1INNBIND(8) InterNetNews Documentation INNBIND(8)
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6 innbind - Helper program to bind sockets to privileged ports
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9 innbind [-p] fd,family,address,port [...]
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12 innbind is a helper program that's not meant to be run directly.
13 Instead, innd and nnrpd use it internally to bind to ports that require
14 root privileges to bind to.
15 This program must be installed setuid root in order for innd or nnrpd
17 to bind to ports under 1024. The only functions that it's willing to
18 perform are to bind an open file descriptor to a given address and port
19 or to create a new socket, bind it, and return the bound socket to its
20 caller. It can only be run as the news user (as specified at configure
21 time), and will only bind to ports 119, 433, 563, an additional port
22 specified with the --with-innd-port argument to configure, or ports
23 numbered 1024 or higher.
24 Each argument to innbind must be a comma-separated list of four
26 elements. The first is the file descriptor number that should be
27 bound, the second is the numeric family of the socket (AF_INET or
28 AF_INET6), the third is the local address to bind to (in dotted-quad
29 format for IPv4 and in colon-separated address format for IPv6), and
30 the fourth is the port number. To bind to all addresses with IPv4, use
31 0.0.0.0 as the address. To bind to all addresses with IPv6, use "::"
32 as the address.
33 Multiple arguments can be specified to tell innbind to bind multiple
35 sockets at the same time. Any errors (other than permission denied
36 -- see below) encountered will cause innbind to abort, and error
37 messages will be sent both to syslog and to standard error.
38 By default, innbind attempts to just bind the already open file
40 descriptor that it inherits from its caller. For each successfully
41 bound file descriptor (in the order given on the command line), innbind
42 prints "ok" and a newline to its standard output.
43 On some systems (apparently just STREAMS-based systems), however, even
45 a setuid root program cannot bind a socket to a privileged port that
46 was created by a process that didn't have permissions. If innbind gets
47 permission denied when trying to bind a socket, it will print "no" and
48 a newline to its standard output. It will then create a new socket,
49 bind it as specified, and then attempt to pass that socket back to its
50 caller using the I_SENDFD STREAMS ioctl. The caller should receive
51 that file descriptor with I_RECVFD and use it instead of the one that
52 it created.
53 Note that file descriptor passing is only supported on STREAMS-based
55 systems since it is done with ioctls over a pipe. However, it is
56 believed that those systems are exactly the systems that can't simply
57 bind the inherited file descriptor. If this assumption proves to be
58 incorrect, traditional BSD file descriptor passing over a Unix domain
59 socket will have to be added.
60
62 -p If given as the first command-line argument, no attempt will be
63 made to bind the inherited file descriptor and innbind will only
64 try creation of a new file descriptor and passing it back via
65 standard output. This option is primarily useful for testing.
66
68 As innbind is normally installed setuid root, security is even more of
69 an issue for it than for other parts of INN. It is a fairly short
70 program, and if you understand C, you are encouraged to audit it
71 yourself to be certain that it does only what it is supposed to do.
72 The only INN library functions it uses are the vector functions, the
73 message functions for error reporting, and xstrdup.
74 The ports that will be bound are restricted to prevent potential
76 attacks made possible by the ability to bind low-numbered ports, such
77 as exploits of the rsh(1) family of commands on some systems. If
78 innbind is installed setuid root, it can only be executed by the news
79 user to prevent other users on the system from being able to bind to
80 even those few privileged ports that it allows.
81 innbind uses no external configuration files; the only files it might
83 open are through the system getpwnam(3) service to get the UID of the
84 news user. The only user input that it accepts are its command-line
85 arguments.
86
88 innbind may log the following messages to syslog and print them to
89 standard error.
90 cannot create socket for %s: %s
92 (Fatal) innbind fell back on attempting to create a new socket to
93 bind for the given argument, and the socket creation failed.
94 cannot bind socket for %s: %s
96 (Fatal) Calling bind for the socket corresponding to the given
97 argument failed with a system error. If the error indicates
98 permission denied, make sure that innbind is setuid root. This can
99 also be caused by trying to use IPv6 on a system whose kernel does
100 not support it.
101 cannot bind to restricted port %hu in %s
103 (Fatal) The port number portion of the given command-line argument
104 is for a port below 1024 which is not 119, 433, 563, or a port
105 given to --with-innd-port at configure time. Other ports are not
106 allowed for security reasons.
107 cannot get socket options for file descriptor %d: %s
109 (Fatal) innbind was unable to get the socket options for that file
110 descriptor. The most likely cause of this error is passing the
111 wrong file descriptor number to innbind (a file descriptor that
112 isn't open, or that corresponds to a regular file rather than a
113 network socket).
114 cannot get UID for %s
116 (Fatal) innbind was unable to get the UID for the news user
117 specified during configure (and defaulting to "news"). This
118 normally means that user isn't in the system passwd file.
119 cannot mark socket reusable for %s: %s
121 (Fatal) innbind created a new socket for the given argument but was
122 unable to mark its bind address reusable (the SO_REUSEADDR socket
123 option).
124 cannot pass file descriptor: %s
126 (Fatal) innbind created and bound a new file descriptor but was
127 unable to pass it back to its caller via its standard output, using
128 the I_SENDFD STREAMS ioctl.
129 invalid file descriptor %d: not SOCK_STREAM
131 (Fatal) The given file descriptor is not a SOCK_STREAM socket.
132 innbind can only bind SOCK_STREAM sockets.
133 invalid IPv4 address %s in %s
135 (Fatal) The IPv4 address specified in the given command-line option
136 could not be parsed by inet_aton(3). IPv4 addresses should be
137 specified in the standard dotted-quad format (10.2.3.4).
138 invalid IPv6 address %s in %s
140 (Fatal) The IPv6 address specified in the given command-line option
141 could not be parsed by inet_pton(3). IPv6 addresses should be
142 specified in RFC 4291 format (1080:0:0:0:8:800:200C:417A or
143 1080::8:800:200C:417A).
144 invalid command-line argument %s
146 (Fatal) The specified command-line argument could not be parsed or
147 was not in the correct format.
148 invalid file descriptor %s in %s
150 (Fatal) The file descriptor portion of the given command-line
151 argument is not a non-negative integer.
152 invalid port number %s in %s
154 (Fatal) The port number portion of the given command-line argument
155 is not a non-negative integer.
156 invalid protocol family %s in %s
158 (Fatal) The protocol family portion of the given command-line
159 argument is not a non-negative integer. It should be equal to
160 either AF_INET or AF_INET6 on the system where innbind is run.
161 must be run by user %s (%lu), not %lu
163 (Fatal) When setuid root, innbind may only be run by the news user
164 as specified at configure time ("news" by default), for security
165 reasons.
166 no addresses specified
168 (Fatal) No arguments were given on the command line (except maybe
169 -p).
170 port may not be zero in %s
172 (Fatal) The port number portion of the given command-line argument
173 was zero.
174 unknown protocol family %s in %s
176 (Fatal) The protocol number portion of the given command-line
177 argument is neither AF_INET nor AF_INET6.
178
180 As mentioned above, innbind is never run directly, only by innd and
181 other programs that need to bind to and listen to network ports.
182 Sample invocations by innd would be:
183 innbind 3,10,::,119
185 to bind the IPv6 socket on file descriptor 3 to port 119, all
187 addresses, or:
188 innbind 6,2,10.0.0.3,433
190 to bind the IPv4 socket on file descriptor 6 to port 433 in the address
192 10.0.0.3.
193
195 Written by Russ Allbery <eagle@eyrie.org> for InterNetNews.
196
198 inet_aton(3), inet_pton(3), innd(8), nnrpd(8).
199INN 2.6.5 2022-01-23 INNBIND(8)