proftpdfaq-linuxdoc.sgml

<!doctype linuxdoc system>

<article>
<!-- Title Information -->

<TITLE>Professional FTP Daemon FAQ
<author>Mark Lowes <tt/&lt;hamster@vom.tm&gt;/
<date>v0.9.0, 05 January 2002

<abstract>$Id$
This document sets out many of the FAQs related to the installation,
functioning and configuration of ProFTPD.  It also provides some guidance
on policy and security issues.</abstract>

<toc>

<!-- the document proper -->


<sect>Introduction to ProFTPD

<P>
<sect1>What is ProFTPD

<P>
ProFTPD is a ftp server primarily written for the various unix
variants though it will now compile under win32.  It has been designed
to be much like Apache in concept taking many of the ideas
(configuration format, modular design, etc) from it.

<sect1>What is the current version?
<p>
<itemize>
<item>Stable:   1.2.4
<item>Release Candidate: 1.2.5rc1
<item>Unstable: 1.3.x 
</itemize>

<sect1>Version numbering scheme

<P>At the moment there is a little irrationality in the numbering scheme however it can be summarised as follows

<sect2>1.0.x
<P>This is the previous stable version.

<sect2>1.1.x
<P>Development code

<sect2>1.2.0prex
<P>Pre-release testing versions, development code.

<sect2>1.2.0rcx
<P>Release candidate code, these releases are pretty much bug free and are testing releases prior to the final stable code.

<sect2>1.2.x
<P>This will be the stable cycle with the final .x being the incremental patches to fix bugs discovered after the release version is issued.

<sect2>1.3.x
<P>1.3.x is in development, nightly tarballs from the CVS tree are
available from ftp.proftpd.org and it"s mirror sites.

<sect1>Website & documentation

<P>http://www.proftpd.org/ is now online and contains copies of this
FAQ, other documentation resources and information on the project.
The documentation is being brought back into shape at the moment, the
configuration on the website is now approaching where it should be but
more work is required and is ongoing.  There are a number of
geographic mirror sites, see http://www.proftpd.org/ for details or
try www.&lt;isocode&gt;.proftpd.org (ie www.uk.proftpd.org).

<sect2>Helping with documentation

<P>Writing documentation is time consuming and requires some
work but it"s not actually difficult.  Get the source code from CVS,
run "ShowUndocumented" in the doc directory.  This will list what
needs work.  Grep through the code in the looking for something like

<tscreen>
<code>
CHECK_CONF(cmd,CONF_ROOT|CONF_VIRTUAL|CONF_ANON|CONF_GLOBAL)
</code>
</tscreen>

<P>to figure out where the directive is valid (server config,
&lt;VirtualHost&gt;, &lt;Anonymous&gt;, &lt;Global&gt; for the above example).  Once you
think you understand what it does, test, play, break (if possible).
Then copy the format in Configuration.html and add the new documentation.

<P>Once the documentation is complete run 

<tscreen><verb>
cvs diff -uw Configuration.html > Configuration.html.patch
</verb></tscreen>

<P>and submit it via the bug reporting system.

<sect1>Bug reporting?  

<P>Bug reports should be made via http://bugs.proftpd.org/ which uses
the bugzilla tracking system.  Patches should be mailed to the
ProFTPD-Devel mailing list or MacGyver directly.

<sect1>I've found a security hole

<P>Please report all security problems with the code to
security@proftpd.org before releasing the information into the public
domain.  It would be appreciated if you give the core team a few days
to put together a patch and/or new release to address the issue.

<P>Please adhere to the proceedures and timescales given in the RF
Policy document http://www.wiretrip.net/rfp/policy.html, this will give
the core development team a chance to get a fix or workaround in place
before the problem becomes fully public domain.

<sect1>Downloading

<P>There are two main methods of getting the software.  Downloading a
compressed tarball or rpm (there is also a Debian package available in
the main distribution) from proftpd.org or from a mirror site,
alternatively if you wish to run the latest bleeding edge code then
collecting from the cvs server is the best method.

<sect2>Mirror sites

<P>There is a complete and maintained list of ftp mirror sites available
from http://www.proftpd.org/download.html

<sect2>CVS

<P>CVS:
cvs -d :pserver:anonymous@cvs.proftp.sourceforge.net:/cvsroot/proftp login
(Hit Enter when prompted for a password.)

Then do:

cvs -d :pserver:anonymous@cvs.proftp.sourceforge.net:/cvsroot/proftp -z3
co proftpd

<P>To obtain the latest/greatest updates, just hop into the
proftpd directory and do: cvs update

<P>A couple of sites generate downloadable tarballs of the latest CVS
code to make obtaining the test code easier.

<sect1>Mailing lists
<P>
There are three lists for ProFTPD

<sect2>Announce
<P>
proftpd-announce@proftpd.org

<P>This is a very low traffic list where only ProFTPD announcements/changes
will be announced.

<P>Subscribe by sending a message to proftpd-announce-request@proftpd.org with
"subscribe" in the subject.

<p>Web interface: https://lists.sourceforge.net/lists/listinfo/proftp-announce

<sect2>Users
<P>
proftpd@proftpd.org

<P>This is intended to the the user support channel for the software,
in most likelihood this is going to be a high traffic list and
slightly chatty.  Please read the FAQ, the documentation and the list
archives before posting a question.

<P>Subscribe by sending a message to proftpd-request@proftpd.org with
"subscribe" in the subject.

<p>Web interface: https://lists.sourceforge.net/lists/listinfo/proftp-user

<sect2>Development
<P>
proftpd-devel@proftpd.org

<P>This list is intended for discussion of development-related issues
of ProFTPD, and feature design.  It is NOT intended to be a "user
help" group.

<P>Subscribe by sending a message to proftpd-devel-request@proftpd.org
with "subscribe" in the subject.

<p>Web interface: https://lists.sourceforge.net/lists/listinfo/proftp-devel

<sect2>Archives
<P>The mailing list archives can be found at
http://www.proftpd.org/proftpd-l-archive/
http://www.proftpd.org/proftpd-devel-archive/

<sect3>Unsubscribing
<p>Before posting to any of the lists or mailing the list admins
please try and remove yourself first.  Either by emailing
&lt;listname&gt;-request@proftpd.org with the subject "unsubscribe" or
visiting the web interface and unsubscribing from there.

<sect4>I've (lost / never had) a password to the interface <p>Easy,
enter the address you are subscribed to the list as into the form and
hit the "email me my password" button.

<sect1>Copyright Issues
<P>
The software is currently distributed under the GNU General Public License
(version 2 or later) as published by the Free Software Foundation.
Copyright is held by Public Flood Software.

<sect>Compilation and installing

<P>
<!-- Basic hints on untaring, rpm"s ./configure etc etc -->

<sect1>What platforms will it compile on?
<P>
There have been reports of ProFTPD compiling on all the following
platforms (and versions).

<itemize>
<item>Linux 2.0.x &amp; 2.2.x (glibc 2.x only) &amp; 2.4.x
<item>BSDI 3.1 & 4.0
<item>IRIX 6.2, 6.3, 6.4, 6.5
<item>Solaris 2.5.1, 2.6, 2.7, 8 (Sparc)
<item>AIX 3.2 & 4.2
<item>OpenBSD 2.2/2.3
<item>FreeBSD 2.2.7 
<item>Digital UNIX 4.0A
<item>DEC OFS/1
</itemize>

<sect2>Why not libc5 on Linux?  
<P>There are several known problems with libc5-based systems,
including improperly implemented library routines (vsprintf and
vsnprintf are examples).  There are known problems with the resolver
library.  For these reasons and others lib5 is not being supported at
all, the latest versions of the major distributions (inc Debian,
Redhat and Suse) are all glibc.

<sect1>CVS

<P>CVS (Concurrent Versions System), is a version control system which
allows multiple developers (scattered across the same room or across
the world) to maintain a single codebase and keep a record of all
changes to the work.

<P>The CVS repository for ProFTPD is available for non-developers in
read-only mode, however this code is right on the bleeding edge and is 
not guaranteed to even compile let alone work.  Access to CVS is given 
to allow important security patches out into the wild and to allow
users and interested users to test out the latest changes on real
systems. 

<sect2>Recommended ~/.cvsrc settings
<P>
<tscreen>
<verb>
cvs -z 3
update -Pd
diff -u
</verb>
</tscreen>

<sect2>Where can I get information on cvs?
<P>CVS is produced by Cyclic Software (http://www.cyclic.com/) and
details on CVS can be found on their website.  The CVS documentation
is clear, detailed and above all heavy when printed.  I'd recommend
reading it if you"re planning on using CVS a lot.

<sect1>How do I get debug output

<P>The easiest way is to fire up proftpd manually from the command
line with the debug level cranked up.

<tscreen>
<verb>
/usr/local/sbin/proftpd -d9 -n
</verb>
</tscreen>

<P>This will result in maximal debug output direct to the
console. Warning, this can get messy on a busy server, for testing I
would suggest copying the config and altering the port the server
binds to and then testing.

<sect1>Patches

<P>Any patches should be submitted in Universal format, this makes
integrating them into the main cvs source a lot easier.  When
generating a diff against the current cvs source use "cvs diff -uw" to
generate the patch.

<tscreen><verb>
cvs diff -u filename > filename.patch

or

cvs diff -u > bigger.patch
</verb></tscreen>

<P>Patches that add configuration directives without proper
documentation.  Will be rejected.  New features without documentation
are less than useless to the community at large.

<sect1>Using non-default modules

<P>Simply configure ProFTPD with 

<tscreen>
<verb>
./configure --with-modules=mod_module1:mod_module2:mod_module3
make
make install
</verb>
</tscreen>

<sect1>Plans for next version (1.3.x)

<P>The new development series will be 1.3.x, using the same number
scheme as the linux kernel developers.  The targets/goals are:

<itemize>
<item>refining/redefining the module API to make it more extensible and useful.
<item>dynamic modules
<item>security APIs and implementations
<item>mod_ls rewrite
<item>Implementing some security-related RFCs
<item>Creating a web and GUI configuration interface to ProFTPD.
</itemize>

<P>2.0.x will be the production release of the 1.3.x development set.

<sect1>NT Support

<P>If/when a port is undertaken for NT, it will only be after a near
complete rethinking of ProFTPD.  This is planned for 2.0 and onwards.

<sect1>New features/modules

<P>While anything new is welcomed it"s probably better to at least
float the idea first on the devel mailing list to ensure that someone
else isn"t already hacking on it.  Also when submitting the patch or
module for inclusion into the ProFTPD source full documentation is
needed.

<sect2>Suggestions made for future development
<P>
<itemize>
<item>GUI based configuration tool
</itemize>

<!-- NEW SECTION -->

<sect>Compatibility and Integration

<sect1>SQL 
<P>ProFTPD has support for authentication and logging via SQL
databases using the mod_sql module as supplied in the main
distribution.

<sect1>SSH
<P>There is a mini-HOWTO at http://www.castaglia.org/proftpd/
detailing how to tunnel ftp connections over ssh.

<sect1>sendfile()

<P>sendfile() is a system call which streamlines the copying of data
between the disk and the tcp socket.  The call copied from the page
cache directly rather than requiring a kernel -> user space -> kernel
space copy for every read() and write() call.  Generally the
advantages are only felt on heavily loaded servers.  The call is
supported in ProFTPD for Linux and FreeBSD.

<sect2>Linux 2.0.x 

<P>sendfile is not supported under 2.0.x, this is not an issue when
compiling for 2.0.x on a 2.0.x system. However when compiling on a
2.2.x system for use on 2.0.x use the --disable-sendfile flag.

<sect2>Runtime detection of sendfile()

<P>There are two patches available for runtime detection of
sendfile() which gets round the 2.0.x problems.

<P>Johnie Ingram (aka netgod)"s:
http://www.proftpd.org/proftpd-devel-archive/99-10/msg00073.html

<P>John Pierce &lt;hawkfan@pyrotechnics.com&gt;
http://www.proftpd.org/proftpd-devel-archive/99-10/msg00112.html

<sect1>IPv6
<P>IPv6 support first appeared in the 1.2.9rc2 release.  To enable
IPv6 support, use the --enable-ipv6 configure option.

<sect1>Filename case sensitivity

<P>ProFTPD is utterly dependant on the underlying OS to handle
filename case sensitivity.  If the underlying OS is case sensitive
then ProFTPD will be, there are currently no plans for a module to
handle this.

<sect1>FXP
<P>FXP is capable of bouncing data between websites.  There have been
a number of reports of problems in configuring ProFTPD to function
cleanly with this program (http://flashfxp.skuz.net/).

<P>To support FXP when connecting as a user place "AllowForeignAddress 
on" in the Global or VirtualHost context.

<P>To support FXP when connecting as anon "AllowForeignAddress on"
must be placed in the Anonymous context.

<P>The config will happily support "AllowForeignAddress on" in
multiple places within the config.

<!-- NEW SECTION -->

<sect>Common Running problems

<sect1>ProFTPD doesn"t seem to work.

<P>Starting ProFTPD in standalone mode it doesn"t show in "ps" It
could be many things, possibly something like not running ProFTPD as
root (it needs to be run as root initially, but will switch to a
non-privileged user). Regardless, ProFTPD logs all errors via the
standard syslog mechanism. You need to check your system logs in order
to determine what the problem is.

<sect2>It doesn"t work!

<P>There are many times when there"s a completely random problem which
appears to be insoluble.  The best place to ask for help is definately
the mailing list (proftpd-l) but it"s not productive to ask for help
without giving enough information for intelligent debugging.

<P>Have you?
<itemize>
<item>Checked your logs
<item>Tried the server in debug mode
<item>Read the FAQ?
<item>Checked the mailing list archive?
<item>Are you running the latest version?
</itemize>

<P>When posting try giving enough information, this might include but
not be limited to.

<itemize>
<item>OS and server version (proftpd -vv)
<item>List of included modules (proftpd -l)
<item>Appropriate log extracts
<item>Output fom debug mode
<item>Configration fragments
</itemize>

<sect1>"inet_create_connection() failed: Operation not permitted".

<P>You aren"t starting ProFTPD as root, or you have inetd configured
to run ProFTPD as a user other than root. The ProFTPD daemon must be
started as root in order to bind to tcp ports lower than 1024, or to
open your shadow password file when authenticating users. The daemon
switches uid/gids to the user and group specified by the User/Group
directives during normal operation, so a `ps" will show it running as
the user you specified.

<sect1>Unable to bind to port/Address already in use

<P>0.0.0.0 is INADDR_ANY, which means to bind to any interface.  The
"address in use" will normally mean that something has already bound
to that address.

<p>Under linux it is possible to run 

<code>fuser -n tcp 21</code> 

<p>to get the PID of the process currently bound to port ProFTPD is
configured to run as.

<P>The most common cause is that ProFTPD is configured standalone and
inetd is still configured for port 21.  Comment out the line starting
"ftp" in /etc/inetd.conf and restart (killall -HUP inetd or something
similar should do the trick) and try again.  

<sect1>"Fatal: Socket operation on non-socket"

<P>You have ProFTPD configured to run in inetd mode rather than
standalone. In this mode, ProFTPD expects that it will be run from the
inetd super-server, which implies that stdin/stdout will be sockets
instead of terminals. As a result, socket operations will fail and the
above error will be printed. If you wish to run ProFTPD from the
shell, in standalone mode, you"ll need to modify your proftpd.conf
configuration file and add or edit the ServerType directive to read:

<tscreen><verb>
ServerType standalone
</verb></tscreen>

<sect1>"Fatal: unable to determine IP address of "hostname""

<P>The hosting machine has a poorly configured hostname setup to the
point where the resolver library cannot determine the IP from the
name.  Solutions include, fixing the DNS for the domain, fixing the
hostname, fixing the /etc/hosts file.  Which one works for you will
largely depend on your OS and exactly what is wrong.

<sect1>I'm having problems with FTP clients behind firewalls

<P>The FTP Specification defines that two sockets should be used for
all communications.  The first runs over port 21 and is the control
channel over which all commands and response codes are sent.  Whenever 
data is required to be transfered, for example for a file download, a
directory listing etc etc.  A second channel is created on demand,
this socket can take one of two forms.

<sect2>non-Passive
<P>The server end of the data socket uses port 20.  This is nice and
easy to work into a firewall configuration.

<sect2>Passive
<P>The port at either end is dynamically allocated.  This is virtually 
impossible to cater for in a firewall configuration given that the
port mapping will be different for every data connection.

<P>The solution is to force the users to configure their clients to
use the non-passive mode (ie port 20)

<sect1>Can I run more that one VirtualHost on a single IP?

<P>No, or at least not in the HTTP/1.1 manner of virtual hosting.
This is an inbuilt limitation of the current FTP RFC., unlike the
HTTP/1.1 spec there is no mechanism comparable to the "Host:
foo.bar.com" HTTP header for specifying which host the connection is
for.  Therefore the only method for determining which VirtualHost the
connection is destined for is by the destination IP.

<P>The one exception to this is if you host multiple servers on the same
IP but using different ports, however this requires that the connecting
client uses a non-standard port and therefore is probably not a good
solution for mass hosting.

<sect2>Is there anything in the pipeline to fix this?

<P>There is a draft standard <url
	      url="http://search.ietf.org/internet-drafts/draft-ietf-ftpext-mlst-12.txt" name="draft standard"> with the IETF which extends and improves on the
FTP specification including support for a HOST command.  However given
that the IP crunch is coming from websites and not virtual ftp servers
this is unlikely to be pushed through any time soon.

<sect1>How do I run ProFTPD from inetd?

<P>Find the line in /etc/inetd.conf that looks something like this:
<quote>   ftp stream tcp nowait root in.ftpd in.ftpd</quote>
<P>Replace it with:
<quote>   ftp stream tcp nowait root in.proftpd in.proftpd</quote>

<P>Then, find your inetd process in the process listing and send it
the SIGHUP signal so that it will rehash and reconfigure itself.  You
may also need to add in.ProFTPD to hosts.allow on your system.

<sect1>Can I use tcp-wrappers with ProFTPD?
<P>
Yup. Although ProFTPD has built-in IP access control (see the Deny
and Allow directives), many admins choose to consolidate IP access
control in one place via in.tcpd. Just configure ProFTPD to run from
inetd as any other tcp-wrapper wrapped daemon and add the
appropriate lines to hosts.allow/deny files.

<P>
If running ProFTPD in standalone mode, mod_wrap can be used to direct the
server to use the normal hosts.allow/deny files.

<sect1>Can I run an FTP server on a non-standard port?

<P>Yes. Use a &lt;VirtualHost&gt; block with your machine"s FQDN
(Fully Qualified Domain Name) or IP address, and a Port directive
inside the &lt;VirtualHost&gt; block. For example, if your host is
named "myhost.mydomain.com" and you want to run an additional FTP
server on port 2001, you would:

<tscreen>
<code>
...
&lt;VirtualHost myhost.mydomain.com&gt;
Port 2001
...
&lt;/VirtualHost&gt;
</code>
</tscreen>

<sect1>Can control upload/download ratios?
<P>Yes the mod_ratio module provides for doing just this.

<P>The ratio directives take four numbers: file ratio, initial file
credit, byte ratio, and initial byte credit.  Setting either ratio
to 0 disables that check.

<P>The directives are HostRatio (matches FQDN, wildcards allowed),
AnonRatio (matches password entered at login), UserRatio (accepts "*"
for "any user"), and GroupRatio. 

<tscreen>
<code>
Ratios on                                    # enable module
UserRatio ftp 0 0 0 0
HostRatio master.debian.org 0 0 0 0          # leech access (default)
GroupRatio proftpd 100 10 5 100000           # 100:1 files, 10 file cred
5:1 bytes, 100k byte cred
AnonRatio billg@microsoft.com 1 0 1 0        # 1:1 ratio, no credits
UserRatio * 5 5 5 50000                      # special default case
</code>
</tscreen>

<P>This example is for someone who (1) has downloaded 1 file of 82k,
(2) has uploaded nothing, (3) has a ratio of 5:1 files and 5:1
bytes, (4) has 4 files and 17k credit remaining, and (5) is now
changing directory to /art/nudes/young/carla.  The initial credit,
not shown, was 5 files and 100k (UserRatio * 5 5 5 100000).

<P>Version 2.0 and above of this module integrate with mod_sql.

<sect2>Limitations of mod_ratio

<P>It appears that the ratio limits in mod_ratio are only maintained
on a per session basis and there is no ongoing tracking of usage.

<sect1>Slow logins

<P>This is probably caused by a firewall or DNS timeout.  By default
ProFTPD will try to do both DNS and ident lookups against the incoming 
connection.  If these are blocked or excessively delayed a slower than 
normal login will result.  To turn off DNS and ident use:

<tscreen>
<code>
  UseReverseDNS off
  IdentLookups                    off
</code>
</tscreen>

<sect2>IdentLookups and tcpwrappers
***

<sect1>Lots of "FTP session closed" messages

<P>

<tscreen>
<verb>
Oct  7 12:30:48 salvage2 proftpd[8874]: FTP session closed.
Oct  7 12:30:48 salvage2 proftpd[8874]: FTP session closed.
Oct  7 12:30:48 salvage2 proftpd[8874]: FTP session closed.
Oct  7 12:30:48 salvage2 proftpd[8874]: FTP session closed.
</verb>
</tscreen>

<P>The above log extract is likely to be caused by a local monitoring
system or a particularly aggressive DoS attack.  Most service
monitoring systems try opening the ftp port on the target server to
detect whether it is active and running.  Most of the time these tests 
are followed by an immediate "QUIT" or disconnection.

<P>TCPdump/TCPshow on the server in question should show which machine
on your network is is generating these connections.

<sect1>How do I see who is connected?

<P>The ftpwho command lists the state of each ftp connection to the
server and what it"s current activity is.  However this does not
detail the connection information on a virtual by virtual basis.

<sect1>Can I force ProFTPD to listen on only one IP?

<P>Sort, of it"s not quite as clean as the socket binding under Apache 
but the principle works something like this.

<sect2>Standalone mode
<P>
<descrip>
<tag>To listen on the primary IP of a host</tag>
Use the SocketBindTight directive

<tag/To listen on a interfaces which are not the primary host interface/

Use the SocketBindTight directive, place your server configuration in
a &lt;VirtualHost ftp.mydomain.com&gt; block and use "Port 0" for the
main host configuration and and "Port 21" inside the VirtualHost
block.

</descrip>

<sect2>inetd

<P>There are two approaches possible, the first is to use the patch
from Daniel Roesen &lt;droesen@entire-systems.com&gt; (check
the mailing list archives).

<P>The second method is to run ProFTPD from xinetd
(http://synack.net/xinetd/), a more advanced replacement of inetd. An
entry for this in xinetd.conf would be something like this:

<tscreen>
<code>
service ftp
{
        disable = no
        flags			= REUSE
        socket_type             = stream
        wait                    = no
        user                    = root
        server                  = /usr/sbin/proftpd
        log_on_success          += DURATION USERID
        log_on_failure          += USERID
        nice                    = 10
	#bind			= [IP to bind to]
}
</code>
</tscreen>

<sect1>"FTP server shut down ... please try again later."
<P>Check for /etc/shutmsg and delete it.

<sect1>How do I shutdown the server without killing proftpd?
<P>ftpshut, allows the server to disallow connections with a message
without actually taking down the service.  The shutdown can be
scheduled for a point in the future or right now, existing connections
can be allowed to finish, or be terminated now.  Re-enabling is done
by removing the /etc/shutmsg file.

<sect1>Is is possible to shutdown a single VirtualHost?

<P>No, the shutmsg file works at a daemon level not at a virtual host
level.

<sect1>Error 421

<P>This appears to be a general catch all error code meaning "something
nasty has gone wrong".

<itemize>
<item>Connection has timed out
<item>The DefaultRoot specified doesn"t exist
<item>The parent server has been killed
<item>Check /etc/services
<item>Wrong permissions on the DefaultRoot
</itemize>

<P>You get the idea...

<sect1>proftpd doesn't show in the processlist

<P>Two possible reasons, first that it is simply not running, try
proftpd -n -d2 to run in debug mode and see what happens.  The other
is that it"s running from inetd and there are no active sessions at
the moment.

<sect1>How do I restart/reload the server?

<P>This depends on the mode you are running the server in.

<sect2>Inetd
<P>Unless you"re making a configuration change to inetd itself nothing 
needs doing.  The server reloads the configuration everytime a new
connection is made.

<sect2>Standalone
<P>Either stop and start the server completely (a little aggressive
for most admin"s tastes) or send a SIGHUP to the master daemon
process.

<sect1>Fatal: unable to determine IP address of

<P>Proftpd was unable to work out what IP is associated with the
hostname in the VirtualHost block.  Normally caused by a problem
with the DNS resolution of the host, check the resolv.conf file
and that your chosen nameservers are functional.

<sect1>451 append/restart not permitted, try again

<P>AllowStoreRestart is disabled by default because it will allow any
writable file to be corrupted by a malicious user.  It is recommended
that this option is only used with authenticated users and then only
in certain directories.

<sect1>501 REST not compatible with server configuration

<P>As mentioned in the description of the HiddenStores configuration directive,
use of that directive is incompatible with the FTP command REST.  Either
disable use of REST with the AllowRetrieveRestart and AllowStoreRestart
directives, or do not use HiddenStores.

<sect1>The time being displayed is wrong

<P>The default behaviour for ProFTPD is to display all times relative
to GMT.  To use local time set "TimesGMT off" in the server section of
the config.  There is a known issue with Redhat 7, with regard to time
handling.
http://www.redhat.com/support/errata/rh7-errata-bugfixes.html

<sect1>Authentication is taking too long

<P>Make sure that ReverseDNS is disabled, turn off ident lookups.
Additionally check the size of your /etc/passwd (or shadow) file, if
it is large then the only solution may be to move to another
authentication scheme.

<sect1>Corrupted files
<P>There appear to be some problems with both the use of sendfile()
in ProFTPD and with the implementation within certain operating systems.

<sect1>Can I upgrade ProFTPD without terminating the current sessions?
<P>Short answer, no.  Longer answer is no, but you can minimise the
effects.  The cleanest approach on servers which have significant
amounts of traffic appears to be to use ftpshut to block new
connections and terminate existing ones after a pre-determined time
period and then to upgrade and restart.  This approach limits the
number of downloads which are terminated part way through.

<sect1>No such group "nogroup"
<p>The default ProFTPD configuration file uses the user "nouser" and
the group "nogroup", some systems / distributions do not have the
group "nogroup" defined.  The solution is to either add the group
"nogroup" to /etc/groups or to change the "nogroup" entry in the
proftpd.conf to a group which does exist.

<sect1>Why do I see "unable to set groups: Invalid argument"? 
<p>The setting of the group privileges for a process uses the setgroups(2)
   system call.  This call will fail with the above error message for
   one of two reasons: there is a negative GID value for one of the
   groups, or the maximum number of groups for a single user has been
   exceeded.
 
<p>Ideally, all IDs, both UID and GID, will be positive.  Unfortunately,
   it is common on many systems to use -1 or -2, especially for such
   users as 'nobody', or group 'nogroup'.  Use of these values uses C's
   treatment of data types to make the actual numeric value very high;
   some functions, like setgroups(), do not like this, though.  In
   general, always use positive ID numbers.
 
<p>The other limitation is the number of supplemental groups for a user
   (eg non-primary groups, the ones configured in /etc/group).  The
   maximum number of supplemental groups to which a user may belong
   is defined by the operating system constant NGROUPS_MAX.  On
   some operating systems, such as Solaris, this limitation may be
   tunable.
 
<p>Some other applications may not encounter this error if they use the
   initgroups(3) function, which reads the /etc/group file for a user's
   supplemental group memberships, and sets those groups.  This function,
   however, silently ignores any supplemental groups for user greater than
   NGROUPS_MAX, unlike setgroups(2), which complains.
 
   If this is the cause of your error message, any solution will most
   likely involve reducing the number of groups your users are members of,
   or tuning the NGROUPS_MAX value, if your operating system allows it.

<sect1>Why do I see PAM error messages like these when I logout?
<p>
<tscreen>
<code>PAM(exit): Permission denied.,
      open_module: stat(/usr/lib/security/pam_unix.so.1) failed: No such
         file or directory
      load_modules: can not open module /usr/lib/security/pam_unix.so.1
      PAM(exit): Dlopen failure.
</code>
</tscreen>

<p>These messages appear when the DefaultRoot configuration directive is
   in effect.  This directive causes a user to be confined using the
   chroot(2) system call.  This call, however, affects other system
   utilities, such as PAM.  In this case, PAM's configuration is causing
   the PAM library to attempt to open PAM modules using a path that is
   no longer valid, thus the errors.  This happens on logout because the
   chroot has already happened by that point; on login, the PAM modules
   are successfully found and loaded before the chroot, so no errors.
   These are merely cosmetic reporting errors, and do not really affect
   the functionality or security of the server.

<!-- -------------------- -->
<!-- Configuration Issues -->
<!-- -------------------- -->

<sect>Configuration problems

<P>Problems encountered in trying to make the server behave 
exactly as required after compilation and installation are 
complete and the server is running.

<sect1>How do I add another anonymous login or guest account?
<P>
You should look in the sample-configurations/ directory from
your distribution tarball. Basically, you"ll need to create another
user on your system for the guest/anonymous ftp login. For security
reasons, it"s very important that you make sure the user account
either has a password or has an "unmatchable" password. The root
directory of the guest/anonymous account doesn"t have to be the user"s
directory, but it makes sense to do so. After you have created the
account, put something like the following in your /etc/proftpd.conf
file (assuming the new user/group name is private/private):

<tscreen><code>
&lt;Anonymous ~private&gt;
AnonRequirePassword off
User private
Group private
RequireValidShell off
&lt;Directory *&gt;
&lt;Limit WRITE&gt;
DenyAll
&lt;/Limit&gt;
&lt;/Directory&gt;
&lt;/Anonymous&gt;
</code></tscreen>

<P>This will allow ftp clients to login to your site with the username
"private" and their e-mail address as a password. You can change the
AnonRequirePassword directive to "on" if you want clients to be
forced to transmit the correct password for the "private" account.
This sample configuration allows clients to change into, list and read
all directories, but denies write access of any kind.

<sect1>How do I ftp as root?

<P>First off this is a <bf>bad idea</bf> ftping as root is insecure,
there are better more secure ways of shifting files as root.

<P>To enable root ftp ensure that the directive "RootLogin on" is
included in your configuration.

<sect1>How do I provide a secure upload facility?
<P>
The following snippet from a sample configuration file
illustrates how to protect an "upload" directory in such a fashion
(which is a very good idea if you don"t want people using your site
for "warez"):

<tscreen><code>
&lt;Anonymous /home/ftp&gt;
  # All files uploaded are set to username.usergroup ownership
  User username
  Group usergroup
  UserAlias ftp username
  RequireValidShell off

  &lt;Limit WRITE&gt;
    DenyAll
  &lt;/Limit&gt;

  &lt;Directory pub/incoming/&gt;
     &lt;Limit STOR CWD&gt;
        AllowAll
     &lt;/Limit&gt;
     &lt;Limit READ RMD DELE MKD&gt;
        DenyAll
     &lt;/Limit&gt;
  &lt;/Directory&gt;
&lt;/Anonymous&gt;
</code></tscreen>

<P>This denies all write operations to the anonymous root directory
and sub-directories, except "incoming/" where the permissions are
reversed and the client can store but not read. If you used &lt;Limit
WRITE&gt; instead of &lt;Limit STOR&gt; on &lt;Directory incoming&gt;,
ftp clients would be allowed to perform all write operations to the
sub-dir, including deleting, renaming and creating directories.

<sect1>How can I stop my users from using their space as a warez repository

<P>The above fragment will control anonymous users however if a local
user with a full account with up and download capability is abusing
their space then the technical measures which can be taken are
limited.  Applying a sane system quota is a good start, using the
mod_quota and mod_ratio modules may control the rates of
upload/download making it less useful as a warez repository.  In the
end it comes down to system monitoring and good site AUP"s and
enforcement.

<sect1>Can I rotate files out of an upload directory after upload?

<P>Yes.  You"ll need to write a script which either checks the
contents of the directory regularly and moves once it"s detected no
size change in a file for xyz seconds.  Or a script which monitors an
upload log.  There is no automatic method for doing this.

<sect1>How can I hide a directory from anonymous clients.

<P>Use the HideUser or HideGroup directive in combination with the
proper user/group ownership on the directive. For example, if you
have the follow directory in your anonymous ftp directory tree:

<tscreen><verb>
	drwxrwxr-x 3 ftp staff 6144 Apr 21 16:40 private
</verb></tscreen>

<P>You can use a directive such as "HideGroup staff" to hide the private
directory from a directory listing. For example:

<tscreen><code>
&lt;Anonymous ~ftp&gt;
...
&lt;Directory Private&gt;
HideGroup staff
&lt;/Directory&gt;
...
&lt;/Anonymous&gt;
</code></tscreen>

<sect1>File/Directory hiding isn"t working for me! 
<P>
You need to make sure that the group you are hiding isn"t the
anonymous ftp user"s primary group, or HideGroup won"t apply.

<sect1>I want to prevent users from accessing a hidden directory

<P>You can either change the permissions on the directory to prevent
the anonymous FTP user from accessing it, or if you want to make it
appear completely invisible (as though there is no such directory),
use the IgnoreHidden directive inside a &lt;Limit&gt; block for one or
more commands that you want to completely ignore the hidden directory
entries (ignore = act as if the directory entry does not exist).

<sect1>How do I setup a virtual FTP server?

<P>You"ll need to configure your host to be able to handle multiple IP
addresses. This is often called "aliasing", and can generally be
configured through an IP alias or dummy interface. You need to read
your operating system documentation to figure out how to do this. Once
your have the host configured to accept the additional IP address that
you wish to offer a virtual FTP server on, use the &lt;VirtualHost&gt;
configuration directive to create the virtual server:

<tscreen><code>
&lt;VirtualHost 10.0.0.1&gt;
ServerName "My virtual FTP server"
&lt;/VirtualHost&gt;
</code></tscreen>

<P>You can add additional directive blocks into the &lt;VirtualHost&gt; block
in order to create anonymous/guest logins and the like which are only
available on the virtual host.

<sect1>I only want to allow anonymous access to a virtual server.

<P>Use a &lt;Limit LOGIN&gt; block to deny access at the top-level of
the virtual host, then use &lt;Limit LOGIN&gt; again in your
&lt;Anonymous&gt; block to allow access to the anonymous login. This
permits logins to a virtual anonymous server, but denies to everything
else. Example:

<tscreen><code>
&lt;VirtualHost 10.0.0.1&gt;
ServerName "My virtual FTP server"
&lt;Limit LOGIN&gt;
DenyAll
&lt;/Limit&gt;
&lt;Anonymous /usr/local/private&gt;
User private
Group private
&lt;Limit LOGIN&gt;
AllowAll
&lt;/Limit&gt;
...
&lt;/Anonymous&gt;
&lt;/VirtualHost&gt;
</code></tscreen>

<sect1>How does &lt;Limit LOGIN&gt; work, and where should I use it?

<P>The &lt;LOGIN&gt; directive is used to control connection or login
access to a particular context (the directive block which contains
it). When a client initially connects to ProFTPD, the daemon searches
the configuration tree for &lt;Limit LOGIN&gt; directives, and
attached parameters (such as Allow, Deny, etc). If it determines that
there is no possible way for the client to ever be allowed to login,
such as a "Deny from" matching the client"s source address, without an
overriding "Allow from" at a lower level, the client is disconnected
without being offered the opportunity to transmit a user and password.

<P>However, if it is possible for the client to be allowed a login,
ProFTPD continues as per normal, allowing the client to login only if
the proper &lt;Limit LOGIN&gt; applies. Normally, &lt;Limit&gt; directive blocks
are allowed in the server config, &lt;VirtualHost&gt;, &lt;Anonymous&gt;
and &lt;Directory&gt; contexts. However, &lt;Limit LOGIN&gt; should not be
used in a &lt;Directory&gt; context, as clients do not connect/login to a
directory (and thus it is meaningless).

<P>By way of example, the following configuration snippet illustrates a
&lt;Limit LOGIN&gt; deny which will cause any incoming connections from the
10.1.1.x subnet to be immediately disconnected, without a welcome
message:

<tscreen><code>
...
&lt;Limit LOGIN&gt;
Order deny,allow
Deny from 10.1.1.
Allow from all
&lt;/Limit&gt;
...
</code></tscreen>

<P>Next, an example of a configuration using &lt;Limit LOGIN&gt; that will not
immediately disconnect an incoming client, but will return "Login
invalid" for all login attempts except anonymous.

<tscreen><code>
...
&lt;Limit LOGIN&gt;
DenyAll
&lt;/Limit&gt;
&lt;Anonymous ~ftp&gt;
...
&lt;Limit LOGIN&gt;
AllowAll
&lt;/Limit&gt;
...
</code></tscreen>

<sect1>How can I limit users to a particular directory tree?

<P>For general open access you can use an &lt;Anonymous&gt; directive context block,
possibly in combination with a UserPassword/AnonRequirePassword directive. 

<P>However if you wish to jail an entire group (or groups) of users,
you can use the DefaultRoot directive.  DefaultRoot lets you specify a
root jailed directory (or "~" for the user"s home directory), and an
optional group-expression argument which can be used to control which
groups of users the jail will be applied to. For example:

<tscreen><code>
...
&lt;VirtualHost myhost.mynet.foo&gt;
DefaultRoot ~
...
&lt;/VirtualHost&gt;
This creates a configuration where all users who log into
myhost.mynet.foo are jailed into their home directories (cannot chdir
into a higher level directory). Alternatively, you could:
...
&lt;VirtualHost myhost.mynet.foo&gt;
DefaultRoot /u2/public users,!staff
...
&lt;/VirtualHost&gt;
</code></tscreen>

<P>In this example, all users who are members of group "users", but
not members of group "staff" are jailed into /u2/public. If a user
does not meet the group-expression requirements, they login as per
normal (not jailed, default directory is their home).  You can use
multiple DefaultRoot directives to create multiple jails inside the
same directive context. If two DefaultRoot directives apply to the
same user, ProFTPD arbitrarily chooses one (based on how the
configuration file was parsed).

<sect2>Security Implications

<P>The DefaultRoot directive is implemented using the chroot(2) system
call.  This moves the "/" (or root) directory to a specified point
within the file system and jails the user into this sub-tree.  However
this is not the holy grail of security, a chroot jail can be broken,
it is not a trivial matter but it"s nowhere near impossible.
DefaultRoot should be used as part of a general system of security not
the only security measure.

<P>A more detailed <url
url="http://www.bpfh.net/simes/computing/chroot-break.html"
name="discussion"> on this subject and on the breaking of chroot jails
has been written by Simon Burr

<sect2>Non-root server issues

<P>The chroot() system call will not work under a non-root ftp server
process, the call requires root privaliges.  Without them it simply
doesn"t work, there doesn"t appear to be any checking in the code of
the uid/gid before calling chroot so using DefaultRoot in such a setup 
will cause the server to fail.

<sect2>Symlinks

<P>Symlinks will not work from within a chrooted area.  The reason
	    should be clear from a casual inspection of the nature of
	    the chroot command.  It is not possible to have a symbolic
	    link to a directory which can"t be reached beacuse it"s
	    outside of the current chroot.  Work arounds to allow
	    access to other parts of the file system include exporting
	    the part of the filesystem to be accessed from inside the
	    chroot and mounting via NFS, using hard file links or (on
	    Solaris) using lofs to mount the directory via the loopback.

<tscreen>
<verb>
mount -Flofs /home/data1 /ftp/data1
mount -Flofs /home/data2 /ftp/data2
</verb>
</tscreen>

<P>As of the 2.4.x Linux kernel tree it is possible to mount filesystems
multiple times and to mount subdirectories of filesystems elsewhere on
the filesystem.

<sect1>How do I create individual anonymous FTP sites for my users?

<P>There are two methods of accomplishing this (possibly more).
First, you can create a directory structure inside your anonymous FTP
root directory, creating a single directory for each user and setting
ownership/permissions as appropriate. Then, either create a symlink
from each user"s home directory into the FTP site, or instruct your
users on how to access their directory.

<P>The alternate method (and more versatile) of accomplishing per-user
anonymous FTP is to use AnonymousGroup in combination with the
DefaultRoot directory. You"ll probably want to do this inside a
&lt;VirtualHost&gt;, otherwise none of your users will be able to access
your system without being stuck inside their per-user FTP site.
Additionally, you"ll want to use a deferred &lt;Directory&gt; block to
carefully limit outside access to each user"s site.

<enum>
<item>Create a new unix group on your system named `anonftp". Please
each user who will have per-user anonymous FTP in this group.

<item>Create an `anon-ftp" and `anon-ftp/incoming" directory in each
user"s home directory.

<item>Modify your /etc/proftpd.conf file to look something like this
(you"ll probably want to customize this to your needs):
</enum>

<tscreen><code>
 &lt;VirtualHost my.per-user.virtual.host.address&gt;
 
 # the next line limits all logins to this virtual host, so that only
 anonftp users can connect
 
 &lt;Limit LOGIN&gt;
 DenyGroup !anonftp
 &lt;/Limit&gt;
 
 # limit access to each user"s anon-ftp directory, we want read-only
 except on incoming
 
 &lt;Directory ~/anon-ftp&gt;
 
 &lt;Limit WRITE&gt;
 DenyAll
 &lt;/Limit&gt;
 
 &lt;/Directory&gt;
 
 # permit stor access to each user"s anon-ftp/incoming directory,
 but deny everything else
 
 &lt;Directory ~/anon-ftp/incoming&gt;
 
 &lt;Limit STOR&gt;
 AllowAll
 &lt;/Limit&gt;
 &lt;Limit READ WRITE&gt;
 DenyAll
 &lt;/Limit&gt;
 
 &lt;/Directory&gt;
 
 # provide a default root for all logins to this virtual host.
 DefaultRoot ~/anon-ftp
 # Finally, force all logins to be anonymous for the anonftp group
 AnonymousGroup anonftp
 
 &lt;/VirtualHost&gt;
</code></tscreen>


<sect1>I want to support normal login and Anonymous under a particular 
user

<P>You can use the AuthAliasOnly directive to control how and
where real usernames get authenticated (as opposed to aliased names,
via the UserAlias directive). Note that it is still impossible to
have two identical aliased names login to different anonymous sites;
for that you would need &lt;VirtualHost&gt;.

<P>Example:

<tscreen><code>
...
&lt;Anonymous ~jrluser&gt;

 User jrluser
 Group jrluser
 UserAlias ftp jrluser
 UserAlias anonymous jrluser
 AuthAliasOnly on
 ...
 
&lt;/Anonymous&gt;
</code></tscreen>

<P>Here, the &lt;Anonymous&gt; configuration for ~jrluser is set to allow
alias authentication only. Thus, if a client attempts to authenticate
as "jrluser", the anonymous config will be ignored and the client will
be authenticated as if they were a normal user (typically resulting in
`jrluser" logging in normally). However, if the client uses the
aliased username `ftp" or `anonymous", the anonymous block is applied.

<sect1>Why doesn"t Anonymous ftp work (550 login incorrect)?
<P>
Things to check
Check the following first:

<enum>
<item>Make sure the user/group you specified inside the &lt;Anonymous&gt;
block actually exists. This must be a real user and group, as it is
used to control whom the daemon runs as and authenticates as.

<item>If RequireValidShell is not specifically turned off, make sure
that your "ftp user" (as specified by the User directive inside an
&lt;Anonymous&gt; block), has a valid shell listed in /etc/shells. If you do
not wish to give the user a valid shell, you can always use
"RequireValidShell off" to disable this check.

<item>If UseFtpUsers is not specifically turned off, make sure that
your "ftp user" is not listed in /etc/ftpusers.

</enum>

<P>If all else fails, you should check your syslog. When authentication
fails for any reason, ProFTPD uses the syslog mechanism to log the
reason for failure; using the AUTH (or AUTHPRIV) facility. If you need
further assistance, you can send email, including related syslog
entries and your configuration file, to the ProFTPD mailing list
mentioned elsewhere in this FAQ.

<sect1>Bandwidth control

<P>The Bandwidth directive has been removed as of 1.2.0pre8, this
directive acted on a per-virtual basis.  It was generally held that it
worked on the principle that a single connection to a given virtual
could take the full bandwidth limit until other connections were made.
However, the server uses either separate server (inetd) or forked
(standalone) model there is no way for the various processes to
communicate, therefore is no way they could share the bandwidth
allocation.

<P>The replacement actually does the same but does it in a more
rigorous manner and more precisely.  The directives RateReadBPS,
RateReadFreeBytes, RateReadHardBPS work by limiting on a
per-connection basis.

<tscreen><verb>
Bandwidth                       81920

is replaced with something like

RateReadBPS                     81920
RateReadFreeBytes               5120
RateReadHardBPS                 on
</verb></tscreen>

<P>To achieve a total limit on a per virtual basis a mix of
RateReadBPS and MaxClients is needed.  ie RateReadBPS x MaxClients =
Total Bandwidth allocation.  There is no way (at the moment) to
specify that virtual server xyz has a maximum total bandwidth of
200K/s that it can use between all connections.

<P>Per-virtual, per-user and global limits are currently in the "to be
coded" pile and are being penciled in for the 1.3.x development
series.  There is some work in providing for a shared communication
system between servers before this can happen.

<sect2>Rate controls aren"t working

<P>
In pre9 and earlier Rate* does not work if sendfile is enabled,
	    recompile with --without-sendfile and all should be as
	    expected.

<sect1>CHMOD isn"t working

<P>As of rc1 the AllowChmod command was added to allow control over
who is allowed to use the CHMOD command.  The default value for this
directive is off.

<sect1>How can I limit the size of uploaded files?

<P>There is no way within ProFTPD itself to control how large a file
can be uploaded.  The best solution to this problem at the moment is
to use whatever disk quota tools are available within your OS.

<sect1>Can I disable Anonymous logins?

<P>Yes, just remove all the &lt;Anonymous&gt; sections from your
configuration file and reload the daemon.

<sect1>Limiting the connections per loginID

<P>This is not possible at this time, the directive appeared in the
docs for a short period but the code was never added.  The closest
possible at the moment is to limit the number of connections from a
given host.


<sect1>How do I configure proftpd to allow transfer resumption (for
     downloads and uploads)?
 
<p>To allow downloads to be resumed, you need to use the
   AllowRetrieveRestart configuration directive.
 
<p>To allow uploads to be resumed, you need to use both the
   AllowOverwrite and AllowStoreRestart directives.  The reason that both
   need to be allowed is that a restarted/resumed upload is a form of
   overwriting the file.
 
<p>Also note that using HiddenStores and AllowStoreRestart is incompatible,
   as mentioned in the documentation for the AllowStoreRestart
   and HiddenStores directives.
 
<sect1>When should the Bind directive be used?
 
<p>The Bind directive is used to specify additional interfaces
   (addresses) for a given server; it is *not* used to configure the
   main interface for the server.  For &lt;VirtualHost&gt; servers,
   this is not a problem, as the main interface for the server is set
   in the &lt;VirtualHost&gt; line.
 
<p>For the main "default" server, however, the controlling of the main
   interface is done using the DefaultAddress configuration directive.

<!-- SECTION BREAK -->

<sect>Security
<P>

<sect1>General

<P>As with all software there have been a number of security issues
during the life of the project.  The most recent information can
always be found on http://www.proftpd.org/security.html

<P>Versions 1.2.0 and above should be considered to be production code
and few if any new features will be added to this code branch to
maintain stability.

<sect2>What about using Stackguard?
<P>Stackguard is a gcc variant which can protect programs from
stack-smashing attacks, programs compiled using Stackguard dies without
executing the stack code.  While this approach is a good first line of
defense against future problems it"s not a complete cure-all.  Some of the
buffer overflows were found on static variables, which are not protected
by stack protection mechanisms. 

<!-- Need link to stackguard -->

<sect1>Surely running ProFTPD as non-root will help?

<P>Running ProFTPD as a non-root user gives only a marginal security
improvement on the normal case and adds some functional problems.
Such as not being able to bind to ports 20 or 21, unless it"s spawned
from inetd.

<P>ProFTPD takes a middle road in terms of security.  It only uses
root privileges where required and drops to the UID defined in the
config file at all other times.  Times when root is required include,
binding to ports < 1024, setting resource limits, reading
configuration information and some network code.

<P>For Linux 2.2.x kernel systems there is the POSIX style
mod_linuxprivs module which allows very fine grain control over
privileges.  This is highly recommended for security-conscious admins.

<sect1>How can I control what commands the server accepts?

<P>Use a sane Allow/DenyFilter, these directives use regular
expressions to control all text sent over the control socket.  (If
anyone has some good examples please let me know.)

<!-- <P>[NB: need examples here] -->

<sect1>How can I prevent the server version from being displayed
<P>Setting SeverIdent to "off" should turn off the information about
what type of server is running.  To have maximum effect this directive 
should either be in the Global context or included in every virtual
host block and the default block.

<tscreen><code>
ServerIdent  On "Linux.co.uk server"

ServerIdent  Off
</code></tscreen>

<sect1>I want to show a message prior to login
<P>Use the DisplayConnect directive to specify a file containing a
message to be displayed prior to login.

<tscreen><code>
DisplayConnect /ftp/ftp.virtualhost/login.msg
</code></tscreen>

<sect1>I want to display a message after login

<P>Use the DisplayLogin directive, this sends a specified ASCII file to the
connected user.

<tscreen><code>
DisplayLogin       /etc/proftp.msg
</code></tscreen>

<sect1>Can I have a custom welcome response?

<P>Use the AccessGrantMsg directive, this sends a simple single line
message back to the user after a successful authentication.  Magic
cookies appear to be honoured in this directive.

<tscreen><code>
AccessGrantMsg "Guest access granted for %u."
</code></tscreen>

<P>Note, this directive has an overriding default and needs to be
specified in both VirtualHost and Anonymous blocks.

<sect1>External Programs

<P>ProFTPD has been designed to run as a secure ftp server, this means 
that it tries to keep as much as possible under it"s control.  An
external program is a security risk in itself because it"s behaviour
is not controllable from within the ftpd code.

<sect1>Why do I see "No certificates found!"? 

<p>This message is generated by mod_tls, the third-party module that can
   be used to encrypt both the control and data connections with TLS
   (Transport Layer Security), the next generation of SSL.  Certificates
   are used to establish the security context for this secure transport.
 
<p>Generation of certifications is beyond the scope of this document;
   however, more information can be found here:
 
<p>     http://en.tldp.org/HOWTO/SSL-Certificates-HOWTO/

<sect>User Authentication

<P>This section is being re-written due to major structural changes to the SQL module prior to 1.2.0

<sect1>Why is PAM the default authentication system?

<P>Security, pure and simple.  PAM is the most secure (or securable)
of the available authentication systems.  Many of the issues and
configuration hints for PAM are contained in README.PAM which is
bundled with the server source and in the various packaged builds.  To 
use /etc/passwd manual compilation will be required with the configure 
script being run with the --without-pam flag.  Unless the PAM
subsystem is properly configured authentication will fail.

<sect1>Authentication methods supported
<P>

<itemize>
<item>PAM
<item>Standard /etc/passwd lookups
<item>NIS
<item>Shadow passwords
<item>Indvidual passwd/group files for each virtual
<item>SQL databases
</itemize>

<P>If these don"t fit in with your system then writing a custom module
or using such as the "ld.so.preload" approach to intercept
getpwbynam() system calls works happily with ProFTPD.


<sect1>Problems with non-PAM authentication

<P>Generally these problems will be cured by either disabling PAM
completely or by ensuring that these directives are set

<tscreen>
<code>
PersistentPasswd   off
AuthPAMAuthoritative off
</code>
</tscreen>

<sect1>AuthPAMAuthorative is an unknown directive!

<P>Check the spelling it should be AuthPAMAuthoritative not
AuthPAMAuthorative or any other variation.

<sect1>Configuring PAM

<P>There is a README.Pam in the top directory of the ProFTPD install
directory :

<sect2>Redhat Linux
<P>
<tscreen><code>
#%PAM-1.0
auth       required     /lib/security/pam_listfile.so item=user
sense=deny file=/etc/ftpusers onerr=succeed
auth       required     /lib/security/pam_pwdb.so shadow nullok
account    required     /lib/security/pam_pwdb.so
session    required     /lib/security/pam_pwdb.so
</code></tscreen>

<sect2>SuSE Linux 
<P>SuSE appears to uses pam_unix rather than pam_pwdb which is the
Redhat approach.  All references to pam_pwdb should be replaced with
"pam_unix" on SuSE systems.

<P>The following fragment is reported to work fine on SuSE 6.2

<tscreen><code>
/etc/pam.d/ftpd
#%PAM-1.0

# Uncomment this to achieve what used to be ftpd -A.
# auth       required     /lib/security/pam_listfile.so item=user sense=allow file=/etc/ftpchroot onerr=fail

auth     required       /lib/security/pam_listfile.so item=user
sense=deny file=/etc/ftpusers onerr=succeed
auth     sufficient     /lib/security/pam_ftp.so
auth     required       /lib/security/pam_unix.so
auth     required       /lib/security/pam_shells.so
account  required       /lib/security/pam_unix.so
password required       /lib/security/pam_unix.so
session  required       /lib/security/pam_unix.so
</code></tscreen>

<sect2>FreeBSD

<P>FreeBSD does not support PAM session directives. If you remove the
following line from the FreeBSD section of README.PAM, PAM should work
properly under recent versions of FreeBSD.

<tscreen><code>
 ftp session required    pam_unix.so         try_first_pass
</code></tscreen>

<sect1>pam_sm_open_session errors
<P>ProFTPD requires PAM version 0.59 or better.  pam_sm_open_session
is not part of previous versions.

<sect1>Normal users can"t login, only anon.

<P>Check that the /etc/pam.d/ftp file exists on the system and is
configured as detailed in README.PAM

<sect1>AuthPAMAuthoritative

<P>Currently AuthPAMAuthoritative defaults on "ON" resulting in login
failures if PAM cannot authenticate the user.  This breaks the
AuthUserFile directive as it never gets a chance to authenticate the
user unless the AuthPAMAuthoritative directive is set to "OFF"

<P>The reasoning behind the current default is to ensure that the
system is secure by default requiring that the admin explicitly and
knowingly has to disable it.  There are discussions underway which
may result in the directive flipping to a default of "Off" if
AuthUserFile is specified.

<P><bf>Note:</bf> as of the current CVS and the forthcoming pre9
release the default has changed to "Off"

<sect1>LDAP
<P>
mod_ldap is currently stable; there were a couple bugs that were
squashed after release 1.0 of the module.  it is still udner
development , check the <url
url="http://horde.net/~jwm/software/mod_ldap/" name="website"> for
more information.  There is an example config fragment on the author"s
site which gives a reasonable idea on how to use this module.

<sect1>Encrypted passwords

<P>There are patches which are being merged in at the moment to provide
SHA encryption.  The plan is to have the server get all user information
except passwords via an anonymous bind.  The server will then reconnect
as a user is logging in and attempt to get the password via an encrypted
connection.  This should be in the next major release (2.5)

<sect1>SecureID
<P>No support yet

<sect1>One time passwords

<P>This is possible using either PAM or the Opie modules.  The module
passes back a challenge which the user puts into a key generator along
with their "pass phrase" and it gives them back 5 words which get sent
as the password.  As long as you do it correctly it will never repeat.

<P>It requires <url url="http://inner.net/opie/" name="opie"> to be installed on the server.
There are key gen clients for win95/98, *nix, mac.

<P>ftp://ftp.urbanrage.com/pub/c/mod_opie.c

<sect1>RADIUS
<P>
Radius support isn"t built into ProFTPD, though there"s nothing
stopping someone writing a module and submitting it for inclusion in
the code tree.  Possibly the easist way to implement Radius is by
using the modules available for PAM and using the inbuilt PAM support.

<sect1>Anonymous password checking

<P>Is it possible to check an offered email address in an anonymous
login before allowing access.  Simple answer, not a hope in hell,
anonymous access is pretty much designed to be freely open without
checks and restrictions other than those placed on upload/download
from the site.  The best that can be hoped for is decent logging and
tracking of accesses, and the requesting IP.

<sect1>Why do I see "PAM(name): Authentication failure", but I can login
     anyway?
<p>If the operating system supports PAM (Pluggable Authentication Modules)
   proftpd will perform PAM authentication by default.  However, this
   authentication is not "authoritative" by default, meaning that
   a PAM authentication failure will not necessarily cause a login to
   fail.  The use of PAM can be configured using the AuthPAM configuration
   directive; the "authoritativeness" of any PAM checks is controlled via
   the AuthPAMAuthoritative configuration directive.

<sect>Hamster droppings
<P>

<sect1>Why...
<P>This chapter is not meant to be meaningful, it"s where I cut
and paster ideas, comments, code fragments before I work them into the 
main part of the document.


<sect1>Odds and ends
<P>Why can"t I delete a directory with dele ?
<P>Port bouncing, ftp bouncing, priv ports
<P>hiding directories
<P>hiding files
<P>authentication methods

<P>user defined permissions in &lt;LIMIT&gt; do not override system level
permissions.

<P>authuserfile: needs a complete password file, not a cutdown.


<sect>FAQ Notes

<sect1>History

<P>The original text for this document was based on the configuration
FAQ on www.proftpd.org.  It was taken over in Sept 1999 when the
maintainer of the software changed.

<P>The faq is usually maintained on a P100 or paper somewhere on the
London Underground while I'm travelling home from work.  The most
recent version can always be obtained from <url
url="http://pdd.sourceforge.net/" name="Sourceforge">.  It is
available as a series of linked html files, a single flat html file,
the original sgml source, ASCII text and a tarball containing all the
formats.

<sect1>Copyrights and Trademarks

<P>(c) 1999-2002 Mark Lowes

<P>This document may be reproduced in whole or in part, without fee,
subject to the following restrictions:
   
<itemize>

<item>The copyright notice above and this permission notice must be
preserved complete on all complete or partial copies

<item>Any translation or derived work must be approved by the author in
writing before distribution.

<item>If you distribute this work in part, instructions for obtaining
the complete version of this manual must be included, and a means
for obtaining a complete version provided.

<item>Small portions may be reproduced as illustrations for reviews or
quotes in other works without this permission notice if proper
citation is given.

</itemize>   

<P>Exceptions to these rules may be granted for academic purposes:
Write to the author and ask. These restrictions are here to protect us
as authors, not to restrict you as learners and educators. 

<sect1>Acknowledgements and Thanks

<P>Thanks to the developers, anyone who"s posted useful information to 
the mailing lists and those who"ve mailed me direct.

<P>This document couldn"t have been maintained without the Sgml Tools
package and the document layout defined by the Linux HOWTO
maintainers. 

<P>Some specific mentions, in no particular order, and I've missed
anyone please drop me a line.

<itemize>
<item>Updates to the SQL section, Michael Grabenstein &lt;mgrabens@popd.isinet.com&gt;
</itemize>

<sect1>Todo
<P>

<itemize>
<item>Get a clear idea of how to split this up
<item>More examples
<item>Clear the mailing list backlog and add information from there
<item>sleep, relax and generally have a good time.
</itemize>
   
</article>