ftpd.8

wu-ftpd类unix下的ftp服务器,可用于嵌入式系统

.\"
.\" Copyright (c) 1999,2000 WU-FTPD Development Group. 
.\" All rights reserved.
.\" 
.\" Portions Copyright (c) 1980, 1985, 1988, 1989, 1990, 1991, 1993, 1994 
.\" The Regents of the University of California.  Portions Copyright (c) 
.\" 1993, 1994 Washington University in Saint Louis.  Portions Copyright 
.\" (c) 1996, 1998 Berkeley Software Design, Inc.  Portions Copyright (c) 
.\" 1998 Sendmail, Inc.  Portions Copyright (c) 1983, 1995, 1996, 1997 Eric 
.\" P. Allman.  Portions Copyright (c) 1989 Massachusetts Institute of 
.\" Technology.  Portions Copyright (c) 1997 Stan Barber.  Portions 
.\" Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997 Free Software 
.\" Foundation, Inc.  Portions Copyright (c) 1997 Kent Landfield. 
.\"
.\" Use and distribution of this software and its source code are governed 
.\" by the terms and conditions of the WU-FTPD Software License ("LICENSE"). 
.\"
.\"	$Id: ftpd.8,v 1.8 2000/07/01 17:49:09 wuftpd Exp $
.\"
.TH FTPD 8 "Jan 10, 1997"
.UC 5
.SH NAME
ftpd \- Internet File Transfer Protocol server
.SH SYNOPSIS
.B ftpd
[
.B \-d
] [
.B \-v
] [
.B \-l
] [
.BR \-t
timeout
] [
.BR \-T
maxtimeout
] [
.BR \-a
] [
.BR \-A
] [
.BR \-L
] [
.BR \-i
] [
.BR \-I
] [
.BR \-o
] [
.BR \-p
ctrlport
] [
.BR \-P
dataport
] [
.BR \-q
] [
.BR \-Q
] [
.BR \-r
rootdir
] [
.BR \-s
] [
.BR \-S
] [
.BR \-u
umask
] [
.BR \-V
] [
.BR \-w
] [
.BR \-W
] [
.BR \-X
]
.SH DESCRIPTION
.I Ftpd
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).
.PP
The
.B \-V
option causes the program to display copyright and version information, then
terminate.
.PP
If the 
.B \-d
or 
.B \-v
option is specified,
debugging information is written to the syslog.
.PP
If the
.B \-l
option is specified,
each ftp session is logged in the syslog.
.PP
The ftp server
will timeout an inactive session after 15 minutes.
If the
.B \-t
option is specified,
the inactivity timeout period will be set to
.I timeout
seconds.
A client may also request a different timeout period;
the maximum period allowed may be set to
.I timeout
seconds with the
.B \-T
option.
The default limit is 2 hours.
.PP
If the
.B \-a
option is specified, the use of the
.IR ftpaccess (5)
configuration file is enabled.
.PP
If the
.B \-A
option is specified, use of the
.IR ftpaccess (5)
configuration file is disabled. This is the default.
.PP
If the
.B \-L
option is specified, commands sent to the
.IR ftpd (8)
server will be logged to the syslog.  The 
.B \-L
option is overridden by the use of the
.IR ftpaccess (5)
file.  If the 
.B \-L 
flag is used, command logging will be on by
default as soon as the ftp server is invoked.
This will cause the server to log all USER
commands, which if a user accidentally enters a
password for that command instead of the
username, will cause passwords to be logged via syslog.
.PP
If the
.B \-i
option is specified, files received by the
.IR ftpd (8)
server will be logged to the
.IR xferlog (5).
The
.B \-i
option is overridden by the use of the
.IR ftpaccess (5)
file.
.PP
The
.B \-I
option disables the use of RFC931 (AUTH/ident) to attempt to determine the
username on the client.
.PP
If the
.B \-o
option is specified, files transmitted by the
.IR ftpd (8)
server will be logged to the 
.IR xferlog (5).  
The 
.B \-o
option is overridden by the use of the
.IR ftpaccess (5)
file.  If the
.B \-X
option is specified, the output created by the
.B \-i
and
.B \-o
options is not saved to the xferlog file but saved via syslog
so you can collect output from several hosts on one central loghost.
.PP
If the
.B \-u
option is specified, the default umask is set to
.I umask.
.PP
If the
.B \-W
option is specified user logins are not recorded in the wtmp file.  The
default (
.B \-w
) is to record every login and logout.
.PP
The
.B \-s
and
.B \-S
options place the daemon in standalone operation mode.  The
.B \-S
option runs the daemon in the background and is useful in startup scripts
during system initialization (ie., in rc.local).  The
.B \-s
option leaves the daemon in foreground and is useful when running from init
(ie., /etc/inittab).
.PP
The
.B \-p
and
.B \-P
options override the port numbers used by the daemon.  Normally, the daemon
determines the port numbers by looking in /etc/services for "ftp" and "ftp-data".
If there is no /etc/services entry for "ftp-data" and the
.B \-P
option is not specified, the daemon uses the port just prior to the control connection
port.
The
.B \-p
option is only available if running as a standalone daemon.
.PP
The
.B \-q
and
.B \-Q
options deterine whether the daemon uses the PID files.  These files are required by the
limit directive to determine the number of current users in each access class.  Disabling
the use of the PID files disables user limits.  The default (
.B \-q
) is to use the PID files.  Specify
.B \-Q
when testing the server as a normal user when access permissions prevent the use of the PID files.
Large, busy sites which do not wish to impose limits on the number of concurrent users may also consider
disabling the PID files.
.PP
The
.B \-r
option instructs the daemon to chroot(2) to the specified rootdir immedeately upon loading.  This can
improve system security by limiting the files which may be damaged should a breakin occur through the
daemon.  Set is much like anonymous FTP, with additional files needed which vary from system to system.
.PP
The ftp server currently supports the following ftp
requests; case is not distinguished.
.PP
.nf
.ta \w'Request        'u
\fBRequest	Description\fP
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 list files in a directory (``ls -lgA'')
MKD	make a directory
MDTM	show last modification time of file
MODE	specify data transfer \fImode\fP
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 \fIstructure\fP
SYST	show operating system type of server system
TYPE	specify data transfer \fItype\fP
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
.PP
The following non-standard or UNIX specific commands are supported
by the SITE request.
.PP
.nf
.ta \w'Request        'u
\fBRequest	Description\fP
UMASK	change umask. \fIE.g.\fP SITE UMASK 002
IDLE	set idle-timer. \fIE.g.\fP SITE IDLE 60
CHMOD	change mode of a file. \fIE.g.\fP SITE CHMOD 755 filename
HELP	give help information. \fIE.g.\fP SITE HELP
NEWER	list files newer than a particular date
MINFO	like SITE NEWER, but gives extra information
GROUP	request special group access. \fIE.g.\fP SITE GROUP foo
GPASS	give special group access password. \fIE.g.\fP SITE GPASS bar
EXEC	execute a program.  \fIE.g.\fP SITE EXEC program params
.fi
.PP
The remaining ftp requests specified in Internet RFC 959 are
recognized, but not implemented.
MDTM and SIZE are not specified in
RFC 959, but will appear in the next updated FTP RFC.
.PP
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.
.PP
.I Ftpd
interprets file names according to the ``globbing''
conventions used by
.IR csh (1).
This allows users to utilize the metacharacters ``*?[]{}~''.
.PP
.I Ftpd
authenticates users according to four rules. 
.IP 1)
The user name must be in the password data base,
.IR /etc/passwd ,
or whatever is appropriate for the operating system,
and the password must not be null.  In this case a password
must be provided by the client before any file operations
may be performed.
.IP 2)
The user name must not appear in the file
.IR /etc/ftpusers .
.IP 3)
The user must have a standard shell returned by 
.IR getusershell (3).
.IP 4)
If the user name is ``anonymous'' or ``ftp'', an
anonymous ftp account must be present in the password
file (user ``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).
.PP
In the last case, 
.I ftpd
takes special measures to restrict the client's access privileges.
The server performs a 
.IR chroot (2)
command to the home directory of the ``ftp'' user.
In order that system security is not breached, it is recommended
that the ``ftp'' subtree be constructed with care;  the following
rules are recommended.
.IP ~ftp)
Make the home directory owned by super-user and unwritable by anyone.
.IP ~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.
.IP ~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 
.I ls
command to be able to produce owner names rather than numbers. Depending
on the operating system, there may be other required files. Check your
manual page for the 
.IR getpwent (3)
library routine.
The password field in
.I passwd
is not used, and should not contain real encrypted passwords.
These files should be mode 444 and owned by the super-user.
Don't use the system's /etc/passwd file as the password file or
the system's /etc/group file as the group file in the ~ftp/etc directory.
.IP ~ftp/pub)
Create a subdirectory in ~ftp/pub
with the appropriate mode (777 or 733) if you want to allow normal
users to upload files.
.PP
.SH AUTHENTICATION MECHANISM ON BSD/OS SYSTEMS ONLY
The authentication mechanism used by ftpd is determined by
the ``auth-ftp'' entry in the
.IR /etc/login.conf
file
(see
.IR login.conf (5))
that matches the users class.
If there is no ``auth-ftp'' entry for the class, the normal ``auth'' entry
will be used instead.
An alternate authentication mechanism may be specified by
appending a colon (``:'') followed by the authentication
style, i.e. ``joe:skey''.
.SH GENERAL FTP EXTENSIONS
.PP
There are some extensions to the FTP server such that if the user
specifies a filename (when using a RETRIEVE command) such that:
.PP
.nf
 True Filename  Specified Filename  Action
 -------------  ------------------  -----------------------------------
 <filename>.Z   <filename>          Decompress file before transmitting
 <filename>     <filename>.Z        Compress <filename> before 
                                            transmitting
 <filename>     <filename>.tar      Tar <filename> before transmitting
 <filename>     <filename>.tar.Z    Tar and compress <filename> before
                                            transmitting
.fi
.PP
Also, the FTP server will attempt to check for valid e-mail addresses and
chide the user if he doesn't pass the test.  For users whose FTP client
will hang on "long replies" (i.e. multiline responses), using a dash as
the first character of the password will disable the server's lreply()
function.
.PP
The FTP server can also log all file transmission and reception,
keeping the following information for each file transmission that takes
place.
.PP
.nf
Mon Dec  3 18:52:41 1990 1 wuarchive.wustl.edu 568881 /files.lst.Z a _ o a [e-mail] ftp 0 *

  %.24s %d %s %d %s %c %s %c %c %s %s %d %s
    1   2  3  4  5  6  7  8  9  10 11 12 13

  1 current time in the form DDD MMM dd hh:mm:ss YYYY
  2 transfer time in seconds
  3 remote host name
  4 file size in bytes
  5 name of file
  6 transfer type (a>scii, b>inary)
  7 special action flags (concatenated as needed):
        C   file was compressed
        U   file was uncompressed
        T   file was tar'ed
        _   no action taken
  8 file was sent to user (o>utgoing) or received from 
    user (i>ncoming)
  9 accessed anonymously (r>eal, a>nonymous, g>uest) -- mostly for FTP
 10 local username or, if guest, ID string given 
    (anonymous FTP password)
 11 service name ('ftp', other)
 12 authentication method (bitmask)
        0   none
        1   RFC931 Authentication
 13 authenticated user id (if available, '*' otherwise)
.fi
.SH "SEE ALSO"
.BR ftp(1) ,
.BR getusershell(3) ,
.BR syslogd(8) ,
.BR ftpaccess(5) ,
.BR xferlog(5) ,
.BR umask(2)
.SH BUGS
The anonymous account is inherently dangerous and should
avoided when possible.
.PP
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 extensively
scrutinized, but are possibly incomplete.