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adis-ftplogin - checkpassword plug-in for FTP logins


adis-ftplogin command


adis-ftplogin is a plug-in that conforms to the checkpassword interface by Dan J. Bernstein that may be used in the context of adis-ftpup and adis-ftpsession(1).



adis-ftplogin does not touch the bidirectional network connection inherited through file descriptor 0. The network connection, however, is closed in case of failures as adis-ftplogin is (in a typical setup) the only process keeping it. Hence, FTP clients will just see a drop of the connection instead of an error message in case of authentication failures.

An exit code of 1 indicates a permanent authorization failure, an exit code of 111 is used for temporary problems.

A log entry is provided to syslog with priority auth.info for each invocation that

The password is not logged.

An email message to root is generated


As long no encrypting network layers are involved, login credentials for FTP are passed as clear text over network connections. Therefore protocols like that of ssh and scp are to be preferred. In many contexts, however, FTP with all its inherent insecurities is the only convenient option to exchange data. The idea of adis-ftplogin is to minimize the risk of clear text passwords for FTP by

It may be wise, however, to apply periodical checks on the root directories and options specified in the user's .ftppasswd files if they match the local policy. The security considerations of FTPUnixFileSystems apply here.


The checkpassword interface is documented on http://cr.yp.to/checkpwd/interface.html.

reads user name and password and provides them to a plug-in like adis-ftplogin.
usually taken for command that runs the FTP session after a successful authorization.
documentation of the file format of .ftppasswd files.

Edited by: borchert, last change: 2001/05/15, revision: 1.1, converted to HTML: 2001/05/15

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