opieftpd.8

.\" opieftpd.8: Manual page describing the FTP daemon.
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.\"     @(#)opieopieftpd.8	6.9 (Berkeley) 3/16/91
.\"
.TH OPIEFTPD 8 "10 January 1995"

.SH NAME
opieftpd \- File Transfer Protocol server that uses OPIE authentication

.SH SYNOPSIS
.B opieftpd
[\-d] [\-l] [\-t 
.I timeout
] [\-T
.I maxtimeout
] [\-u
.I umask
]

.SH DESCRIPTION
.I opieftpd
is the Internet File Transfer Protocol server process. The server uses the
TCP protocol and listens at the port specified in the ftp service 
specification; see
.IR services (5).

.SH OPTIONS
.TP
.B \-d
Debugging information is written to the system logs.
.TP
.B \-l
Each
.IR ftp (1)
session is logged in the system logs.
.TP
.B \-t
The inactivity timeout period is set to
.I timeout
seconds (the default is 15 minutes).
.TP
.B \-T
A client may also request a different timeout period;
the maximum period allowed may be set to
.I maxtimeout
seconds with the
.B \-T
option. The default limit is 2 hours.
.B \-u
Set the default umask value to 
.I umask.
.SH COMMANDS
The ftp server currently supports the following ftp
requests; case is not distinguished:
.PP
.nf
.ta \w'Request      'u
Request      Description
ABOR	abort previous command
ACCT	specify account (ignored)
ALLO	allocate storage (vacuously)
APPE	append to a file
CDUP	change to parent of current working directory
CWD	change working directory
DELE	delete a file
HELP	give help information
LIST	give a list of files in a directory
MKD	make a directory
MDTM	show last modification time of file
MODE	specify data transfer mode
NLST	give name list of files in directory
NOOP	do nothing
PASS	specify password
PASV	prepare for server-to-server transfer
PORT	specify data connection port
PWD	print the current working directory
QUIT	terminate session
REST	restart incomplete transfer
RETR	retrieve a file
RMD	remove a directory
RNFR	specify rename-from file name
RNTO	specify rename-to file name
SITE	non-standard commands (see next section)
SIZE	return size of file
STAT	return status of server
STOR	store a file
STOU	store a file with a unique name
STRU	specify data transfer structure
SYST	show operating system type of server system
TYPE	specify data transfer type
USER	specify user name
XCUP	change to parent of current working directory (deprecated)
XCWD	change working directory (deprecated)
XMKD	make a directory (deprecated)
XPWD	print the current working directory (deprecated)
XRMD	remove a directory (deprecated)
.fi

The following non-standard or UNIX-specific commands are supported
by the SITE request:
.PP
.nf
.ta \w'Request      'u
Request      Description
UMASK	change umask (e.g. SITE UMASK 002)
IDLE	set idle-timer (e.g. SITE IDLE 60)
CHMOD	change mode of a file (e.g. SITE CHMOD 755 file)
HELP	give help information (e.g. SITE HELP)
.fi
.sp
The remaining ftp requests specified in Internet RFC-959 are
recognized, but not implemented.
.sp
MDTM and SIZE are not specified in RFC-959, but will appear
in the next updated FTP RFC.

The ftp server will abort an active file transfer only when the
ABOR command is preceded by a Telnet "Interrupt Process" (IP)
signal and a Telnet "Synch" signal in the command Telnet stream,
as described in Internet RFC-959.
If a STAT command is received during a data transfer, preceded by
a Telnet IP and Synch, transfer status will be returned.
.I opieftpd
interprets file names according to the globbing conventions used by
.IR csh (1).
This allows users to utilize the metacharacters
\&*?[]{}~.
.sp
.I opieftpd
authenticates users according to three rules: 
.sp
The user name must be in the password data base,
.I /etc/passwd,
and not have a null password. In this case, a password
must be provided by the client before any file operations
may be performed.
.sp
The user name must not appear in the file
.I /etc/ftpusers.
.sp
The user must have a standard shell returned by 
.IR getusershell (3).
.sp
If the user name is
.I anonymous
or
.I ftp,
an anonymous ftp account must be present in the password
file (user
.I ftp ).
In this case, the user is allowed to log in by specifying any
password (by convention, this is given as the client host's name).

In the last case, 
.I opieftpd
takes special measures to restrict the client's access privileges.
The server performs a 
.IR chroot (2)
command to the home directory of the
.I ftp
user.
In order that system security is not breached, it is recommended
that the
.I ftp
subtree be constructed with care;  the following
rules are recommended:
.sp
.TP
.B ~ftp
Make the home directory owned by
.I ftp
and unwritable by anyone.
.TP
.B ~ftp/bin
Make this directory owned by the super-user and unwritable by
anyone. The program
.IR ls (1)
must be present to support the LIST command.  This
program should have mode 111.
.TP
.B ~ftp/etc
Make this directory owned by the super-user and unwritable by
anyone. The files
.IR passwd (5)
and
.IR group (5)
must be present for the 
.IR ls (1)
command to be able to produce owner names rather than numbers.
The password field in
.I passwd
is not used, and should not contain real encrypted passwords.
These files should be mode 444.
.TP
.B ~ftp/pub
Make this directory mode 777 and owned by
.I ftp.
Users should then place files which are to be accessible via the
anonymous account in this directory.
.SH SEE ALSO
.BR ftpd (8),
.BR ftp (1),
.BR opie (4),
.BR opiekey (1),
.BR opiepasswd (1),
.BR opieinfo (1),
.BR opiesu (1),
.BR opieftpd (8),
.BR opiekeys (5),
.BR opieaccess (5)

.SH BUGS
The anonymous account is inherently dangerous and should
avoided when possible. In
.I opieftpd,
it is a compile-time option that should be disabled if it is not
being used.
The server must run as the super-user
to create sockets with privileged port numbers.  It maintains
an effective user id of the logged in user, reverting to
the super-user only when binding addresses to sockets.  The
possible security holes have been scrutinized, but are possibly incomplete.

.SH HISTORY
The
.I ftpd
command appeared in 4.2BSD.

.SH AUTHOR
Originally written for BSD, 
.I ftpd
was modified at NRL by Randall Atkinson, Dan McDonald, and Craig Metz to 
support OTP authentication.

.SH CONTACT
OPIE is discussed on the Bellcore "S/Key Users" mailing list. To join,
send an email request to:
.sp
skey-users-request@thumper.bellcore.com