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156 lines
5.5 KiB
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156 lines
5.5 KiB
Plaintext
The GNU C library contains an NSS module for the Hesiod name service.
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Hesiod is a general name service for a variety of applications and is
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based on the Berkeley Internet Name Daemon (BIND).
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Introduction
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============
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The Hesiod NSS module implements access to all relevant standard
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Hesiod types, which means that Hesiod can be used for the `group',
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`passwd' and `services' databases. There is however a restriction.
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In the same way that it is impossible to use `gethostent()' to iterate
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over all the data provided by DNS, it is not possible to scan the
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entire Hesiod database by means of `getgrent()', `getpwent()' and
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`getservent()'. Besides, Hesiod only provides support for looking up
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services by name and not for looking them up by port. In essence this
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means that the Hesiod name service is only consulted as a result of
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one of the following function calls:
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* getgrname(), getgrgid()
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* getpwname(), getpwuid()
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* getservbyname()
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and their reentrant counterparts.
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Configuring your systems
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========================
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Configuring your systems to make use the Hesiod name service requires
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one or more of the following steps, depending on whether you are
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already running Hesiod in your network.
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Configuring NSS
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---------------
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First you should modify the file `/etc/nsswitch.conf' to tell
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NSS for which database you want to use the Hesiod name service. If
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you want to use Hesiod for all databases it can handle your
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configuration file could look like this:
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# /etc/nsswitch.conf
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#
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# Example configuration of GNU Name Service Switch functionality.
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#
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passwd: db files hesiod
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group: db files hesiod
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shadow: db files
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hosts: files dns
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networks: files dns
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protocols: db files
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services: db files hesiod
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ethers: db files
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rpc: db files
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For more information on NSS, please refer to the `The GNU C Library
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Reference Manual'.
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Configuring Hesiod
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------------------
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Next, you will have to configure Hesiod. If you are already running
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Hesiod in your network, you probably already have a file named
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`hesiod.conf' on your machines (probably as `/etc/hesiod.conf' or
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`/usr/local/etc/hesiod.conf'). The Hesiod NSS module looks for
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`/etc/hesiod.conf' by default. If there is no configuration file you
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will want to create your own. It should look something like:
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rhs=.your.domain
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lhs=.ns
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classes=in,hs
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The optional classes settings specifies which DNS classes Hesiod
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should do lookups in. Possible values are IN (the preferred class)
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and HS (the deprecated class, still used by some sites).
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You may specify both classes separated by a comma to try one class
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first and then the other if no entry is available in the first
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class. The default value of the classes variable is `IN,HS'.
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The value of rhs can be overridden by the environment variable
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`HES_DOMAIN'.
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Configuring your name servers
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-----------------------------
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In addition, if you are not already running Hesiod in your network,
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you need to create Hesiod information on your central name servers.
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You need to run `named' from BIND 4.9 or higher on these servers, and
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make them authoritative for the domain `ns.your.domain' with a line in
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`/etc/named.boot' reading something like:
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primary ns.your.domain named.hesiod
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or if you are using the new BIND 8.1 or higher add something to
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`/etc/named.conf' like:
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zone "ns.your.domain" {
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type master;
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file "named.hesiod";
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};
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Then in the BIND working directory (usually `/var/named') create the
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file `named.hesiod' containing data that looks something like:
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; SOA and NS records.
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@ IN SOA server1.your.domain admin-address.your.domain (
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40000 ; serial - database version number
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1800 ; refresh - sec servers
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300 ; retry - for refresh
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3600000 ; expire - unrefreshed data
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7200 ) ; min
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NS server1.your.domain
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NS server2.your.domain
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; Actual Hesiod data.
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libc.group TXT "libc:*:123:gnu,gnat"
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123.gid CNAME libc.group
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gnu.passwd TXT "gnu:*:4567:123:GNU:/home/gnu:/bin/bash"
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456.uid CNAME mark.passwd
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nss.service TXT "nss tcp 789 switch sw "
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nss.service TXT "nss udp 789 switch sw"
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where `libc' is an example of a group, `gnu' an example of an user,
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and `nss' an example of a service. Note that the format used to
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describe services differs from the format used in `/etc/services'.
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For more information on `named' refer to the `Name Server Operations
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Guide for BIND' that is included in the BIND distribution.
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Security
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========
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Note that the information stored in the Hesiod database in principle
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is publicly available. Care should be taken with including vulnerable
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information like encrypted passwords in the Hesiod database. There
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are some ways to improve security by using features provided by
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`named' (see the discussion about `secure zones' in the BIND
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documentation), but one should keep in mind that Hesiod was never
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intended to distribute passwords. In the origional design
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authenticating users was the job of the Kerberos service.
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More information
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================
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For more information on the Hesiod name service take a look at some of
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the papers in ftp://athena-dist.mit.edu:/pub/ATHENA/usenix and the
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documentation that accompanies the source code for the Hesiod name
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service library in ftp://athena-dist.mit.edu:/pub/ATHENA/hesiod.
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There is a mailing list at MIT for Hesiod users, hesiod@mit.edu. To
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get yourself on or off the list, send mail to hesiod-request@mit.edu.
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