skeud

commit: af92291786c15c4263e6fde408b75709d991ac5e
parent ac7eca22806f1d17e66b640bcebfec06a19a6bf1
Author: Haelwenn (lanodan) Monnier <contact@hacktivis.me>
Date:   Mon, 10 Nov 2025 09:13:09 +0100

login: function-wrap fallible pwent processing

Fixes on-exit memory leaks due to lack of free(username_buf)
on it returning errorneously.

Diffstat:
M
login.c
110
++++++++++++++++++++++++++++++++++++++++++++-----------------------------------

1 file changed, 61 insertions(+), 49 deletions(-)
diff --git a/login.c b/login.c
@@ -29,6 +29,60 @@
 extern char **environ;
 char *envclear[] = {NULL};
 
+static int
+process_pwent(struct passwd *pwent)
+{
+	int tty_gid             = pwent->pw_gid;
+	struct group *tty_group = getgrnam(TTY_GROUP);
+	if(tty_group == NULL)
+	{
+		perror("login: warning: getgrnam");
+	}
+	else
+	{
+		tty_gid = tty_group->gr_gid;
+	}
+
+	/* considers that STDIN_FILENO is close enough to the current tty */
+	if(fchown(STDIN_FILENO, pwent->pw_uid, tty_gid) < 0)
+	{
+		perror("login: error: fchown");
+		return 1;
+	}
+	if(fchmod(STDIN_FILENO, TTY_PERMS))
+	{
+		perror("login: error: fchmod");
+		return 1;
+	}
+	if(setgid(pwent->pw_gid) < 0)
+	{
+		perror("login: error: setgid");
+		return 1;
+	}
+	if(initgroups(pwent->pw_name, pwent->pw_gid) < 0)
+	{
+		perror("login: error: initgroups");
+		return 1;
+	}
+	if(setuid(pwent->pw_uid) < 0)
+	{
+		perror("login: error: setuid");
+		return 1;
+	}
+
+	if(pwent->pw_dir != NULL)
+	{
+		setenv("HOME", pwent->pw_dir, 1);
+
+		if(chdir(pwent->pw_dir) != 0)
+		{
+			fprintf(stderr, "login: warning: Failed to change current directory to: %s\n", pwent->pw_dir);
+		}
+	}
+
+	return 0;
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -187,62 +241,20 @@ main(int argc, char *argv[])
 
 	if(pwent != NULL)
 	{
-		int tty_gid             = pwent->pw_gid;
-		struct group *tty_group = getgrnam(TTY_GROUP);
-		if(tty_group == NULL)
-		{
-			perror("login: warning: getgrnam");
-		}
-		else
-		{
-			tty_gid = tty_group->gr_gid;
-		}
-
-		/* considers that STDIN_FILENO is close enough to the current tty */
-		if(fchown(STDIN_FILENO, pwent->pw_uid, tty_gid) < 0)
-		{
-			perror("login: error: fchown");
-			return 1;
-		}
-		if(fchmod(STDIN_FILENO, TTY_PERMS))
-		{
-			perror("login: error: fchmod");
-			return 1;
-		}
-		if(setgid(pwent->pw_gid) < 0)
-		{
-			perror("login: error: setgid");
-			return 1;
-		}
-		if(initgroups(pwent->pw_name, pwent->pw_gid) < 0)
-		{
-			perror("login: error: initgroups");
-			return 1;
-		}
-		if(setuid(pwent->pw_uid) < 0)
-		{
-			perror("login: error: setuid");
-			return 1;
-		}
-
 		if(pwent->pw_shell != NULL)
 		{
 			shell = pwent->pw_shell;
 		}
 
-		if(pwent->pw_dir != NULL)
-		{
-			setenv("HOME", pwent->pw_dir, 1);
-
-			if(chdir(pwent->pw_dir) != 0)
-			{
-				fprintf(
-				    stderr, "login: warning: Failed to change current directory to: %s\n", pwent->pw_dir);
-			}
-		}
-
+		int ret = process_pwent(pwent);
 		explicit_bzero(pwent, sizeof(pwent));
 		pwent = NULL;
+
+		if(ret != 0)
+		{
+			free(username_buf);
+			return ret;
+		}
 	}
 
 	setenv("USER", username, 1);