FTPD(ADMN) UNIX System V
Name
ftpd - DARPA Internet File Transfer Protocol server
Syntax
/etc/ftpd [ -d ] [ -l ] [ -ttimeout ]
Description
ftpd is the DARPA Internet File Transfer Protocol server
process. The server uses the TCP protocol and listens at
the port specified in the ftp service specification; see
services(SFF).
ftpd is started by the super-server inetd, and therefore
must have an entry in inetd's configuration file
/etc/inetd.conf. [See inetd(ADMN) and inetd.conf(SFF).]
If the -d option is specified, debugging information is
written to the syslog.
If the -l option is specified, each FTP session is logged in
the syslog.
The FTP server will timeout an inactive session after 15
minutes. If the -t option is specified, the inactivity
timeout period will be set to timeout.
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 -l)
MKD make a directory
MODE specify data transfer mode
NLST give name list of files in directory (ls)
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 Internet RFC 959 are
recognized, 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 Internet RFC 959.
ftpd interprets file names according to the globbing
conventions used by sh(C). This allows users to utilize the
metacharacters *?[]{}~.
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 can be performed.
2) The user name must not appear in the file
/etc/ftpusers.
3) 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. To
make sure system security is not breached, it is recommended
that the ftp subtree be constructed with care; the
following rules are recommended. (Note: ~ftp means ``the
home directory of user ftp'')
~ftp)
Make it so the home directory is owned by ftp and
unwritable by anyone.
~ftp/bin)
Make it so this directory is owned by the superuser and
unwritable by anyone. The program ls(C) must be
present to support the list commands. This program
should have mode 111.
~ftp/etc)
Make it so this directory owned by the superuser and
unwritable by anyone. The files passwd(SFF) and
group(SFF) must be present for the ls command to work
properly. These files should be mode 444.
~ftp/pub)
Make this directory mode 777 and owned by ftp. Users
should then place files that are to be accessible via
the anonymous account in this directory.
See Also
ftp(TC), syslog(SLIB)
Notes
The anonymous account is inherently dangerous and should
avoided when possible.
The server must run as the superuser to create sockets with
privileged port numbers. It maintains an effective user id
of the logged in user, reverting to the superuser only when
binding addresses to sockets. The possible security holes
have been extensively scrutinized, but are possibly
incomplete.
Files
/etc/ftpusers - restricted user list
/etc/passwd - the user database
/etc/group - the group database
/usr/adm/syslog - the system log file
The following files are needed for anonymous ftp:
~ftp/etc/passwd - used by ~ftp/bin/ls
~ftp/etc/group - used by ~ftp/bin/ls
~ftp/bin/ls - to support the LIST and NLST commands
In addition, if your /bin/ls is linked with shared
libraries, you will need to copy /shlib/libc_s to
~ftp/shlib/libc_s. If your implementation is using the
SIOCSOCKSYS ioctl, you will need to run the mdnod(ADMN)
command on ~ftp/dev/socksys.
(printed 8/17/89) FTPD(ADMN)