common: allow disabling of timeout for password entry

In case a user has to enter a complicated password it is sometimes
desireable to give the user more time than the default timeout.
Enabling this feature will disable the timeout entirely in case the user
presses the <Enter> key before entering any other character.
Signed-off-by: NSteffen Jaeckel <jaeckel-floss@eyet-services.de>
Reviewed-by: NSimon Glass <sjg@chromium.org>

common/Kconfig.boot

@@ -860,6 +860,14 @@ config AUTOBOOT_KEYED_CTRLC
 	  Setting this variable	provides an escape sequence from the
 	  limited "password" strings.
 
+config AUTOBOOT_NEVER_TIMEOUT
+	bool "Make the password entry never time-out"
+	depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION && CRYPT_PW
+	help
+	  This option removes the timeout from the password entry
+	  when the user first presses the <Enter> key before entering
+	  any other character.
+
 config AUTOBOOT_STOP_STR_ENABLE
 	bool "Enable fixed string to stop autobooting"
 	depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION

common/autoboot.c

@@ -63,6 +63,10 @@ static int menukey;
  * or
  *   the config value CONFIG_AUTOBOOT_STOP_STR_CRYPT
  *
+ * In case the config value CONFIG_AUTOBOOT_NEVER_TIMEOUT has been enabled
+ * this function never times out if the user presses the <Enter> key
+ * before starting to enter the password.
+ *
  * @etime: Timeout value ticks (stop when get_ticks() reachs this)
  * @return 0 if autoboot should continue, 1 if it should stop
  */
@@ -72,6 +76,7 @@ static int passwd_abort_crypt(uint64_t etime)
 	char presskey[DELAY_STOP_STR_MAX_LENGTH];
 	u_int presskey_len = 0;
 	int abort = 0;
+	int never_timeout = 0;
 	int err;
 
 	if (IS_ENABLED(CONFIG_AUTOBOOT_STOP_STR_ENABLE) && !crypt_env_str)
@@ -91,6 +96,11 @@ static int passwd_abort_crypt(uint64_t etime)
 
 			if ((presskey[presskey_len] == '\r') ||
 			    (presskey[presskey_len] == '\n')) {
+				if (IS_ENABLED(CONFIG_AUTOBOOT_NEVER_TIMEOUT) &&
+				    !presskey_len) {
+					never_timeout = 1;
+					continue;
+				}
 				presskey[presskey_len] = '\0';
 				err = crypt_compare(crypt_env_str, presskey,
 						    &abort);
@@ -104,7 +114,7 @@ static int passwd_abort_crypt(uint64_t etime)
 				presskey_len++;
 			}
 		}
-	} while (get_ticks() <= etime);
+	} while (never_timeout || get_ticks() <= etime);
 
 	return abort;
 }