Refactor key fingerprint generation.

app/models/key.rb

@@ -16,7 +16,6 @@ require 'digest/md5'
 
 class Key < ActiveRecord::Base
   include Sortable
-  include Gitlab::Popen
 
   belongs_to :user
 
@@ -79,44 +78,9 @@ class Key < ActiveRecord::Base
 
   def generate_fingerprint
     self.fingerprint = nil
-    return unless key.present?
-
-    cmd_status = 0
-    cmd_output = ''
-    explicit_fingerprint_algorithm = false
-    Tempfile.open('gitlab_key_file') do |file|
-      file.puts key
-      file.rewind
-
-      # OpenSSH 6.8 introduces a new default output format for fingerprints.
-      # Check the version and decide which command to use.
-      version_output, version_status = popen(%W(ssh -V))
-      if version_status.zero?
-        out, _ = version_output.scan /.*?(\d)\.(\d).*?,/
-        major, minor = out[0], out[1]
-        if major.to_i > 6 or (major.to_i == 6 and minor.to_i >= 8)
-          explicit_fingerprint_algorithm = true
-        end
-      end
 
-      if explicit_fingerprint_algorithm
-        cmd_output, cmd_status = popen(%W(ssh-keygen -E md5 -lf #{file.path}), '/tmp')
-      else
-        cmd_output, cmd_status = popen(%W(ssh-keygen -lf #{file.path}), '/tmp')
-      end
-    end
+    return unless self.key.present?
 
-    if cmd_status.zero?
-      if explicit_fingerprint_algorithm
-        cmd_output.gsub /(MD5:)(\h{2}:)+\h{2}/ do |match|
-          match.slice! /^MD5:/
-          self.fingerprint = match
-        end
-      else
-        cmd_output.gsub /(\h{2}:)+\h{2}/ do |match|
-          self.fingerprint = match
-        end
-      end
-    end
+    self.fingerprint = Gitlab::KeyFingerprint.new(self.key).fingerprint
   end
 end

lib/gitlab/key_fingerprint.rb

+module Gitlab
+  class KeyFingerprint
+    include Gitlab::Popen
+
+    attr_accessor :key
+
+    def initialize(key)
+      @key = key
+    end
+
+    def fingerprint
+      cmd_status = 0
+      cmd_output = ''
+
+      Tempfile.open('gitlab_key_file') do |file|
+        file.puts key
+        file.rewind
+
+        cmd = []
+        cmd.push *%W(ssh-keygen)
+        cmd.push *%W(-E md5) if explicit_fingerprint_algorithm?
+        cmd.push *%W(-lf #{file.path})
+
+        cmd_output, cmd_status = popen(cmd, '/tmp')
+      end
+
+      return nil unless cmd_status.zero?
+
+      # 16 hex bytes separated by ':', optionally starting with "MD5:"
+      fingerprint_match = cmd_output.match(/(MD5:)?(?<fingerprint>(?:\h{2}:){15}\h{2})/)
+      return nil unless fingerprint_match
+
+      fingerprint_match[:fingerprint]
+    end
+
+    private
+
+    def explicit_fingerprint_algorithm?
+      # OpenSSH 6.8 introduces a new default output format for fingerprints.
+      # Check the version and decide which command to use.
+
+      version_output, version_status = popen(%W(ssh -V))
+      return false unless version_status.zero?
+
+      version_matches = version_output.match(/OpenSSH_(?<major>\d+)\.(?<minor>\d+)/)
+      return false unless version_matches
+
+      version_info = Gitlab::VersionInfo.new(version_matches[:major].to_i, version_matches[:minor].to_i)
+
+      required_version_info = Gitlab::VersionInfo.new(6, 8)
+
+      version_info >= required_version_info 
+    end
+  end
+end

spec/lib/gitlab/key_fingerprint_spec.rb

+require "spec_helper"
+
+describe Gitlab::KeyFingerprint do
+  let(:key)         { "ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAIEAiPWx6WM4lhHNedGfBpPJNPpZ7yKu+dnn1SJejgt4596k6YjzGGphH2TUxwKzxcKDKKezwkpfnxPkSMkuEspGRt/aZZ9wa++Oi7Qkr8prgHc4soW6NUlfDzpvZK2H5E7eQaSeP3SAwGmQKUFHCddNaP0L+hM7zhFNzjFvpaMgJw0=" }
+  let(:fingerprint) { "3f:a2:ee:de:b5:de:53:c3:aa:2f:9c:45:24:4c:47:7b" }
+
+  describe "#fingerprint" do
+    it "generates the key's fingerprint" do
+      expect(Gitlab::KeyFingerprint.new(key).fingerprint).to eq(fingerprint)
+    end
+  end
+end