$NetBSD: ftpd.8,v 1.8 1996/01/14 20:55:23 thorpej Exp $
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@(#)ftpd.8 8.2 (Berkeley) 4/19/94
.Dd June 18, 1996 .Dt FTPD 8 .Os .Sh NAME .Nm ftpd .Nd Internet File Transfer Protocol server .Sh SYNOPSIS .Nm ftpd .Op Fl AdDhlMPSU .Op Fl T Ar maxtimeout .Op Fl t Ar timeout .Op Fl u Ar mask .Sh DESCRIPTION .Nm Ftpd is the Internet File Transfer Protocol server process. The server uses the .Tn TCP protocol and listens at the port specified in the .Dq ftp service specification; see .Xr services 5 .
p Available options: l -tag -width Ds t Fl A Permit only anonymous ftp connections or accounts listed in
a /etc/ftpchroot . Other connection attempts are refused. t Fl d Debugging information is written to the syslog using LOG_FTP. t Fl D With this option set, .Nm 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 .Nm ftpd from .Xr inetd 8 and is thus useful on busy servers to reduce load. t Fl h The server will use data ports in the high port range for passive connections. This range is defined by the .Ev IPPORT_HIFIRSTAUTO and .Ev IPPORT_HILASTAUTO defines in <netinet/in.h>. In .Ox they are set to 49152 and 65535 respectively. t Fl l Each successful and failed .Xr 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. t Fl M Enables multihomed mode. Instead of simply using
a ~ftp for anonymous transfers, a directory matching the fully qualified name of the IP number the client connected to, and located inside
a ~ftp is used instead. t Fl p Disable passive mode ftp connections. This is useful if you are behind a firewall that refuses connections to arbitrary high numbered ports. Many ftp clients try passive mode first and do not always react gracefully to a server that refuses connections to the port it asked the client to connect to. t Fl P Permit illegal port numbers or addresses for PORT command initiated connects. By default .Xr 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. t Fl S With this option set, .Nm ftpd logs all anonymous downloads to the file
a /var/log/ftpd when this file exists. t Fl U Each concurrent .Xr ftp 1 session is logged to the file
a /var/run/utmp , making them visible to commands such as .Xr who 1 . t Fl T Ar maxtimeout A client may also request a different timeout period; the maximum period allowed may be set to .Ar maxtimeout seconds with the .Fl T option. The default limit is 2 hours. t Fl t Ar timeout The inactivity timeout period is set to .Ar timeout seconds (the default is 15 minutes). t Fl u Ar mask Change the default umask from 027 to .Ar mask . .El
p The file
a /etc/nologin can be used to disable ftp access. If the file exists, .Nm displays it and exits. If the file
a /etc/ftpwelcome exists, .Nm prints it before issuing the .Dq ready message. If the file
a /etc/motd exists, .Nm prints it after a successful login. If the file
a .message exists in a directory, .Nm prints it when that directory is entered.
p The ftp server currently supports the following ftp requests. The case of the requests is ignored. l -column "Request" -offset indent t Request Ta "Description" t ABOR Ta "abort previous command" t ACCT Ta "specify account (ignored)" t ALLO Ta "allocate storage (vacuously)" t APPE Ta "append to a file" t CDUP Ta "change to parent of current working directory" t CWD Ta "change working directory" t DELE Ta "delete a file" t HELP Ta "give help information" t LIST Ta "give list files in a directory" Pq Dq Li "ls -lgA" t MKD Ta "make a directory" t MDTM Ta "show last modification time of file" t MODE Ta "specify data transfer" Em mode t NLST Ta "give name list of files in directory" t NOOP Ta "do nothing" t PASS Ta "specify password" t PASV Ta "prepare for server-to-server transfer" t PORT Ta "specify data connection port" t PWD Ta "print the current working directory" t QUIT Ta "terminate session" t REST Ta "restart incomplete transfer" t RETR Ta "retrieve a file" t RMD Ta "remove a directory" t RNFR Ta "specify rename-from file name" t RNTO Ta "specify rename-to file name" t SITE Ta "non-standard commands (see next section)" t SIZE Ta "return size of file" t STAT Ta "return status of server" t STOR Ta "store a file" t STOU Ta "store a file with a unique name" t STRU Ta "specify data transfer" Em structure t SYST Ta "show operating system type of server system" t TYPE Ta "specify data transfer" Em type t USER Ta "specify user name" t XCUP Ta "change to parent of current working directory (deprecated)" t XCWD Ta "change working directory (deprecated)" t XMKD Ta "make a directory (deprecated)" t XPWD Ta "print the current working directory (deprecated)" t XRMD Ta "remove a directory (deprecated)" .El
p The following non-standard or .Tn UNIX specific commands are supported by the SITE request.
p l -column Request -offset indent t Sy Request Ta Sy Description t UMASK Ta change umask, e.g., ``SITE UMASK 002'' t IDLE Ta set idle-timer, e.g., ``SITE IDLE 60'' t CHMOD Ta change mode of a file, e.g., ``SITE CHMOD 755 filename'' t HELP Ta give help information. .El
p 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.
p 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.
p .Nm Ftpd interprets file names according to the .Dq globbing conventions used by .Xr csh 1 . This allows users to utilize the metacharacters .Dq Li *?[]{}~ .
p .Nm Ftpd authenticates users according to five rules.
p l -enum -offset indent t The login name must be in the password data base,
a /etc/pwd.db , 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 .Xr skey 1 for more information on S/Key authentication. S/Key is a Trademark of Bellcore. t The login name must not appear in the file
a /etc/ftpusers . t The user must have a standard shell returned by .Xr getusershell 3 . t If the user name appears in the file
a /etc/ftpchroot the session's root will be changed to the user's login directory by .Xr chroot 2 as for an .Dq anonymous or .Dq 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. t If the user name is .Dq anonymous or .Dq ftp , an anonymous ftp account must be present in the password file (user .Dq 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). .El
p In the last case, .Nm ftpd takes special measures to restrict the client's access privileges. The server performs a .Xr chroot 2 to the home directory of the .Dq ftp user. In order that system security is not breached, it is recommended that the .Dq ftp subtree be constructed with care, following these rules: l -tag -width "~ftp/pub" -offset indent t Pa ~ftp Make the home directory owned by .Dq root and unwritable by anyone (mode 555). t Pa ~ftp/bin Make this directory owned by .Dq root and unwritable by anyone (mode 511). This directory is optional unless you have commands you wish the anonymous ftp user to be able to run (the .Xr ls 1 command exists as a builtin). Any programs in this directory should be mode 111 (executable only). t Pa ~ftp/etc Make this directory owned by .Dq root and unwritable by anyone (mode 511). The files pwd.db (see .Xr pwd_mkdb 8 ) and .Xr group 5 must be present for the .Xr ls command to be able to produce owner names rather than numbers. The password field in .Xr pwd.db is not used, and should not contain real passwords. The file
a motd , if present, will be printed after a successful login. These files should be mode 444. t Pa ~ftp/pub Make this directory mode 555 and owned by .Dq root . This is traditionally where publically accessible files are stored for download. .El
p If logging to the
a /var/log/ftpd file is enabled, information will be written in the following format:
p l -tag -width XXXXXXXXXXXXXX -offset indent -compact t time The time and date of the download, in .Xr ctime 3 format. t elapsed time The elapsed time, in seconds. t remote host The remote host (or IP number). t bytes The number of bytes transfered. t path The full path (relative the ftp chroot space) of the file transfered. t type The type of transfer; either .Dq a for ASCII or .Dq b for binary. t unused Unused field containing a .Dq * , for compatibility. t unused Unused field containing a .Dq o , for compatibility. t user type The type of user, either .Dq a for anonymous, or .Dq r for a real user (should always be anonymous). t name Either a system login name or the value given for .Dq email address if an anonymous user. t unused Unused field, containing a .Dq 0 , for compatibility. t real name The system login name if the connection is not anonymous, or a .Dq * if it is. t virtual host The virtual host that the connection was made to. .El
p Although fields exist for logging information on real users, this file is only used for anonymous downloads. Unused fields exist only for compatility with other .Nm ftpd implementations. .Sh FILES l -tag -width /var/run/ftpd.pid -compact t Pa /etc/ftpusers List of unwelcome/restricted users. t Pa /etc/ftpchroot List of normal users who should be chroot'd. t Pa /etc/ftpwelcome Welcome notice. t Pa /etc/motd Welcome notice after login. t Pa /etc/nologin Displayed and access refused. t Pa /var/run/utmp List of users on the system. t Pa /var/run/ftpd.pid Process id if running in daemon mode. t Pa /var/log/ftpd Log file for anonymous downloads. .El .Sh SEE ALSO .Xr ftp 1 , .Xr skey 1 , .Xr who 1 , .Xr getusershell 3 , .Xr syslogd 8 .Sh 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. .Sh HISTORY The .Nm command appeared in x 4.2 .