AllowForeignAddress

Name

AllowForeignAddress -- Control the use of the PORT command

Synopsis

AllowForeignAddress [ on|off ]

Default

AllowForeignAddress off

Context

server config, <VirtualHost>, <Anonymous>, <Global>

Module

mod_core

Compatibility

1.1.7 and later

Description

Normally, proftpd disallows clients from using the ftp PORT command with anything other than their own address (the source address of the ftp control connection), as well as preventing the use of PORT to specify a low-numbered (< 1024) port. In either case, the client is sent an "Invalid port" error and a message is syslog'd indicating either "address mismatch" or "bounce attack". By enabling this directive, proftpd will allow clients to transmit foreign data connection addresses that do not match the client's address. This allows such tricks as permitting a client to transfer a file between two FTP servers without involving itself in the actual data connection. Generally it's considered a bad idea, security-wise, to permit this sort of thing. AllowForeignAddress only affects data connection addresses; not tcp ports. There is no way (and no valid reason) to allow a client to use a low-numbered port in its PORT command.

See also

Examples