Unquote Gem.ruby when spawning it as a separate argv element

lib/bundler/self_manager.rb

@@ -75,7 +75,12 @@ def restart_with(version)
 
       argv0 = File.exist?($PROGRAM_NAME) ? $PROGRAM_NAME : Process.argv0
       cmd = [argv0, *ARGV]
-      cmd.unshift(Gem.ruby) unless File.executable?(argv0)
+      unless File.executable?(argv0)
+        # Gem.ruby is quoted if it contains whitespace, so split it into argv
+        # elements to keep the quotes out of the exec'd command.
+        require "shellwords"
+        cmd.unshift(*Shellwords.split(Gem.ruby))
+      end
 
       Bundler.with_original_env do
         Kernel.exec(

lib/rubygems/commands/push_command.rb

@@ -147,16 +147,19 @@ def send_push_request_with_attestation(name, args)
 
   def attest!(name)
     require "open3"
+    require "shellwords"
     require "tempfile"
 
     tempfile = Tempfile.new([File.basename(name, ".*"), ".sigstore.json"])
     bundle = tempfile.path
     tempfile.close(false)
 
     env = defined?(Bundler.unbundled_env) ? Bundler.unbundled_env : ENV.to_h
+    # Gem.ruby is quoted if it contains whitespace, so split it into argv
+    # elements to keep the quotes out of the spawned command.
     out, st = Open3.capture2e(
       env,
-      Gem.ruby, "-S", "gem", "exec", "--conservative",
+      *Shellwords.split(Gem.ruby), "-S", "gem", "exec", "--conservative",
       "sigstore-cli", "sign", name, "--bundle", bundle,
       unsetenv_others: true
     )

lib/rubygems/commands/update_command.rb

@@ -183,7 +183,10 @@ def install_rubygems(spec) # :nodoc:
       say "Installing RubyGems #{version}" unless options[:silent]
 
       installed = preparing_gem_layout_for(version) do
-        system Gem.ruby, "--disable-gems", "setup.rb", *args
+        # Gem.ruby is quoted if it contains whitespace, so split it into argv
+        # elements to keep the quotes out of the spawned command.
+        require "shellwords"
+        system(*Shellwords.split(Gem.ruby), "--disable-gems", "setup.rb", *args)
       end
 
       unless options[:silent]

lib/rubygems/ext/rake_builder.rb

@@ -14,7 +14,9 @@ def self.build(extension, dest_path, results, args = [], lib_dir = nil, extensio
     end
 
     if /mkrf_conf/i.match?(File.basename(extension))
-      run([Gem.ruby, File.basename(extension), *args], results, class_name, extension_dir)
+      # Gem.ruby is quoted if it contains whitespace, so split it into argv
+      # elements to keep the quotes out of the spawned command.
+      run([*shellsplit(Gem.ruby), File.basename(extension), *args], results, class_name, extension_dir)
     end
 
     rake = ENV["rake"]

spec/bundler/self_manager_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+RSpec.describe Bundler::SelfManager do
+  describe "#restart_with" do
+    # When the running Ruby lives under a path containing whitespace, Gem.ruby
+    # returns a quoted string. That quoting must not leak into the argv passed
+    # to Kernel.exec, or the interpreter can't be found and the auto-switch to
+    # the locked bundler version fails to spawn.
+    it "does not embed quotes in the ruby executable when Gem.ruby is quoted" do
+      manager = described_class.new
+
+      allow(Gem).to receive(:ruby).and_return('"/path with space/bin/ruby"')
+
+      # Force the branch that prepends Gem.ruby to the command.
+      allow(File).to receive(:executable?).and_return(false)
+      allow(Bundler).to receive(:with_original_env).and_yield
+
+      captured = nil
+      allow(Kernel).to receive(:exec) do |_env, *cmd|
+        captured = cmd
+      end
+
+      manager.send(:restart_with, Gem::Version.new("1.0.0"))
+
+      expect(captured.first).to eq("/path with space/bin/ruby")
+      expect(captured.first).not_to include('"')
+    end
+  end
+end

test/rubygems/test_gem_commands_push_command.rb

@@ -219,6 +219,36 @@ def test_execute_attestation_skipped_on_jruby
     end
   end
 
+  # When the running Ruby lives under a path containing whitespace, Gem.ruby
+  # returns a quoted string. That quoting must not leak into the argv passed to
+  # Open3.capture2e, or signing spawns fail and push silently falls back to an
+  # unsigned upload.
+  def test_attest_unquotes_ruby
+    require "open3"
+
+    fake_status = Object.new
+    def fake_status.success?
+      true
+    end
+
+    captured = nil
+    capture_stub = lambda do |*args, **_kwargs|
+      captured = args
+      ["", fake_status]
+    end
+    Gem.stub(:ruby, '"/path with space/bin/ruby"') do
+      Open3.stub(:capture2e, capture_stub) do
+        @cmd.send(:attest!, @path)
+      end
+    end
+
+    refute_nil captured, "signing command should have been spawned"
+    # captured[0] is the env hash; the interpreter follows it.
+    assert_equal "/path with space/bin/ruby", captured[1]
+    refute_includes captured[1], '"'
+    assert_equal "-S", captured[2]
+  end
+
   def test_execute_allowed_push_host
     @spec, @path = util_gem "freebird", "1.0.1" do |spec|
       spec.metadata["allowed_push_host"] = "https://privategemserver.example"

test/rubygems/test_gem_commands_update_command.rb

@@ -816,6 +816,36 @@ def test_update_gem_unresolved_dependency
     assert_empty @cmd.updated
   end
 
+  # When the running Ruby lives under a path containing whitespace, Gem.ruby
+  # returns a quoted string. That quoting must not leak into the argv passed to
+  # the non-shell `system` call that runs setup.rb, or the interpreter can't be
+  # found and `gem update --system` fails to spawn.
+  def test_install_rubygems_unquotes_ruby
+    version = Gem::Version.new("99.0.0")
+    update_dir = File.join @tempdir, "gems", "rubygems-update-#{version}"
+    FileUtils.mkdir_p update_dir
+
+    spec = Struct.new(:version, :base_dir).new(version, @tempdir)
+
+    captured = nil
+    @cmd.define_singleton_method(:system) do |*args|
+      captured = args
+      true
+    end
+
+    @cmd.options[:silent] = true
+
+    Gem.stub(:ruby, '"/path with space/bin/ruby"') do
+      @cmd.install_rubygems(spec)
+    end
+
+    refute_nil captured, "setup.rb should have been spawned"
+    assert_equal "/path with space/bin/ruby", captured.first
+    refute_includes captured.first, '"'
+    assert_includes captured, "--disable-gems"
+    assert_includes captured, "setup.rb"
+  end
+
   def test_update_rubygems_arguments
     @cmd.options[:system] = true
 

test/rubygems/test_gem_ext_rake_builder.rb

@@ -101,6 +101,24 @@ def test_class_build_fail
     end
   end
 
+  # When the running Ruby lives under a path containing whitespace, Gem.ruby
+  # returns a quoted string. That quoting must not leak into the argv passed to
+  # the non-shell spawn that runs mkrf_conf.rb, or the interpreter can't be found.
+  def test_class_build_mkrf_conf_unquotes_ruby
+    commands = []
+
+    Gem.stub(:ruby, '"/path with space/bin/ruby"') do
+      Gem::Ext::RakeBuilder.stub(:run, ->(command, *) { commands << command }) do
+        Gem::Ext::RakeBuilder.build "mkrf_conf.rb", @dest_path, [], [], nil, @ext
+      end
+    end
+
+    mkrf_command = commands.find {|command| command.include?("mkrf_conf.rb") }
+    refute_nil mkrf_command, "mkrf_conf.rb should have been spawned"
+    assert_equal "/path with space/bin/ruby", mkrf_command.first
+    refute_includes mkrf_command.first, '"'
+  end
+
   def create_temp_mkrf_file(rakefile_content)
     File.open File.join(@ext, "mkrf_conf.rb"), "w" do |mkrf_conf|
       mkrf_conf.puts <<-EO_MKRF