ftp/ftpd/ftpd.8

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.\"     @(#)ftpd.8	8.2 (Berkeley) 4/19/94
.\"
.Dd April 19, 1997
.Dt FTPD 8
.Os BSD 4.2
.Sh NAME
.Nm ftpd
.Nd Internet File Transfer Protocol server
.Sh SYNOPSIS
.Nm ftpd
.Op Fl a Ar authmode
.Op Fl dilv
.Op Fl g Ar umask
.Op Fl p Ar port
.Op Fl T Ar maxtimeout
.Op Fl t Ar timeout
.Op Fl u Ar default umask
.Sh DESCRIPTION
.Nm Ftpd
is the
Internet File Transfer Protocol
server process.  The server uses the
.Tn TCP
protocol
and listens at the port specified in the
.Dq ftp
service specification; see
.Xr services 5 .
.Pp
Available options:
.Bl -tag -width Ds
.It Fl a
Select the level of authentication required.  Kerberised login can not
be turned off. The default is to only allow kerberised login.  Other
possibilities can be turned on by giving a string of comma separated
flags as argument to
.Fl a .
Recognised flags are:
.Bl -tag -width plain
.It Ar plain
Allow logging in with plaintext password. The password can be a(n) OTP
or an ordinary password.
.It Ar otp
Same as
.Ar plain ,
but only OTP is allowed.
.It Ar ftp
Allow anonymous login.
.El
.Pp
The following combination modes exists for backwards compatibility:
.Bl -tag -width plain
.It Ar none
Same as
.Ar plain,ftp .
.It Ar safe
Same as
.Ar ftp .
.It Ar user
Ignored.
.El
.It Fl d
Debugging information is written to the syslog using LOG_FTP.
.It Fl g
Anonymous users will get a umask of
.Ar umask .
.It Fl i
Open a socket and wait for a connection. This is mainly used for
debugging when ftpd isn't started by inetd.
.It Fl l
Each successful and failed
.Xr ftp 1
session is logged using syslog with a facility of LOG_FTP.
If this option is specified twice, the retrieve (get), store (put), append,
delete, make directory, remove directory and rename operations and
their filename arguments are also logged.
.It Fl p
Use
.Ar port
(a service name or number) instead of the default
.Ar ftp/tcp .
.It Fl T
A client may also request a different timeout period;
the maximum period allowed may be set to
.Ar timeout
seconds with the
.Fl T
option.
The default limit is 2 hours.
.It Fl t
The inactivity timeout period is set to
.Ar timeout
seconds (the default is 15 minutes).
.It Fl u
Set the initial umask to something else than the default 027.
.It Fl v
Verbose mode.
.El
.Pp
The file
.Pa /etc/nologin
can be used to disable ftp access.
If the file exists,
.Nm
displays it and exits.
If the file
.Pa /etc/ftpwelcome
exists,
.Nm
prints it before issuing the
.Dq ready
message.
If the file
.Pa /etc/motd
exists,
.Nm
prints it after a successful login.
.Pp
The ftp server currently supports the following ftp requests.
The case of the requests is ignored.
.Bl -column "Request" -offset indent
.It Request Ta "Description"
.It ABOR Ta "abort previous command"
.It ACCT Ta "specify account (ignored)"
.It ALLO Ta "allocate storage (vacuously)"
.It APPE Ta "append to a file"
.It CDUP Ta "change to parent of current working directory"
.It CWD Ta "change working directory"
.It DELE Ta "delete a file"
.It HELP Ta "give help information"
.It LIST Ta "give list files in a directory" Pq Dq Li "ls -lgA"
.It MKD Ta "make a directory"
.It MDTM Ta "show last modification time of file"
.It MODE Ta "specify data transfer" Em mode
.It NLST Ta "give name list of files in directory"
.It NOOP Ta "do nothing"
.It PASS Ta "specify password"
.It PASV Ta "prepare for server-to-server transfer"
.It PORT Ta "specify data connection port"
.It PWD Ta "print the current working directory"
.It QUIT Ta "terminate session"
.It REST Ta "restart incomplete transfer"
.It RETR Ta "retrieve a file"
.It RMD Ta "remove a directory"
.It RNFR Ta "specify rename-from file name"
.It RNTO Ta "specify rename-to file name"
.It SITE Ta "non-standard commands (see next section)"
.It SIZE Ta "return size of file"
.It STAT Ta "return status of server"
.It STOR Ta "store a file"
.It STOU Ta "store a file with a unique name"
.It STRU Ta "specify data transfer" Em structure
.It SYST Ta "show operating system type of server system"
.It TYPE Ta "specify data transfer" Em type
.It USER Ta "specify user name"
.It XCUP Ta "change to parent of current working directory (deprecated)"
.It XCWD Ta "change working directory (deprecated)"
.It XMKD Ta "make a directory (deprecated)"
.It XPWD Ta "print the current working directory (deprecated)"
.It XRMD Ta "remove a directory (deprecated)"
.El
.Pp
The following commands are specified by RFC2228.
.Bl -column Request -offset indent
.It AUTH Ta "authentication/security mechanism"
.It ADAT Ta "authentication/security data"
.It PROT Ta "data channel protection level"
.It PBSZ Ta "protection buffer size"
.It MIC Ta "integrity protected command"
.It CONF Ta "confidentiality protected command"
.It ENC Ta "privacy protected command"
.It CCC Ta "clear command channel"
.El
.Pp
The following non-standard or
.Tn UNIX
specific commands are supported
by the
SITE request.
.Pp
.Bl -column Request -offset indent
.It UMASK Ta change umask, (e.g.
.Ic "SITE UMASK 002" )
.It IDLE Ta set idle-timer, (e.g.
.Ic "SITE IDLE 60" )
.It CHMOD Ta change mode of a file (e.g.
.Ic "SITE CHMOD 755 filename" )
.It FIND Ta quickly find a specific file with GNU
.Xr locate 1 .
.It HELP Ta give help information.
.El
.Pp
The following Kerberos related site commands are understood.
.Bl -column Request -offset indent
.It KAUTH Ta obtain remote tickets.
.It KLIST Ta show remote tickets
.El
.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
.Nm Ftpd
interprets file names according to the
.Dq globbing
conventions used by
.Xr csh 1 .
This allows users to utilize the metacharacters
.Dq Li \&*?[]{}~ .
.Pp
.Nm Ftpd
authenticates users according to these rules.
.Pp
.Bl -enum -offset indent
.It
If Kerberos authentication is used, the user must pass valid tickets
and the principal must be allowed to login as the remote user.
.It
The login name must be in the password data base, and not have a null
password (if kerberos is used the password field is not checked).  In
this case a password must be provided by the client before any file
operations may be performed.  If the user has an OTP key, the response
from a successful USER command will include an OTP challenge. The
client may choose to respond with a PASS command giving either a
standard password or an OTP one-time password. The server will
automatically determine which type of password it has been given and
attempt to authenticate accordingly. See
.Xr otp 1
for more information on OTP authentication.
.It
The login name must not appear in the file
.Pa /etc/ftpusers .
.It
The user must have a standard shell returned by
.Xr getusershell 3 .
.It
If the user name appears in the file
.Pa /etc/ftpchroot
the session's root will be changed to the user's login directory by
.Xr chroot 2
as for an
.Dq anonymous
or
.Dq ftp
account (see next item).  However, the user must still supply a password.
This feature is intended as a compromise between a fully anonymous account
and a fully privileged account.  The account should also be set up as for an
anonymous account.
.It
If the user name is
.Dq anonymous
or
.Dq ftp ,
an
anonymous ftp account must be present in the password
file (user
.Dq ftp ) .
In this case the user is allowed
to log in by specifying any password (by convention an email address for
the user should be used as the password).
.El
.Pp
In the last case,
.Nm ftpd
takes special measures to restrict the client's access privileges.
The server performs a
.Xr chroot 2
to the home directory of the
.Dq ftp
user.
In order that system security is not breached, it is recommended
that the
.Dq ftp
subtree be constructed with care, consider following these guidelines
for anonymous ftp.
.Pp
In general all files should be owned by
.Dq root ,
and have non-write permissions (644 or 755 depending on the kind of
file). No files should be owned or writable by
.Dq ftp
(possibly with exception for the
.Pa ~ftp/incoming ,
as specified below).
.Bl -tag -width "~ftp/pub" -offset indent
.It Pa ~ftp
The
.Dq ftp
homedirectory should be owned by root.
.It Pa ~ftp/bin
The directory for external programs (such as
.Xr ls 1 ) .
These programs must either be statically linked, or you must setup an
environment for dynamic linking when running chrooted.
These programs will be used if present:
.Bl -tag -width "locate" -offset indent
.It ls
Used when listing files.
.It compress
When retrieving a filename that ends in
.Pa .Z ,
and that file isn't present,
.Nm
will try to find the filename without
.Pa .Z
and compress it on the fly.
.It gzip
Same as compress, just with files ending in
.Pa .gz .
.It gtar
Enables retrieval of whole directories as files ending in
.Pa .tar .
Can also be combined with compression. You must use GNU Tar (or some
other that supports the
.Fl z
and
.Fl Z
flags).
.It locate
Will enable ``fast find'' with the
.Ic SITE FIND
command. You must also create a
.Pa locatedb
file in
.Pa ~ftp/etc .
.El
.It Pa ~ftp/etc
If you put copies of the
.Xr passwd 5
and
.Xr group 5
files here, ls will be able to produce owner names rather than
numbers. Remember to remove any passwords from these files.
.Pp
The file
.Pa motd ,
if present, will be printed after a successful login.
.It Pa ~ftp/dev
Put a copy of
.Xr /dev/null 7
here.
.It Pa ~ftp/pub
Traditional place to put whatever you want to make public.
.El
.Pp
If you want guests to be able to upload files, create a
.Pa ~ftp/incoming
directory owned by
.Dq root ,
and group
.Dq ftp
with mode 730 (make sure
.Dq ftp
is member of group
.Dq ftp ) .
The following restrictions apply to anonymous users:
.Bl -bullet
.It
Directories created will have mode 700.
.It
Uploaded files will be created with an umask of 777, if not changed
with the
.Fl g
option.
.It
These command are not accessible:
.Ic DELE , RMD , RNTO , RNFR ,
.Ic SITE UMASK ,
and
.Ic SITE CHMOD .
.It
Filenames must start with an alpha-numeric character, and consist of
alpha-numeric characters or any of the following:
.Li \&+
(plus),
.Li \&-
(minus),
.Li \&=
(equal),
.Li \&_
(underscore),
.Li \&.
(period), and
.Li \&,
(comma).
.El
.Sh FILES
.Bl -tag -width /etc/ftpwelcome -compact
.It Pa /etc/ftpusers
Access list for users.
.It Pa /etc/ftpchroot
List of normal users who should be chroot'd.
.It Pa /etc/ftpwelcome
Welcome notice.
.It Pa /etc/motd
Welcome notice after login.
.It Pa /etc/nologin
Displayed and access refused.
.It Pa ~/.klogin
Login access for Kerberos.
.El
.Sh SEE ALSO
.Xr ftp 1 ,
.Xr otp 1 ,
.Xr getusershell 3 ,
.Xr ftpusers 5 ,
.Xr syslogd 8 ,
.Sh STANDARDS
.Bl -tag -compact -width "RFC 1938"
.It Cm RFC 959
FTP PROTOCOL SPECIFICATION
.It Cm RFC 1938
OTP Specification
.It Cm RFC 2228
FTP Security Extensions.
.El
.Sh BUGS
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.
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .