[PATCH] chsh: remove local /etc/shells parsing in favour of getusershell(3)

* [PATCH] chsh: remove local /etc/shells parsing in favour of getusershell(3)
@ 2017-08-28 20:38 Sami Kerola
  2017-08-30  7:32 ` Karel Zak
  0 siblings, 1 reply; 4+ messages in thread
From: Sami Kerola @ 2017-08-28 20:38 UTC (permalink / raw)
  To: util-linux; +Cc: Sami Kerola

Less code, less bugs.  And if there are bugs at least share them with all
other programs that use getusershell(3) from libc.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
---
 login-utils/chsh.c | 98 ++++++++++--------------------------------------------
 1 file changed, 18 insertions(+), 80 deletions(-)

diff --git a/login-utils/chsh.c b/login-utils/chsh.c
index 4721c870e..c267c7272 100644
--- a/login-utils/chsh.c
+++ b/login-utils/chsh.c
@@ -67,9 +67,6 @@ struct sinfo {
 	char *shell;
 };
 
-/* global due readline completion */
-static char **global_shells;
-
 static void __attribute__((__noreturn__)) usage(void)
 {
 	FILE *fp = stdout;
@@ -89,79 +86,26 @@ static void __attribute__((__noreturn__)) usage(void)
 	exit(EXIT_SUCCESS);
 }
 
-/*
- *  free_shells () -- free shells allocations.
- */
-static void free_shells(void)
-{
-	if (global_shells) {
-		char **s;
-
-		for (s = global_shells; *s; s++)
-			free(*s);
-		free(global_shells);
-	}
-}
-
-/*
- *  init_shells () -- reads /etc/shells into global_shells
- */
-static int init_shells(void)
-{
-	FILE *fp;
-	char *buf = NULL;
-	size_t sz = 0, shellsz = 8, n = 0;
-	ssize_t len;
-
-	if (global_shells)
-		return 0;	/* already initialized */
-
-	fp = fopen(_PATH_SHELLS, "r");
-	if (!fp)
-		return 1;
-
-	global_shells = xmalloc(sizeof(char *) * shellsz);
-
-	while ((len = getline(&buf, &sz, fp)) != -1) {
-		/* ignore comments and blank lines */
-		if (*buf == '#' || len < 2)
-			continue;
-		/* strip the ending newline */
-		if (buf[len - 1] == '\n')
-			buf[len - 1] = 0;
-		global_shells[n++] = buf;
-		if (shellsz < n) {
-			shellsz *= 2;
-			global_shells = xrealloc(global_shells, sizeof(char *) * shellsz);
-		}
-		buf = NULL;
-	}
-
-	free(buf);
-	global_shells[n] = NULL;
-
-	fclose(fp);
-	atexit(free_shells);
-
-	return 0;
-}
-
 /*
  *  is_known_shell() -- if the given shell appears in /etc/shells,
  *	return true.  if not, return false.
  */
 static int is_known_shell(const char *shell_name)
 {
-	char **s;
+	char *s, ret = 0;
 
-	if (!global_shells || !shell_name)
+	if (!shell_name)
 		return 0;
 
-	for (s = global_shells; *s; s++) {
-		if (strcmp(shell_name, *s) == 0)
-			return 1;
+	setusershell();
+	while ((s = getusershell())) {
+		if (strcmp(shell_name, s) == 0) {
+			ret = 1;
+			break;
+		}
 	}
-	return 0;
+	endusershell();
+	return ret;
 }
 
 /*
@@ -169,29 +113,25 @@ static int is_known_shell(const char *shell_name)
  */
 static void print_shells(void)
 {
-	char **s;
-
-	if (!global_shells)
-		return;
+	char *s;
 
-	for (s = global_shells; *s; s++)
-		printf("%s\n", *s);
+	while ((s = getusershell()))
+		printf("%s\n", s);
+	endusershell();
 }
 
 #ifdef HAVE_LIBREADLINE
 static char *shell_name_generator(const char *text, int state)
 {
-	static size_t len, idx;
+	static size_t len;
 	char *s;
 
-	if (!global_shells)
-		return NULL;
-
 	if (!state) {
-		idx = 0;
+		setusershell();
 		len = strlen(text);
 	}
-	while ((s = global_shells[idx++])) {
+
+	while ((s = getusershell())) {
 		if (strncmp(s, text, len) == 0)
 			return xstrdup(s);
 	}
@@ -232,7 +172,6 @@ static void parse_argv(int argc, char **argv, struct sinfo *pinfo)
 		case 'h':
 			usage();
 		case 'l':
-			init_shells();
 			print_shells();
 			exit(EXIT_SUCCESS);
 		case 's':
@@ -386,7 +325,6 @@ int main(int argc, char **argv)
 		    _("running UID doesn't match UID of user we're "
 		      "altering, shell change denied"));
 	}
-	init_shells();
 	if (uid != 0 && !is_known_shell(oldshell)) {
 		errno = EACCES;
 		err(EXIT_FAILURE, _("your shell is not in %s, "
-- 
2.14.1


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