.\" $NetBSD: libblocklist.3,v 1.3.6.1 2024/10/08 11:16:17 martin Exp $ .\" .\" Copyright (c) 2015 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Christos Zoulas. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 THE FOUNDATION 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. .\" .Dd August 2, 2024 .Dt LIBBLOCKLIST 3 .Os .Sh NAME .Nm blocklist_open , .Nm blocklist_open2 , .Nm blocklist_close , .Nm blocklist_r , .Nm blocklist , .Nm blocklist_sa , .Nm blocklist_sa_r .Nd Blocklistd notification library .Sh LIBRARY .Lb libblocklist .Sh SYNOPSIS .In blocklist.h .Ft struct blocklist * .Fn blocklist_open "void" .Ft struct blocklist * .Fn blocklist_open2 "void (*logger)(int, struct syslog_data *, va_list)" .Ft void .Fn blocklist_close "struct blocklist *cookie" .Ft int .Fn blocklist "int action" "int fd" "const char *msg" .Ft int .Fn blocklist_r "struct blocklist *cookie" "int action" "int fd" "const char *msg" .Ft int .Fn blocklist_sa "int action" "int fd" "const struct sockaddr *sa" "socklen_t salen" "const char *msg" .Ft int .Fn blocklist_sa_r "struct blocklist *cookie" "int action" "int fd" "const struct sockaddr *sa" "socklen_t salen" "const char *msg" .Sh DESCRIPTION These functions can be used by daemons to notify .Xr blocklistd 8 about successful and failed remote connections so that blocklistd can block or release port access to prevent Denial of Service attacks. .Pp The function .Fn blocklist_open creates the necessary state to communicate with .Xr blocklistd 8 and returns a pointer to it, or .Dv NULL on failure. .Pp The function .Fn blocklist_open2 is similar to .Fn blocklist_open but allows a .Fa logger to be specified. If the .Fa logger is .Dv NULL , then no logging is performed. .Pp The .Fn blocklist_close function frees all memory and resources used. .Pp The .Fn blocklist function sends a message to .Xr blocklistd 8 , with an integer .Ar action argument specifying the type of notification, a file descriptor .Ar fd specifying the accepted file descriptor connected to the client, and an optional message in the .Ar msg argument. .Pp The .Ar action parameter can take these values: .Bl -tag -width ".Dv BLOCKLIST_ABUSIVE_BEHAVIOR" .It Dv BLOCKLIST_AUTH_FAIL There was an unsuccessful authentication attempt. .It Dv BLOCKLIST_AUTH_OK A user successfully authenticated. .It Dv BLOCKLIST_ABUSIVE_BEHAVIOR The sending daemon has detected abusive behavior from the remote system. The remote address should be blocked as soon as possible. .It Dv BLOCKLIST_BAD_USER The sending daemon has determined the username presented for authentication is invalid. The .Xr blocklistd 8 daemon compares the username to a configured list of forbidden usernames and blocks the address immediately if a forbidden username matches. (The .Dv BLOCKLIST_BAD_USER support is not currently available.) .El .Pp The .Fn blocklist_r function is more efficient because it keeps the blocklist state around. .Pp The .Fn blocklist_sa and .Fn blocklist_sa_r functions can be used with unconnected sockets, where .Xr getpeername 2 will not work, the server will pass the peer name in the message. .Pp In all cases the file descriptor passed in the .Fa fd argument must be pointing to a valid socket so that .Xr blocklistd 8 can establish ownership of the local endpoint using .Xr getsockname 2 . .Pp By default, .Xr syslogd 8 is used for message logging. The internal .Fn bl_create function can be used to create the required internal state and specify a custom logging function. .Sh RETURN VALUES The function .Fn blocklist_open returns a cookie on success and .Dv NULL on failure setting .Dv errno to an appropriate value. .Pp The functions .Fn blocklist , .Fn blocklist_sa , and .Fn blocklist_sa_r return .Dv 0 on success and .Dv \-1 on failure setting .Dv errno to an appropriate value. .Sh SEE ALSO .Xr blocklistd.conf 5 , .Xr blocklistd 8 .Sh AUTHORS .An Christos Zoulas