Remove keys from authorized_keys in-place

This will speed up the rm-key operation. The downside is that
authorized_keys will not shrink when you remove a key. If this ever
becomes a problem it can be fixed by running 'rake gitlab:shell:setup'.

CHANGELOG

+v2.6.4
+  - Remove keys from authorized_keys in-place
 v2.6.3
   - Prevent keys with a very specific comment from accidentally being deleted.
 

lib/gitlab_keys.rb

-require 'tempfile'
 require 'timeout'
 
 require_relative 'gitlab_config'
@@ -82,14 +81,14 @@ class GitlabKeys
   def rm_key
     lock do
       $logger.info "Removing key #{@key_id}"
-      Tempfile.open('authorized_keys') do |temp|
-        open(auth_file, 'r+') do |current|
-          current.each do |line|
-            temp.puts(line) unless line.start_with?("command=\"#{key_command(@key_id)}\"")
-          end
+      open(auth_file, 'r+') do |f|
+        while line = f.gets do
+          next unless line.start_with?("command=\"#{key_command(@key_id)}\"")
+          f.seek(-line.length, IO::SEEK_CUR)
+          # Overwrite the line with #'s. Because the 'line' variable contains
+          # a terminating '\n', we write line.length - 1 '#' characters.
+          f.write('#' * (line.length - 1))
         end
-        temp.close
-        FileUtils.cp(temp.path, auth_file)
       end
     end
     true

spec/gitlab_keys_spec.rb

@@ -109,17 +109,19 @@ describe GitlabKeys do
     it "removes the right line" do
       create_authorized_keys_fixture
       other_line = "command=\"#{ROOT_PATH}/bin/gitlab-shell key-742\",options ssh-rsa AAAAB3NzaDAxx2E"
+      delete_line = "command=\"#{ROOT_PATH}/bin/gitlab-shell key-741\",options ssh-rsa AAAAB3NzaDAxx2E"
       open(tmp_authorized_keys_path, 'a') do |auth_file|
-        auth_file.puts "command=\"#{ROOT_PATH}/bin/gitlab-shell key-741\",options ssh-rsa AAAAB3NzaDAxx2E"
+        auth_file.puts delete_line
         auth_file.puts other_line
       end
       gitlab_keys.send :rm_key
-      File.read(tmp_authorized_keys_path).should == "existing content\n#{other_line}\n"
+      erased_line = delete_line.gsub(/./, '#')
+      File.read(tmp_authorized_keys_path).should == "existing content\n#{erased_line}\n#{other_line}\n"
     end
 
     context "without file writing" do
       before do
-        Tempfile.stub(:open)
+        gitlab_keys.stub(:open)
         gitlab_keys.stub(:lock).and_yield
       end