NAME

ftpd − The DARPA Internet File Transfer Protocol server

SYNOPSIS

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

FLAGS

-dDebugging information is written to the syslogd(8). 

-lEach FTP session is logged in the syslog,

as well as additional information, such as the file name retrieved or stored, the number of bytes, and the attempted logins that failed. 

-ttime-outThe 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). 

If the −d flag is specified, debugging information is written to the syslogd(8). 

If the −l flag is specified, each ftp session is logged in the syslog. 

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. 

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 filename

RNTOSpecify rename-to filename

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 RFC959 are recognized, but not implemented.  MDTM and SIZE are not specified in RFC959, 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 filenames according to the “globbing” conventions used by csh(1).  This 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 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). 

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 recommended that the ftp subtree be constructed with care;  the following rules are recommended. 

~ftpMake the home directory owned by ftp and unwritable by anyone. 

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

Copy the ls from /sbin/ls. 

~ftp/etcMake this directory owned by the superuser and unwritable by anyone.  The files 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 passwd 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/pubMake 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. 

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

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

FILES

/usr/sbin/ftpd
Specifies the command path.

/etc/ftpusers
Contains the list of unauthorized users.

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)

Daemons: syslogd(8)

Functions: getusershell(3)

Files: iptos(4)