ftpd(1M) MISC. REFERENCE MANUAL PAGES ftpd(1M)
NAME
ftpd - file transfer protocol server
SYNOPSIS
in.ftpd [ -dl ] [ -ttimeout ] host.socket
DESCRIPTION
ftpd is the Internet File Transfer Protocol (FTP) server
process. The server is invoked by the Internet daemon
inetd(1M) each time a connection to the FTP service [see
services(4)] is made, with the connection available as
descriptor 0 and the host and socket the connection ori-
ginated from (in hex and decimal respectively) as argument.
Inactive connections are timed out after 90 seconds.
The following options are available:
-ttimeout
Set the inactivity timeout period to timeout, in
seconds. The FTP server will timeout an inactive ses-
sion after 15 minutes.
Requests
The FTP server currently supports the following FTP
requests; case is not distinguished.
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 list files in a directory (ls -lg)
MKD make a directory
MODE specify data transfer mode
NLST give name list of files in directory (ls)
Last change: TCP/IP 1
ftpd(1M) MISC. REFERENCE MANUAL PAGES ftpd(1M)
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
RETR retrieve a file
RMD remove a directory
RNFR specify rename-from file name
RNTO specify rename-to file name
STOR store a file
STOU store a file with a unique name
STRU specify data transfer structure
TYPE specify data transfer type
USER specify user name
XCUP change to parent of current working directory
XCWD change working directory
XMKD make a directory
XPWD print the current working directory
XRMD remove a directory
The remaining FTP requests specified in RFC 959 are recog-
nized, but not implemented.
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 RFC 959.
ftpd interprets file names according to the globbing conven-
tions used by sh(1). This allows users to utilize the meta-
characters: * ? [ ] { } ~
Last change: TCP/IP 2
ftpd(1M) MISC. REFERENCE MANUAL PAGES ftpd(1M)
ftpd authenticates users according to three rules.
1) The user name must be in the password data base,
/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.
2) If the user name appears in the file /etc/ftpusers, ftp
access is denied.
3) ftp access is denied unless the user's shell (from
/etc/passwd) is listed in the file /etc/shells, or the
user's shell is one of the following:
/bin/sh
/bin/ksh
/bin/csh
/usr/bin/sh
/usr/bin/ksh
/usr/bin/csh
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).
In the last case, ftpd takes special measures to restrict
the client's access privileges. The server performs a
chroot(2) command to the home directory of the ftp user. In
order that system security is not breached, it is recom-
mended that the ftp subtree be constructed with care; the
following rules are recommended.
home_directory
Make the home directory owned by ftp and unwritable
by anyone.
home_directory/usr/bin
Make this directory owned by the super-user and
unwritable by anyone. The program ls(1) must be
present to support the list commands. This program
should have mode 111.
home_directory/etc
Make this directory owned by the super-user and
unwritable by anyone. Copies of the files
passwd(4), group(4), and netconfig must be present
for the ls command to work properly. These files
should be mode 444.
home_directory/pub
Make this directory mode 777 and owned by ftp.
Last change: TCP/IP 3
ftpd(1M) MISC. REFERENCE MANUAL PAGES ftpd(1M)
Users should then place files which are to be acces-
sible via the anonymous account in this directory.
home_directory/dev
Make this directory owned by the super-user and
unwritable by anyone. Change directories to this
directory and do the following:
FTP="`grep ^ftp: /etc/passwd | cut -d: -f6`"
MAJORMINOR="`ls -l /dev/tcp | nawk '{ gsub(/,/, ""); print $5, $6}'`
mknod $FTP/dev/tcp c $MAJORMINOR
chmod 666 $FTP/dev/tcp
SEE ALSO
ftp(1), getsockopt(3N), passwd(4), services(4).
Postel, Jon, and Joyce Reynolds, File Transfer Protocol
(FTP), RFC 959, Network Information Center, SRI Interna-
tional, Menlo Park, Calif., October 1985.
NOTES
The anonymous account is inherently dangerous and should be
avoided when possible.
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 incom-
plete.
/etc/ftpusers contains a list of users who cannot access the
system; the format of the file is one username per line.
Last change: TCP/IP 4