lguest: --username and --chroot options
I've attached a patch which implements dropping to privileges
and chrooting to a directory.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index dc73bc54..f64b85b 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -39,6 +39,9 @@
#include <limits.h>
#include <stddef.h>
#include <signal.h>
+#include <pwd.h>
+#include <grp.h>
+
#include <linux/virtio_config.h>
#include <linux/virtio_net.h>
#include <linux/virtio_blk.h>
@@ -1872,6 +1875,8 @@
{ "block", 1, NULL, 'b' },
{ "rng", 0, NULL, 'r' },
{ "initrd", 1, NULL, 'i' },
+ { "username", 1, NULL, 'u' },
+ { "chroot", 1, NULL, 'c' },
{ NULL },
};
static void usage(void)
@@ -1894,6 +1899,12 @@
/* If they specify an initrd file to load. */
const char *initrd_name = NULL;
+ /* Password structure for initgroups/setres[gu]id */
+ struct passwd *user_details = NULL;
+
+ /* Directory to chroot to */
+ char *chroot_path = NULL;
+
/* Save the args: we "reboot" by execing ourselves again. */
main_args = argv;
@@ -1950,6 +1961,14 @@
case 'i':
initrd_name = optarg;
break;
+ case 'u':
+ user_details = getpwnam(optarg);
+ if (!user_details)
+ err(1, "getpwnam failed, incorrect username?");
+ break;
+ case 'c':
+ chroot_path = optarg;
+ break;
default:
warnx("Unknown argument %s", argv[optind]);
usage();
@@ -2021,6 +2040,37 @@
/* If we exit via err(), this kills all the threads, restores tty. */
atexit(cleanup_devices);
+ /* If requested, chroot to a directory */
+ if (chroot_path) {
+ if (chroot(chroot_path) != 0)
+ err(1, "chroot(\"%s\") failed", chroot_path);
+
+ if (chdir("/") != 0)
+ err(1, "chdir(\"/\") failed");
+
+ verbose("chroot done\n");
+ }
+
+ /* If requested, drop privileges */
+ if (user_details) {
+ uid_t u;
+ gid_t g;
+
+ u = user_details->pw_uid;
+ g = user_details->pw_gid;
+
+ if (initgroups(user_details->pw_name, g) != 0)
+ err(1, "initgroups failed");
+
+ if (setresgid(g, g, g) != 0)
+ err(1, "setresgid failed");
+
+ if (setresuid(u, u, u) != 0)
+ err(1, "setresuid failed");
+
+ verbose("Dropping privileges completed\n");
+ }
+
/* Finally, run the Guest. This doesn't return. */
run_guest();
}