WU-FTPD - Internet File Transfer Protocol server
Synopsis
Description
Options
TLS CONFIGURATION OPTIONS (-z parameter)
Ftp Protocol Commands
Authentication Mechanism On Bsd/os Systems Only
General Ftp Extensions
Bugs
ftpd [ -d ] [ -v ] [ -l ] [ -t timeout ] [ -T maxtimeout ] [ -4 ] [ -a ] [ -A ] [ -C ] [ -G ] [ -h ] [ -H ] [ -i ] [ -I ] [ -K ] [ -L ] [ -o ] [ -p ctrlport ] [ -P dataport ] [ -q ] [ -Q ] [ -r rootdir ] [ -s ] [ -S ] [ -u umask ] [ -U ] [ -V ] [ -w ] [ -W ] [ -x ] [ -X ] [ -z option ]
FTPD is the 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(5).
-4 When running in standalone operation mode, listen for connections on an AF_INET type socket. When built with IPv6 support, the default is to listen on an AF_INET6 type socket. -a Use the ftpaccess(5) configuration file. -A Use of the ftpaccess(5) configuration file is disabled. This is the default. -C If this option is specified when built with GSS-API support, non-anonymous users need local credentials (for example, to authenticate to remote fileservers), and so they should be prompted for a password unless they forwarded credentials as part of authentication. -d -v Debugging information is written to the syslog. -G If this option is specified when built with GSS-API support, the use of the GSS-API authentication support is disabled. By default, the server will accept "AUTH GSS" and attempt to authenticate the client. -H Enables the use of remote IP (RIP) files, required by the host-limit directive to determine the number of current users from the same IP address in each access class. By default, RIP files are not used. Only enable the use of RIP files if you wish to impose limits on the number of connections per remote IP address in a given class. -h Prints a brief summary of WU-FTPD(8) command-line options. -i Files received by the WU-FTPD(8) server will be logged to the xferlog(5). The -i option is overridden by the use of the ftpaccess(5) file. -I Disables the use of RFC931 (AUTH/ident) to attempt to determine the username on the client. -K If this option is specified when built with GSS-API support, users are required to present GSS-API authentication credentials in order to login, standard name/password login will not work. -l Each ftp session is logged in the syslog. -L Commands sent to the WU-FTPD(8) server will be logged to the syslog. The -L option is overridden by the use of the ftpaccess(5) file. If the -L flag is used, command logging will be on by default as soon as the ftp server is invoked. This will cause the server to log all USER commands, which if a user accidentally enters a password for that command instead of the username, will cause passwords to be logged via syslog. -o Files transmitted by the WU-FTPD(8) server will be logged to the xferlog(5). The -o option is overridden by the use of the ftpaccess(5) file. If the -X option is specified, the output created by the -i and -o options is not saved to the xferlog file but saved via syslog so you can collect output from several hosts on one central loghost. If the -x option is specified, the output created by the -i and -o options is saved to the xferlog file and via syslog. -p -P options override the port numbers used by the daemon. Normally, the daemon determines the port numbers by looking in /etc/services for "ftp" and "ftp-data". If there is no /etc/services entry for "ftp-data" and the -P option is not specified, the daemon uses the port just prior to the control connection port. The -p option is only available if running as a standalone daemon. -q -Q Deterines whether the daemon uses the PID files. These files are required by the limit directive to determine the number of current users in each access class. Disabling the use of the PID files disables user limits. The default ( -q ) is to use the PID files. Specify -Q when testing the server as a normal user when access permissions prevent the use of the PID files. Large, busy sites which do not wish to impose limits on the number of concurrent users may also consider disabling the PID files. -r Instructs the daemon to chroot(2) to the specified rootdir immedeately upon loading. This can improve system security by limiting the files which may be damaged should a breakin occur through the daemon. Set is much like anonymous FTP, with additional files needed which vary from system to system. -s -S Place the daemon in standalone operation mode. The -S option runs the daemon in the background and is useful in startup scripts during system initialization (ie., in rc.local). The -s option leaves the daemon in foreground and is useful when running from init (ie., /etc/inittab). -t The inactivity timeout period will be set to timeout seconds as opposed to the default value of 15 minutes. A client may also request a different timeout period; the maximum period allowed may be set to timeout seconds with the -T option. The default limit is 2 hours. -u Set the default umask to umask. -U User logins are recorded in the utmp file. The default is to not record every login and logout. -V Causes the program to display copyright and version information, then terminate. -W User logins are not recorded in the wtmp file. The default ( -w ) is to record every login and logout. -z Used for the SSL/TLS configuration. See the next section for details. - Lists the foregoing command-line options that can be passed to the daemon.
See the doc/HOWTO/ssl_and_tls_ftpd.HOWTO file for details on the usage of the options listed here.
-z cert=file or -z rsacert=file provides the file location of the X.509 certificate for the WU-FTPD server, in PEM format.
-z key=file or -z rsakey=file provides the file location of the PEM encoded private key for the WU-FTPD server.
-z dsacert=file provides the file location of the DSA certificate for the WU-FTPD server.
-z dsakey=file provides the file location of the DSA private key for the WU-FTPD server.
-z dhparam=file provides the file location of the file containing Diffie-Hellman parameters.
-z crlfile=file provides the file location of the CRL file for the WU-FTPD server.
-z crldir=dir provides the directory location of the CRL directory for the WU-FTPD server.
-z cipher=cipher_suites provides the list of TLS cipher suites to use - see README.TLS for format and meaning. Common values are ALL or ALL:!EXP
-z randfile=file provides the file location of the random data file for the WU-FTPD server.
-z debugfile=file provides the file location of the TLS debug file (if -z debug is specified and TLS_DEBUG or --enable-tls-debug were used at compile time).
-z systemcertdir=dir provides the location of the directory that contains the certificate mapping files for system-wide certificate mapping. See README.TLS for more info.
-z systemcertdir=dir provides the location of the directory that contains the certificate mapping files for system-wide certificate mapping. See README.TLS for more info.
-z config=file provides the location of the configuration file which can contain these -z options instead of passing them on the command line.
-z authmode=OPTION specifies the authentication mode of the TLS session. OPTION is one of "server", "client_can" and "client_must". The default value is "client_can".
-z certpass=OPTION specifies more authentication options for a TLS session. OPTION is one of "certok" or "needpass". The default value is "certok". Determines the behavior for PASS if the session is client authenticated.
-z password=PASSWORD specifies the password to be used to decrypt the pem key file(s).
-z CAfile=FILE specifies the file containing the list of acceptable Client Certificate Issuers
-z CApath=PATH specifies the directory containing the certificates and hashes of acceptable Client Certificate Issuers
-z certsok instructs the WU-FTPD server not to check the CA chain of client presented certificates.
-z debug makes the WU-FTPD server write debugging info to the file specified in debugfile
-z tlsonly/protect_user tells the WU-FTPD server to only accept USER commands on a secured control connection.
-z tlsdata tells the WU-FTPD server to only allow data conenctions when in the PROT P state.
-z clientcert tells the WU-FTPD server to only allow user authentication via client certificates. (disables the PASS command).
-z allow_auth_ssl (this option is not recommended) allows the WU-FTPD server to operate with the old AUTH SSL logic.
-z bad_auth_ssl_reply (this option is not recommended) causes the WU-FTPD server to reply with the incorrect 334 reply to an AUTH command. Only provided for users who are migrating the incorrectly implemented WU-FTPD 2.5 patch.
-z allowccc (this option is not recommended) lets the client drop protection on the control connection. Use with caution.
-z rsader RSA certificates are in DER and not PEM. Why - I don’t know.
-z logalldata log all secured data connections - not just the first.
-z notls don’t allow this server to do TLS. Allows TLS compiled servers to not do TLS.
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 FEAT return features supported by FTP server HELP give help information LIST give list files in a directory (‘‘ls -lgA’’) MKD make a directory MDTM show last modification time of file MODE specify data transfer mode MLSD list directory contents MLST ask for data about the given object NLST give name list of files in directory NOOP do nothing OPTS modify options list of FTP commands that support it. 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 incomplete transfer RETR retrieve a file RMD remove a directory RNFR specify rename-from file name RNTO specify rename-to file name SBUF set the TCP Window size. 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 show operating system type of server system TYPE specify data transfer type 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 remaining ftp requests specified in Internet RFC 959 are recognized, but not implemented.
The following non-standard or UNIX-specific commands are supported by the SITE request.
Request Description ALIAS enquire about directory aliases listed in ftpaccess. CDPATH enquire about cdpaths defined in ftpaccess. CHECKMETHOD switch between checksum types, crc, md5, posix or rfc1321. CHECKSUM generate a checksum on the remote filename CHMOD change mode of a file. E.g. SITE CHMOD 755 filename EXEC execute a program. E.g. SITE EXEC program params GPASS give special group access password. E.g. SITE GPASS bar GROUP request special group access. E.g. SITE GROUP foo GROUPS request group membership info. HELP give help information. E.g. SITE HELP IDLE set idle-timer. E.g. SITE IDLE 60 INDEX backward compatibility before the arrival of SITE EXEC MINFO like SITE NEWER, but gives extra information NEWER list files newer than a particular date UMASK change umask. E.g. SITE UMASK 002The SBUF, SITE commands BUFSIZE and BUFSIZEMEASURE are not documented in any RFC, rather they are special extensions that allow TCP buffer sizes to be set and measured, respectively. These commands only work if the feature has been enabled at compile time and with a client that will make use of them. Also, there’s no guarantee that the requested TCP window size will be honored due to system constraints defined as a maximum, for example.
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.
WU-FTPD interprets file names according to the ‘‘globbing’’ conventions used by csh(1). This allows users to utilize the metacharacters ‘‘*?[]{}~’’.
WU-FTPD authenticates users according to four rules.
1) The user name must be in the password data base, /etc/passwd, or whatever is appropriate for the operating system, and the password must not be null. In this case a password must be provided by the client before any file operations may be performed. 2) The user name must not appear in the file /etc/ftpusers. 3) The user must have a standard shell returned by getusershell(3). 4) 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, WU-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. ~ftp) Make the home directory owned by super-user and unwritable by anyone. ~ftp/bin) Make this directory owned by the super-user and unwritable by anyone. The program ls(1) must be present to support the list command. This program should have mode 111. ~ftp/etc) Make this directory owned by the super-user and unwritable by anyone. The files passwd(5) and group(5) must be present for the ls command to be able to produce owner names rather than numbers. Depending on the operating system, there may be other required files. Check your manual page for the getpwent(3) library routine. The password field in passwd is not used, and should not contain real encrypted passwords. These files should be mode 444 and owned by the super-user. Don’t use the system’s /etc/passwd file as the password file or the system’s /etc/group file as the group file in the ~ftp/etc directory. ~ftp/pub) Create a subdirectory in ~ftp/pub with the appropriate mode (777 or 733) if you want to allow normal users to upload files.
The authentication mechanism used by WU-FTPD is determined by the ‘‘auth-ftp’’ entry in the /etc/login.conf file (see login.conf(5)) that matches the users class. If there is no ‘‘auth-ftp’’ entry for the class, the normal ‘‘auth’’ entry will be used instead. An alternate authentication mechanism may be specified by appending a colon (‘‘:’’) followed by the authentication style, i.e. ‘‘joe:skey’’.
There are some extensions to the FTP server such that if the user specifies a filename (when using a RETRIEVE command) such that:
True Filename Specified Filename Action ------------- ------------------ ----------------------------------- <filename>.Z <filename> Decompress file before transmitting <filename> <filename>.Z Compress <filename> before transmitting <filename> <filename>.tar Tar <filename> before transmitting <filename> <filename>.tar.Z Tar and compress <filename> before transmittingAlso, the FTP server will attempt to check for valid e-mail addresses and chide the user if he doesn’t pass the test. For users whose FTP client will hang on "long replies" (i.e. multiline responses), using a dash as the first character of the password will disable the server’s lreply() function.
The FTP server can also log all file transmission and reception, keeping the following information for each file transmission that takes place.
Mon Dec 3 18:52:41 1990 1 wuarchive.wustl.edu 568881 /files.lst.Z a _ o a chris@wugate.wustl.edu ftp 0 *%.24s %d %s %d %s %c %s %c %c %s %s %d %s 1 2 3 4 5 6 7 8 9 10 11 12 13
1 current time in the form DDD MMM dd hh:mm:ss YYYY 2 transfer time in seconds 3 remote host name 4 file size in bytes 5 name of file 6 transfer type (a>scii, b>inary) 7 special action flags (concatenated as needed): C file was compressed U file was uncompressed T file was tar’ed _ no action taken 8 file was sent to user (o>utgoing) or received from user (i>ncoming) 9 accessed anonymously (r>eal, a>nonymous, g>uest) -- mostly for FTP 10 local username or, if guest, ID string given (anonymous FTP password) 11 service name (’ftp’, other) 12 authentication method (bitmask) 0 none 1 RFC931 Authentication 13 authenticated user id (if available, ’*’ otherwise)
ftp(1) , getusershell(3) , syslogd(8) , ftpaccess(5) , xferlog(5) , umask(2)
The anonymous account is inherently dangerous and should 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. The possible security holes have been extensively scrutinized, but are possibly incomplete.
| WU-FTPD (8) | Jul 19, 2011 |