Add setsid option to child_process

doc/api/child_processes.markdown

@@ -59,12 +59,15 @@ The third argument is used to specify additional options, which defaults to:
 
     { cwd: undefined,
       env: process.env,
-      customFds: [-1, -1, -1] }
+      customFds: [-1, -1, -1],
+      setsid: false
+    }
 
 `cwd` allows you to specify the working directory from which the process is spawned.
 Use `env` to specify environment variables that will be visible to the new process.
 With `customFds` it is possible to hook up the new process' [stdin, stout, stderr] to
-existing streams; `-1` means that a new stream should be created.
+existing streams; `-1` means that a new stream should be created. `setsid`,
+if set true, will cause the subprocess to be run in a new session.
 
 Example of running `ls -lh /usr`, capturing `stdout`, `stderr`, and the exit code:
 

lib/child_process.js

@@ -25,6 +25,7 @@ exports.execFile = function(file /* args, options, callback */) {
                   timeout: 0,
                   maxBuffer: 200 * 1024,
                   killSignal: 'SIGTERM',
+                  setsid: false,
                   cwd: null,
                   env: null };
   var args, optionArg, callback;
@@ -184,7 +185,7 @@ ChildProcess.prototype.kill = function(sig) {
 ChildProcess.prototype.spawn = function(path, args, options, customFds) {
   args = args || [];
 
-  var cwd, env;
+  var cwd, env, setuid;
   if (!options || options.cwd === undefined &&
       options.env === undefined &&
       options.customFds === undefined) {
@@ -192,11 +193,13 @@ ChildProcess.prototype.spawn = function(path, args, options, customFds) {
     cwd = '';
     env = options || process.env;
     customFds = customFds || [-1, -1, -1];
+    setuid = false;
   } else {
     // Recommended API: (path, args, options)
     cwd = options.cwd || '';
     env = options.env || process.env;
     customFds = options.customFds || [-1, -1, -1];
+    setuid = options.setuid ? true : false;
   }
 
   var envPairs = [];
@@ -206,7 +209,12 @@ ChildProcess.prototype.spawn = function(path, args, options, customFds) {
     envPairs.push(key + '=' + env[key]);
   }
 
-  var fds = this._internal.spawn(path, args, cwd, envPairs, customFds);
+  var fds = this._internal.spawn(path,
+                                 args,
+                                 cwd,
+                                 envPairs,
+                                 customFds,
+                                 setuid);
   this.fds = fds;
 
   if (customFds[0] === -1 || customFds[0] === undefined) {

src/node_child_process.cc

@@ -150,9 +150,15 @@ Handle<Value> ChildProcess::Spawn(const Arguments& args) {
     }
   }
 
+  int do_setuid = false;
+  if (args[5]->IsBoolean()) {
+    do_setuid = args[5]->BooleanValue();
+  }
+
+
   int fds[3];
 
-  int r = child->Spawn(argv[0], argv, cwd, env, fds, custom_fds);
+  int r = child->Spawn(argv[0], argv, cwd, env, fds, custom_fds, do_setuid);
 
   for (i = 0; i < argv_length; i++) free(argv[i]);
   delete [] argv;
@@ -226,7 +232,8 @@ int ChildProcess::Spawn(const char *file,
                         const char *cwd,
                         char **env,
                         int stdio_fds[3],
-                        int custom_fds[3]) {
+                        int custom_fds[3],
+                        bool do_setuid) {
   HandleScope scope;
   assert(pid_ == -1);
   assert(!ev_is_active(&child_watcher_));
@@ -267,6 +274,10 @@ int ChildProcess::Spawn(const char *file,
       return -4;
 
     case 0:  // Child.
+      if (do_setuid && setsid() < 0) {
+        perror("setuid");
+      }
+
       if (custom_fds[0] == -1) {
         close(stdin_pipe[1]);  // close write end
         dup2(stdin_pipe[0],  STDIN_FILENO);

src/node_child_process.h

@@ -58,7 +58,13 @@ class ChildProcess : ObjectWrap {
   // are readable.
   // The user of this class has responsibility to close these pipes after
   // the child process exits.
-  int Spawn(const char *file, char *const argv[], const char *cwd, char **env, int stdio_fds[3], int custom_fds[3]);
+  int Spawn(const char *file,
+            char *const argv[],
+            const char *cwd,
+            char **env,
+            int stdio_fds[3],
+            int custom_fds[3],
+            bool do_setuid);
 
   // Simple syscall wrapper. Does not disable the watcher. onexit will be
   // called still.