From 8aaf18e08a2ee95a1d2687fbfdb584548375b5e1 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Thu, 6 Feb 2020 09:50:35 +0100
Subject: [PATCH] shared/ask-password-api: show "(press TAB for no echo)"

For #8495: it is arguably useful to not show the length of the password
in public spaces. It is possible to press TAB or BS to cancel the asterisks,
but this is not very discoverable. Let's make it discoverable by showing
a message (in gray). The message is "erased" after the first character
is entered.
---
 src/shared/ask-password-api.c    | 25 +++++++++++++++++++++----
 src/test/test-ask-password-api.c |  2 +-
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index a6c83e181a..7abe7d1711 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -394,6 +394,10 @@ finish:
         return r;
 }
 
+#define NO_ECHO "(no echo) "
+#define PRESS_TAB "(press TAB for no echo) "
+#define SKIPPED "(skipped)"
+
 int ask_password_tty(
                 int ttyfd,
                 const char *message,
@@ -409,7 +413,7 @@ int ask_password_tty(
                 _POLL_MAX,
         };
 
-        bool reset_tty = false, dirty = false, use_color = false;
+        bool reset_tty = false, dirty = false, use_color = false, press_tab_visible = false;
         _cleanup_close_ int cttyfd = -1, notify = -1;
         struct termios old_termios, new_termios;
         char passphrase[LINE_MAX + 1] = {}, *x;
@@ -465,6 +469,13 @@ int ask_password_tty(
                 (void) loop_write(ttyfd, message, strlen(message), false);
                 (void) loop_write(ttyfd, " ", 1, false);
 
+                if (!(flags & ASK_PASSWORD_SILENT)) {
+                        if (use_color)
+                                (void) loop_write(ttyfd, ANSI_GREY, STRLEN(ANSI_GREY), false);
+                        (void) loop_write(ttyfd, PRESS_TAB, strlen(PRESS_TAB), false);
+                        press_tab_visible = true;
+                }
+
                 if (use_color)
                         (void) loop_write(ttyfd, ANSI_NORMAL, STRLEN(ANSI_NORMAL), false);
 
@@ -550,13 +561,19 @@ int ask_password_tty(
 
                 }
 
+                if (press_tab_visible) {
+                        assert(ttyfd >= 0);
+                        backspace_chars(ttyfd, strlen(PRESS_TAB));
+                        press_tab_visible = false;
+                }
+
                 /* We treat EOF, newline and NUL byte all as valid end markers */
                 if (n == 0 || c == '\n' || c == 0)
                         break;
 
                 if (c == 4) { /* C-d also known as EOT */
                         if (ttyfd >= 0)
-                                (void) loop_write(ttyfd, "(skipped)", 9, false);
+                                (void) loop_write(ttyfd, SKIPPED, strlen(SKIPPED), false);
 
                         goto skipped;
                 }
@@ -606,7 +623,7 @@ int ask_password_tty(
                                  * first key (and only as first key), or ... */
 
                                 if (ttyfd >= 0)
-                                        (void) loop_write(ttyfd, "(no echo) ", 10, false);
+                                        (void) loop_write(ttyfd, NO_ECHO, strlen(NO_ECHO), false);
 
                         } else if (ttyfd >= 0)
                                 (void) loop_write(ttyfd, "\a", 1, false);
@@ -619,7 +636,7 @@ int ask_password_tty(
                         /* ... or by pressing TAB at any time. */
 
                         if (ttyfd >= 0)
-                                (void) loop_write(ttyfd, "(no echo) ", 10, false);
+                                (void) loop_write(ttyfd, NO_ECHO, strlen(NO_ECHO), false);
 
                 } else if (p >= sizeof(passphrase)-1) {
 
diff --git a/src/test/test-ask-password-api.c b/src/test/test-ask-password-api.c
index 13a1064b45..098bb35bce 100644
--- a/src/test/test-ask-password-api.c
+++ b/src/test/test-ask-password-api.c
@@ -8,7 +8,7 @@ static void test_ask_password(void) {
         int r;
         _cleanup_strv_free_ char **ret = NULL;
 
-        r = ask_password_tty(-1, "hello?", "da key", 0, 0, NULL, &ret);
+        r = ask_password_tty(-1, "hello?", "da key", 0, ASK_PASSWORD_CONSOLE_COLOR, NULL, &ret);
         if (r == -ECANCELED)
                 assert_se(ret == NULL);
         else {
-- 
2.25.1