libbb: switch bb_ask_noecho() to "mallocing" string return API

function                                             old     new   delta
bb_ask_noecho                                        313     330     +17
get_cred_or_die                                      125     115     -10
passwd_main                                          995     958     -37
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 17/-47)            Total: -30 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 31 insertions, 14 deletions

diff --git a/libbb/bb_askpass.c b/libbb/bb_askpass.c
index aadc69108..2dcead35a 100644
--- a/libbb/bb_askpass.c
+++ b/libbb/bb_askpass.c
@@ -13,16 +13,9 @@ static void askpass_timeout(int UNUSED_PARAM ignore)
 {
 }
 
-char* FAST_FUNC bb_ask_noecho_stdin(const char *prompt)
-{
-        return bb_ask_noecho(STDIN_FILENO, 0, prompt);
-}
-char* FAST_FUNC bb_ask_noecho(const int fd, int timeout, const char *prompt)
+char* FAST_FUNC bb_ask_noecho(int fd, int timeout, const char *prompt)
 {
-        /* Was static char[BIGNUM] */
-        enum { sizeof_passwd = 128 };
-
-        char *passwd;
+#define MAX_LINE 0xfff
         char *ret;
         int i;
         struct sigaction sa, oldsa;
@@ -37,7 +30,17 @@ char* FAST_FUNC bb_ask_noecho(const int fd, int timeout, const char *prompt)
 
         tcgetattr(fd, &oldtio);
         tio = oldtio;
-        /* Switch off echo */
+        /* Switch off echo. ECHOxyz meaning:
+         * ECHO    echo input chars
+         * ECHOE   echo BS-SP-BS on erase character
+         * ECHOK   echo kill char specially, not as ^c (ECHOKE controls how exactly)
+         * ECHOKE  erase all input via BS-SP-BS on kill char (else go to next line)
+         * ECHOCTL Echo ctrl chars as ^c (else echo verbatim:
+         *         e.g. up arrow emits "ESC-something" and thus moves cursor up!)
+         * ECHONL  Echo NL even if ECHO is not set
+         * ECHOPRT On erase, echo erased chars
+         *         [qwe<BS><BS><BS> input looks like "qwe\ewq/" on screen]
+         */
         tio.c_lflag &= ~(ECHO|ECHOE|ECHOK|ECHONL);
         tcsetattr(fd, TCSANOW, &tio);
 
@@ -51,20 +54,30 @@ char* FAST_FUNC bb_ask_noecho(const int fd, int timeout, const char *prompt)
                 alarm(timeout);
         }
 
-        passwd = auto_string(xmalloc(sizeof_passwd));
-        ret = passwd;
+        ret = NULL;
         i = 0;
         while (1) {
-                int r = read(fd, &ret[i], 1);
+                int r;
+
+                /* User input is uber-slow, no need to optimize reallocs.
+                 * Grow it on every char.
+                 */
+                ret = xrealloc(ret, i + 2);
+                r = read(fd, &ret[i], 1);
+
                 if ((i == 0 && r == 0) /* EOF (^D) with no password */
                  || r < 0 /* read is interrupted by timeout or ^C */
                 ) {
+                        ret[i] = '\0'; /* paranoia */
+                        nuke_str(ret); /* paranoia */
+                        free(ret);
                         ret = NULL;
                         break;
                 }
+
                 if (r == 0 /* EOF */
                  || ret[i] == '\r' || ret[i] == '\n' /* EOL */
-                 || ++i == sizeof_passwd-1 /* line limit */
+                 || ++i == MAX_LINE /* line limit */
                 ) {
                         ret[i] = '\0';
                         break;
@@ -80,3 +93,7 @@ char* FAST_FUNC bb_ask_noecho(const int fd, int timeout, const char *prompt)
         fflush_all();
         return ret;
 }
+char* FAST_FUNC bb_ask_noecho_stdin(const char *prompt)
+{
+        return bb_ask_noecho(STDIN_FILENO, 0, prompt);
+}