windows: fix compatibility with cygwin pipes

This makes libuv more tolerant to the properties of the pipes
that it can use without any issue. This is necessary because Cygwin
(and hence Mintty) opens STDIN without FILE_WRITE_ATTRIBUTES.

src/win/pipe.c

@@ -230,7 +230,7 @@ static int uv_set_pipe_handle(uv_loop_t* loop,
   NTSTATUS nt_status;
   IO_STATUS_BLOCK io_status;
   FILE_MODE_INFORMATION mode_info;
-  DWORD mode = PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT;
+  DWORD mode = PIPE_READMODE_BYTE | PIPE_WAIT;
   DWORD current_mode = 0;
   DWORD err = 0;
 
@@ -246,11 +246,9 @@ static int uv_set_pipe_handle(uv_loop_t* loop,
       if (!GetNamedPipeHandleState(pipeHandle, &current_mode, NULL, NULL,
                                    NULL, NULL, 0)) {
         return -1;
-      } else if (current_mode != mode) {
+      } else if (current_mode & PIPE_NOWAIT) {
         SetLastError(ERROR_ACCESS_DENIED);
         return -1;
-      } else {
-        duplex_flags &= ~UV_HANDLE_WRITABLE;
       }
     } else {
       /* If this returns ERROR_INVALID_PARAMETER we probably opened
@@ -1772,7 +1770,34 @@ static void eof_timer_close_cb(uv_handle_t* handle) {
 
 int uv_pipe_open(uv_pipe_t* pipe, uv_file file) {
   HANDLE os_handle = uv__get_osfhandle(file);
-  DWORD duplex_flags = UV_HANDLE_READABLE | UV_HANDLE_WRITABLE;
+  NTSTATUS nt_status;
+  IO_STATUS_BLOCK io_status;
+  FILE_ACCESS_INFORMATION access;
+  DWORD duplex_flags = 0;
+
+  /* Determine what kind of permissions we have on this handle.
+   * Cygwin opens the pipe in message mode, but we can support it,
+   * just query the access flags and set the stream flags accordingly.
+   */
+  nt_status = pNtQueryInformationFile(os_handle,
+                                      &io_status,
+                                      &access,
+                                      sizeof(access),
+                                      FileAccessInformation);
+  if (nt_status != STATUS_SUCCESS)
+    return UV_EINVAL;
+
+  if (pipe->ipc) {
+    if (!(access.AccessFlags & FILE_WRITE_DATA) ||
+        !(access.AccessFlags & FILE_READ_DATA)) {
+      return UV_EINVAL;
+    }
+  }
+
+  if (access.AccessFlags & FILE_WRITE_DATA)
+    duplex_flags |= UV_HANDLE_WRITABLE;
+  if (access.AccessFlags & FILE_READ_DATA)
+    duplex_flags |= UV_HANDLE_READABLE;
 
   if (os_handle == INVALID_HANDLE_VALUE ||
       uv_set_pipe_handle(pipe->loop, pipe, os_handle, duplex_flags) == -1) {