1 files changed, 55 insertions, 0 deletions
diff --git a/lib/gitlab/key_fingerprint.rb b/lib/gitlab/key_fingerprint.rb
new file mode 100644
index 00000000000..baf52ff750d
--- /dev/null
+++ b/lib/gitlab/key_fingerprint.rb
@@ -0,0 +1,55 @@
+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_matches = cmd_output.match(/(MD5:)?(?<fingerprint>(\h{2}:){15}\h{2})/)
+      return nil unless fingerprint_matches
+
+      fingerprint_matches[: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