1 files changed, 76 insertions, 0 deletions
diff --git a/usr.bin/mdo/mdo.c b/usr.bin/mdo/mdo.c
new file mode 100644
index 000000000000..22e2838daa08
--- /dev/null
+++ b/usr.bin/mdo/mdo.c
@@ -0,0 +1,76 @@
+/*-
+ * Copyright(c) 2024 Baptiste Daroussin <bapt@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/limits.h>
+
+#include <err.h>
+#include <paths.h>
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static void
+usage(void)
+{
+	fprintf(stderr, "usage: mdo [-u username] [-i] [--] [command [args]]\n");
+	exit(EXIT_FAILURE);
+}
+
+int
+main(int argc, char **argv)
+{
+	struct passwd *pw;
+	const char *username = "root";
+	bool uidonly = false;
+	int ch;
+
+	while ((ch = getopt(argc, argv, "u:i")) != -1) {
+		switch (ch) {
+		case 'u':
+			username = optarg;
+			break;
+		case 'i':
+			uidonly = true;
+			break;
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if ((pw = getpwnam(username)) == NULL) {
+		if (strspn(username, "0123456789") == strlen(username)) {
+			const char *errp = NULL;
+			uid_t uid = strtonum(username, 0, UID_MAX, &errp);
+			if (errp != NULL)
+				err(EXIT_FAILURE, "%s", errp);
+			pw = getpwuid(uid);
+		}
+		if (pw == NULL)
+			err(EXIT_FAILURE, "invalid username '%s'", username);
+	}
+	if (!uidonly) {
+		if (initgroups(pw->pw_name, pw->pw_gid) == -1)
+			err(EXIT_FAILURE, "failed to call initgroups");
+		if (setgid(pw->pw_gid) == -1)
+			err(EXIT_FAILURE, "failed to call setgid");
+	}
+	if (setuid(pw->pw_uid) == -1)
+		err(EXIT_FAILURE, "failed to call setuid");
+	if (*argv == NULL) {
+		const char *sh = getenv("SHELL");
+		if (sh == NULL)
+			sh = _PATH_BSHELL;
+		execlp(sh, sh, "-i", NULL);
+	} else {
+		execvp(argv[0], argv);
+	}
+	err(EXIT_FAILURE, "exec failed");
+}