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[dragonfly.git] / libexec / ftpd / ftpd.8
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32.\" @(#)ftpd.8 8.2 (Berkeley) 4/19/94
33.\" $FreeBSD: src/libexec/ftpd/ftpd.8,v 1.31.2.18 2003/02/11 14:28:28 yar Exp $
34.\"
35.Dd January 27, 2000
36.Dt FTPD 8
37.Os
38.Sh NAME
39.Nm ftpd
40.Nd Internet File Transfer Protocol server
41.Sh SYNOPSIS
42.Nm
43.Op Fl 46AdDEhmMoOrRSUvW
44.Op Fl l Op Fl l
45.Op Fl a Ar address
46.Op Fl p Ar file
47.Op Fl P Ar port
48.Op Fl t Ar timeout
49.Op Fl T Ar maxtimeout
50.Op Fl u Ar umask
51.Sh DESCRIPTION
52.Nm Ftpd
53is the
54Internet File Transfer Protocol
55server process. The server uses the
56.Tn TCP
57protocol
58and listens at the port specified with the
59.Fl P
60option or in the
61.Dq ftp
62service specification; see
63.Xr services 5 .
64.Pp
65Available options:
66.Bl -tag -width indent
67.It Fl 4
68When
69.Fl D
70is specified, accept IPv4 connections.
71When
72.Fl 6
73is also specified, accept IPv4 connection via
74.Dv AF_INET6
75socket.
76When
77.Fl 6
78is not specified, accept IPv4 connection via
79.Dv AF_INET
80socket.
81.It Fl 6
82When
83.Fl D
84is specified, accept connections via
85.Dv AF_INET6
86socket.
87.It Fl a
88When
89.Fl D
90is specified, accept connections only on the specified
91.Ar address .
92.It Fl A
93Allow only anonymous ftp access.
94.It Fl d
95Debugging information is written to the syslog using
96.Dv LOG_FTP .
97.It Fl D
98With this option set,
99.Nm
100will detach and become a daemon, accepting connections on the FTP port and
101forking children processes to handle them.
102This is lower overhead than starting
103.Nm
104from
105.Xr inetd 8
106and is thus useful on busy servers to reduce load.
107.It Fl E
108Disable the EPSV command.
109This is useful for servers behind older firewalls.
110.It Fl h
111Disable printing host-specific information, such as the
112server software version or hostname, in server messages.
113.It Fl l
114Each successful and failed
115.Xr ftp 1
116session is logged using syslog with a facility of
117.Dv LOG_FTP .
118If this option is specified twice, the retrieve (get), store (put), append,
119delete, make directory, remove directory and rename operations and
120their filename arguments are also logged.
121Note:
122.Dv LOG_FTP
123messages
124are not displayed by
125.Xr syslogd 8
126by default, and may have to be enabled in
127.Xr syslogd 8 Ns 's
128configuration file.
129.It Fl m
130Permit anonymous users to overwrite or modify
131existing files if allowed by filesystem permissions.
132By default, anonymous users cannot modify existing files;
133in particular, files to upload will be created under a unique name.
134.It Fl M
135Prevent anonymous users from creating directories.
136.It Fl o
137Put server in write-only mode.
138RETR is disabled, preventing downloads.
139.It Fl O
140Put server in write-only mode for anonymous users only.
141RETR is disabled for anonymous users, preventing anonymous downloads.
142This has no effect if
143.Fl o
144is also specified.
145.It Fl p
146When
147.Fl D
148is specified, write the daemon's process ID to
149.Ar file .
150.It Fl P
151When
152.Fl D
153is specified, accept connections at
154.Ar port ,
155specified as a numeric value or service name, instead of at the default
156.Dq ftp
157port.
158.It Fl r
159Put server in read-only mode.
160All commands which may modify the local filesystem are disabled.
161.It Fl R
162With this option set,
163.Nm
164will revert to historical behavior with regard to security checks on
165user operations and restrictions on PORT requests.
166Currently,
167.Nm
168will only honor PORT commands directed to unprivileged ports on the
169remote user's host (which violates the FTP protocol specification but
170closes some security holes).
171.It Fl S
172With this option set,
173.Nm
174logs all anonymous file downloads to the file
175.Pa /var/log/ftpd
176when this file exists.
177.It Fl t
178The inactivity timeout period is set to
179.Ar timeout
180seconds (the default is 15 minutes).
181.It Fl T
182A client may also request a different timeout period;
183the maximum period allowed may be set to
184.Ar timeout
185seconds with the
186.Fl T
187option.
188The default limit is 2 hours.
189.It Fl u
190The default file creation mode mask is set to
191.Ar umask ,
192which is expected to be an octal numeric value.
193Refer to
194.Xr umask 2
195for details.
196.It Fl U
197In previous versions of
198.Nm ,
199when a passive mode client requested a data connection to the server,
200the server would use data ports in the range 1024..4999. Now, by default,
201the server will use data ports in the range 49152..65535. Specifying this
202option will revert to the old behavior.
203.It Fl v
204A synonym for
205.Fl d .
206.It Fl W
207Don't log FTP sessions to
208.Pa /var/log/wtmp .
209.El
210.Pp
211The file
212.Pa /var/run/nologin
213can be used to disable ftp access.
214If the file exists,
215.Nm
216displays it and exits.
217If the file
218.Pa /etc/ftpwelcome
219exists,
220.Nm
221prints it before issuing the
222.Dq ready
223message.
224If the file
225.Pa /etc/ftpmotd
226exists,
227.Nm
228prints it after a successful login. Note the motd file used is the one
229relative to the login environment. This means the one in
230.Pa ~ftp/etc
231in the anonymous user's case.
232.Pp
233The ftp server currently supports the following ftp requests.
234The case of the requests is ignored. Requests marked [RW] are
235disabled if
236.Fl r
237is specified.
238.Bl -column "Request" -offset indent
239.It Sy Request Ta Sy "Description"
240.It ABOR Ta "abort previous command"
241.It ACCT Ta "specify account (ignored)"
242.It ALLO Ta "allocate storage (vacuously)"
243.It APPE Ta "append to a file [RW]"
244.It CDUP Ta "change to parent of current working directory"
245.It CWD Ta "change working directory"
246.It DELE Ta "delete a file [RW]"
247.It EPRT Ta "specify data connection port, multiprotocol"
248.It EPSV Ta "prepare for server-to-server transfer, multiprotocol"
249.It HELP Ta "give help information"
250.It LIST Ta "give list files in a directory" Pq Dq Li "ls -lgA"
251.It LPRT Ta "specify data connection port, multiprotocol"
252.It LPSV Ta "prepare for server-to-server transfer, multiprotocol"
253.It MDTM Ta "show last modification time of file"
254.It MKD Ta "make a directory [RW]"
255.It MODE Ta "specify data transfer" Em mode
256.It NLST Ta "give name list of files in directory"
257.It NOOP Ta "do nothing"
258.It PASS Ta "specify password"
259.It PASV Ta "prepare for server-to-server transfer"
260.It PORT Ta "specify data connection port"
261.It PWD Ta "print the current working directory"
262.It QUIT Ta "terminate session"
263.It REST Ta "restart incomplete transfer"
264.It RETR Ta "retrieve a file"
265.It RMD Ta "remove a directory [RW]"
266.It RNFR Ta "specify rename-from file name [RW]"
267.It RNTO Ta "specify rename-to file name [RW]"
268.It SITE Ta "non-standard commands (see next section)"
269.It SIZE Ta "return size of file"
270.It STAT Ta "return status of server"
271.It STOR Ta "store a file [RW]"
272.It STOU Ta "store a file with a unique name [RW]"
273.It STRU Ta "specify data transfer" Em structure
274.It SYST Ta "show operating system type of server system"
275.It TYPE Ta "specify data transfer" Em type
276.It USER Ta "specify user name"
277.It XCUP Ta "change to parent of current working directory (deprecated)"
278.It XCWD Ta "change working directory (deprecated)"
279.It XMKD Ta "make a directory (deprecated) [RW]"
280.It XPWD Ta "print the current working directory (deprecated)"
281.It XRMD Ta "remove a directory (deprecated) [RW]"
282.El
283.Pp
284The following non-standard or
285.Tn UNIX
286specific commands are supported
287by the
288SITE request.
289.Pp
290.Bl -column Request -offset indent
291.It Sy Request Ta Sy Description
292.It UMASK Ta change umask, e.g. ``SITE UMASK 002''
293.It IDLE Ta set idle-timer, e.g. ``SITE IDLE 60''
294.It CHMOD Ta "change mode of a file [RW], e.g. ``SITE CHMOD 755 filename''"
295.It MD5 Ta "report the files MD5 checksum, e.g. ``SITE MD5 filename''"
296.It HELP Ta give help information
297.El
298.Pp
299Note: SITE requests are disabled in case of anonymous logins.
300.Pp
301The remaining ftp requests specified in Internet RFC 959
302are
303recognized, but not implemented.
304MDTM and SIZE are not specified in RFC 959, but will appear in the
305next updated FTP RFC.
306To avoid possible denial-of-service attacks, SIZE requests against
307files larger than 10240 bytes will be denied if the current transfer
308type is ASCII.
309.Pp
310The ftp server will abort an active file transfer only when the
311ABOR
312command is preceded by a Telnet "Interrupt Process" (IP)
313signal and a Telnet "Synch" signal in the command Telnet stream,
314as described in Internet RFC 959.
315If a
316STAT
317command is received during a data transfer, preceded by a Telnet IP
318and Synch, transfer status will be returned.
319.Pp
320.Nm Ftpd
321interprets file names according to the
322.Dq globbing
323conventions used by
324.Xr csh 1 .
325This allows users to utilize the metacharacters
326.Dq Li \&*?[]{}~ .
327.Pp
328.Nm Ftpd
329authenticates users according to six rules.
330.Pp
331.Bl -enum -offset indent
332.It
333The login name must be in the password data base
334and not have a null password.
335In this case a password must be provided by the client before any
336file operations may be performed.
337If the user has an S/Key key, the response from a successful USER
338command will include an S/Key challenge.
339The client may choose to respond with a PASS command giving either
340a standard password or an S/Key one-time password.
341The server will automatically determine which type of
342password it has been given and attempt to authenticate accordingly.
343See
344.Xr key 1
345for more information on S/Key authentication.
346S/Key is a Trademark of Bellcore.
347.It
348The login name must not appear in the file
349.Pa /etc/ftpusers .
350.It
351The login name must not be a member of a group specified in the file
352.Pa /etc/ftpusers .
353Entries in this file interpreted as group names are prefixed by an "at"
354.Ql \&@
355sign.
356.It
357The user must have a standard shell returned by
358.Xr getusershell 3 .
359.It
360If the user name appears in the file
361.Pa /etc/ftpchroot ,
362or the user is a member of a group with a group entry in this file,
363i.e. one prefixed with
364.Ql \&@ ,
365the session's root will be changed to the directory specified
366in this file or to the user's login directory by
367.Xr chroot 2
368as for an
369.Dq anonymous
370or
371.Dq ftp
372account (see next item).
373See
374.Xr ftpchroot 5
375for a detailed description of the format of this file.
376This facility may also be triggered by enabling the boolean "ftp-chroot"
377capability in
378.Xr login.conf 5 .
379However, the user must still supply a password.
380This feature is intended as a compromise between a fully anonymous
381account and a fully privileged account.
382The account should also be set up as for an anonymous account.
383.It
384If the user name is
385.Dq anonymous
386or
387.Dq ftp ,
388an
389anonymous ftp account must be present in the password
390file (user
391.Dq ftp ) .
392In this case the user is allowed
393to log in by specifying any password (by convention an email address for
394the user should be used as the password).
395When the
396.Fl S
397option is set, all transfers are logged as well.
398.El
399.Pp
400In the last case,
401.Nm
402takes special measures to restrict the client's access privileges.
403The server performs a
404.Xr chroot 2
405to the home directory of the
406.Dq ftp
407user.
408As a special case if the
409.Dq ftp
410user's home directory pathname contains the
411.Dq \&/./
412separator,
413.Nm
414uses its left-hand side as the name of the directory to do
415.Xr chroot 2
416to, and its right-hand side to change the current directory to afterwards.
417A typical example for this case would be
418.Pa /usr/local/ftp/./pub .
419In order that system security is not breached, it is recommended
420that the
421.Dq ftp
422subtree be constructed with care, following these rules:
423.Bl -tag -width "~ftp/pub" -offset indent
424.It Pa ~ftp
425Make the home directory owned by
426.Dq root
427and unwritable by anyone.
428.It Pa ~ftp/etc
429Make this directory owned by
430.Dq root
431and unwritable by anyone (mode 555).
432The files pwd.db (see
433.Xr passwd 5 )
434and
435.Xr group 5
436must be present for the
437.Xr ls
438command to be able to produce owner names rather than numbers.
439The password field in
440.Xr passwd
441is not used, and should not contain real passwords.
442The file
443.Pa ftpmotd ,
444if present, will be printed after a successful login.
445These files should be mode 444.
446.It Pa ~ftp/pub
447This directory and the subdirectories beneath it should be owned
448by the users and groups responsible for placing files in them,
449and be writable only by them (mode 755 or 775).
450They should
451.Em not
452be owned or writable by
453.Dq ftp
454or its group, otherwise guest users
455can fill the drive with unwanted files.
456.El
457.Pp
458If the system has multiple IP addresses,
459.Nm
460supports the idea of virtual hosts, which provides the ability to
461define multiple anonymous ftp areas, each one allocated to a different
462internet address.
463The file
464.Pa /etc/ftphosts
465contains information pertaining to each of the virtual hosts.
466Each host is defined on its own line which contains a number of
467fields separated by whitespace:
468.Bl -tag -offset indent -width hostname
469.It hostname
470Contains the hostname or IP address of the virtual host.
471.It user
472Contains a user record in the system password file.
473As with normal anonymous ftp, this user's access uid, gid and group
474memberships determine file access to the anonymous ftp area.
475The anonymous ftp area (to which any user is chrooted on login)
476is determined by the home directory defined for the account.
477User id and group for any ftp account may be the same as for the
478standard ftp user.
479.It statfile
480File to which all file transfers are logged, which
481defaults to
482.Pa /var/log/ftpd .
483.It welcome
484This file is the welcome message displayed before the server ready
485prompt.
486It defaults to
487.Pa /etc/ftpwelcome .
488.It motd
489This file is displayed after the user logs in.
490It defaults to
491.Pa /etc/ftpmotd .
492.El
493.Pp
494Lines beginning with a '#' are ignored and can be used to include
495comments.
496.Pp
497Defining a virtual host for the primary IP address or hostname
498changes the default for ftp logins to that address.
499The 'user', 'statfile', 'welcome' and 'motd' fields may be left
500blank, or a single hyphen '-' used to indicate that the default
501value is to be used.
502.Pp
503As with any anonymous login configuration, due care must be given
504to setup and maintenance to guard against security related problems.
505.Pp
506.Nm
507has internal support for handling remote requests to list
508files, and will not execute
509.Pa /bin/ls
510in either a chrooted or non-chrooted environment. The
511.Pa ~/bin/ls
512executable need not be placed into the chrooted tree, nor need the
513.Pa ~/bin
514directory exist.
515.Sh FILES
516.Bl -tag -width /etc/ftpwelcome -compact
517.It Pa /etc/ftpusers
518List of unwelcome/restricted users.
519.It Pa /etc/ftpchroot
520List of normal users who should be chroot'd.
521.It Pa /etc/ftphosts
522Virtual hosting configuration file.
523.It Pa /etc/ftpwelcome
524Welcome notice.
525.It Pa /etc/ftpmotd
526Welcome notice after login.
527.It Pa /var/run/nologin
528Displayed and access refused.
529.It Pa /var/log/ftpd
530Log file for anonymous transfers.
531.El
532.Sh SEE ALSO
533.Xr ftp 1 ,
534.Xr key 1 ,
535.Xr umask 2 ,
536.Xr getusershell 3 ,
537.Xr ftpchroot 5 ,
538.Xr login.conf 5 ,
539.Xr inetd 8 ,
540.Xr syslogd 8
541.Sh BUGS
542The server must run as the super-user
543to create sockets with privileged port numbers. It maintains
544an effective user id of the logged in user, reverting to
545the super-user only when binding addresses to sockets. The
546possible security holes have been extensively
547scrutinized, but are possibly incomplete.
548.Sh HISTORY
549The
550.Nm
551command appeared in
552.Bx 4.2 .
553IPv6 support was added in WIDE Hydrangea IPv6 stack kit.