YPSERV.ACL(5) | File Formats Manual | YPSERV.ACL(5)

# NAME

`ypserv.acl` — ypserv(8) access control configuration

# DESCRIPTION

The `ypserv.acl` file controls which hosts can connect to the yp(8) server.

The format is more complex than the format for securenet(5). The first two words on each line controls if the line will `allow` or `deny` access for a `host`, network (`net`), or `all` hosts.

The YP server reads the configuration file and builds a list in memory. This list is processed from the beginning for every incoming request. As soon as a match is found in the list, the search terminates and it returns success or failure depending on which of `allow` or `deny` was specified. If no match was found in the list, success is returned.

If access is denied, every call will cause a “no such domain” error for the caller.

Normally both the local hostname and localhost must be allowed access. Otherwise ypserv(8) might not work correctly.

There is no default name for this file. Start ypserv(8) with `-a` filename to read a file with this format.

The following syntax may be used:

`allow`|`deny` `host` hostname|ip-address

If `hostname` has more than one IP address, they will all be added to the list.

`allow`|`deny` `net` netnumber [`netmask` netnumber]

If the `netmask` part of the command isn't given then the netmask will be assumed to be a class A, B or C net depending on the net number.

`allow`|`deny` `all`

A line containing one of these commands will always match any host.

# FILES

/var/yp/ypserv.acl
  a ypserv(8) configuration file

# EXAMPLES

A configuration file might look like the following:

    # This is an example of an access control file to be used by ypserv.
    #
    # This file is parsed line by line. First match will terminate the check
    # of the caller.
    #

    ###########################################################################
    # This is the commands that will match a single host
    #
    #	allow host <hostname|ip-address>
    #	deny host <hostname|ip-address>
    #
    # To process hostname gethostbyname is called. If the hostname has
    # multiple ip-addresses all will be added (I hope). ip-address
    # processed by inet_aton.
    allow host localhost
    allow host myypserver
    deny host jodie

    ###########################################################################
    # This is the commands that will match a network
    #
    #	allow net <netnumber> [netmask <netnumber>]
    #	deny net <netnumber> [netmask <netnumber>]
    #
    # inet_aton is used for netnumber.
    # inet_aton both access numbers as 255.255.255.0 and 0xffffff00.
    #
    # If netmask isn't given the parser will assume netmask from the first bits
    # of the network number. So if the network is subneted the you have to add
    # the netmask. In my case I've got the network 139.58.253.0 at home so to
    # allow any of my computers to talk with the server I need the following
    # line
    #
    allow net 139.58.253.0 netmask 255.255.255.0

    ###########################################################################
    # At last we have a command that will match any caller:
    #
    #	allow all
    #	deny all
    #

    # reject all connections
    deny all

# SEE ALSO

securenet(5), yp(8), ypserv(8)

# AUTHORS

Mats O Jansson <moj@stacken.kth.se>

March 31, 2022 | Debian