1 files changed, 69 insertions, 0 deletions
diff --git a/lib/sub.c b/lib/sub.c
new file mode 100644
index 0000000..d8e2447
--- /dev/null
+++ b/lib/sub.c
@@ -0,0 +1,69 @@
+/*
+ * SPDX-FileCopyrightText: 1989 - 1991, Julianne Frances Haugh
+ * SPDX-FileCopyrightText: 1996 - 1999, Marek Michałkiewicz
+ * SPDX-FileCopyrightText: 2003 - 2006, Tomasz Kłoczko
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <config.h>
+
+#ident "$Id$"
+
+#include <pwd.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include "prototypes.h"
+#include "defines.h"
+#define	MAX_SUBROOT2	"maximum subsystem depth reached\n"
+#define	BAD_SUBROOT2	"invalid root `%s' for user `%s'\n"
+#define	NO_SUBROOT2	"no subsystem root `%s' for user `%s'\n"
+#define	MAX_DEPTH	1024
+/*
+ * subsystem - change to subsystem root
+ *
+ *	A subsystem login is indicated by the presence of a "*" as
+ *	the first character of the login shell.  The given home
+ *	directory will be used as the root of a new filesystem which
+ *	the user is actually logged into.
+ */
+void subsystem (const struct passwd *pw)
+{
+	static int depth = 0;
+
+	/*
+	 * Prevent endless loop on misconfigured systems.
+	 */
+	if (++depth > MAX_DEPTH) {
+		printf (_("Maximum subsystem depth reached\n"));
+		SYSLOG ((LOG_WARN, MAX_SUBROOT2));
+		closelog ();
+		exit (EXIT_FAILURE);
+	}
+
+	/*
+	 * The new root directory must begin with a "/" character.
+	 */
+
+	if (pw->pw_dir[0] != '/') {
+		printf (_("Invalid root directory '%s'\n"), pw->pw_dir);
+		SYSLOG ((LOG_WARN, BAD_SUBROOT2, pw->pw_dir, pw->pw_name));
+		closelog ();
+		exit (EXIT_FAILURE);
+	}
+
+	/*
+	 * The directory must be accessible and the current process
+	 * must be able to change into it.
+	 */
+
+	if (   (chroot (pw->pw_dir) != 0)
+	    || (chdir ("/") != 0)) {
+		(void) printf (_("Can't change root directory to '%s'\n"),
+		               pw->pw_dir);
+		SYSLOG ((LOG_WARN, NO_SUBROOT2, pw->pw_dir, pw->pw_name));
+		closelog ();
+		exit (EXIT_FAILURE);
+	}
+}
+