nbdkit-ip-filter - Man Page

filter clients by IP address, process ID, user ID or group ID

Synopsis

 nbdkit --filter=ip PLUGIN [allow=addr[,addr...]]
                           [deny=addr[,addr...]]

Description

nbdkit-ip-filter can allow or deny client connections by their IP address.  Usually it is better to control this outside nbdkit, for example using TCP wrappers or a firewall, but this filter can be used if these are not available.

nbdkit ≥ 1.24 added the ability to filter clients connecting over Unix domain sockets by client process ID, user ID and group ID.  Also this version added support for filtering AF_VSOCK sockets by peer CID or port.

Examples

Filter by IP address

 nbdkit --filter=ip [...] allow=127.0.0.1,::1 deny=all

Allow clients to connect on the loopback IPv4 or loopback IPv6 address, deny all other clients.

 nbdkit --filter=ip [...] deny=8.0.0.0/8

Allow any client except connections from the IPv4 8.0.0.0/8 network.

 nbdkit --filter=ip [...] allow=anyipv6 deny=all

Allow IPv6 clients to connect from anywhere, deny all other sources.

Filter by Unix domain socket peer

 nbdkit -U $tmpdir/sock --filter=ip [...] allow=uid:`id -u` deny=all

Only allow the current user (id -u) to connect over the socket.

Layer extra security by creating the socket inside a temporary directory only accessible by the user.

 nbdkit -U $tmpdir/sock --filter=ip [...] allow=gid:`id -g` deny=all

Allow anyone in the same group as the current user to connect to the Unix domain socket.

As in the previous example, layer extra security by creating the socket inside a temporary directory only accessible by the group.

Rules

When a client connects, this filter checks its source address against the allow and deny lists as follows:

  1. If the address matches any in the allow list, permission is granted.
  2. If the address matches any in the deny list, permission is denied.
  3. Otherwise permission is granted.

If either the allow or deny parameter is not present then it is assumed to be an empty list.  The order in which the parameters appear on the command line does not matter; the allow list is always processed first and the deny list second.

The allow and deny parameters each contain a comma-separated list of any of the following:

all
any

These keywords (which both have the same meaning) match any source.

allipv4
anyipv4

These keywords match any IPv4 address.

allipv6
anyipv6

These keywords match any IPv6 address.

allunix
anyunix

These keywords match any connection over a Unix domain socket.

allvsock
anyvsock

These keywords match any connection over an AF_VSOCK socket.

A.B.C.D

This matches the single IPv4 address A.B.C.D, for example 127.0.0.1.

A.B.C.D/NN

This matches the range of IPv4 addresses A.B.C.D/NN, for example 192.168.2.0/24 or 10.0.0.0/8.

A:B:...

This matches the single IPv6 address A:B:....  The usual IPv6 address representations can be used (see RFC 5952).

A:B:.../NN

This matches a range of IPv6 addresses A:B:.../NN.

pid:PID

(nbdkit ≥ 1.24, Linux only)

This matches the process ID PID, if the client connects over a Unix domain socket.

Note that process IDs are recycled so this alone is not secure enough to ensure that only a single desired process can connect.  However you could use it as an additional check.

uid:UID

(nbdkit ≥ 1.24)

This matches the numeric user ID UID, if the client connects over a Unix domain socket.

gid:GID

(nbdkit ≥ 1.24)

This matches the numeric group ID GID, if the client connects over a Unix domain socket.

vsock-cid:CID
vsock-port:PORT

(nbdkit ≥ 1.24)

These match the CID or port number for AF_VSOCK sockets.

Not filtered

If neither the allow nor the deny parameter is given the filter does nothing.

Unix domain sockets and AF_VSOCK sockets were always unfiltered in nbdkit ≤ 1.22.  In nbdkit ≥ 1.24 the ability to filter them was added.

Common patterns of usage

Permit known good connections and deny everything else:

 nbdkit --filter=ip ... allow=good1,good2,... deny=all

Block troublemakers but allow everything else:

 nbdkit --filter=ip ... deny=bad1,bad2,...

Parameters

allow=addr[,...]

Set list of allow rules.  This parameter is optional, if omitted the allow list is empty.

deny=addr[,...]

Set list of deny rules.  This parameter is optional, if omitted the deny list is empty.

Files

$filterdir/nbdkit-ip-filter.so

The filter.

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

Version

nbdkit-ip-filter first appeared in nbdkit 1.18.

See Also

nbdkit(1), nbdkit-exitlast-filter(1), nbdkit-exitwhen-filter(1), nbdkit-limit-filter(1), nbdkit-filter(3).

Authors

Richard W.M. Jones

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-exitlast-filter(1), nbdkit-exitwhen-filter(1), nbdkit-filter(3), nbdkit-limit-filter(1), nbdkit-ondemand-plugin(1), nbdkit-plugin(3), nbdkit-release-notes-1.18(1), nbdkit-release-notes-1.24(1), nbdkit-service(1), nbdkit-tmpdisk-plugin(1).

2021-06-11 nbdkit-1.27.1