rpki.net/openssl

$Id$ -*- Text -*-

This directory once held a hacked version of OpenSSL with support for
the RFC 3779 X.509 v3 extensions. The resulting patch was accepted by
the OpenSSL project and is now part of the standard OpenSSL release.
You do, however, need to enable the RFC 3779 support when compiling
OpenSSL, as it's off by default (normal for new additions). To build,
do:

./config enable-rfc3779

The normal build process for the RPKI toolkit detects whether it needs
its own copy of the OpenSSL libraries and builds one from the sources
here if necessary. In theory, this is all automatic and you never
need to do anything about it, at least on platforms where we've tested
this code. If you're on a new platform and this doesn't just work,
please report the problem, but if it's 03:00 and you need this to work
-now-, start by looking at ../configure.ac, or just try building
OpenSSL yourself here with the RFC 3779 code enabled.

The next section of this file describes the openssl.conf syntax
associated with the RFC 3779 extensions; the rest is primarily of
historical interest at this point.



This is what the current openssl.conf syntax looks like for the RFC
3779 certificate extensions. Syntax is admittedly wretched, because
it has to work with the existing OpenSSL code. Within that
restriction, I've attempted to make this look as much as practical
like the existing OpenSSL support for "multi-valued" extensions. RFC
3779 ASN.1 provided for easy reference.

Notes:

* Ranges are denoted with a hyphen, prefix lengths with a slash.

* The "@" syntax indicating indirection through a separate section
is part of the stock OpenSSL multi-valued extension support.

* I didn't attempt to guess which addresses are IPv4 and which are
IPv6 from the syntax, since the opensssl.conf multi-value syntax
needs tags anyway.

* SAFI support is present but minimal. If you want a SAFI, you have
to specify its numeric value. It would be trivial to add additional
keywords for specific SAFIs if there were a reason to do so.

* The "sbgp-" names were already present in OpenSSL's table of known
extension OIDs, so we just used them.

###

# An address extension, all specified on one line

sbgp-ipAddrBlock = critical, IPv4:10.1.1.1/32, IPv4:10.2.0.0-10.3.255.255

# An address extension, all specified on one line, with inheritance

sbgp-ipAddrBlock = critical, IPv4:inherit, IPv6:2002::/16

# An address extension using SAFIs

sbgp-ipAddrBlock = critical, IPv4-SAFI:1:10.1.1.1/32, IPv6-SAFI:1:2002::/16

# Address extension using an indirect section

sbgp-ipAddrBlock = critical, @addr-section

[addr-section]

IPv4.0 = 10.0.0.1
IPv4.1 = 10.0.1.0/24
IPv4.2 = 10.2.0.0 - 10.3.255.255
IPv6.0 = 2002:1::/64
IPv6.1 = 2002:2:: - 2002:8::ffff:ffff:ffff:ffff:ffff

###

# An ASID extension, all specified on one line:

sbgp-autonomousSysNum = critical, AS:44, RDI:33-45

# ASID extension on one line using inheritance

sbgp-autonomousSysNum = critical, AS:55, RDI:inherit

# ASID extension using an indirect section

sbgp-autonomousSysNum = critical, @asid-section

[asid-section]

AS.0 = 44
AS.1 = 55 - 77
RDI.0 = 33



Some notes on OpenSSL internals.

O'Reilly "Network Security with OpenSSL" is a bit dated (four years
old, corresponds roughly to OpenSSL 0.9.7), but still appears to be
the closest thing there is to coherent documentation. Some updates
and machine readable copies of examples are available at
http://www.opensslbook.com/. In spite of its age, the book is useful
as it gives a readable overview of bit and pieces of OpenSSL's
internal programming environment which one would otherwise have to
absorb from the code via osmosis. Chapter 10 is particularly useful,
as are the sections on error handling and abstract I/O (the ERR and
BIO packages, respectively) in chapter 4.

OpenSSL's own doc is very patchy, although fairly extensive in places.
Most of it eventually comes down to "Use the Source, Luke" with
pointers on which bit of source serves as an interesting example.

For x509v3 extentions, the place to start is doc/openssl.txt,
which, oddly, turns out to be mostly about certificate extensions. It
gives an overview of the mechanisms, in particular of the method
routine interface for certificate extensions. For something like the
RFC 3779 extensions, it's pretty clear that we need to use a "raw"
extension (which, as far as I can tell, just means that the RFC 3779
stuff is complicated enough that the extension handler has to do a lot
of work to deal with a complex ASN.1 structure that the rest of the
code doesn't know much about).

General note on global symbols in OpenSSL: always look at the header
file for any global symbol you're using. In fact, it's probably best
to do a global search (m-x tags-search if you're an emacs user) for
all instances of a global symbol before attempting to use it, as there
are a lot of things that one just has to know about how all the global
stuff hangs together. There are header files full of magic
definitions that one just has to know need to be extended. There are
magic pre-sorted lists of handlers that one just needs to know about.
Little or none of this is documented. Use the Source, Luke.

In some cases -portions- of files are automatically generated by Perl
scripts (eg, the per-type stack definitions in safestack.h). Ouch.
If you see a large block of very repetitive stuff, check for comments
indicating that it's automatically generated.

Oh, and the indentation style is demented.

Header files you definitely need to read if you're going to touch this
stuff:

crypto/x509v3/x509v3.h
crypto/x509v3/ext_dat.h
crypto/stack/safestack.h
crypto/asn1/asn1t.h
crypto/asn1/asn1.h
crypto/objects/objects.h

Automatically generated header files you'll need to skim, then go read
the input files listed in the header comments and perhaps the
generating Perl code:

crypto/objects/obj_mac.h
crypto/objects/obj_dat.h

Much of the code shows a heavy Perl influence, presumably dating back
clear to Eric Young. Some of the internal data structure operators
have names that only make sense to a Perl programmer. Stacks are
really lists, and may be sorted. Where code is automatically
generated, it's done by Perl scripts. The configuration language for
the whole package is a Perl script. Assembly code is all wrapped up
inside perl scripts in a moderately clever attempt at being able to
write the assembly language only once and use it with various
assemblers with nontrivially different syntax. Much of the
documentation markup (including manual pages) for the C code is .pod.

A lot of the missing documentation is buried in ssleay.txt, which the
other documentation says not to read because it's so old. But it's
where Eric explains all the basic data structures and expected usage
as of the dawn of time, so most of the stuff that's so old that it's
undocumented is really documented there.

xxx_new() functions set pointers of sub-structures to NULL or allocate
the substructures (one can leak memory if one doesn't know or check
which a particular xxx_new() function has done...), and the xxx_free()
functions clean up complex structures. So be sure to set unused
pointers to NULL if one has been fiddling.

Make sure that memory leak detection (CRYPTO_MDEBUG) is turned on when
debugging.

"make update" in the top level runs all the magic perl code that
grovels through the code generating error codes, safestacks, etc.
util/mkstack.pl finds DECLARE_STACK_OF() declarations and generates
safestack definitions automatically if you run "make update". Be
afraid. Be very very afraid.

My initial test configuration was:

./Configure debug -DDEBUG_SAFESTACK

which tried to pull in -lefence (/usr/ports/devel/ElectricFence), so I
installed that. Sadly, ElectricFence is not kidding when it says it
is very very very slow, but it was the bignum debugging printouts that
were driving me nuts, so I ended up creating my own "debug-sra"
configuration for the options I want:

"debug-sra", "gcc:-DOPENSSL_RFC3779 -DDEBUG_SAFESTACK -DREF_CHECK -DCONF_DEBUG -DCRYPTO_MDEBUG -ggdb -g2 -Wall -Wshadow -Wmissing-prototypes -Wmissing-declarations -Werror::(unknown)::::::",

You may have to remove -Werror when working with OpenSSL snapshots,
since snapshots sometimes generate compilation warnings.

Other random notes:

- The reference for RDIs in RFC 3779 is incorrect. I've been told
that the authoritative definition of RDIs is ISO 10747, available as
http://www.acm.org/sigs/sigcomm/standards/iso_stds/IDRP/10747.TXT.

- OpenSSL already checks for duplicate extensions: more precisely,
unless we explicitly tell X509_get_ext_d2i() that we allow multiple
extensions (by providing the idx parameter), it returns NULL if it
finds duplicates. If we really want to check for presence of
exactly one extension of a particular type, we call this function
twice with the idx parameter and make sure that the second call
returns NULL.

- Request extensions: see X509_REQ_get_extensions(),
X509_REQ_add_extensions(), and copy_extensions().



The RFC 3997 patches were committed to the OpenSSL Project's CVS
repository on 27 November 2006, on both HEAD and the
OpenSSL_0_9_8-stable branch (thanks, Ben!), and shipped with OpenSSL
0.9.8e. The patches are disabled by default, but turning them on is
easy:

./config enable-rfc3779

If for some reason you need the modified OpenSSL source tree that used
to be in this directory, look at subversion revision 645.