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FTPD(8) UNIX Programmer's Manual FTPD(8) NAME ftpd - DARPA Internet File Transfer Protocol server SYNOPSIS /usr/libexec/ftpd [ -d ] [ -l ] [ -ttimeout ] [ -Tmaxtimeout ] 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(5). 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 seconds. 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. 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 -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 Printed 11/24/99 February 23, 1989 1 FTPD(8) UNIX Programmer's Manual FTPD(8) 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. E.g. SITE HELP 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 Tel- net 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 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) The user name must not appear in the file /etc/ftpusers. Printed 11/24/99 February 23, 1989 2 FTPD(8) UNIX Programmer's Manual FTPD(8) 3) The user must have a standard shell returned by getusershell(3). 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. ~ftp) Make the home directory owned by ``ftp'' and unwritable by anyone. ~ftp/bin) Make this directory owned by the super-user and unwrit- able by anyone. The program ls(1) must be present to support the list command. This program should have mode 111. ~ftp/etc) Make this directory owned by the super-user and unwrit- able by anyone. 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 encrypted passwords. 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(1), getusershell(3), syslogd(8) BUGS The anonymous account is inherently dangerous and should 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. Printed 11/24/99 February 23, 1989 3
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