RE: chrooted users: how to see directory content ?

From: Michael Brennen <[email protected]>
Subject: wu-ftpd guest accounts

NOTE: I NO LONGER MAINTAIN THE GUEST HOWTO.  IN MID 2000 I TURNED IT
OVER TO THE WU-FTPD DEVELOPERS.  THIS VERSION IS ACCURATE AS FAR AS
I KNOW, BUT FOR THE LATEST VERSION, OR FOR BUG FIXES, PLEASE CONTACT
THE DEVELOPERS DIRECTLY.  THANK YOU.

There are three kinds of FTP logins that wu-ftpd provides:

  1: anonymous FTP
  2: real FTP
  3: guest FTP

Anonymous FTP is well known; one logs in with the username 'anonymous'
and an email type password.

Real FTP is when someone logs in with a real username and password and
has access to the entire disk structure.  This form of access can be
extremely dangerous to system security and should be avoided unless
absolutely necessary and well controlled.

Guest FTP is a form of real FTP; one logs in with a real user name and
password, but the user is chroot'ed to his home directory and cannot
escape from it.  This is much safer, and it is a useful way for remote
clients to maintain their Web accounts.

If you want to learn more about 'chroot', the following two commands
should help, as should any good Unix text.

man chroot

There may be different man pages in sections 1, 2 and 8 (or others,
perhaps) depending on your operating system.  ('man # chroot')

This howto will describe in detail the steps necessary to set up a
guest FTP account.  It does not describe anonymous or real FTP setup,
though the procedures for setting up an operational 'ls' command will
apply equally to anonymous FTP because of the chroot'ed nature of
anonymous FTP.

***********************************************************************

The working example here will be as if it were a directory under a Web
tree, /home/web.  The Web account will be maintained remotely by FTP.
The remote user is Mortimer.  Mortimer's account name is "mort", group
"client". 

(Yes, there is some droll humor here for the French speakers...)


1. Create Mort's entry in /etc/passwd and /etc/group.  Do so manually,
   or use adduser or whatever your Unix supports.  If you use adduser,
   you will probably have to make manual modifications to get the /./
   information in the home path.
   
   There are also entries to make in /etc/ftpaccess.


/etc/passwd:
mort:*:403:400:Mortimer Snerd:/home/web/mort/./:/etc/ftponly
                                            ^^^
   The /./ sequence determines where the chroot() is done to.  If you 
   want the chroot() done to the web directory and a chdir() to mort,
   it would look like this:

mort:*:403:400:Mortimer Snerd:/home/web/./mort/:/etc/ftponly
                                       ^^^

   --------> (make sure "/etc/ftponly" is in /etc/shells.)



/etc/group:
client::400:mort



Set Mort's password as you wish, or better yet use S/KEY.




The  current releases of wu-ftpd come with /etc/ftpaccess enabled by 
default.  If your version does not do this for some reason, you must
do one of two thing to properly use /etc/ftpaccess:

1)  compile the source to use /etc/ftpaccess by default;
    modify the source to set use_accessfile = 1;

OR

2)  run the daemon with the -a option.



/etc/ftpaccess:
class   local   real,guest,anonymous ......
...                  ^^^^^
...                    +----------- define 'guest' in the proper classes;
...                                 this is site dependent.
...
...
delete     no   anonymous,guest               # delete permission?
overwrite  no   anonymous,guest               # overwrite permission?
rename     no   anonymous,guest               # rename permission?
chmod      no   anonymous,guest               # chmod permission?
umask      no   anonymous,guest               # umask permission?
...                       ^^^^^
...                         +------ decide if guest should be in this 
...                                 permission list; this is site dependent.
...
...
path-filter  guest      /etc/pathmsg  ^[-A-Za-z0-9_\.]*$  ^\.  ^-
...
guestgroup client
...




2. Create Mort's home directory and set its ownership and protections.

mkdir /home/web/mort

chown mort.client /home/web/mort

chmod 755 /home/web/mort




3. Build the directory structure under Mort's account.
   Create the /etc, /lib, and any other directory you need
   in the directory that the chroot() is done into.

cd /home/web/mort

mkdir etc bin [dev lib]   (dev and lib are optional and are OS dependent.)

chown root.daemon etc bin

chmod 111 etc bin




4. Build the contents of the ~/bin directory.


NOTE WELL: if you cannot see the directory contents after you login
as the guest user, the 'ls' program that you installed is not working.
If you use an 'ls' linked for dynamic libraries, and you do not have
the required libraries and/or devices installed properly in the guest
tree, 'ls' will not work and you will not see the contents of the
guest directory.

This is the single most FAQ on the wu-ftpd list.  Repeating: if you
cannot see the contents of the directory, your installed 'ls' is not
working.  The proper installation procedures for 'ls' vary by operating
system.  There are some OS specific notes at the bottom of this howto
that may be of help.

Another problem that has been reported is that the chroot() directory 
given in your /etc/passwd file for the guest account must be to the
directory where your ~/bin directory is located.  That is, if your
chroot directory is /u01/ftp/ftptest/ and your /etc/passwd account is

yourftp:x:42:42:guest ftp account:/u01/ftp/./ftptest:/etc/ftponly

it will not work, as the ~/bin directory is not under the chroot()ed
directory.  It must be set as follows.

yourftp:x:42:42:guest ftp account:/u01/ftp/ftptest/./:/etc/ftponly

There are additional resources to help if you still cannot see files
after an FTP login.  See the FAQ and resource center at
http://www.wuftpd.org/ for more information.

USE STATIC LINKED COPIES OF ALL UTILITIES IF POSSIBLE.

You may get the source to build your own static 'ls' by downloading the
GNU fileutils source package from <ftp://ftp.gnu.org/pub/gnu/>.


cp /.../bin/ls bin
chown root.bin bin/ls
chmod 111 bin/ls

Optional for on the fly compression and tar:

cp /.../bin/gzip bin
cp /.../bin/tar  bin
chown root.bin bin/gzip
chown root.bin bin/tar
chmod 111 bin/gzip
chmod 111 bin/tar


If the utilities are not static, create the necessary devices in ~/dev and 
copy the necessary libraries into ~/lib.  Check the man page for ftpd that 
comes with your system; it may be of help.

REGARDING HARD AND SOFT/SYMBOLIC LINKS:

The chroot() obviates the use of soft links in this case.  However, it
it is possible to make these hard links back to the master copy of the
utilities rather than copies.  This can save some disk space if that is
a concern.




5. Build the contents of the ~/etc directory.

Edit "passwd" to contain the following:

root:*:0:0::/:/etc/ftponly
mort:*:403:400::/home/web/mort/./:/etc/ftponly


Edit "group" to contain the following:

root::0:root
client::400:mort


chown root.daemon passwd group

chmod 444 passwd group




6. Add some extra security touches

cd /home/web/mort
touch .rhosts .forward
chown root.root .rhosts .forward
chmod 400 .rhosts .forward




You should now be the proud owner of a working guest group FTP login. 
Connect to the machine via FTP and login as "mort".  You should end up in
Mort's account with a current directory of "/".

If not, go over it carefully again, as there is a lot of detail here.  If
you still can't get it to work, yell for help on
[email protected].

**************************************************************************

OS DEPENDENCIES / QUIRKS

LINUX:

  Linux does not need a ~/dev dir.  It does need the ~/lib dir if the
  utilities in ~/bin are dynamically linked. 

  Use the 'ldd' command to find out what libraries are necessary for a given
  dynamically linked utility. 


LINUX REDHAT 6.1:   (reported by Steven Schramm <[email protected]>)

I found the following steps for the lib directory critical to my
success:

   - create the lib directory with mode 111
   - cd lib
   - cp /lib/ld-2.1.1.so .
   - cp /lib/libc-2.1.1.so .
   - ln -s ld-2.1.1.so ld-linux.so.2
   - ln -s libc-2.1.1.so libc.so.6
   - chmod 111 ld-2.1.1.so
   - chmod 555 libc-2.1.1.so


SOLARIS: 

  Solaris can't handle SETPROCTITLE, so turn the compile time option off.


  (The following was culled from a post by Tom Leach to the wu-ftpd list.)

  >For people who are having problems with ls -al and dir on solaris 2.x
  >systems, you might try the following to find out what's missing... 
  >
  >truss -f chroot ~ftp /bin/ls
  >
  >This will run the ls command in the same chroot'd environment that
  >anonymous FTP runs in.  The truss will show you what
  >files/libraries/devices are accessed and where the ls is looking for them. 
  >
  >Tom Leach
  >[email protected]


  (The following is from Chris Hoekstra <[email protected]>, 1/12/2002.)

  >Here is one thing that using the Sun 10/2001 build of Solaris 8 I had to
  >do to get a guest Account setup.  Actually, it is more of getting ls to
  >work on wu-ftpd, but I figured it would be a good thing to add anyway
  >since it won't work unless you do this.
  >
  >And also, I am not sure if this is specific to the 10/01 build, or
  >solaris8 in general, but I know for sure solaris7 did not suffer from
  >this change.
  >
  >In /etc/inetd.conf, change :
  >ftp     stream  tcp6     nowait  root    /usr/sbin/in.ftpd       in.ftpd
  >to
  >ftp     stream  tcp     nowait  root    /usr/sbin/in.ftpd       in.ftpd
  >
  >This is so wu-ftpd can bind to a ipv4 socket instead of an ipv6 one.


SOLARIS 2.6:

  Contents of ~ftp/usr/lib
  Solaris expects to find the libraries in ~ftp/usr/lib , not in ~ftp/lib
  Copy the following libraries out of /usr/lib into ~ftp/usr/lib
  Also, I'm not sure that intl and w are necessary.
  ld.so
  ld.so.1
  libc.so.1
  libdl.so.1
  libintl.so (can be a symlink to libintl.so.1)
  libintl.so.1
  libw.so.1


  Contents of ~ftp/dev:
  Create "zero" and "tcp" entries. Check your existing /dev/zero and
  /dev/tcp to make sure that these major and minor numbers are correct
  for your system, then use "mknod" to create the device files in ~ftp/dev
  mknod tcp c 11 42
  mknod zero c 13 12

  The above notes are gratefully acknowledged from
  Gregor Mosheh <[email protected]>


SUN 4.1.x:

  Create a ~dev/zero and ~dev/tcp device for the FTP directory as follows.
  Run the following 'ls' command, then create the devices in the ~/dev
  directory with the 'mknod' command, using the major and minor numbers
  from the 'ls' results (thanks to Jim Davis <[email protected]>).

  ls -lL /dev/zero /dev/tcp
  cd dev
  mknod zero c <major> <minor>
  mknod tcp  c <major> <minor>
  cd ..
  chmod 555 dev

  You may also wish to use the following method to create the device,
  per Ian Willis <ianw.sco.com>; repeat this command for each device
  (zero, tcp, etc.).

  find /dev/zero -print | cpio -pd ~ftp

  Also, you probably need the following shared libraries:
  ~lib/ld.so
  ~lib/libc.so
  ~lib/libdl.so



BSDI:

  Set 555 protections on the ~ftp/shlib and its contents if shared
  libraries are used.

  From Darci Chapman ([email protected]):

  The following directories and files need to be created in whatever
  directory/ies are being chrooted to (~ftp for anon ftp or for whatever
  directory guest users are chrooted): 

  dr-xr-xr-x root/wheel        0 Nov  3 01:43 1995 bin/
  -r-xr-xr-x root/wheel    12288 Nov  3 01:43 1995 bin/compress
  -r-xr-xr-x root/wheel    45056 Nov  3 01:43 1995 bin/gzip
  -r-xr-xr-x root/wheel    12288 Nov  3 01:43 1995 bin/ls
  -r-xr-xr-x root/wheel    65536 Nov  3 01:43 1995 bin/pax
  dr-xr-xr-x root/wheel        0 Nov  3 01:43 1995 etc/
  -r--r--r-- root/wheel      793 Nov  3 01:43 1995 etc/group
  -r--r--r-- root/wheel      817 Nov  3 01:43 1995 etc/localtime
  -r--r--r-- root/wheel    40960 Nov  3 01:43 1995 etc/pwd.db
  dr-xr-xr-x root/wheel        0 Feb  3 12:34 1995 pub/
  dr-xr-xr-x root/wheel        0 Nov  3 01:43 1995 shlib/
  -r-xr-xr-x root/wheel   298407 Nov  3 01:43 1995 shlib/libc_s.2.0


IRIX (5.3, 6.x)

 from frans stekelenburg <[email protected]>:

 (as in SUN 4.1.x, but without /dev/tcp)

 Create a ~dev/zero device for the FTP directory as follows. (tip:
 search on 'dev/zero' in your IRIX systems' Online Books.)
 Run the following 'ls' command, then create the devices in the ~/dev
 directory with the 'mknod' command, using the major and minor numbers
 from the 'ls' results (thanks to Jim Davis <[email protected]>).

 ls -lL /dev/zero
 cd dev
 mknod zero c <major> <minor>
 cd ..
 chmod 555 dev

 You may also wish to use the following method to create the device,
 per Ian Willis <ianw.sco.com>; repeat this command for each device
 (zero, tcp, etc.).

 find /dev/zero -print | cpio -pd ~ftp

 Also, you probably need the following shared libraries:
 ~lib/rld
 ~lib/libc.so.1
 (found in /lib)

 Also read the manpages on FTPD, or look in the IRIX Insight Library
 (Online Books) in the book/chapter "IRIX Admin: Networking and Mail"
 for the paragraph 'How to Set Up a Proper Anonymous FTP Account'
 (search helps:-)) on your IRIX system.


AIX:

 Per Chuque Berry <[email protected]> and Joseph Matusiewicz
 <[email protected]>, AIX needs the following files for
 the external ls to work:

 ~lib/libc.a
 ~lib/libcurses.a  (???)
 
You may also need:

 ~lib/libcrypt.a

**************************************************************************

Don't contact me individually for help. 

Michael Brennen