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.\" $NetBSD: libblacklist.3,v 1.10 2020/03/30 15:47:15 christos Exp $
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.\"
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.\" Copyright (c) 2015 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Christos Zoulas.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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2022-10-12 13:23:39 +00:00
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.Dd March 30, 2020
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2016-06-01 21:48:22 +00:00
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.Dt LIBBLACKLIST 3
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.Os
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.Sh NAME
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.Nm blacklist_open ,
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.Nm blacklist_close ,
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.Nm blacklist_r ,
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.Nm blacklist ,
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.Nm blacklist_sa ,
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.Nm blacklist_sa_r
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.Nd Blacklistd notification library
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.Sh LIBRARY
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.Lb libblacklist
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.Sh SYNOPSIS
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.In blacklist.h
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.Ft struct blacklist *
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.Fn blacklist_open "void"
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.Ft void
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.Fn blacklist_close "struct blacklist *cookie"
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.Ft int
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.Fn blacklist "int action" "int fd" "const char *msg"
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.Ft int
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.Fn blacklist_r "struct blacklist *cookie" "int action" "int fd" "const char *msg"
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.Ft int
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.Fn blacklist_sa "int action" "int fd" "const struct sockaddr *sa" "socklen_t salen" "const char *msg"
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.Ft int
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.Fn blacklist_sa_r "struct blacklist *cookie" "int action" "int fd" "const struct sockaddr *sa" "socklen_t salen" "const char *msg"
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.Sh DESCRIPTION
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These functions can be used by daemons to notify
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.Xr blacklistd 8
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about successful and failed remote connections so that blacklistd can
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block or release port access to prevent Denial of Service attacks.
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.Pp
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The function
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.Fn blacklist_open
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creates the necessary state to communicate with
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.Xr blacklistd 8
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and returns a pointer to it, or
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.Dv NULL
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on failure.
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.Pp
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The
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.Fn blacklist_close
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function frees all memory and resources used.
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.Pp
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The
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.Fn blacklist
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function sends a message to
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.Xr blacklistd 8 ,
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with an integer
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.Ar action
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argument specifying the type of notification,
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a file descriptor
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.Ar fd
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specifying the accepted file descriptor connected to the client,
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and an optional message in the
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.Ar msg
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argument.
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.Pp
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The
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.Ar action
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parameter can take these values:
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.Bl -tag -width ".Va BLACKLIST_ABUSIVE_BEHAVIOR"
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.It Va BLACKLIST_AUTH_FAIL
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There was an unsuccessful authentication attempt.
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.It Va BLACKLIST_AUTH_OK
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A user successfully authenticated.
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.It Va BLACKLIST_ABUSIVE_BEHAVIOR
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The sending daemon has detected abusive behavior
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from the remote system.
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The remote address should
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be blocked as soon as possible.
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.It Va BLACKLIST_BAD_USER
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The sending daemon has determined the username
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presented for authentication is invalid.
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The
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.Xr blacklistd 8
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daemon compares the username to a configured list of forbidden
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usernames and
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blocks the address immediately if a forbidden username matches.
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(The
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.Ar BLACKLIST_BAD_USER
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support is not currently available.)
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.El
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.Pp
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The
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.Fn blacklist_r
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function is more efficient because it keeps the blacklist state around.
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.Pp
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The
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.Fn blacklist_sa
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and
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.Fn blacklist_sa_r
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functions can be used with unconnected sockets, where
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.Xr getpeername 2
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will not work, the server will pass the peer name in the message.
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.Pp
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In all cases the file descriptor passed in the
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.Fa fd
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argument must be pointing to a valid socket so that
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.Xr blacklistd 8
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can establish ownership of the local endpoint
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using
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.Xr getsockname 2 .
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.Pp
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By default,
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.Xr syslogd 8
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is used for message logging.
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The internal
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.Fn bl_create
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function can be used to create the required internal
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state and specify a custom logging function.
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.Sh RETURN VALUES
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The function
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.Fn blacklist_open
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returns a cookie on success and
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.Dv NULL
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on failure setting
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.Dv errno
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to an appropriate value.
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.Pp
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The functions
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.Fn blacklist ,
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.Fn blacklist_sa ,
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and
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.Fn blacklist_sa_r
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return
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.Dv 0
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on success and
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.Dv \-1
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on failure setting
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.Dv errno
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to an appropriate value.
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.Sh SEE ALSO
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.Xr blacklistd.conf 5 ,
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.Xr blacklistd 8
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.Sh AUTHORS
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.An Christos Zoulas
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