1nbdkit-tls-fallback-filter(1) NBDKIT nbdkit-tls-fallback-filter(1)
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6 nbdkit-tls-fallback-filter - nbdkit TLS protection filter
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9 nbdkit --tls=on --filter=tls-fallback plugin [plugin-args...]
10 [tlsreadme=MESSAGE]
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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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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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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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46 "nbdkit-tls-fallback-filter" first appeared in nbdkit 1.22.
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49 nbdkit(1), nbdkit-tls(1), nbdkit-filter(3).
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52 Eric Blake
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55 Copyright (C) 2020 Red Hat Inc.
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58 Redistribution and use in source and binary forms, with or without
59 modification, are permitted provided that the following conditions are
60 met:
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62 • Redistributions of source code must retain the above copyright
63 notice, this list of conditions and the following disclaimer.
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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.
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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.
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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-1.32.5 2023-01-03 nbdkit-tls-fallback-filter(1)