ftpd(1M) ftpd(1M)NAME ftpd - Internet File Transfer Protocol server SYNOPSIS /usr/etc/in.ftpd [-d] [-l] [-ttimeout] DESCRIPTION ftpd is the DARPA Internet File Transfer Prototocol server process. The server uses the TCP protocol and listens at the port specified in the ftp service specification; see services(4N). If the -d flag option is specified, debugging information is written to the standard output. If the -l flag option is specified, each ftp session is logged on the standard error output. The ftp server will timeout an inactive session after 15 minutes. If the -t flag option is specified, the inactivity timeout period will be set to timeout. The ftp server currently supports the following ftp re- quests; 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'') 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 April, 1990 1
ftpd(1M) ftpd(1M)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 Pro- cess'' (IP) signal and a Telnet ``Synch'' signal in the com- mand Telnet stream, as described in Internet RFC 959. 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 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. ftpd also exam- ines the shell field of the user's entry in /etc/passwd. If the shell field is /bin/sh, /bin/csh, or empty, the login is allowed. If the shell field con- tains the name of any other shell, such as /bin/ksh, the file /etc/shells must contain the specified name, or the authentification will fail. 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. 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. ~ftp) Make the home directory owned by ``ftp'' and unwritable by anyone. 2 April, 1990
ftpd(1M) ftpd(1M)~ftp/bin) Make this directory owned by the superuser and unwrit- able by anyone. The program ls(1) must be present to support the list commands. This program should have mode 111. ~ftp/etc) Make this directory owned by the superuser and unwrit- able by anyone. The files passwd(4) and group(4) 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 which are to be accessi- ble via the anonymous account in this directory. SEE ALSO ftp(1N). BUGS The anonymous account is inherently dangerous and should be 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 incom- plete. April, 1990 3