uv_spawn: support setting the child process' user and group id

include/uv-private/uv-unix.h

@@ -33,6 +33,7 @@
 #include <netinet/tcp.h>
 #include <arpa/inet.h>
 #include <netdb.h>
+#include <pwd.h>
 #include <termios.h>
 #include <pthread.h>
 
@@ -51,6 +52,10 @@ typedef pthread_t uv_thread_t;
 typedef pthread_mutex_t uv_mutex_t;
 typedef pthread_rwlock_t uv_rwlock_t;
 
+/* Platform-specific definitions for uv_spawn support. */
+typedef gid_t uv_gid_t;
+typedef uid_t uv_uid_t;
+
 /* Platform-specific definitions for uv_dlopen support. */
 typedef void* uv_lib_t;
 #define UV_DYNAMIC /* empty */

include/uv-private/uv-win.h

@@ -165,6 +165,10 @@ typedef struct uv_once_s {
   HANDLE padding;
 } uv_once_t;
 
+/* Platform-specific definitions for uv_spawn support. */
+typedef unsigned char uv_uid_t;
+typedef unsigned char uv_gid_t;
+
 /* Platform-specific definitions for uv_dlopen support. */
 typedef HMODULE uv_lib_t;
 #define UV_DYNAMIC FAR WINAPI

include/uv.h

@@ -1105,12 +1105,18 @@ typedef struct uv_process_options_s {
    * in. Stands for current working directory.
    */
   char* cwd;
-
   /*
-   * TODO describe how this works.
+   * Various flags that control how uv_spawn() behaves. See the definition of
+   * `enum uv_process_flags` below.
    */
-  int windows_verbatim_arguments;
-
+  unsigned int flags;
+  /*
+   * Libuv can change the child process' user/group id. This happens only when
+   * the appropriate bits are set in the flags fields. This is not supported on
+   * windows; uv_spawn() will fail and set the error to UV_ENOTSUP.
+   */
+  uv_uid_t uid;
+  uv_gid_t gid;
   /*
    * The user should supply pointers to initialized uv_pipe_t structs for
    * stdio. This is used to to send or receive input from the subprocess.
@@ -1121,6 +1127,30 @@ typedef struct uv_process_options_s {
   uv_pipe_t* stderr_stream;
 } uv_process_options_t;
 
+/*
+ * These are the flags that can be used for the uv_process_options.flags field.
+ */
+enum uv_process_flags {
+  /*
+   * Set the child process' user id. The user id is supplied in the `uid` field
+   * of the options struct. This does not work on windows; setting this flag
+   * will cause uv_spawn() to fail.
+   */
+  UV_PROCESS_SETUID = (1 << 0),
+  /*
+   * Set the child process' group id. The user id is supplied in the `gid`
+   * field of the options struct. This does not work on windows; setting this
+   * flag will cause uv_spawn() to fail.
+   */
+  UV_PROCESS_SETGID = (1 << 1),
+  /*
+   * Do not wrap any arguments in quotes, or perform any other escaping, when
+   * converting the argument list into a command line string. This option is
+   * only meaningful on Windows systems. On unix it is silently ignored.
+   */
+  UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS = (1 << 2)
+};
+
 /*
  * uv_process_t is a subclass of uv_handle_t
  */
@@ -1135,6 +1165,7 @@ struct uv_process_s {
 UV_EXTERN int uv_spawn(uv_loop_t*, uv_process_t*,
     uv_process_options_t options);
 
+
 /*
  * Kills the process with the specified signal. The user must still
  * call uv_close on the process.

src/unix/process.c

@@ -174,6 +174,12 @@ int uv_spawn(uv_loop_t* loop, uv_process_t* process,
   pid_t pid;
   int flags;
 
+  assert(options.file != NULL);
+  assert(!(options.flags & ~(UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS |
+                             UV_PROCESS_SETGID |
+                             UV_PROCESS_SETUID)));
+
+
   uv__handle_init(loop, (uv_handle_t*)process, UV_PROCESS);
   loop->counters.process_init++;
 
@@ -263,6 +269,16 @@ int uv_spawn(uv_loop_t* loop, uv_process_t* process,
       _exit(127);
     }
 
+    if ((options.flags & UV_PROCESS_SETGID) && setgid(options.gid)) {
+      perror("setgid()");
+      _exit(127);
+    }
+
+    if ((options.flags & UV_PROCESS_SETUID) && setuid(options.uid)) {
+      perror("setuid()");
+      _exit(127);
+    }
+
     environ = options.env;
 
     execvp(options.file, options.args);

src/win/process.c

@@ -872,17 +872,22 @@ int uv_spawn(uv_loop_t* loop, uv_process_t* process,
   STARTUPINFOW startup;
   PROCESS_INFORMATION info;
 
-  if (!options.file) {
-    uv__set_artificial_error(loop, UV_EINVAL);
+  if (options.flags & (UV_PROCESS_SETGID | UV_PROCESS_SETUID)) {
+    uv__set_artificial_error(loop, UV_ENOTSUP);
     return -1;
   }
 
+  assert(options.file != NULL);
+  assert(!(options.flags & ~(UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS |
+                             UV_PROCESS_SETGID |
+                             UV_PROCESS_SETUID)));
+
   uv_process_init(loop, process);
 
   process->exit_cb = options.exit_cb;
   UTF8_TO_UTF16(options.file, application);
   arguments = options.args ? make_program_args(options.args,
-      options.windows_verbatim_arguments) : NULL;
+      options.flags & UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS) : NULL;
   env = options.env ? make_program_env(options.env) : NULL;
 
   if (options.cwd) {