Provided by: ftpd-ssl_0.17.33+0.3-1build1_amd64 bug

NAME

     ftpd — Internet File Transfer Protocol server

SYNOPSIS

     ftpd [-AdDhlMnPSU] [-T maxtimeout] [-t timeout] [-u mask] [-z debug] [-z certsok]
          [-z certrequired] [-z secure] [-z verify=flags] [-z cert=certfile] [-z key=keyfile]
          [-z ciper=list]

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. The 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 no longer 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.

     -z SSL-parameter
             This option is only valid if ftpd has been built with SSL (Secure Socket Layer)
             support.

             debug       Enable SSL related debugging.

             ssl         Negotiate SSL at first, then use ftp protocol. In this mode ftpd only
                         accepts connections from SSL enhanced ftp with option -z ssl.  (Not yet
                         implemented)

             nossl, !ssl
                         switch off SSL negotiation

             certsok     Look username up in /etc/ssl.users. The format of this file is lines of
                         this form: user1,user2:/C=US/..... where user1 and user2 are usernames.
                         If client certificate is valid, authenticate without password.

             certrequired
                         client certificate is mandatory

             secure      Don't switch back to unencrypted mode (no SSL) if SSL is not available.

             verify=int  Set the SSL verify flags (SSL_VERIFY_* in ssl/ssl.h ).

             cert=cert_file
                         Use the certificate(s) in cert_file.

             key=key_file
                         Use the key(s) in key_file.

             cipher=ciph_list
                         Set the preferred ciphers to ciph_list.  (See ssl/ssl.h ).

     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.