make echo -e "foo\nfoo" | passwd USER work

Suggested by Michael Zhu (linuxsir320 AT gmail.com)

function                                             old     new   delta
bb_ask                                               333     340      +7

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

1 files changed, 21 insertions, 17 deletions

diff --git a/libbb/bb_askpass.c b/libbb/bb_askpass.c
index f9b918cec..bdb756659 100644
--- a/libbb/bb_askpass.c
+++ b/libbb/bb_askpass.c
@@ -30,10 +30,6 @@ char* FAST_FUNC bb_ask(const int fd, int timeout, const char *prompt)
 	struct sigaction sa, oldsa;
 	struct termios tio, oldtio;
 
-	if (!passwd)
-		passwd = xmalloc(sizeof_passwd);
-	memset(passwd, 0, sizeof_passwd);
-
 	tcgetattr(fd, &oldtio);
 	tcflush(fd, TCIFLUSH);
 	tio = oldtio;
@@ -46,7 +42,7 @@ char* FAST_FUNC bb_ask(const int fd, int timeout, const char *prompt)
 
 	memset(&sa, 0, sizeof(sa));
 	/* sa.sa_flags = 0; - no SA_RESTART! */
-	/* SIGINT and SIGALRM will interrupt read below */
+	/* SIGINT and SIGALRM will interrupt reads below */
 	sa.sa_handler = askpass_timeout;
 	sigaction(SIGINT, &sa, &oldsa);
 	if (timeout) {
@@ -56,18 +52,26 @@ char* FAST_FUNC bb_ask(const int fd, int timeout, const char *prompt)
 
 	fputs(prompt, stdout);
 	fflush_all();
-	ret = NULL;
-	/* On timeout or Ctrl-C, read will hopefully be interrupted,
-	 * and we return NULL */
-	if (read(fd, passwd, sizeof_passwd - 1) > 0) {
-		ret = passwd;
-		i = 0;
-		/* Last byte is guaranteed to be 0
-		   (read did not overwrite it) */
-		do {
-			if (passwd[i] == '\r' || passwd[i] == '\n')
-				passwd[i] = '\0';
-		} while (passwd[i++]);
+
+	if (!passwd)
+		passwd = xmalloc(sizeof_passwd);
+	memset(passwd, 0, sizeof_passwd);
+	ret = passwd;
+	i = 0;
+	while (1) {
+		int r = read(fd, &ret[i], 1);
+		if (r < 0) {
+			/* read is interrupted by timeout or ^C */
+			ret = NULL;
+			break;
+		}
+		if (r == 0 /* EOF */
+		 || ret[i] == '\r' || ret[i] == '\n' /* EOL */
+		 || ++i == sizeof_passwd-1 /* line limit */
+		) {
+			ret[i] = '\0';
+			break;
+		}
 	}
 
 	if (timeout) {