nbdkit-tls-fallback-filter - Man Page

nbdkit TLS protection filter

Synopsis

 nbdkit --tls=on --filter=tls-fallback plugin [plugin-args...]
        [tlsreadme=MESSAGE]

Description

nbdkit-tls-fallback-filter is designed to be used when offering a connection that allows but does not require TLS from clients, in order to offer safe alternative content to plaintext clients, only exposing the underlying plugin to authenticated users.  This may provide a nicer failure mode for plaintext clients than the harsher nbdkit --tls=require.

When this filter detects a plaintext connection, it ignores the client's export name, and provides a single read-only export with 512 bytes of data and content that defaults to the message “This NBD server requires TLS authentication before it will serve useful data.”

When using this filter, it is recommended to place this filter first in the command line, to reduce the chance that any work done by .open in earlier filters can be exploited by plaintext connections as a denial of service attack to starve further authenticated connections.  Note that this filter will fail to load if the plugin requests the SERIALIZE_CONNECTIONS thread model, as a plaintext client holding its connection open indefinitely would be such a starvation.

Parameters

tlsreadme=MESSAGE

This optional parameter can be used to use MESSAGE as the contents of the dummy export exposed to plaintext clients, using trailing NUL bytes to round the size up to 512 bytes.

Files

$filterdir/nbdkit-tls-fallback-filter.so

The filter.

Use nbdkit --dump-config to find the location of $filterdir.

Version

nbdkit-tls-fallback-filter first appeared in nbdkit 1.22.

See Also

nbdkit(1), nbdkit-tls(1), nbdkit-filter(3).

Authors

Eric Blake

License

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Referenced By

nbdkit(1), nbdkit-filter(3), nbdkit-plugin(3), nbdkit-release-notes-1.22(1), nbdkit-tls(1).

2021-10-19 nbdkit-1.29.1