Initial docs for the OpenSSL library configuration via openssl.cnf

The OpenSSL CONF library can be used to read configuration files.

It is used for the OpenSSL master configuration file B<openssl.cnf>

and in a few other places like B<SPKAC> files and certificate extension

files for the B<x509> utility.

files for the B<x509> utility. OpenSSL applications can also use the

CONF library for their own purposes.

A configuration file is divided into a number of sections. Each section

starts with a line B<[ section_name ]> and ends when a new section is

a B<value> string can be spread across multiple lines. In addition

the sequences B<\n>, B<\r>, B<\b> and B<\t> are recognized.

=head1 OPENSSL LIBRARY CONFIGURATION

In OpenSSL 0.9.7 and later applications can automatically configure certain

aspects of OpenSSL using the master OpenSSL configuration file, or optionally

an alternative configuration file. The B<openssl> utility includes this

functionality: any sub command uses the master OpenSSL configuration file

unless an option is used in the sub command to use an alternative configuration

file.

To enable library configuration the default section needs to contain an 

appropriate line which points to the main configuration section. The default

name is B<openssl_conf> which is used by the B<openssl> utility. Other

applications may use an alternative name such as B<myapplicaton_conf>.

The configuration section should consist of a set of name value pairs which

contain specific module configuration information. The B<name> represents

the name of the I<configuration module> the meaning of the B<value> is 

module specific: it may, for example, represent a further configuration

section containing configuration module specific information. E.g.

 openssl_conf = openssl_init

 [openssl_init]

 oid_section = new_oids

 engines = engine_section

 [new_oids]

 ... new oids here ...

 [engine_section]

 ... engine stuff here ...

Currently there are two supported configuration modules supported. One for

ASN1 objects another for ENGINE configuration.

=head2 ASN1 OBJECT CONFIGURATION MODULE

This module has the name B<oid_section>. The value of this variable points

to a section containing name value pairs of OIDs: the name is the OID short

and long name, the value is the numerical form of the OID. Although some of

the B<openssl> utility sub commands already have their own ASN1 OBJECT section

functionality not all do. By using the ASN1 OBJECT configuration module

B<all> the B<openssl> utility sub commands can see the new objects as well

as any compliant applications. For example:

 [new_oids]

 some_new_oid = 1.2.3.4

 some_other_oid = 1.2.3.5

=head2 ENGINE CONFIGURATION MODULE

To be continued...

=head1 NOTES

If a configuration file attempts to expand a variable that doesn't exist

then an error is flagged and the file will not load. This can happen

if an attempt is made to expand an environment variable that doesn't

exist. For example the default OpenSSL master configuration file used

the value of B<HOME> which may not be defined on non Unix systems.

exist. For example in a previous version of OpenSSL the default OpenSSL

master configuration file used the value of B<HOME> which may not be

defined on non Unix systems and would cause an error.

This can be worked around by including a B<default> section to provide

a default value: then if the environment lookup fails the default value