Merge pull request #4905 from mitchellh/gc-fix-docker-agent-forwarding

providers/docker: fix support of agent forwarding

CHANGELOG.md

@@ -93,6 +93,7 @@ BUG FIXES:
   - providers/docker: Fix issue where multiple identical proxy VMs would
       be created. [GH-3963]
   - providers/docker: Multiple links with the same name work. [GH-4571]
+  - providers/docker: Add support of SSH agent forwarding. [GH-4905]
   - providers/virtualbox: Show a human-friendly error if VirtualBox didn't
       clean up an existing VM. [GH-4681]
   - providers/virtualbox: Detect case when VirtualBox reports 0.0.0.0 as

plugins/providers/docker/action/prepare_ssh.rb

@@ -19,14 +19,19 @@ module VagrantPlugins
           # Modify the SSH options for when we `vagrant ssh`...
           ssh_opts = env[:ssh_opts] || {}
 
-          # Build the command we'll execute within the host machine
+          # Build the command we'll execute within the Docker host machine:
           ssh_command = env[:machine].communicate.container_ssh_command
           if !Array(ssh_opts[:extra_args]).empty?
             ssh_command << " #{Array(ssh_opts[:extra_args]).join(" ")}"
           end
 
+          # Modify the SSH options for the original command:
           # Append "-t" to force a TTY allocation
           ssh_opts[:extra_args] = ["-t"]
+          # Enable Agent forwarding when requested for the target VM
+          if env[:machine].ssh_info[:forward_agent]
+            ssh_opts[:extra_args] << "-o ForwardAgent=yes"
+          end
           ssh_opts[:extra_args] << ssh_command
 
           # Set the opts

plugins/providers/docker/communicator.rb

@@ -137,18 +137,21 @@ module VagrantPlugins
         info[:port] ||= 22
 
         # Make sure our private keys are synced over to the host VM
-        key_args = sync_private_keys(info).map do |path|
+        ssh_args = sync_private_keys(info).map do |path|
           "-i #{path}"
-        end.join(" ")
+        end
+
+        # Use ad-hoc SSH options for the hop on the docker proxy 
+        if info[:forward_agent]
+          ssh_args << "-o ForwardAgent=yes"
+        end
+        ssh_args.concat(["-o Compression=yes",
+                         "-o ConnectTimeout=5",
+                         "-o StrictHostKeyChecking=no",
+                         "-o UserKnownHostsFile=/dev/null"])
 
         # Build the SSH command
-        "ssh #{key_args} " +
-          "-o Compression=yes " +
-          "-o ConnectTimeout=5 " +
-          "-o StrictHostKeyChecking=no " +
-          "-o UserKnownHostsFile=/dev/null " +
-          "-p#{info[:port]} " +
-          "#{info[:username]}@#{info[:host]}"
+        "ssh #{info[:username]}@#{info[:host]} -p#{info[:port]} #{ssh_args.join(" ")}"
       end
 
       protected