1 files changed, 108 insertions, 0 deletions
diff --git a/lib/root_flag.c b/lib/root_flag.c
new file mode 100644
index 0000000..5572831
--- /dev/null
+++ b/lib/root_flag.c
@@ -0,0 +1,108 @@
+/*
+ * SPDX-FileCopyrightText: 2011       , Julian Pidancet
+ * SPDX-FileCopyrightText: 2011       , Nicolas François
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <config.h>
+
+#ident "$Id$"
+
+#include <stdio.h>
+#include <assert.h>
+#include "defines.h"
+#include "prototypes.h"
+/*@-exitarg@*/
+#include "exitcodes.h"
+#include "shadowlog.h"
+
+static void change_root (const char* newroot);
+
+/*
+ * process_root_flag - chroot if given the --root option
+ *
+ * This shall be called before accessing the passwd, group, shadow,
+ * gshadow, useradd's default, login.defs files (non exhaustive list)
+ * or authenticating the caller.
+ *
+ * The audit, syslog, or locale files shall be open before
+ */
+extern void process_root_flag (const char* short_opt, int argc, char **argv)
+{
+	/*
+	 * Parse the command line options.
+	 */
+	int i;
+	const char *newroot = NULL, *val;
+
+	for (i = 0; i < argc; i++) {
+		val = NULL;
+		if (   (strcmp (argv[i], "--root") == 0)
+		    || ((strncmp (argv[i], "--root=", 7) == 0)
+			&& (val = argv[i] + 7))
+		    || (strcmp (argv[i], short_opt) == 0)) {
+			if (NULL != newroot) {
+				fprintf (log_get_logfd(),
+				         _("%s: multiple --root options\n"),
+				         log_get_progname());
+				exit (E_BAD_ARG);
+			}
+
+			if (val) {
+				newroot = val;
+			} else if (i + 1 == argc) {
+				fprintf (log_get_logfd(),
+				         _("%s: option '%s' requires an argument\n"),
+				         log_get_progname(), argv[i]);
+				exit (E_BAD_ARG);
+			} else {
+				newroot = argv[++ i];
+			}
+		}
+	}
+
+	if (NULL != newroot) {
+		change_root (newroot);
+	}
+}
+
+static void change_root (const char* newroot)
+{
+	/* Drop privileges */
+	if (   (setregid (getgid (), getgid ()) != 0)
+	    || (setreuid (getuid (), getuid ()) != 0)) {
+		fprintf (log_get_logfd(), _("%s: failed to drop privileges (%s)\n"),
+		         log_get_progname(), strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+
+	if ('/' != newroot[0]) {
+		fprintf (log_get_logfd(),
+		         _("%s: invalid chroot path '%s', only absolute paths are supported.\n"),
+		         log_get_progname(), newroot);
+		exit (E_BAD_ARG);
+	}
+
+	if (access (newroot, F_OK) != 0) {
+		fprintf(log_get_logfd(),
+		        _("%s: cannot access chroot directory %s: %s\n"),
+		        log_get_progname(), newroot, strerror (errno));
+		exit (E_BAD_ARG);
+	}
+
+	if (chroot (newroot) != 0) {
+		fprintf(log_get_logfd(),
+			        _("%s: unable to chroot to directory %s: %s\n"),
+				log_get_progname(), newroot, strerror (errno));
+		exit (E_BAD_ARG);
+	}
+
+	if (chdir ("/") != 0) {
+		fprintf(log_get_logfd(),
+			_("%s: cannot chdir in chroot directory %s: %s\n"),
+		        log_get_progname(), newroot, strerror (errno));
+		exit (E_BAD_ARG);
+	}
+}
+