569 lines
15 KiB
Groff
569 lines
15 KiB
Groff
.\" $OpenBSD: ftpd.8,v 1.77 2022/03/31 17:27:18 naddy Exp $
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.\" $NetBSD: ftpd.8,v 1.8 1996/01/14 20:55:23 thorpej Exp $
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.\"
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.\" Copyright (c) 1985, 1988, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ftpd.8 8.2 (Berkeley) 4/19/94
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.\"
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.Dd $Mdocdate: March 31 2022 $
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.Dt FTPD 8
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.Os
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.Sh NAME
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.Nm ftpd
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.Nd Internet File Transfer Protocol server
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.Sh SYNOPSIS
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.Nm ftpd
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.Op Fl 46ADdlMnPSUW
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.Op Fl m Ar minuid
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.Op Fl T Ar maxtimeout
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.Op Fl t Ar timeout
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.Op Fl u Ar mask
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.Sh DESCRIPTION
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.Nm
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is the Internet File Transfer Protocol server process.
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The server uses the TCP protocol
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and listens at the port specified in the
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.Dq ftp
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service specification; see
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.Xr services 5 .
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl 4
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When
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.Fl D
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is specified, forces
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.Nm
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to use IPv4 addresses only.
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.It Fl 6
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When
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.Fl D
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is specified, forces
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.Nm
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to use IPv6 addresses only.
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.It Fl A
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Permit only anonymous FTP connections
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(unless the
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.Fl n
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option is specified),
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accounts listed in
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.Pa /etc/ftpchroot
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or users in a login class with the
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.Dq ftp-chroot
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variable set (see below).
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Other connection attempts are refused.
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.It Fl D
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With this option set,
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.Nm
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will detach and become a daemon, accepting connections on the FTP port and
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forking child processes to handle them.
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This has lower overhead than starting
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.Nm
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from
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.Xr inetd 8
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and is thus useful on busy servers to reduce load.
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.It Fl d
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Debugging information is written to the syslog using
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.Dv LOG_FTP .
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.It Fl l
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Each successful and failed
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FTP session is logged using syslog with a facility of
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.Dv LOG_FTP .
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If this option is specified twice, the retrieve (get), store (put), append,
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delete, make directory, remove directory and rename operations and
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their filename arguments are also logged.
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.It Fl M
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Enables multihomed mode.
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Instead of simply using
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.Pa ~ftp
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for anonymous transfers, a directory matching the fully qualified name of
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the IP number the client connected to, and located inside
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.Pa ~ftp ,
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is used instead.
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.It Fl m Ar minuid
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Disallow login to user accounts with a UID below
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.Ar minuid .
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The default is 1000, to prevent access to administrative and daemon accounts.
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Anonymous access is allowed even if the UID of the FTP user is smaller than
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.Ar minuid .
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.It Fl n
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Do not permit anonymous FTP logins.
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Normally they are permitted.
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.It Fl P
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Permit illegal port numbers or addresses for PORT command initiated connects.
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By default
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.Nm
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violates the RFC and thus constrains the PORT command to non-reserved ports
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and requires it use the same source address as the connection came from.
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This prevents the "FTP bounce attack" against services on both the local
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machine and other local machines.
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.It Fl S
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With this option set,
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.Nm
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logs all anonymous downloads to the file
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.Pa /var/log/ftpd
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when this file exists.
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.It Fl T Ar maxtimeout
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A client may also request a different timeout period;
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the maximum period allowed may be set to
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.Ar maxtimeout
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seconds with the
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.Fl T
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option.
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The default limit is 2 hours.
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.It Fl t Ar timeout
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The inactivity timeout period is set to
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.Ar timeout
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seconds (the default is 15 minutes).
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.It Fl U
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Each concurrent
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FTP session is logged to the file
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.Pa /var/run/utmp ,
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making them visible to commands such as
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.Xr who 1 .
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.Fl U
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and
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.Fl W
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are mutually exclusive.
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.It Fl u Ar mask
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Force the umask to
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.Ar mask ,
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instead of the default specified in
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.Pa /etc/login.conf
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(usually 022).
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Also disallows chmod.
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.It Fl W
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Do not save login records to
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.Pa /var/log/wtmp .
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.Fl W
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and
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.Fl U
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are mutually exclusive.
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.El
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.Pp
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The file
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.Pa /etc/nologin
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can be used to disable FTP access.
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If the file exists,
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.Nm
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displays it and exits.
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Note: this method will disable
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.Em all
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non-root logins; see
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.Xr login 1
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for further details.
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If the file
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.Pa /etc/ftpwelcome
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exists,
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.Nm
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prints it before issuing the
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.Dq ready
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message.
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If the welcome file exists
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.Pa ( /etc/motd
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by default),
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.Nm
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prints it after a successful login.
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If the file
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.Pa .message
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exists in a directory,
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.Nm
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prints it when that directory is entered.
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.Pp
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The FTP server currently supports the following FTP requests.
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The case of the requests is ignored.
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.Bl -column "Request" -offset indent
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.It Sy Request Ta Sy Description
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.It ABOR Ta "abort previous command"
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.It ACCT Ta "specify account (not implemented)"
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.It ALLO Ta "allocate storage (vacuously)"
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.It APPE Ta "append to a file"
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.It CDUP Ta "change to parent of current working directory"
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.It CWD Ta "change working directory"
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.It DELE Ta "delete a file"
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.It EPRT Ta "specify data connection port"
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.It EPSV Ta "prepare for server-to-server transfer"
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.It HELP Ta "give help information"
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.It LIST Ta "give list of files in a directory" Pq Li "ls -lgA"
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.It LPRT Ta "specify data connection port"
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.It LPSV Ta "prepare for server-to-server transfer"
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.It MDTM Ta "show last modification time of file"
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.It MKD Ta "make a directory"
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.It MODE Ta "specify data transfer" Em mode
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.It NLST Ta "give name list of files in directory"
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.It NOOP Ta "do nothing"
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.It PASS Ta "specify password"
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.It PASV Ta "prepare for server-to-server transfer"
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.It PORT Ta "specify data connection port"
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.It PWD Ta "print the current working directory"
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.It QUIT Ta "terminate session"
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.It REIN Ta "reinitialize (not implemented)"
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.It REST Ta "restart incomplete transfer"
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.It RETR Ta "retrieve a file"
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.It RMD Ta "remove a directory"
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.It RNFR Ta "specify rename-from file name"
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.It RNTO Ta "specify rename-to file name"
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.It SITE Ta "non-standard commands (see next section)"
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.It SIZE Ta "return size of file"
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.It SMNT Ta "structure mount (not implemented)"
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.It STAT Ta "return status of server"
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.It STOR Ta "store a file"
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.It STOU Ta "store a file with a unique name"
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.It STRU Ta "specify data transfer" Em structure
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.It SYST Ta "show operating system type of server system"
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.It TYPE Ta "specify data transfer" Em type
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.It USER Ta "specify user name; not valid after login"
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.It XCUP Ta "change to parent of current working directory (deprec.)"
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.It XCWD Ta "change working directory (deprecated)"
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.It XMKD Ta "make a directory (deprecated)"
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.It XPWD Ta "print the current working directory (deprecated)"
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.It XRMD Ta "remove a directory (deprecated)"
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.El
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.Pp
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|
The following non-standard or UNIX specific commands
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|
are supported by the SITE request:
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|
.Bl -column Request -offset indent
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.It Sy Request Ta Sy Description
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|
.It CHMOD Ta "change mode of a file, e.g., SITE CHMOD 755 filename"
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.It HELP Ta "give help information"
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.It IDLE Ta "set idle-timer, e.g., SITE IDLE 60"
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.It UMASK Ta "change umask, e.g., SITE UMASK 002"
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.El
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.Pp
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The remaining FTP requests specified in Internet RFC 959 are recognized,
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but not implemented.
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MDTM and SIZE are specified in RFC 3659.
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.Pp
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The FTP server will abort an active file transfer only when the
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ABOR
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command is preceded by a Telnet "Interrupt Process" (IP)
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signal and a Telnet "Synch" signal in the command Telnet stream,
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as described in Internet RFC 959.
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If a
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STAT
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command is received during a data transfer, preceded by a Telnet IP
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and Synch, transfer status will be returned.
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.Pp
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.Nm
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interprets file names according to the
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.Dq globbing
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conventions used by
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.Xr csh 1 .
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|
This allows users to utilize the metacharacters
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.Dq Li \&*?[]{}~ .
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.Pp
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.Nm
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authenticates users by using the service and type of
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.Ar ftp ,
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as defined in the
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.Pa /etc/login.conf
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file (see
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.Xr login.conf 5 ) .
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|
An authentication style
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|
may be specified by appending with a colon
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|
.Pq Sq :\&
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|
following the authentication style, i.e.\&
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.Dq joe:skey .
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|
The allowed authentication styles for
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.Nm
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|
may be explicitly specified by the
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.Dq auth-ftp
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entry in
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.Pa /etc/login.conf .
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.Pp
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.Nm
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authenticates users according to the following rules.
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.Bl -enum -offset indent
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.It
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The login name must be in the password database and not have a null password.
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|
In this case a password must be provided by the client before any
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file operations may be performed.
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.It
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The login name must not appear in the file
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.Pa /etc/ftpusers .
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.It
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The user account must have a UID not less than
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.Ar minuid .
|
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.It
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The user must have a standard shell as described by
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.Xr shells 5 .
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.It
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|
If the user name appears in the file
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.Pa /etc/ftpchroot ,
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|
which is a text file containing one user name per line,
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|
the session's root will be changed to the user's login directory by
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.Xr chroot 2
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|
as for an
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|
.Dq anonymous
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|
or
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.Dq ftp
|
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account (see next item).
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However, the user must still supply a password.
|
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This feature is intended as a compromise between a fully anonymous account
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|
and a fully privileged account.
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|
The account should also be set up as for an anonymous account.
|
|
.It
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If the user name is
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.Dq anonymous
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or
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.Dq ftp ,
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an
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anonymous FTP account must be present in the password
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file (user
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.Dq ftp ) .
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|
In this case the user is allowed
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to log in by specifying any password (by convention an email address for
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the user should be used as the password).
|
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.El
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.Pp
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Once a user is authenticated, the user must be approved by any approval
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script defined (see
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.Xr login.conf 5 ) .
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|
If a valid approval script (by either :approve=...: or :approve-ftp=...:
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for the user's class) is defined then it is run and must exit with a 0
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(success) status.
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|
When
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.Nm
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is running under the
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.Fl D
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flag (and debugging is not turned on) then the approval script will be
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called with at least the following variables specified via the
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.Fl v
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option (see
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.Xr login.conf 5 )
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to the approve script:
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.Bl -column "Variable" -offset indent
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.It Sy Variable Ta Sy Description
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.It FTPD_HOST Ta "The server's (virtual) hostname"
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.El
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.Pp
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|
For example (the line is broken to fit the page):
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|
.Bd -literal -offset indent
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/usr/libexec/auth/approve_ftpd -v FTPD_HOST=ftp.mycompany.com \e
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username class service
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.Ed
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.Pp
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|
When the user logs in to the anonymous FTP account,
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.Nm
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takes special measures to restrict the client's access privileges.
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|
The server performs a
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.Xr chroot 2
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to the home directory of the
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.Dq ftp
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user.
|
|
In order that system security is not breached, it is recommended
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|
that the
|
|
.Dq ftp
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subtree be constructed with care, following these rules:
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|
.Bl -tag -width "~ftp/pub" -offset indent
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|
.It Pa ~ftp
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Make the home directory owned by
|
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.Dq root
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|
and unwritable by anyone (mode 555).
|
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.It Pa ~ftp/etc
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Make this directory owned by
|
|
.Dq root
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|
and unwritable by anyone (mode 511).
|
|
The files pwd.db (see
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|
.Xr pwd_mkdb 8 )
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|
and
|
|
.Xr group 5
|
|
must be present for the
|
|
.Xr ls 1
|
|
command to be able to produce owner names rather than numbers.
|
|
The password field in
|
|
.Pa pwd.db
|
|
is not used, and should not contain real passwords.
|
|
The file
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.Pa motd ,
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|
if present, will be printed after a successful login.
|
|
These files should be mode 444.
|
|
.It Pa ~ftp/pub
|
|
Make this directory mode 555 and owned by
|
|
.Dq root .
|
|
This is traditionally where publicly accessible files are
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|
stored for download.
|
|
.El
|
|
.Pp
|
|
If logging to the
|
|
.Pa /var/log/ftpd
|
|
file is enabled, information will be written in the following format:
|
|
.Pp
|
|
.Bl -tag -width XXXXXXXXXXXXXX -offset indent -compact
|
|
.It time
|
|
The time and date of the download, in
|
|
.Xr ctime 3
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|
format.
|
|
.It elapsed time
|
|
The elapsed time, in seconds.
|
|
.It remote host
|
|
The remote host (or IP number).
|
|
.It bytes
|
|
The number of bytes transferred.
|
|
.It path
|
|
The full path (relative to the FTP chroot space) of the file transferred.
|
|
.It type
|
|
The type of transfer; either
|
|
.Sq a
|
|
for ASCII or
|
|
.Sq b
|
|
for binary.
|
|
.It unused
|
|
Unused field containing a
|
|
.Sq * ,
|
|
for compatibility.
|
|
.It unused
|
|
Unused field containing an
|
|
.Sq o ,
|
|
for compatibility.
|
|
.It user type
|
|
The type of user; either
|
|
.Sq a
|
|
for anonymous or
|
|
.Sq r
|
|
for a real user (should always be anonymous).
|
|
.It name
|
|
Either a system login name or the value given for
|
|
.Dq email address
|
|
if an anonymous user.
|
|
.It service name
|
|
The network service name (always ftp).
|
|
.It unused
|
|
Unused field containing a
|
|
.Sq 0 ,
|
|
for compatibility.
|
|
.It real name
|
|
The system login name if the connection is not anonymous, or a
|
|
.Sq *
|
|
if it is.
|
|
.\" .It virtual host
|
|
.\" The virtual host that the connection was made to.
|
|
.El
|
|
.Pp
|
|
Although fields exist for logging information on real users, this file is
|
|
only used for anonymous downloads.
|
|
Unused fields exist only for compatibility with other
|
|
.Nm
|
|
implementations.
|
|
.Sh LOGIN.CONF VARIABLES
|
|
The
|
|
.Nm
|
|
daemon uses the following FTP-specific parameters:
|
|
.Bl -tag -width ftp-chroot
|
|
.It Pa auth-ftp
|
|
The list of authentication types available to this class.
|
|
See
|
|
.Xr login.conf 5 .
|
|
.It Pa ftp-chroot
|
|
A boolean value.
|
|
If set, users in this class will be automatically chrooted to
|
|
the user's login directory.
|
|
.It Pa ftp-dir
|
|
A path to a directory.
|
|
This value overrides the login directory for users in this class.
|
|
A leading tilde
|
|
.Pq Ql ~
|
|
in
|
|
.Pa ftp-dir
|
|
will be expanded to the user's home directory based on the
|
|
contents of the password database.
|
|
.It Pa welcome
|
|
The path of the file containing the welcome message.
|
|
If this variable is not set,
|
|
.Pa /etc/motd
|
|
is used.
|
|
.El
|
|
.Sh PORT ALLOCATION
|
|
For passive mode data connections,
|
|
.Nm
|
|
will listen to a random high TCP port.
|
|
The interval of ports used are configurable using
|
|
.Xr sysctl 8
|
|
variables
|
|
.Va net.inet.ip.porthifirst
|
|
and
|
|
.Va net.inet.ip.porthilast .
|
|
.Sh FILES
|
|
.Bl -tag -width /etc/ftpwelcome -compact
|
|
.It Pa /etc/ftpchroot
|
|
list of normal users who should be chrooted
|
|
.It Pa /etc/ftpusers
|
|
list of unwelcome/restricted users
|
|
.It Pa /etc/ftpwelcome
|
|
welcome notice
|
|
.It Pa /etc/login.conf
|
|
authentication styles
|
|
.It Pa /etc/motd
|
|
printed after a successful login
|
|
.It Pa /etc/nologin
|
|
displayed and access refused
|
|
.It Pa /var/log/ftpd
|
|
log file for anonymous downloads
|
|
.It Pa /var/log/wtmp
|
|
login account records
|
|
.It Pa /var/run/utmp
|
|
list of users on the system
|
|
.El
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|
.Sh SEE ALSO
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.Xr ftp 1 ,
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.Xr login 1 ,
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.Xr skey 1 ,
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.Xr who 1 ,
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.Xr chroot 2 ,
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.Xr ctime 3 ,
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.Xr group 5 ,
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.Xr login.conf 5 ,
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.Xr motd 5 ,
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.Xr services 5 ,
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.Xr shells 5 ,
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.Xr ftp-proxy 8 ,
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.Xr inetd 8 ,
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.Xr pwd_mkdb 8 ,
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.Xr sysctl 8 ,
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.Xr syslogd 8
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.Sh STANDARDS
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.Rs
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.%A J. Postel
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.%A J. Reynolds
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.%D October 1985
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.%R RFC 959
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.%T FILE TRANSFER PROTOCOL (FTP)
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.Re
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.Pp
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.Rs
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.%A P. Hethmon
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.%D March 2007
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.%R RFC 3659
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.%T Extensions to FTP
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.Re
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Bx 4.2 .
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