1nbdkit-tls-fallback-filter(1)       NBDKIT       nbdkit-tls-fallback-filter(1)
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NAME

6       nbdkit-tls-fallback-filter - nbdkit TLS protection filter
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SYNOPSIS

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

13       "nbdkit-tls-fallback-filter" is designed to be used when offering a
14       connection that allows but does not require TLS from clients, in order
15       to offer safe alternative content to plaintext clients, only exposing
16       the underlying plugin to authenticated users.  This may provide a nicer
17       failure mode for plaintext clients than the harsher "nbdkit
18       --tls=require".
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20       When this filter detects a plaintext connection, it ignores the
21       client's export name, and provides a single read-only export with 512
22       bytes of data and content that defaults to the message "This NBD server
23       requires TLS authentication before it will serve useful data."
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25       When using this filter, it is recommended to place this filter first in
26       the command line, to reduce the chance that any work done by ".open" in
27       earlier filters can be exploited by plaintext connections as a denial
28       of service attack to starve further authenticated connections.  Note
29       that this filter will fail to load if the plugin requests the
30       "SERIALIZE_CONNECTIONS" thread model, as a plaintext client holding its
31       connection open indefinitely would be such a starvation.
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PARAMETERS

34       tlsreadme=MESSAGE
35           This optional parameter can be used to use "MESSAGE" as the
36           contents of the dummy export exposed to plaintext clients, using
37           trailing NUL bytes to round the size up to 512 bytes.
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FILES

40       $filterdir/nbdkit-tls-fallback-filter.so
41           The filter.
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43           Use "nbdkit --dump-config" to find the location of $filterdir.
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VERSION

46       "nbdkit-tls-fallback-filter" first appeared in nbdkit 1.22.
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SEE ALSO

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

52       Eric Blake
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55       Copyright (C) 2020 Red Hat Inc.
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LICENSE

58       Redistribution and use in source and binary forms, with or without
59       modification, are permitted provided that the following conditions are
60       met:
61
62       •   Redistributions of source code must retain the above copyright
63           notice, this list of conditions and the following disclaimer.
64
65       •   Redistributions in binary form must reproduce the above copyright
66           notice, this list of conditions and the following disclaimer in the
67           documentation and/or other materials provided with the
68           distribution.
69
70       •   Neither the name of Red Hat nor the names of its contributors may
71           be used to endorse or promote products derived from this software
72           without specific prior written permission.
73
74       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
75       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
76       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
77       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
78       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
79       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
80       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
81       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
82       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
83       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
84       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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88nbdkit-1.25.8                     2021-05-25     nbdkit-tls-fallback-filter(1)
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