From 0aaaa866e4b8aae24eaff7ffdd1d7f7cea1d8d4e Mon Sep 17 00:00:00 2001
From: Girish Ramakrishnan <girish@cloudron.io>
Date: Sun, 22 May 2016 00:13:56 -0700
Subject: [PATCH] Add a whole bunch of magic for docker.exec to work

---
 src/apps.js        | 19 ++++++++++++++++---
 src/routes/apps.js | 12 +++++++++---
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/apps.js b/src/apps.js
index 12b2a8503..be8d92671 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -748,10 +748,14 @@ function exec(appId, options, callback) {
 
         var container = docker.connection.getContainer(app.containerId);
 
-       var execOptions = {
+        var execOptions = {
             AttachStdin: true,
             AttachStdout: true,
             AttachStderr: true,
+            // A pseudo tty is a terminal which processes can detect (for example, disable colored output)
+            // Creating a pseudo terminal also assigns a terminal driver which detects control sequences
+            // When passing binary data, tty must be disabled. In addition, the stdout/stderr becomes a single
+            // unified stream because of the nature of a tty (see https://github.com/docker/docker/issues/19696)
             Tty: options.tty,
             Cmd: cmd
         };
@@ -761,9 +765,18 @@ function exec(appId, options, callback) {
             var startOptions = {
                 Detach: false,
                 Tty: options.tty,
-                stdin: true // this is a dockerode option that enabled openStdin in the modem
+                // hijacking upgrades the docker connection from http to tcp. because of this upgrade,
+                // we can work with half-close connections (not defined in http). this way, the client
+                // can properly signal that stdin is EOF by closing it's side of the socket. In http,
+                // the whole connection will be dropped when stdin get EOF.
+                // https://github.com/apocas/dockerode/commit/b4ae8a03707fad5de893f302e4972c1e758592fe
+                hijack: true,
+                stream: true,
+                stdin: true,
+                stdout: true,
+                stderr: true
             };
-            exec.start(startOptions, function(error, stream) {
+            exec.start(startOptions, function(error, stream /* in hijacked mode, this is a net.socket */) {
                 if (error) return callback(new AppsError(AppsError.INTERNAL_ERROR, error));
 
                 if (options.rows && options.columns) {
diff --git a/src/routes/apps.js b/src/routes/apps.js
index ce3ec11f5..6ae8da71d 100644
--- a/src/routes/apps.js
+++ b/src/routes/apps.js
@@ -357,7 +357,7 @@ function exec(req, res, next) {
 
     var tty = req.query.tty === 'true' ? true : false;
 
-    apps.exec(req.params.id, { cmd: cmd, rows: rows, columns: columns, tty: tty }, function (error, duplexStream) {
+    apps.exec(req.params.id, { cmd: cmd, rows: rows, columns: columns, tty: tty }, function (error, execStream) {
         if (error && error.reason === AppsError.NOT_FOUND) return next(new HttpError(404, 'No such app'));
         if (error && error.reason === AppsError.BAD_STATE) return next(new HttpError(409, error.message));
         if (error) return next(new HttpError(500, error));
@@ -367,8 +367,14 @@ function exec(req, res, next) {
         req.clearTimeout();
         res.sendUpgradeHandshake();
 
-        duplexStream.pipe(res.socket);
-        res.socket.pipe(duplexStream);
+        // allowHalfOpen allows the client to close it's connection (end()) to signal a stdin EOF. If allowHalfOpen
+        // is not set, our socket will call end() automatically. Setting this to true, leaves our socket open
+        // and allows us to send the result of the command (made possible by docker hijacking feature).
+        res.socket.allowHalfOpen = true;
+
+        // When tty is disabled, the execStream is a duplex stream. When enabled, it has stdout/stderr merged.
+        execStream.pipe(res.socket);
+        res.socket.pipe(execStream);
     });
 }