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>

5 files changed, 39 insertions, 22 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 5388d9d..ed9a562 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1408,10 +1408,11 @@ extern int set_loop(char **devname, const char *file, unsigned long long offset,
 #define BB_LO_FLAGS_READ_ONLY 1
 #define BB_LO_FLAGS_AUTOCLEAR 4
 
-/* Like bb_ask_noecho below, but asks on stdin with no timeout.  */
+/* Returns malloced str */
+char *bb_ask_noecho(int fd, int timeout, const char *prompt) FAST_FUNC;
+/* Like bb_ask_noecho, but asks on stdin with no timeout.  */
 char *bb_ask_noecho_stdin(const char *prompt) FAST_FUNC;
-//TODO: pass buf pointer or return allocated buf (avoid statics)?
-char *bb_ask_noecho(const int fd, int timeout, const char *prompt) FAST_FUNC;
+
 int bb_ask_y_confirmation_FILE(FILE *fp) FAST_FUNC;
 int bb_ask_y_confirmation(void) FAST_FUNC;
 
diff --git a/libbb/bb_askpass.c b/libbb/bb_askpass.c
index aadc691..2dcead3 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);
+}
diff --git a/loginutils/cryptpw.c b/loginutils/cryptpw.c
index 3ca7eda..fbb7f05 100644
--- a/loginutils/cryptpw.c
+++ b/loginutils/cryptpw.c
@@ -133,7 +133,7 @@ int cryptpw_main(int argc UNUSED_PARAM, char **argv)
 	if (!password) {
 		/* Only mkpasswd, and only from tty, prompts.
 		 * Otherwise it is a plain read. */
-		password = (ENABLE_MKPASSWD && isatty(STDIN_FILENO) && applet_name[0] == 'm')
+		password = (ENABLE_MKPASSWD && applet_name[0] == 'm' && isatty(STDIN_FILENO))
 			? bb_ask_noecho_stdin("Password: ")
 			: xmalloc_fgetline(stdin)
 		;
diff --git a/loginutils/passwd.c b/loginutils/passwd.c
index 02303b5..d0408d8 100644
--- a/loginutils/passwd.c
+++ b/loginutils/passwd.c
@@ -65,11 +65,9 @@ static char* new_password(const struct passwd *pw, uid_t myuid, const char *algo
 		if (ENABLE_FEATURE_CLEAN_UP)
 			free(encrypted);
 	}
-	orig = xstrdup(orig); /* or else bb_ask_noecho_stdin() will destroy it */
 	newp = bb_ask_noecho_stdin("New password: "); /* returns ptr to static */
 	if (!newp)
 		goto err_ret;
-	newp = xstrdup(newp); /* we are going to bb_ask_noecho_stdin() again, so save it */
 	if (ENABLE_FEATURE_PASSWD_WEAK_CHECK
 	 && obscure(orig, newp, pw)
 	 && myuid != 0
@@ -99,6 +97,7 @@ static char* new_password(const struct passwd *pw, uid_t myuid, const char *algo
 	if (ENABLE_FEATURE_CLEAN_UP) free(newp);
 
 	nuke_str(cp);
+	if (ENABLE_FEATURE_CLEAN_UP) free(cp);
 	return ret;
 }
 
diff --git a/mailutils/mail.c b/mailutils/mail.c
index 0fc615a..7af7edd 100644
--- a/mailutils/mail.c
+++ b/mailutils/mail.c
@@ -163,8 +163,8 @@ void FAST_FUNC encode_base64(char *fname, const char *text, const char *eol)
 void FAST_FUNC get_cred_or_die(int fd)
 {
 	if (isatty(fd)) {
-		G.user = xstrdup(bb_ask_noecho(fd, /* timeout: */ 0, "User: "));
-		G.pass = xstrdup(bb_ask_noecho(fd, /* timeout: */ 0, "Password: "));
+		G.user = bb_ask_noecho(fd, /* timeout: */ 0, "User: ");
+		G.pass = bb_ask_noecho(fd, /* timeout: */ 0, "Password: ");
 	} else {
 		G.user = xmalloc_reads(fd, /* maxsize: */ NULL);
 		G.pass = xmalloc_reads(fd, /* maxsize: */ NULL);