sslinfo - information about current SSL certificate for PostgreSQL
==================================================================
Author: Victor Wagner <vitus@cryptocom.ru>, Cryptocom LTD
E-Mail of Cryptocom OpenSSL development group: <openssl@cryptocom.ru>


1. Notes
--------
This extension won't build unless your PostgreSQL server is configured
with --with-openssl.  Information provided with these functions would
be completely useless if you don't use SSL to connect to database.


2. Functions Description
------------------------

2.1. ssl_is_used()
~~~~~~~~~~~~~~~~~~

	ssl_is_used() RETURNS boolean;

Returns TRUE, if current connection to server uses SSL and FALSE
otherwise.

2.2. ssl_client_cert_present()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	ssl_client_cert_present() RETURNS boolean

Returns TRUE if current client have presented valid SSL client
certificate to the server and FALSE otherwise (e.g., no SSL,
certificate hadn't be requested by server).

2.3. ssl_client_serial() 
~~~~~~~~~~~~~~~~~~~~~~~~

	ssl_client_serial() RETURNS numeric

Returns serial number of current client certificate.  The combination
of certificate serial number and certificate issuer is guaranteed to
uniquely identify certificate (but not its owner -- the owner ought to
regularily change his keys, and get new certificates from the issuer).

So, if you run you own CA and allow only certificates from this CA to
be accepted by server, the serial number is the most reliable (albeit
not very mnemonic) means to indentify user.

2.4. ssl_client_dn()
~~~~~~~~~~~~~~~~~~~~
	
	ssl_client_dn() RETURNS text

Returns the full subject of current client certificate, converting
character data into the current database encoding.  It is assumed that
if you use non-Latin characters in the certificate names, your
database is able to represent these characters, too.  If your database
uses the SQL_ASCII encoding, non-Latin characters in the name will be
represented as UTF-8 sequences.

The result looks like '/CN=Somebody /C=Some country/O=Some organization'.

2.5. ssl_issuer_dn()
~~~~~~~~~~~~~~~~~~~~

Returns the full issuer name of the client certificate, converting
character data into current database encoding.

The combination of the return value of this function with the
certificate serial number uniquely identifies the certificate.

The result of this function is really useful only if you have more
than one trusted CA certificate in your server's root.crt file, or if
this CA has issued some intermediate certificate authority
certificates.

2.6. ssl_client_dn_field()
~~~~~~~~~~~~~~~~~~~~~~~~~~

	ssl_client_dn_field(fieldName text) RETURNS text

This function returns the value of the specified field in the
certificate subject.  Field names are string constants that are
converted into ASN1 object identificators using the OpenSSL object
database.  The following values are acceptable:

	commonName (alias CN)
	surname (alias SN)
	name
	givenName (alias GN)
	countryName (alias C) 
	localityName (alias L)
	stateOrProvinceName (alias ST)
	organizationName (alias O)
	organizationUnitName (alias OU)
	title
	description
	initials
	postalCode
	streetAddress
	generationQualifier
	description
	dnQualifier
	x500UniqueIdentifier
	pseudonim
	role
	emailAddress
	
All of these fields are optional, except commonName.  It depends
entirely on your CA policy which of them would be included and which
wouldn't.  The meaning of these fields, howeer, is strictly defined by
the X.500 and X.509 standards, so you cannot just assign arbitrary
meaning to them.

2.7 ssl_issuer_field()
~~~~~~~~~~~~~~~~~~~

	ssl_issuer_field(fieldName text) RETURNS text;

Does same as ssl_client_dn_field, but for the certificate issuer
rather than the certificate subject.