From 64fd2f71d64efe1c4b3dc55d1364a99a20c10604 Mon Sep 17 00:00:00 2001
From: Chris Roberts <code@chrisroberts.org>
Date: Thu, 16 Feb 2017 15:18:18 -0800
Subject: [PATCH] communicator/ssh: discard stderr data before command run

---
 plugins/communicators/ssh/communicator.rb     | 21 +++++++++++++---
 .../communicators/ssh/communicator_test.rb    | 24 +++++++++++++++++--
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/plugins/communicators/ssh/communicator.rb b/plugins/communicators/ssh/communicator.rb
index 4c3eb40ac..8e71ad02f 100644
--- a/plugins/communicators/ssh/communicator.rb
+++ b/plugins/communicators/ssh/communicator.rb
@@ -496,6 +496,8 @@ module VagrantPlugins
 
           marker_found = false
           data_buffer = ''
+          stderr_marker_found = false
+          stderr_data_buffer = ''
 
           ch.exec(shell_cmd(opts)) do |ch2, _|
             # Setup the channel callbacks so we can get data and exit status
@@ -512,7 +514,7 @@ module VagrantPlugins
                   if marker_index
                     marker_found = true
                     data_buffer.slice!(0, marker_index + CMD_GARBAGE_MARKER.size)
-                    data.replace data_buffer
+                    data.replace(data_buffer)
                     data_buffer = nil
                   end
                 end
@@ -527,7 +529,20 @@ module VagrantPlugins
               # Filter out the clear screen command
               data = remove_ansi_escape_codes(data)
               @logger.debug("stderr: #{data}")
-              yield :stderr, data if block_given?
+              if !stderr_marker_found
+                stderr_data_buffer << data
+                marker_index = stderr_data_buffer.index(CMD_GARBAGE_MARKER)
+                if marker_index
+                  marker_found = true
+                  stderr_data_buffer.slice!(0, marker_index + CMD_GARBAGE_MARKER.size)
+                  data.replace(stderr_data_buffer)
+                  data_buffer = nil
+                end
+              end
+
+              if block_given? && marker_found
+                yield :stderr, data
+              end
             end
 
             ch2.on_request("exit-status") do |ch3, data|
@@ -583,7 +598,7 @@ module VagrantPlugins
               data = data.force_encoding('ASCII-8BIT')
               ch2.send_data data
             else
-              ch2.send_data "printf '#{CMD_GARBAGE_MARKER}'\n#{command}\n".force_encoding('ASCII-8BIT')
+              ch2.send_data "printf '#{CMD_GARBAGE_MARKER}'\n(>&2 printf '#{CMD_GARBAGE_MARKER}')\n#{command}\n".force_encoding('ASCII-8BIT')
               # Remember to exit or this channel will hang open
               ch2.send_data "exit\n"
             end
diff --git a/test/unit/plugins/communicators/ssh/communicator_test.rb b/test/unit/plugins/communicators/ssh/communicator_test.rb
index 7de5b90d6..6a9c94fe0 100644
--- a/test/unit/plugins/communicators/ssh/communicator_test.rb
+++ b/test/unit/plugins/communicators/ssh/communicator_test.rb
@@ -132,7 +132,7 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
 
     it "prepends UUID output to command for garbage removal" do
       expect(command_channel).to receive(:send_data).
-        with("printf '#{command_garbage_marker}'\nls /\n")
+        with("printf '#{command_garbage_marker}'\n(>&2 printf '#{command_garbage_marker}')\nls /\n")
       expect(communicator.execute("ls /")).to eq(0)
     end
 
@@ -159,13 +159,33 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
         stdout = ''
         expect(
           communicator.execute("ls /") do |type, data|
-            stdout << data
+            if type == :stdout
+              stdout << data
+            end
           end
         ).to eq(0)
         expect(stdout).to eq("bin\ntmp\n")
       end
     end
 
+    context "with garbage content prepended to command stderr output" do
+      let(:command_stderr_data) do
+        "Line of garbage\nMore garbage\n#{command_garbage_marker}bin\ntmp\n"
+      end
+
+      it "removes any garbage output prepended to command stderr output" do
+        stderr = ''
+        expect(
+          communicator.execute("ls /") do |type, data|
+            if type == :stderr
+              stderr << data
+            end
+          end
+        ).to eq(0)
+        expect(stderr).to eq("bin\ntmp\n")
+      end
+    end
+
     context "with pty enabled" do
       before do
         expect(ssh).to receive(:pty).and_return true