passwd: rework:

* do not make backup copy by copying (just retain old file)
* correctly fall back to /etc/passwd if user is not in shadow
* fix bug with overlong passwd entries
* be permissive on some kinds of failures
* reduce stack usage
* code size: -500 bytes

libbb/bb_askpass.c

@@ -60,7 +60,7 @@ char *bb_askpass(int timeout, const char * prompt)
 		   (read did not overwrite it) */
 		do {
 			if (passwd[i] == '\r' || passwd[i] == '\n')
-				passwd[i] = 0;
+				passwd[i] = '\0';
 		} while (passwd[i++]);
 	}
 

libbb/get_line_from_file.c

@@ -9,11 +9,9 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-#include <stdio.h>
-#include <stdlib.h>
 #include "libbb.h"
 
-/* get_line_from_file() - This function reads an entire line from a text file,
+/* This function reads an entire line from a text file,
  * up to a newline or NUL byte.  It returns a malloc'ed char * which must be
  * stored and free'ed  by the caller.  If end is null '\n' isn't considered
  * end of line.  If end isn't null, length of the chunk read is stored in it. */
@@ -37,10 +35,12 @@ char *bb_get_chunk_from_file(FILE * file, int *end)
 	if (end)
 		*end = idx;
 	if (linebuf) {
-		if (ferror(file)) {
-			free(linebuf);
-			return NULL;
-		}
+		// huh, is fgets discards prior data on error like this?
+		// I don't think so....
+		//if (ferror(file)) {
+		//	free(linebuf);
+		//	return NULL;
+		//}
 		linebuf = xrealloc(linebuf, idx+1);
 		linebuf[idx] = 0;
 	}

libbb/obscure.c

@@ -157,14 +157,14 @@ static const char *obscure_msg(const char *old_p, const char *new_p, const struc
 	return NULL;
 }
 
-int obscure(const char *old, const char *newval, const struct passwd *pwdp)
+int obscure(const char *old, const char *newval, const struct passwd *pw)
 {
 	const char *msg;
 
-	if ((msg = obscure_msg(old, newval, pwdp))) {
-		printf("Bad password: %s.\n", msg);
-		/* If user is root warn only */
-		return getuid() ? 1 : 0;
+	msg = obscure_msg(old, newval, pw);
+	if (msg) {
+		printf("Bad password: %s\n", msg);
+		return 1;
 	}
 	return 0;
 }