Enable Windows users with SSH installed to use 'vagrant ssh'

lib/vagrant/ssh.rb

@@ -1,5 +1,6 @@
 require 'log4r'
 
+require 'vagrant/util/file_util'
 require 'vagrant/util/file_mode'
 require 'vagrant/util/platform'
 require 'vagrant/util/safe_exec'
@@ -55,15 +56,18 @@ def exec(opts={})
       # Get the SSH information and cache it here
       ssh_info = info
 
-      if Util::Platform.windows?
-        raise Errors::SSHUnavailableWindows, :host => ssh_info[:host],
-                                             :port => ssh_info[:port],
-                                             :username => ssh_info[:username],
-                                             :key_path => ssh_info[:private_key_path]
+      # Ensure the platform supports ssh. On Windows there are several programs which
+      # include ssh, notably git, mingw and cygwin, but make sure ssh is in the path!
+      if !Util::FileUtil.which("ssh")
+        if Util::Platform.windows?
+          raise Errors::SSHUnavailableWindows, :host => ssh_info[:host],
+                                               :port => ssh_info[:port],
+                                               :username => ssh_info[:username],
+                                               :key_path => ssh_info[:private_key_path]
+        end
+        raise Errors::SSHUnavailable 
       end
 
-      raise Errors::SSHUnavailable if !Kernel.system("which ssh > /dev/null 2>&1")
-
       # If plain mode is enabled then we don't do any authentication (we don't
       # set a user or an identity file)
       plain_mode = opts[:plain_mode]

lib/vagrant/util/file_util.rb

@@ -0,0 +1,36 @@
+module Vagrant
+  module Util
+    class FileUtil
+      # Cross-platform way of finding an executable in the $PATH.
+      #
+      #   which('ruby') #=> /usr/bin/ruby
+      #   by http://stackoverflow.com/users/11687/mislav
+      #
+      # This code is adapted from the following post by mislav:
+      #   http://stackoverflow.com/questions/2108727/which-in-ruby-checking-if-program-exists-in-path-from-ruby
+      def self.which(cmd)
+
+        # If the PATHEXT variable is empty, we're on *nix and need to find the exact filename
+        exts = nil
+        if !Util::Platform.windows? || ENV['PATHEXT'].nil?
+          exts = ['']
+        # On Windows: if filename contains an extension, we must match that exact filename
+        elsif File.extname(cmd).length != 0
+          exts = ['']
+        # On Windows: otherwise try to match all possible executable file extensions (.EXE .COM .BAT etc.)
+        else
+          exts = ENV['PATHEXT'].split(';')
+        end
+
+        ENV['PATH'].split(File::PATH_SEPARATOR).each do |path|
+          exts.each do |ext|
+            exe = "#{path}#{File::SEPARATOR}#{cmd}#{ext}"
+            return exe if File.executable? exe
+          end
+        end
+
+        return nil
+      end
+    end
+  end
+end

templates/locales/en.yml

@@ -149,9 +149,10 @@ en:
         guest port value, or specify an explicit SSH port with `config.ssh.port`.
       ssh_unavailable: "`ssh` binary could not be found. Is an SSH client installed?"
       ssh_unavailable_windows: |-
-        `vagrant ssh` isn't available on the Windows platform. You are still able
-        to SSH into the virtual machine if you get a Windows SSH client (such as
-        PuTTY). The authentication information is shown below:
+        `ssh` executable not found in any directories in the %PATH% variable. Is an
+        SSH client installed? Try installing Cygwin, MinGW or Git, all of which
+        contain an SSH client. Or use the PuTTY SSH client with the following
+        authentication information shown below:
 
         Host: %{host}
         Port: %{port}

test/unit/vagrant/util/file_util_test.rb

@@ -0,0 +1,46 @@
+require File.expand_path("../../../base", __FILE__)
+
+require 'vagrant/util/file_util'
+require 'vagrant/util/platform'
+
+describe Vagrant::Util::FileUtil do
+
+  def tester (file_extension, test_extension, mode, &block)
+    # create file in temp directory
+    filename = '__vagrant_unit_test__'
+    dir = Dir.tmpdir
+    file = Pathname(dir) + (filename + file_extension)
+    file.open("w") { |f| f.write("#") }
+    file.chmod(mode)
+
+    # set the path to the directory where the file is located
+    savepath = ENV['PATH']
+    ENV['PATH'] = dir.to_s
+    block.call filename + test_extension
+    ENV['PATH'] = savepath
+
+    file.unlink
+  end
+
+  it "should return a path for an executable file" do
+    tester '.bat', '.bat', 0755 do |name|
+      Vagrant::Util::FileUtil.which(name).should_not be_nil
+    end
+  end
+
+  if Vagrant::Util::Platform.windows?
+    it "should return a path for a Windows executable file" do
+      tester '.bat', '', 0755 do |name|
+        Vagrant::Util::FileUtil.which(name).should_not be_nil
+      end
+    end
+  end
+
+  it "should return nil for a non-executable file" do
+    tester '.txt', '.txt', 0644 do |name|
+      Vagrant::Util::FileUtil.which(name).should be_nil
+    end
+  end
+
+end
+