1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
.\" $NetBSD: libblocklist.3,v 1.7 2025/02/05 20:14:30 christos 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 February 5, 2025
.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 Va BLOCKLIST_BAD_USER
The sending daemon has determined the username presented for
authentication is invalid.
This is considered as one failure count.
.It Va BLOCKLIST_AUTH_FAIL
There was an unsuccessful authentication attempt.
This is considered as two failure counts together.
.It Va BLOCKLIST_ABUSIVE_BEHAVIOR
The sending daemon has detected abusive behavior from the remote system.
This is considered as a total immediate failure.
The remote address will be blocked as soon as possible.
.It Va BLOCKLIST_AUTH_OK
A valid user successfully authenticated.
Any entry for the remote address will be removed as soon as possible.
.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
|
