MAN page from Other ftp-server-krb5-1.3-6sls.i586.rpm

FTPD

Section: Maintenance Commands (8)
Index

NAME

ftpd - DARPA Internet File Transfer Protocol server

SYNOPSIS

ftpd[-A | -a] [-C] [-c] [-d] [-l][-v] [-T maxtimeout] [-t timeout][-p port] [-U ftpusers-file] [-u umask][-r realm-file] [-s srvtab][-w{ip|maxhostlen[,{striplocal|nostriplocal}]}]

DESCRIPTION

Ftpdis theDARPAInternet File Transfer Protocol server process. The server uses theTCPprotocol and listens at the port specified in the ``ftp'' servicespecification; seeservices(5).

Available options:

-A: Connections are only allowed for users who can authenticate via theftp AUTH mechanism. (Anonymous ftp may also be allowed if it is configured.) Ftpd will ask the user for a password if one isrequired.
-a: Connections are only allowed for users who can authenticate (via theftp AUTH mechanism) and who are authorized to connect to the named account without a password. (Anonymous ftp may also be allowed if it is configured.)
-C: Non-anonymous users need local credentials (for example, to authenticateto remote fileservers), and so they should be prompted for a passwordunless they forwarded credentials as part of authentication.
-c: Allow the CCC (Clear Command Channel) command to be used. This allowsless secure connections, and should probably only be used when debugging.
-d: Debugging information is written to the syslog. (Identical to -v)
-l: Eachftp(1)session is logged in the syslog. If this flag appears twice, additionalinformation about operations performed (such as files retrieved, directoriescreated, etc.) will be logged via syslog. If it appears three times, someother statistics such as the number of bytes transferred will be logged viasyslog as well.
-v: Debugging information is written to the syslog. (Identical to -d)
-T maxtimeout: A client may request a maximum timeout period allowed set totimeoutseconds with the-Toption. The default limit is 2 hours. This is different from the normalinactivity timeout specified by the-toption (see below).
-t timeout: The inactivity timeout period is set totimeoutseconds (the default is 15 minutes).
-p port: Run as a server and accept a connection onport.Normally the ftp server is invoked byinetd(8).
-U ftpusers-file: Sets the full path and name of theftpusersfile to use. The default value is normally/etc/ftpusers.
-u umask: Sets the umask for the ftpd process. The default value is normally 027.
-r realm-file: Sets the name of thekrb.conffile to use. The default value is normally set by/etc/krb5.conf.
-s srvtab: Sets the name of thesrvtabfile to use for Kerberos V4 authentication. The default value is normally/etc/srvtab.
-w {ip|maxhostlen[,{striplocal|nostriplocal}]}: Controls the form of the remote hostname passed to login(1).Specifying ip results in the numeric IP address always beingpassed to login(1). Specifying a number, maxhostlen, sets themaximum length of the hostname passed to login(1) before it will bepassed as a numeric IP address. If maxhostlen is 0, then thesystem default, as determined by the utmp or utmpx structures, isused. The nostriplocal and striplocal options, which mustbe preceded by a comma, control whether or not the local host domainis stripped from the remote hostname. By default, the equivalent ofstriplocal is in effect.

The ftp server currently supports the following ftp requests; case isnot distinguished.

Request: Description
ABOR: abort previous command
ACCT: specify account (ignored)
ADAT: send an authentication protocol message
ALLO: allocate storage (vacuously)
APPE: append to a file
AUTH: specify an authentication protocol to be performed
CCC: set the command channel protection mode to "Clear" (no protection).Only available if the -c command-line option was given.
CDUP: change to parent of current working directory
CWD: change working directory
DELE: delete a file
ENC: send a privacy and integrity protected command (given in argument)
HELP: give help information
LIST: give list files in a directory (``ls -lgA'')
MIC: send an integrity protected command (given in argument)
MKD: make a directory
MDTM: show last modification time of file
MODE: specify data transfermode
NLST: give name list of files in directory
NOOP: do nothing
PASS: specify password
PASV: prepare for server-to-server transfer
PBSZ: specify a protection buffer size
PORT: specify data connection port
PROT: specify a protection level under which to protect data transfers
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 transferstructure
SYST: show operating system type of server system
TYPE: specify data transfertype
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 orUNIXspecific 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 InternetRFC 959are recognized, but not implemented. MDTM and SIZE are not specified inRFC959,but will appear in the next updated FTP RFC.

The ftp server will abort an active file transfer only when the ABORcommand is preceded by a Telnet "Interrupt Process" (IP) signal and aTelnet "Synch" signal in the command Telnet stream, as described inInternetRFC959.If a STAT command is received during a data transfer, preceded by aTelnet IP and Synch, transfer status will be returned.

Ftpdinterprets file names according to the``globbing''conventions used bycsh(1).This allows users to utilize the metacharacters ``*?[]{}~''.

Ftpdauthenticates users according to the following rules:

1.: The user name must be in the password data base,/etc/passwd.
2.: AnAUTHcommand must be accepted, the ensuing authentication protocol (conductedviaADATcommands and replies) must successfully complete, and the authenticateduser must permitted access. Otherwise, a valid password which is notnull must be provided by the client.
3.: The user name must not appear in the file/etc/ftpusers.
4.: The user must have a standard shell returned by getusershell(3).
5.: If the user name is ``anonymous'' or ``ftp'', an anonymous ftp accountmust be present in the password file (user ``ftp''). In this case theuser is allowed to log in by specifying any password (by convention thisis given as the client host's name).

In the last case,ftpdtakes special measures to restrict the client's access privileges. Theserver performs achroot(2)command to the home directory of the ``ftp'' user. In order that systemsecurity is not breached, it is recommended that the ``ftp'' subtree beconstructed 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 unwritable by anyone.The programls(1)must be present to support the list command. This program should havemode 111.
~ftp/etc: Make this directory owned by the super-user and unwritable by anyone.The filespasswd(5)andgroup(5)must be present for thelscommand to be able to produce owner names rather than numbers. Thepassword field inpasswdis not used, and should not contain real encrypted passwords. Thesefiles should be mode 444.
~ftp/pub: Make this directory mode 777 and owned by ``ftp''. Users should thenplace files which are to be accessible via the anonymous account in thisdirectory.

If anADATcommand succeeds, the control channel must be either integrity orprivacy protected. In this case, theMICandENCcommands are the only commands allowed over the control channel. Theargument to theMICcommand is a base 64 encoded string which, when decoded, is an ftpcommand integrity protected with a cryptographic checksum. The argumentto theENCcommand is a base 64 encoded string which, when decoded, is an ftpcommand privacy and integrity protected with encryption.

If anADATcommand succeeds, ftp replies will also be either integrity or privacyprotected.

If anADATcommand succeeds, the data channel can also be integrity or privacyprotected. ThePROTcommand accepts S for integrity and P for privacy protection. Unless anADATcommand succeeds, the only protection level accepted by thePROTcommand is C (clear).

BUGS

The anonymous account is inherently dangerous and should avoided whenpossible.

The server must run as the super-user to create sockets with privilegedport numbers. It maintains an effective user id of the logged in user,reverting to the super-user only when binding addresses to sockets. Thepossible security holes have been extensively scrutinized, but arepossibly incomplete.

HISTORY

Theftpdcommand appeared in 4.2BSD.

This document was created byman2html,using the manual pages.