Provided by: ftpd_0.17-31_i386 bug

NAME

     ftpd - Internet File Transfer Protocol server

SYNOPSIS

     ftpd [-AdDhlMnPSU] [-T maxtimeout] [-t timeout] [-u mask]

DESCRIPTION

     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 services(5).

     Available options:

     -4      Use IPv4 addressing only. Th default is to offer service for both
             families, IPv6 and IPv4.

     -6      Only provide IPv6 addressing capability.

     -A      Permit only anonymous ftp connections or accounts listed in
             /etc/ftpchroot. Other connection attempts are refused.  This
             option is nolonger effective if PAM is enabled.  Please refer to
             the README file for instructions to doing this with PAM.

     -d      Debugging information is written to the syslog using LOG_FTP.

     -D      With this option set, ftpd will detach and become a daemon,
             accepting connections on the FTP port and forking child processes
             to handle them. This has lower overhead than starting ftpd from
             inetd(8) and is thus useful on busy servers to reduce load.

     -h      The server will use data ports in the high port range for passive
             connections.  This range is defined by the IPPORT_HIFIRSTAUTO and
             IPPORT_HILASTAUTO defines in <netinet/in.h>.  In OpenBSD they are
             set to 49152 and 65535 respectively.

     -l      Each successful and failed 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.

     -M      Enables multihomed mode.  Instead of simply using ~ftp for
             anonymous transfers, a directory matching the fully qualified
             name of the IP number the client connected to, and located inside
             ~ftp is used instead.

     -n      Use numeric IP addresses in logs instead of doing hostname
             lookup.

     -P      Permit illegal port numbers or addresses for PORT command
             initiated connects.  By default ftpd(8) violates the RFC and thus
             constrains the PORT command to non-reserved ports and requires it
             use the same source address as the connection came from.  This
             prevents the "FTP bounce attack" against services on both the
             local machine and other local machines.

     -S      With this option set, ftpd logs all anonymous transfers to the
             file /var/log/ftpd when this file exists.

     -U      Each concurrent ftp(1) session is logged to the file
             /var/run/utmp, making them visible to commands such as who(1).
             This option at present is unsupporte and will always silently
             fail.

     -T      A client may also request a different timeout period; the maximum
             period allowed may be set to timeout seconds with the -T option.
             The default limit is 2 hours.

     -t      The inactivity timeout period is set to timeout seconds (the
             default is 15 minutes).

     -u      Change the default umask from 027 to mask.

     The file /etc/nologin can be used to disable ftp access.  If the file
     exists, ftpd displays it and exits.  If the file /etc/ftpwelcome exists,
     ftpd prints it before issuing the “ready” message.  If the file /etc/motd
     exists, ftpd prints it after a successful login.  If the file .message
     exists in a directory, ftpd prints it when that directory is entered.

     The ftp server currently supports the following ftp requests.  The case
     of the requests is ignored.

           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
           EPRT       specify data connection port, either IPv4 or IPv6
           EPSV       ask for a server port for fetching data
           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 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)

     The following non-standard or UNIX specific commands are supported by the
     SITE request.

           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 filename’’
           HELP       give help information.

     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.

     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.

     Ftpd interprets file names according to the “globbing” conventions used
     by csh(1).  This allows users to utilize the metacharacters “*?[]{}~”.

     Ftpd authenticates users according to five rules.

           1.   The login 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.  If the user has an S/Key key, the response from a
                successful USER command will include an S/Key challenge. The
                client may choose to respond with a PASS command giving either
                a standard password or an S/Key one-time password. The server
                will automatically determine which type of password it has
                been given and attempt to authenticate accordingly. See
                skey(1) for more information on S/Key authentication. S/Key is
                a Trademark of Bellcore.

           2.   The login name must not appear in the file /etc/ftpusers.

           3.   The user must have a standard shell returned by
                getusershell(3).

           4.   If the user name appears in the file /etc/ftpchroot the
                session’s root will be changed to the user’s login directory
                by chroot(2) as for an “anonymous” or “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.

           5.   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 an email address for the user should
                be used as the password).

     In the last case, ftpd takes special measures to restrict the client’s
     access privileges.  The server performs a chroot(2) 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, following
     these rules:

           ~ftp      Make the home directory owned by “root” and unwritable by
                     anyone (mode 555).

           ~ftp/bin  Make this directory owned by “root” and unwritable by
                     anyone (mode 511).  This directory is required, and
                     should contain at least a statically linked copy of
                     ls(1.) Any programs in this directory should be mode 111
                     (executable only).

           ~ftp/etc  Make this directory owned by “root” and unwritable by
                     anyone (mode 511).  The files passwd(5) and group(5) must
                     be present for the ls command to be able to produce owner
                     names rather than numbers.  The password field in passwd
                     is not used, and should not contain real passwords.  The
                     file motd, if present, will be printed after a successful
                     login.  These files should be mode 444.

           ~ftp/lib  Make this directory owned by “root” and unwritable by
                     anyone (mode 511).  The libraries ld-linux.so.2 and
                     libc.so.6 (or whatever your ls command is linked to) must
                     be present.  In order to read passwd(5) and group(5), the
                     library libnss_files.so.2 is also needed.  Note that if
                     you’re using a 2.2.* or later Linux kernel, ld-linux.so.2
                     must be executable as well as readable (555).  All other
                     files should be mode 444.

           ~ftp/pub  Make this directory mode 555 and owned by “root”.  This
                     is traditionally where publically accessible files are
                     stored for download.

FILES

     /etc/ftpusers    List of unwelcome/restricted users.
     /etc/ftpchroot   List of normal users who should be chroot’d.
     /etc/ftpwelcome  Welcome notice.
     /etc/motd        Welcome notice after login.
     /etc/nologin     Displayed and access refused.
     /var/run/utmp    List of users on the system.
     /var/log/ftpd    Log file for anonymous transfers.

SEE ALSO

     ftp(1), skey(1), who(1), getusershell(3), ftpusers(5), syslogd(8)

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.

HISTORY

     The ftpd command appeared in 4.2BSD.