Allow the optional setting of a user, primary group, or grouplist

when chrooting.

Obtained from:	NetBSD
MFC after:	4 weeks

usr.sbin/chroot/chroot.8

@@ -32,7 +32,7 @@
 .\"     @(#)chroot.8	8.1 (Berkeley) 6/9/93
 .\" $FreeBSD$
 .\"
-.Dd January 24, 2002
+.Dd June 7, 2003
 .Dt CHROOT 8
 .Os
 .Sh NAME
@@ -40,6 +40,9 @@
 .Nd change root directory
 .Sh SYNOPSIS
 .Nm
+.Op Fl u Ar user
+.Op Fl g Ar group
+.Op Fl G Ar group,group,...
 .Ar newroot
 .Op Ar command
 .Sh DESCRIPTION
@@ -49,7 +52,20 @@ utility changes its current and root directories to the supplied directory
 .Ar newroot
 and then exec's
 .Ar command ,
-if supplied, or an interactive copy of the user's login shell.
+if supplied,
+or an interactive copy of the user's login shell.
+.Pp
+If the
+.Fl u ,
+.Fl g
+or
+.Fl G
+options are given,
+the user,
+group and group list of the process are set to
+these values after the
+.Xr chroot 8
+has taken place.
 .Sh ENVIRONMENT
 The following environment variable is referenced by
 .Nm :
@@ -69,6 +85,10 @@ is used.
 .Sh SEE ALSO
 .Xr chdir 2 ,
 .Xr chroot 2 ,
+.Xr setgid 2 ,
+.Xr setgroups 2 ,
+.Xr setuid 2 ,
+.Xr getgrnam 3 ,
 .Xr environ 7 ,
 .Xr jail 8
 .Sh HISTORY

usr.sbin/chroot/chroot.c

@@ -47,8 +47,12 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/types.h>
 
+#include <ctype.h>
 #include <err.h>
+#include <grp.h>
+#include <limits.h>
 #include <paths.h>
+#include <pwd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -56,29 +60,112 @@ __FBSDID("$FreeBSD$");
 
 static void usage(void);
 
+char	*user;		/* user to switch to before running program */
+char	*group;		/* group to switch to ... */
+char	*grouplist;	/* group list to switch to ... */
+
 int
 main(argc, argv)
 	int argc;
 	char *argv[];
 {
-	int ch;
+	struct group	*gp;
-	const char *shell;
+	struct passwd	*pw;
+	char		*endp, *p;
+	const char	*shell;
+	gid_t		gid, gidlist[NGROUPS_MAX];
+	uid_t		uid;
+	int		ch, gids;
 
-	while ((ch = getopt(argc, argv, "")) != -1)
+	gid = 0;
+	uid = 0;
+	while ((ch = getopt(argc, argv, "G:g:u:")) != -1) {
 		switch(ch) {
+		case 'u':
+			user = optarg;
+			if (*user == '\0')
+				usage();
+			break;
+		case 'g':
+			group = optarg;
+			if (*group == '\0')
+				usage();
+			break;
+		case 'G':
+			grouplist = optarg;
+			if (*grouplist == '\0')
+				usage();
+			break;
 		case '?':
 		default:
 			usage();
 		}
+	}
 	argc -= optind;
 	argv += optind;
 
 	if (argc < 1)
 		usage();
 
+	if (group != NULL) {
+		if (isdigit((unsigned char)*group)) {
+			gid = (gid_t)strtoul(group, &endp, 0);
+			if (*endp != '\0')
+				goto getgroup;
+		} else {
+ getgroup:
+			if ((gp = getgrnam(group)) != NULL)
+				gid = gp->gr_gid;
+			else
+				errx(1, "no such group `%s'", group);
+		}
+	}
+
+	for (gids = 0;
+	    (p = strsep(&grouplist, ",")) != NULL && gids < NGROUPS_MAX; ) {
+		if (*p == '\0')
+			continue;
+
+		if (isdigit((unsigned char)*p)) {
+			gidlist[gids] = (gid_t)strtoul(p, &endp, 0);
+			if (*endp != '\0')
+				goto getglist;
+		} else {
+ getglist:
+			if ((gp = getgrnam(p)) != NULL)
+				gidlist[gids] = gp->gr_gid;
+			else
+				errx(1, "no such group `%s'", p);
+		}
+		gids++;
+	}
+	if (p != NULL && gids == NGROUPS_MAX)
+		errx(1, "too many supplementary groups provided");
+
+	if (user != NULL) {
+		if (isdigit((unsigned char)*user)) {
+			uid = (uid_t)strtoul(user, &endp, 0);
+			if (*endp != '\0')
+				goto getuser;
+		} else {
+ getuser:
+			if ((pw = getpwnam(user)) != NULL)
+				uid = pw->pw_uid;
+			else
+				errx(1, "no such user `%s'", user);
+		}
+	}
+
 	if (chdir(argv[0]) == -1 || chroot(".") == -1)
 		err(1, "%s", argv[0]);
 
+	if (gids && setgroups(gids, gidlist) == -1)
+		err(1, "setgroups");
+	if (group && setgid(gid) == -1)
+		err(1, "setgid");
+	if (user && setuid(uid) == -1)
+		err(1, "setuid");
+
 	if (argv[1]) {
 		execvp(argv[1], &argv[1]);
 		err(1, "%s", argv[1]);
@@ -94,6 +181,7 @@ main(argc, argv)
 static void
 usage()
 {
-	(void)fprintf(stderr, "usage: chroot newroot [command]\n");
+	(void)fprintf(stderr, "usage: chroot [-g group] [-G group,group,...] "
+	    "[-u user] newroot [command]\n");
 	exit(1);
 }