pure-ftpd(8) Pure-FTPd Team pure-ftpd(8)
Pure-FTPd Pure-FTPd
1.0.8
NAME
pure-ftpd - simple File Transfer Protocol server
SYNOPSIS
pure-ftpd [-1] [-4] [-A] [-a gid]
Alternative style, unless compiled with --without-longoptions:
-1 --logpid
-4 --ipv4only
-A --chrooteveryone
-a --trustedgid
-b --brokenclientscompatibility
-B --daemonize
-c --maxclientsnumber
-C --maxclientsperip
-d --verboselog
-D --displaydotfiles
-e --anonymousonly
-E --noanonymous
-f --syslogfacility
-F --fortunesfile
-g --pidfile
-G --norename
-h --help
-H --dontresolve
-I --maxidletime
-i --anonymouscantupload
-j --createhomedir
-k --maxdiskusagepct
-K --keepallfiles
-l --login
-L --limitrecursion
-M --anonymouscancreatedirs
-m --maxload
-N --natmode
-n --quota
-o --uploadscript
-O --altlog
-p --passiveportrange
-P --forcepassiveip
-q --anonymousratio
-Q --userratio
-r --autorename
-R --nochmod
-s --antiwarez
-S --bind
-t --anonymousbandwidth
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-T --userbandwidth
-U --umask
-u --minuid
-V --trustedip
-w --allowuserfxp
-W --allowanonymousfxp
-x --prohibitdotfileswrite
-X --prohibitdotfilesread
-z --allowdotfiles
DESCRIPTION
PureFTPd is a small, simple server for the old and hairy File Transfer
Protocol, designed to use less resources than older servers, be
smaller and very secure, and to never execute any external program.
It support most-used features and commands of FTP (including many
modern extensions), and leaves out everything which is deprecated,
meaningless, insecure, or correlates with trouble.
IPv6 is fully supported.
OPTIONS
-1 Add the PID to the syslog output. Ignored if -f none is set.
-4 Listen only for IPv4 connections. MANDATORY FOR IPV NETWORKS ON
OPENBSD.
-A Chroot() everyone, but root.
-a gid
Regular users will be chrooted to their home directories, unless
they belong to the specified gid. Note that root is always
trusted, and that chroot() occurs only for anonymous ftp without
this option.
-b Be broken. Turns on some compatibility hacks for shoddy clients,
and for broken Netfilter gateways.
-B Start the standalone server in background (daemonize).
-c clients
Allow a maximum of clients to be connected. clients must be at
least 1, and if you combine it with -p it will be forced down to
half the number of ports specified by -p. If more than clients
are connected, new clients are rejected at once, even clients
wishing to upload, or to log in as normal users. Therefore, it
is advisable to use -m as primary overload protection. The
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default value is 50.
-C max connection per ip
Limit the number of simultanous connections coming from the same
IP address. This is yet another very effective way to prevent
stupid denial of services and bandwidth starvation by a single
user. It works only when the server is launched in standalone
mode (if you use a super-server, it is supposed to do that). If
the server is launched with -C 2 , it doesn't mean that the total
number of connection is limited to 2. But the same client,
coming from the same machine (or at least the same IP), can't
have more than two simultaneous connections. This features needs
some memory to track IP addresses, but it's recommended to use
it.
-d turns on debug logging. Every command is logged, except that the
argument to PASS is changed to "<password>". If you repeat -d ,
responses too are logged.
-e Only allow anonymous users to log in.
-E Only allow authenticated login. Anonymous users are prohibited.
-F fortunes file
Display a funny random message in the initial login banner. The
random cookies are extracted from a text file, in the standard
fortune format. If you installed the fortune package, you should
have a directory (usually /usr/share/fortune ) with binary files
( xxxx.dat ) and text files (without the .dat extension).
-f facility
makes ftpd use facility for all syslog(3) messages. facility
defaults to ftp. The facility names are normally listed in
/usr/include/sys/syslog.h. Note that if -f is not the first
option on the command line, a couple of messages may be logged to
local2 before the -f option is parsed. Use -f none to disable
logging.
-h pidfile
In standalone mode, write the pid to that file in instead of
/var/run/pure-ftpd.pid .
-H Don't resolve host names ("213.41.14.252" will be logged instead
of "www.toolinux.com"). It can significantly speed up connections
and reduce bandwidth usage on busy servers. Use it especially on
public FTP sites.
-k percentage
Disallow upload if the partition is more than percentage full.
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Example: -k 95 will ensure that your disk will never get filled
more than 95% by FTP users.
-K Allow users to resume and upload files, but NOT to delete them.
Directories can be removed, but only if they are empty.
-I timeout
Change the maximum idle time. The timeout is in minutes, and
defaults to 15.
-i Disallow upload for anonymous users, whatever directory
permissions are. This option is especially useful for virtual
hosting, to avoid your users create warez sites in their account.
-j If the home directory of an user doesn't exist, automatically
create it. The newly created home directory belongs to the user,
and permissions are set according to the current directory mask.
To avoid local attacks, the parent directory should never belong
to an untrusted user.
-L max files:max depth
Avoid denial-of-service attacks by limiting the number of
displayed files in a 'ls' and the maximum depth of a recursive
'ls'. Defaults are 2000:5 (2000 files displayed for a single 'ls'
and walk through 5 subdirectories max).
-l authentication:file
Enable a new authentication method. It can be one of : -l unix
For standard (/etc/passwd) authentication. -l pam For PAM
authentication. -l ldap:LDAP config file For LDAP directories.
-l mysql:MySQL config file For MySQL databases. -l
pgsql:Postgres config file For Postgres databases. -l
puredb:PureDB database file For PureDB databases. -l
extauth:path to pure-authd socket For external authentication
handlers.
Different authentication methods can be mixed together. For
instance if you run the server with -lpuredb:/etc/pwd.pdb
-lmysql:/etc/my.cf -lunix Accounts will first be authenticated
from a PureDB database. If it fails, a MySQL server will be
asked. If the account is still not found is the database,
standard unix accounts will be scanned. Authentication methods
are tried in the order you give the -l options.
See the README.LDAP and README.MySQL files for info about the
built-in LDAP and SQL directory support.
-M Allow anonymous users to create directories.
-m load
Do not allow anonymous users to download files if the load is
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above load when the user connects. Uploads and file listings are
still allowed, as are downloads by real users. The user is not
told about this until he/she tries to download a file.
-N NAT mode. Force active mode. If your FTP server is behind a NAT
box that doesn't support applicative FTP proxying, or if you use
port redirection without a transparent FTP proxy, use this.
Well... the previous sentence isn't very clear. Okay: if your
network looks like this:
FTP--NAT.gateway/router--Internet
and if you want people coming from the internet to have access to
your FTP server, please try without this option first. If
Netscape clients can connect without any problem, your NAT
gateway rulez. If Netscape doesn't display directory listings,
your NAT gateway sucks. Use -N as a workaround.
-n maxfiles:maxsize
Enable virtual quotas When virtual quotas are enabled, .ftpquota
files are created, and the number of files for an user is
restricted to 'maxfiles'. The max total size of his directory is
also restricted to 'maxsize' Megabytes. Members of the trusted
group aren't subject to quotas.
-o Enable pure-uploadscript.
-O format:log file
Record all file transfers into a specific log file, in an
alternative format. Currently, three formats are supported : CLF,
Stats and W3C.
If you add
-O clf:/var/log/pureftpd.log
to your starting options, Pure-FTPd will log transfers in
/var/log/pureftpd.log in a format similar to the Apache web
server in default configuration.
If you add
-O stats:/var/log/pureftpd.log
to your starting options, Pure-FTPd will create accurate log
files designed for traffic analys software like ftpStats.
If you add
-O w3c:/var/log/pureftpd.log
to your starting options, Pure-FTPd will create W3C-conformant
log files .
For security purposes, the path must be absolute (eg.
/var/log/pureftpd.log , not
../log/pureftpd.log ) .
-P ip address
Force the specified IP address in reply to a PASV/EPSV/SPSV
command. If the server is behind a masquerading (NAT) box that
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doesn't properly handle stateful FTP masquerading, put the ip
address of that box here.
-p first:last
Use only ports in the range R first to last inclusive for
passive-mode downloads. This means that clients will not try to
open connections to TCP ports outside the range R first - last ,
which makes pure-ftpd more compatible with packet filters. Note
that the maximum number of clients (specified with -c) is forced
down to R ( last +1- first if it is greater, as the default is.
(The syntax for the port range is, conveniently, the same as that
of iptables).
-q upload:download
Enable an upload/download ratio for anonymous users (ex: -q 1:5
means that 1 Mb of goodies have to be uploaded to leech 5 Mb).
-Q upload:download
Enable ratios for anonymous and non-anonymous users. If the -a
option is also used, users from the trusted group have no ratio.
-r Never overwrite existing files. Uploading a file whoose name
already exists cause an automatic rename. Files are called xyz.1,
xyz.2, xyz.3, etc.
-R Disallow users (even non-anonymous ones) usage of the CHMOD
command. On hosting services, it may prevent newbies from doing
mistakes, like setting bad permissions on their home directory.
Only root can use CHMOD when this switch is enabled.
-s Don't allow anonymous users to retrieve files owned by "ftp"
(generally, files uploaded by other anonymous users).
-S [{ip address|hostname}] [,{port|service name}]
This option is only effective when the server is launched as a
standalone server. Connections are accepted on the specified IP
and port. IPv4 and IPv6 are supported. Numeric and
fully-qualified host names are accepted. A service name (see
/etc/services) can be used instead of a numeric port number.
-t bandwidth
or -t upload bandwidth:download bandwidth Enable process priority
lowering and bandwidth throttling for anonymous users. Delay
should be in kilobytes/seconds.
-T bandwidth
or -T upload bandwidth:download bandwidth Enable process priority
lowering and bandwidth throttling for *ALL* users. Pure-FTPd
should have been explicitely compiled with throttling support to
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have these flags work. It is possible to have different
bandwidth limits for uploads and for downloads. '-t' and '-T' can
indeed be followed by two numbers delimited by a column (':').
The first number is the upload bandwidth and the next one applies
only to downloads. One of them can be left blank which means
infinity. A single number without any column means that the same
limit applies to upload and download.
-U umask files:umask dirs
Change the mask for creation of new files and directories. The
default are 133 (files are readable -but not writable- by other
users) and 022 (same thing for directory, with the execute bit
on). If new files should only be readable by the user, use
177:077. If you want uploaded files to be executable, use 022:022
(files will be readable by other people) or 077:077 (files will
only be readable by their owner).
-u uid
Do not allow uids below uid to log in (typically, low-numbered R
uid s are used for administrative accounts). -u 100 is
sufficient to deny access to all administrative accounts on many
linux boxes, where 99 is the last administrative account.
Anonymous FTP is allowed even if the uid of the ftp user is
smaller than uid. -u 1 denies access only to root accounts. The
default is to allow FTP access to all accounts.
-V ip address
Allow non-anonymous FTP access only on this specific local IP
address. All other IP addresses are only anonymous. With that
option, you can have routed IPs for public access, and a local IP
(like 10.x.x.x) for administration. You can also have a routable
trusted IP protected by firewall rules, and only that IP can be
used to login as a non-anonymous user.
-w Enable support for the FXP protocol, for non-anonymous users
only.
-W Enable the FXP protocol for everyone. FXP IS AN UNSECURE
PROTOCOL. NEVER ENABLE IT ON UNTRUSTED NETWORKS.
-x In normal operation mode, authenticated users can read/write
files beginning with a dot ('.'). Anonymous users can't, for
security reasons (like changing banners or a forgotten .rhosts).
When '-x' is used, authenticated users can download dot-files,
but not overwrite/create them, even if they own them. That way,
you can prevent hosted users from messing
-X This flag is identical to the previous one (writing dot-files is
prohibited), but in addition, users can't even *read* files and
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directories beginning with a dot (like "cd .ssh").
-z Allow anonymous users to read files and directories starting with
a dot ('.').
AUTHENTICATION
Some of the complexities of older servers are left out.
This version of pure-ftpd can use PAM for authentication. If you wan't
it to consult any files like /etc/shells or /etc/ftpd/ftpusers consult
pam docs. LDAP directories and SQL databases are also supported.
Anonymous users are authenticated in any of three ways:
1. The user logs in as "ftp" or "anonymous" and there is an account
called "ftp" with an existing home directory. This server does not
ask anonymous users for an email address or other password.
2. The user connects to an IP address which resolves to the name of a
directory in /etc/pure-ftpd (or a symlink in that directory to a real
directory), and there is an account called "ftp" (which does not need
to have a valid home directory). See Virtual Servers below.
Ftpd does a chroot(2) to the relevant base directory when an anonymous
user logs in.
Note that ftpd allows remote users to log in as root if the password
is known and -u not used.
UNUSUAL FEATURES
Ftpd never switches uid and euid, it uses setfsuid(2) instead. The
main reason is that uid switching has been exploited in several
breakins, but the sheer ugliness of uid switching counts too. Ftpd
only calls setfsuid(2) once, at login.
If a user's home directory is /path/to/home/./, FTP sessions under
that UID will be chroot()ed. In addition, if a users's home directory
is /path/to/home/./directory the session will be chroot()ed to
/path/to/home and the FTP session will start in 'directory'.
As noted above, this pure-ftpd omits several features that are
required by the RFC or might be considered useful at first. Here is a
list of the most important omissions.
On-the-fly tar is not supported, for several reasons. I feel that
users who want to get many files should use a special FTP client such
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as "mirror," which also supports incremental fetch. I don't want to
either add several hundred lines of code to create tar files or
execute an external tar. Finally, on-the-fly tar distorts log files.
On-the-fly compression is left out too. Most files on an FTP site are
compressed already, and if a file isn't, there presumably is a reason
why. (As for decompression: Don't FTP users waste bandwidth enough
without help from on-the-fly decompression?)
DIRECTORY ALIASES
Shortcuts for the "cd" command can be set up if the server has been
compiled with the --with-diraliases feature.
To enable directory aliases, create a file called
/etc/pureftpd-dir-aliases and alternate lines of alias names and
associated directories.
ANONYMOUS FTP
This server leaves out some of the commands and features that have
been used to subvert anonymous FTP servers in the past, but still you
have to be a little bit careful in order to support anonymous FTP
without risk to the rest of your files.
Make ~ftp and all files and directories below this directory owned by
some user other than "ftp," and only the .../incoming
directory/directories writable by "ftp." It is probably best if all
directories are writable only by a special group such as "ftpadmin"
and "ftp" is not a member of this group.
If you do not trust the local users, put ~ftp on a separate partition,
so local users can't hard-link unapproved files into the anonymous FTP
area.
Use of the -s option is strongly suggested. (Simply add "-s" to the
end of the ftpd line in /etc/inetd.conf to enable it.)
Most other FTP servers require that a number of files such as
~ftp/bin/ls exist. This server does not require that any files or
directories within ~/ftp whatsoever exist, and I recommend that all
such unnecessary files are removed (for no real reason).
It may be worth considering to run the anonymous FTP service as a
virtual server, to get automatic logins and to firewall off the FTP
address/port to which real users can log in.
If your server is a public FTP site, you may want to allow only 'ftp'
and 'anonymous' users to log in. Use the -e option for this. Real
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accounts will be ignored and you will get a secure, anonymous-only FTP
server.
MAGIC FILES
The files <ftproot>/.banner and .message are magical.
If there is a file called .banner in the root directory of the
anonymous FTP area, or in the root directory of a virtual host, and it
is shorter than 1024 bytes, it is printed upon login. (If the client
does not log in explicitly, and an implicit login is triggered by a
CWD or CDUP command, the banner is not printed. This is regrettable
but hard to avoid.)
If there is a file called .message in any directory and it is shorter
than 1024 bytes, that file is printed whenever a user enters that
directory using CWD or CDUP.
VIRTUAL SERVERS
You can run several different anonymous FTP servers on one host, by
giving the host several IP addresses with different DNS names.
Here are the steps needed to create an extra server using an IP alias
on linux 2.4.x, called "ftp.example.com" on address 10.11.12.13. on
the IP alias eth0.
1. Create an "ftp" account if you do not have one. It it best if the
account does not have a valid home directory and shell. I prefer to
make /dev/null the ftp account's home directory and shell. Ftpd uses
this account to set the anonymous users' uid.
2. Create a directory as described in Anonymous FTP and make a symlink
called /etc/pure-ftpd/10.11.12.13 which points to this directory.
3. Make sure your kernel has support for IP aliases.
4. Make sure that the following commands are run at boot:
/sbin/ifconfig eth0:1 10.11.12.13
That should be all. If you have problems, here are some things to
try.
First, symlink /etc/pure-ftpd/127.0.0.1 to some directory and say "ftp
localhost". If that doesn't log you in, the problem is with ftpd.
If not, "ping -v 10.11.12.13" and/or "ping -v ftp.example.com" from
the same host. If this does not work, the problem is with the IP
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alias.
Next, try "ping -v 10.11.12.13" from a host on the local ethernet, and
afterwards "/sbin/arp -a". If 10.11.12.13 is listed among the ARP
entries with the correct hardware address, the problem is probably
with the IP alias. If 10.11.12.13 is listed, but has hardware address
0:0:0:0:0:0, then proxy-ARP isn't working.
If none of that helps, I'm stumped. Good luck.
Warning: If you setup a virtual hosts, normal users will not be able
to login via this name, so don't create link/directory in
/etc/pure-ftpd for your regular hostname.
FILES
/etc/passwd is used via libc (and PAM is this case), to get the uid
and home directory of normal users, the uid and home directory of
"ftp" for normal anonymous ftp, and just the uid of "ftp" for virtual
ftp hosts.
/etc/shadow is used like /etc/passwd if shadow support is enabled.
/etc/group is used via libc, to get the group membership of normal
users.
/proc/net/tcp is used to count existing FTP connections, if the -c or
-p options are used
/etc/pure-ftpd/<ip address> is the base directory for the <ip address>
virtual ftp server, or a symbolic link to its base directory. Ftpd
does a chroot(2) into this directory when a user logs in to <ip
address>, thus symlinks outside this directory will not work.
~ftp is the base directory for "normal" anonymous FTP. Ftpd does a
chroot(2) into this directory when an anonymous user logs in, thus
symlinks outside this directory will not work.
LS
The behaviour of LIST and NLST is a tricky issue. Few servers send
RFC-compliant responses to LIST, and some clients depend on
non-compliant responses.
This server uses glob(3) to do filename globbing.
The response to NLST is by default similar to that of ls(1), and that
to LIST is by default similar to that of ls -l or ls -lg on most Unix
systems, except that the "total" count is meaningless. Only regular
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files, directories and symlinks are shown. Only important ls options
are supported:
-1 Undoes -l and -C.
-a lists even files/directories whose names begin with ".".
-C lists files in as many colums as will fit on the screen. Undoes
-1 and -l.
-d lists argument directories' names rather their contents.
-D List files beginning with a dot ('.') even when the client
doesn't append the -a option to the list command.
-F appends '*' to executable regular files, '@' to symlinks and '/'
to directories.
-l shows various details about the file, including file group. See
ls(1) for details. Undoes -1 and -C.
-r reverses the sorting order (modifies -S and -t and the default
alphabetical ordering).
-R recursively descends into subdirectories of the argument
directories.
-S Sorts by file size instead of by name. Undoes -t.
-t Sorts by file modification time instead of by name. Undoes -S.
PROTOCOL
Here are the FTP commands supported by this server. ABOR NOOP ALLO
USER PASS QUIT SYST PORT EPRT PASV EPSV SPSV PWD XPWD CWD XCWD CDUP
XCUP HELP RETR REST DELE STOR APPE STOU MKD XMKD RMD XRMD LIST NLST
TYPE MODE STRU XDBG MDTM SIZE RNFR RNTO STAT MLST MLSD FEAT SITE IDLE
SITE CHMOD SITE HELP
BUGS
Please report bugs to the mailing-list (see below). Pure-FTPd looks
very stable and is used on production servers. However it comes with
no warranty and it can have nasty bugs or security flaws.
HOME PAGE
http://www.pureftpd.org
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NEW VERSIONS
See the mailing-list on http://www.pureftpd.org.
AUTHOR AND LICENCE
Troll-FTPd written by Arnt Gulbrandsen <agulbra@troll.no> and
copyright 1995-1999 Troll Tech AS, Waldemar Thranes gate 98B, N-0175
Oslo, Norway, fax +47 22806380.
Pure-FTPd (C)opyleft 2001 by Frank DENIS <j@pureftpd.org> and the
Pure-FTPd team.
Use, modification and distribution is allowed without limitation,
warranty, or liability of any kind.
Contributors:
Arnt Gulbrandsen,
Troll Tech AS,
Janos Farkas,
August Fullford,
Ximenes Zalteca,
Patrick Michael Kane,
Arkadiusz Miskiewicz,
Michael K. Johnson,
Kelley Lingerfelt,
Sebastian Andersson,
Andreas Westin,
Jason Lunz,
Mathias Gumz,
Claudiu Costin,
Ping,
Paul Lasarev,
Jean-Mathieux Schaffhauser,
Emmanuel Hocdet,
Sami Koskinen,
Sami Farin,
Luis Llorente Campo,
Peter Pentchev,
Darren Casey,
The Regents of the University of California,
Theo de Raadt (OpenBSD),
Matthias Andree,
Isak Lyberth,
Steve Reid,
RSA Data Security Inc,
Trilucid,
Dmtry Lebkov,
Johan Huisman,
Thorsten Kukuk,
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Jan van Veen,
Roger Constantin Demetrescu,
Stefano F.,
Robert Varga,
Freeman,
James Metcalf,
Im Eunjea,
Philip Gladstone,
Kenneth Stailey,
Brad Smith,
Ulrik Sartipy,
Cindy Marasco,
Nicolas Doye,
Thomas Briggs,
Stanton Gallegos.
SEE ALSO
ftp(1), pure-ftpd(8) pure-ftpwho(8) pure-mrtginfo(8) pure-
uploadscript(8) pure-statsdecode(8) pure-pw(8) pure-quotacheck(8)
pure-authd(8)
RFC 959, RFC 2228 and RFC 2428.
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