fix sftp.exe client to work using password authentication

ssh.exe client invoked underneath was not able to send password prompt
and read password from user as stdin and stdout handles were redirected
to sockets by sftp.exe ; stderr which is not redirected is used to show
prompt to users and data is read from console

contrib/win32/win32compat/socket.c

@@ -72,6 +72,7 @@ static fd_set write_sfd_set;
 
 int PassInputFd  = STDIN_FILENO;
 int PassOutputFd = STDOUT_FILENO;
+int PassErrorFd = STDERR_FILENO;
 
 /*
  * We store cookies for authorize 

readpass.c

@@ -54,6 +54,7 @@
   
   extern int PassInputFd;
   extern int PassOutputFd;
+  extern int PassErrorFd;
 
 #endif
 
@@ -334,109 +335,39 @@ read_passphrase(const char *prompt, int flags)
    * Show prompt for user.
    */
 
-  _write(PassOutputFd, prompt, strlen(prompt));
+  _write(PassErrorFd, prompt, strlen(prompt));
-
-  /*
-   * Disable stdin echo.
-   */
-   
-  GetConsoleMode(GetStdHandle(STD_INPUT_HANDLE), &mode);
-    
-  SetConsoleMode(GetStdHandle(STD_INPUT_HANDLE), mode & (~ENABLE_ECHO_INPUT));
-  
-  /*
-   * Read pass from stdin socket.
-   */
 
   len = retr = 0;
+  int bufsize = sizeof(buf);
 
-  do
+	while (_kbhit())
-  {
+		_getch();
-    retr = _read(PassInputFd, buf + len, sizeof(buf) - 1 - len);
 
-    /*
+	while ( len < bufsize ) {
-     * If read error.
-     */
 
-    if (retr == -1)
+	 	buf[len] = (unsigned char) _getch() ;
-    {
-      int winerr = GetLastError();
 
-      /*
-       * Non fatal. Only write message and try again.
-       */
 
-      if (errno == EINTR || errno == EAGAIN ||
+		if ( buf[len] == '\r' ) {
-              winerr == WSAENOTSOCK || winerr == WSAEWOULDBLOCK)
+			if (_kbhit() )
-      {
+				_getch(); // read linefeed if its there
-        debug("ERROR. read_passphrase() : [errno = %d, winerr = %d], "
+			break;
-                  "trying again...\n", errno, winerr);
+		}
+		else if ( buf[len] == '\n' ) {
+			break;
+		}
+		else if ( buf[len] == '\b' ) { // backspace
+			if (len > 0 )
+				len--; // overwrite last character
+		}
+		else {
 
-        fflush(stderr);        
+			_putch( (int) '*' ); // show a star in place of what is typed
-      }
+			len++; // keep reading in the loop
+		}
+	}
 
-      /*
+	buf[len] = '\0' ; // get rid of the cr/lf
-       * Fatal error. Break loop with empty string.
-       */
-
-      else
-      {
-        error("ERROR. read_passphrase() : fatal error"
-                  " [errno = %d, winerr = %d]...\n", errno, winerr);
-      
-        fflush(stderr);
-      
-        buf[0] = 0;
-      
-        len = 1;
-      
-        break;
-      }  
-    }
-
-    /*
-     * No error.
-     */
-    
-    else
-    {
-      len += retr;
-    }
-  } while (len < sizeof(buf) - 1 && buf[len] == '\r');
-
-  /*
-   * Put zero at string end.
-   */
-
-  if (len > 0)
-  {
-    buf[len - 1] = '\0';
-  }
-  else
-  {
-    buf[0] = '\0';
-  }
-  
-  _write(PassOutputFd, "\n", strlen("\n"));
-
-  len = strlen(buf);
-  
-  while (len > 0 && buf[len - 1] == 0xa || buf[len - 1] == 0xd)
-  {
-    buf[len - 1] = 0;
-    
-    len --;
-  }
-  
-  /*
-   * Set stdin echo back.
-   */
-   
-  SetConsoleMode(GetStdHandle(STD_INPUT_HANDLE), mode | ENABLE_ECHO_INPUT);
-  
-  /*
-   * Return copy of pass readed from stdin.
-   */
 
   ret = xstrdup(buf);