The purpose is to cause as few changes to the code you are trying to port as
possible. Some changes are inevitable, particularly when crypto outside of
SSL is being used, but for a general-purpose SSL client or server the goal
is that 80% of the code can remain untouched.

Currently Supports:

    * Creating an SSL server listener and accepting requests
    * Creating an SSL client socket and making requests
    * Ciphers that should be compatible with OpenSSL
    * Client certificate authentication
    * Token password prompting/handlng

Requires:

NSPR 4.6.4 or higher
NSS 3.11.4 or higher

How Do I Use the Library:

For the short term you will need to use an NSS database. This consists of 3
files: cert8.db, key3.db and secmod.db located in the same directory. In order
for the target to find the right database you need to set the environment
variable SSL_DIR to the location of your NSS database (unless you have a
server cert installed in the default NSS database in /etc/pki/nssdb)

The code doesn't currently support file-based certificates. It uses the path
of the certificate passed to SSL_CTX_use_certificate_file() and
SSL_CTX_use_certificate_chain_file() as the nickname of the certificate in
the NSS database. To list the certificates (and their nickname) in an NSS
database you can use this:

% certutil -L -d /path/to/database

If you have a PKCS#12 file containing you can import it into your NSS database
with:

% pk12util -i mycert.p12 -d /path/to/database

We currently lack nice, importable autoconf rules. You will need to tell your
application where to find the NSPR and NSS include and libraries. You can use
pkg-config to determine this. The package names are nss and nspr.

So far we are use HAVE_NSS and HAVE_OPENSSL to differentiate between NSS and
OpenSSL.

You want to include "nss_compat_ossl.h". Be careful to not include any OpenSSL
header files.

Some specific things to watch out for:

- OpenSSL CRL handling is very different from NSS so any OpenSSL CRL handling
code should be ifdef'd out. NSS handles CRLs directly. Users can use the
crlutil tool to load them into the NSS database.

- The callbacks for info_callback and verify_callback are made but from what
I've seen those functions use very diverse OpenSSL calls that aren't supported
yet (and may never be). These callbacks will likely all need to be rewritten
for NSS.

- Few of the BIO_ calls are implemented. If these are used extensively in the
target application then some major rewriting may be needed. Best to request
some assistance before proceeding.

- I didn't use OpenSSL structures in most cases so any programs trying to
access specific elements may need to change (or the library does).

- NSS supports two modes for its SSL cache: threaded and multi-process. The
nss_compat_ossl code currently initializes the cache for multi-threaded
operation. If you need multi-process you will need to call these in your
application:

    SSL_CTX_set_timeout(ctx, timeout);
    SSL_ShutdownServerSessionIDCache();
    SSL_ConfigMPServerSIDCache(0, timeout, timeout, NULL);

Things to be done:

- We should import referenced certificates on the fly into our NSS database.
A PKCS#11 module to do this has been started but requires NSS 3.12 so it is
of limited use in the short-term.

- Many missing pieces of the API