ftpd(ADMN) 06 January 1993 ftpd(ADMN) Name ftpd - DARPA Internet File Transfer Protocol server Syntax /etc/ftpd [ -d ] [ -v ] [ -l ] [ -umask ] [ -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(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 -v option is specified, debugging information is written to the syslog (same as the -d option). If the -l option is specified, each FTP session is logged in the syslog. If the -u option is specified, the file creation mask will be set to mask. 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 timeout limit allowed may be set to maxtimeout 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 -l) MKD make a directory MDTM show last modification time of file 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 REST restart a file 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 display operating system information 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 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 com- mand 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 sh(C). This allows users to utilize the metacharacters * ? [ ] { } and ~. ftpd authenticates users according to four rules. + 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. + The user name must not appear in the file /etc/ftpusers. This file is checked on each non-anonymous ftp connection request. If the requested user name is located in the file, the request for service is denied. It is suggested that this file contain at least the following names: uucp, root. + The FTP server will not allow FTP logins to accounts whose shell is not listed in /etc/shells. This typically restricts access by UUCP signons, etc. + 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(S) command 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; the following rules are recommended. ( N.B. ~ftp means ``the home directory of user ftp'') ~ftp Make the home directory owned by ``ftp'' and unwritable by any- one. ~ftp/bin Make this directory owned by the super user and unwritable by anyone. The program ls(C) must be present to support the list commands. This program should have mode 111. The programs pwd(C) and sh(C) and the special file /dev/null must be present to support the pwd command. ~ftp/etc Make this directory owned by the super user and unwritable by anyone. The files passwd(C) and group(F) 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 accessible via the anonymous account in this directory. For full details, see the System Administrator's Guide. Files /etc/ftpusers restricted user list /etc/shells allowable shell 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. You will also need to mknod(C) ~ftp/dev/socksys. Supporting PWD requires ~ftp/dev/null, ~ftp/bin/sh, and ~ftp/bin/pwd. Notes The anonymous account is inherently dangerous and should be 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. See also ftp(TC), syslog(SLIB)