285 lines
8.8 KiB
Groff
285 lines
8.8 KiB
Groff
.\" Copyright (c) 1985, 1988, 1991 The Regents of the University of California.
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.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" from: @(#)ftpd.8 6.9 (Berkeley) 3/16/91
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.\" $Id: ftpd.8,v 1.4 1994/05/24 06:53:36 deraadt Exp $
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.\"
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.Dd March 16, 1991
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.Dt FTPD 8
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.Os BSD 4.2
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.Sh NAME
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.Nm ftpd
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.Nd
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.Tn DARPA
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Internet File Transfer Protocol server
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.Sh SYNOPSIS
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.Nm ftpd
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.Op Fl d
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.Op Fl l
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.Op Fl t Ar timeout
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.Op Fl T Ar maxtimeout
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.Sh DESCRIPTION
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.Nm Ftpd
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is the
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.Tn DARPA
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Internet File Transfer Protocol
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server process. The server uses the
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.Tn TCP
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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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Available options:
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.Bl -tag -width Ds
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.It Fl d
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Debugging information is written to the syslog.
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.It Fl l
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Each
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.Xr ftp 1
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session is logged in the syslog.
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.It Fl t
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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 T
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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 timeout
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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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.El
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.Pp
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The ftp server currently supports the following ftp
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requests; case is not distinguished.
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.Bl -column "Request" -offset indent
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.It Request Ta "Description"
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.It ABOR Ta "abort previous command"
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.It ACCT Ta "specify account (ignored)"
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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 HELP Ta "give help information"
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.It LIST Ta "give list files in a directory" Pq Dq Li "ls -lgA"
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.It MKD Ta "make a directory"
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.It MDTM Ta "show last modification time of file"
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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 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 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"
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.It XCUP Ta "change to parent of current working directory (deprecated)"
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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
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.Tn UNIX
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specific commands are supported
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by the
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SITE request.
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.Pp
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.Bl -column Request -offset indent
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.It Sy Request Ta Sy Description
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.It UMASK Ta change umask. Em E.g. SITE UMASK 002
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.It IDLE Ta set idle-timer. Em E.g. SITE IDLE 60
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.It CHMOD Ta change mode of a file. Em E.g.
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SITE CHMOD 755 filename
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.It HELP Ta give help information. Em E.g. SITE HELP
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.El
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.Pp
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The remaining ftp requests specified in Internet
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.%T "RFC 959"
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are
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recognized, but not implemented.
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MDTM and SIZE are not specified in
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.%T "RFC 959" ,
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but will appear in the next updated FTP RFC.
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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
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.%T "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 Ftpd
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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 Ftpd
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authenticates users according to five rules.
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.Pp
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.Bl -enum -offset indent
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.It
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The user name must be in the password data base,
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.Pa /etc/passwd ,
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and not have a null password. In this case a password
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must be provided by the client before any file operations
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may be performed.
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If the user has an S/Key key, the response from a successful USER
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command will include an S/Key challenge. The client may choose to respond
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with a PASS command giving either a standard password or an S/Key
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one-time password. The server will automaticly determine which type of
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password it has been given and attempt to authenticate accordingly. See
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.Xr skey 1
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for more information on S/Key authentication. S/Key is a Trademark of
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Bellcore.
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.It
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The user 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 must have a standard shell returned by
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.Xr getusershell 3 .
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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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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). 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. The account should also be set up as for an
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anonymous account.
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.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 this
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is given as the client host's name).
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.El
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.Pp
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In the last case,
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.Nm ftpd
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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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command to the home directory of the
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.Dq ftp
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user.
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In order that system security is not breached, it is recommended
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that the
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.Dq ftp
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subtree be constructed with care; the following
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rules are recommended.
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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 ftp
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and unwritable by anyone.
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.It Pa ~ftp/bin
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Make this directory owned by the super-user and unwritable by
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anyone. The program
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.Xr ls 1
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must be present to support the list command. This
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program should have mode 111.
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.It Pa ~ftp/etc
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Make this directory owned by the super-user and unwritable by
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anyone. The files
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.Xr passwd 5
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and
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.Xr group 5
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must be present for the
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.Xr ls
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command to be able to produce owner names rather than numbers.
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The password field in
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.Xr passwd
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is not used, and should not contain real encrypted passwords.
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These files should be mode 444.
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.It Pa ~ftp/pub
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Make this directory mode 777 and owned by
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.Dq ftp .
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Users
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should then place files which are to be accessible via the
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anonymous account in this directory.
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.El
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.Sh SEE ALSO
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.Xr ftp 1 ,
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.Xr skey 1 ,
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.Xr getusershell 3 ,
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.Xr syslogd 8
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.Sh BUGS
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The anonymous account is inherently dangerous and should
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avoided when possible.
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.Pp
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The server must run as the super-user
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to create sockets with privileged port numbers. It maintains
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an effective user id of the logged in user, reverting to
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the super-user only when binding addresses to sockets. The
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possible security holes have been extensively
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scrutinized, but are possibly incomplete.
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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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