component|
+            key.respond_to?(component) ? encode_mpi(key.public_send(component)) : component
+          end
+
+          # Ruby tries to be helpful and adds new lines every 60 bytes :(
+          'ssh-rsa ' + [pack_pubkey_components(components)].pack('m').delete("\n")
+        end
+
+        private
+
+        # Encodes an openssh-mpi-encoded integer.
+        def encode_mpi(n)
+          chars, n = [], n.to_i
+          chars << (n & 0xff) && n >>= 8 while n != 0
+          chars << 0 if chars.empty? || chars.last >= 0x80
+          chars.reverse.pack('C*')
+        end
+
+        # Packs string components into an openssh-encoded pubkey.
+        def pack_pubkey_components(strings)
+          (strings.map { |s| [s.length].pack('N') }).zip(strings).flatten.join
+        end
+      end
+    end
+  end
+end