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/*++
/* NAME
/* chroot_uid 3
/* SUMMARY
/* limit possible damage a process can do
/* SYNOPSIS
/* #include <chroot_uid.h>
/*
/* void chroot_uid(root_dir, user_name)
/* const char *root_dir;
/* const char *user_name;
/* DESCRIPTION
/* \fBchroot_uid\fR changes the process root to \fIroot_dir\fR and
/* changes process privileges to those of \fIuser_name\fR.
/* DIAGNOSTICS
/* System call errors are reported via the msg(3) interface.
/* All errors are fatal.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include <sys_defs.h>
#include <pwd.h>
#include <unistd.h>
#include <grp.h>
/* Utility library. */
#include "msg.h"
#include "chroot_uid.h"
/* chroot_uid - restrict the damage that this program can do */
void chroot_uid(const char *root_dir, const char *user_name)
{
struct passwd *pwd;
uid_t uid;
gid_t gid;
/*
* Look up the uid/gid before entering the jail, and save them so they
* can't be clobbered. Set up the primary and secondary groups.
*/
if (user_name != 0) {
if ((pwd = getpwnam(user_name)) == 0)
msg_fatal("unknown user: %s", user_name);
uid = pwd->pw_uid;
gid = pwd->pw_gid;
if (setgid(gid) < 0)
msg_fatal("setgid(%ld): %m", (long) gid);
if (initgroups(user_name, gid) < 0)
msg_fatal("initgroups: %m");
}
/*
* Enter the jail.
*/
if (root_dir) {
if (chroot(root_dir))
msg_fatal("chroot(%s): %m", root_dir);
if (chdir("/"))
msg_fatal("chdir(/): %m");
}
/*
* Drop the user privileges.
*/
if (user_name != 0)
if (setuid(uid) < 0)
msg_fatal("setuid(%ld): %m", (long) uid);
/*
* Give the desperate developer a clue of what is happening.
*/
if (msg_verbose > 1)
msg_info("chroot %s user %s",
root_dir ? root_dir : "(none)",
user_name ? user_name : "(none)");
}