NAME

ftpd − Describes File Transfer Protocol server daemon, including anonymous service

SYNOPSIS

ftpd [-dl] [-ttimeout] [-Tmaxtimeout]

FLAGS

−dDebugging information is sent to the syslogd daemon (see
syslogd(8)). 

−lEach FTP session, as well as additional information, such as the file name retrieved or stored, the number of bytes, and the attempted logins that failed, is sent to the syslogd daemon (see syslogd(8)). 

−ttime-out
The inactivity time-out period will be set to time-out seconds. 

−Tmaxtime-out
The maximum timeout period allowed may be set to timeout seconds with this option. 

SECURITY NOTE

This security-sensitive command uses the SIA (Security Integration Architecture) routine as an interface to the security mechanisms. See matrix.conf(4) for more information. 

DESCRIPTION

The ftpd command is the DARPA (Defense Advanced Research Projects Agency) 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(4). 

The ftpd command includes two flags to control the information logged for the ftpd daemon.  If the −d flag is specified, debugging information is logged.  If the −l flag is specified, each ftp session, along with data for login failures and file operations, is logged.  Refer to the syslogd(8) reference page for information on system log files. 

The FTP server will time out an inactive session after 15 minutes.  If the −t flag is specified, the inactivity time-out period will be set to time-out seconds.  A client may also request a different time-out period; the maximum period allowed may be set to time-out seconds with the −T flag. The default limit is 2 hours. 

If you want to use a customized banner, create an /etc/banner file.  The ftpd daemon reads the file, if it exists, and writes its contents over a new FTP connection prior to starting the login dialog. 

The FTP server currently supports the following ftp requests; case is not distinguished:

RequestDescription

ABORAbort previous command

ACCTSpecify account (ignored)

ALLOAllocate storage (vacuously)

APPEAppend to a file

CDUPChange to parent of current working directory

CWDChange working directory

DELEDelete a file

HELPGive help information

LISTGive list files in a directory (ls -lgA)

MKDMake a directory

MDTMShow last modification time of file

MODESpecify data transfer mode

NLSTGive name list of files in directory

NOOPDo nothing

PASSSpecify password

PASVPrepare for server-to-server transfer

PORTSpecify data connection port

PWDPrint the current working directory

QUITTerminate session

RESTRestart incomplete transfer

RETRRetrieve a file

RMDRemove a directory

RNFRSpecify rename-from file name

RNTOSpecify rename-to file name

SITENonstandard commands (see next section)

SIZEReturn size of file

STATReturn status of server

STORStore a file

STOUStore a file with a unique name

STRUSpecify data transfer structure

SYSTShow operating system type of server system

TYPESpecify data transfer type

USERSpecify username

XCUPChange to parent of current working directory (deprecated)

XCWDChange working directory (deprecated)

XMKDMake a directory (deprecated)

XPWDPrint the current working directory (deprecated)

XRMDRemove a directory (deprecated)

The following nonstandard or UNIX compatible commands are supported by the SITE request:

RequestDescription

UMASKChange umask (for example, SITE UMASK 002)

IDLESet idle timer (for example, SITE IDLE 60)

CHMODChange mode of a file (for example, SITE CHMOD 755 filename)

HELPGive help information (for example, 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 Telnet stream, as described in Internet RFC959.  If a STAT command is received during a data transfer, preceded by a Telnet IP and Synch, transfer status will be returned. 

The ftpd command interprets file names according to the “globbing” conventions used by the C shell (see csh(1)).  This interpretation allows users to utilize the metacharacters “∗?[]{}~”. 

The ftpd command authenticates users according to four rules:

       •The username must be in the password database, /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 username must not appear in the /etc/ftpusers file. 

       •The user must have a standard shell returned by the getusershell() call (see getusershell(3)). 

       •If the username 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). 

The ftp command uses the default Type-of-Service values recommended by RFC1060, which are as follows:

ftp-control
Low delay

ftp-data
High throughput

Anonymous FTP Configuration

If you are creating an anonymous FTP account, ftpd takes special measures to restrict the client’s access privileges when the user logs in.  The server executes a chroot call (see chroot(2)) to the home directory of the ftp user.  In order that system security is not breached, it is recommended that you adhere to the following rules when creating directories and files in the ftp subtree:

~ftpMake the home directory owned by the superuser (root) and unwritable by anyone. 

~ftp/bin
Make this directory owned by the superuser and unwritable by anyone.  The ls program (see ls(1)) must be present to support the list command.  This program should have mode 111. 

Copy the ls program from /sbin/ls. This is the statically linked version of the ls command, which does not require shared library support.  Be sure to copy the static version of ls from the /sbin directory, not the shared version from the /usr/bin directory. 

~ftp/etc
Make this directory owned by the superuser and unwritable by anyone.  The passwd and group files (see passwd(4) and group(4) ) must be present for the ls command to be able to produce owner names rather than numbers.  The password field in the passwd file is not used, and should not contain real encrypted passwords.  These files should be mode 444. 

In this environment, the sia subdirectory (which you can copy from /etc/sia) must also be present for the ls command to be able to produce owner names rather than numbers. 

~ftp/pub
Make this directory mode 777 and owned by ftp.  Users should then place files that are to be accessible via the anonymous account in this directory. 

You can configure these values by specifying them in the /etc/iptos file. For more information, see iptos(4). 

FILES

/usr/sbin/ftpdSpecifies the command path. 

/etc/ftpusersContains the list of unauthorized users. 

/etc/bannerSpecifies the path name for the banner file. 

CAUTIONS

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 incomplete. 

RELATED INFORMATION

Commands: ftp(1), syslogd(8)

Functions: getusershell(3)

Files: iptos(4)