path: root/openssl/README

$Id$ -*- Text -*- 

OpenSSL hacked to add support for the RFC 3779 X.509 v3 extensions.

Current status:

- Not (yet) for distribution outside the RIRs.

- Reads and writes RFC 3779 extensions but does not (yet) perform the
  additional validation described in RFC 3779 2.3 & 3.3.

- Not (yet) tested extensively.

Please report any problems to me (sra) or the rescert mailing list.



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.
  I could tag ranges differently from the atomic types, but this
  seemed easier for the user to understand.

* The "@" syntax indicating indirection through a separate section
  is lifted from 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.  We can talk to the folks at the OpenSSL project
  about changing the names if there's a reason to do so.

### 

# 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 one 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.

I have not yet figured out where to hook in the extra goop that RFC
3779 will need for verification.  Making extensions critical is easy
enough, but the validation stuff in RFC 3779 2.3 and 3.3 needs to go
somewhere.

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.



Random reminders and notes to myself:

- The new stuff in crypto/x509v3/x509v3.h is not organized properly
  yet, it's all lumped in one place rather than being interleved with
  the other supported extensions.  This was to make it easier for me
  to debug, but will proably need to be cleaned up eventually.

- 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 verify" only accepts PEM, not DER, which is annoying.
  An -inform switch would be nice, but the library routines
  don't know how to read a CAfile full of DER anyway.  Pity -CApath
  doesn't seem to work for us.  Oh well, live with PEM for now.

- 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.

- May need to check AKID in crypto/x509/x509_vfy.c:get_crl().



Notes from the June meeting at APNIC on desired OpenSSL primitives (as
transcribed by Geoff), with current status:

1. Read a resource certificate and print nominated certificate
   field(s) (CLI command) or access data structure elements from the
   certificate (API)

   Status: Done

2. Verify a resource certificate (use the existing openssl interface
   which provides as inputs a) a set of 'trusted' certs and CRLs and
   b) a set of untrusted certs and CRLs and c) the cert to be
   verified. output is YES or NO and both a CLI and an API interface
   is desired

   Status: API done.  CLI...is a crock, but it was a crock before I
   touched it and I have not made it worse.  CLI "verify" tool is
   intended for diagnostic use only, real applications should use the
   API.

3. 3779_canonicalise - read in a data structure of a resource set and
   produce as output the 3779 canonical form of the resource set - the
   CLI interface will print this to stdout and the API interface will
   pass a ref to a data structure (or fill in a data struct or
   whatever makes sense!)

   Status: Done

4. 3779_cmp reads in 2 x 3779_canonicalised data sets and outputs a
   comparison = EQUAL is the two are equal, or =SUBSET if data1 is a
   strict subset of data2, or = NOT in all other cases (CLI or API)
   (EQUAL, SUBSET, NOT)

   Status: Not done.  Some supporting code exists.

5. is_3379_canonical tests a single data set and returns CANONICAL if
   the resource is formatted according to 3779 or NOT is otherwise

   Status: API done.   No CLI tool for this (yet?).

6. is_in_cert takes a certificate and a resource set description and
   checks if the certificate 'covers' the resource set The outpouts
   are EQUAL if the resource cert precisely matches the resource set,
   SUBSET if the resource set is a subset of the certificate resource
   list, or NOT otherwise

   Status: Not done. Some supporting code exists.

7. generate_resource_certificate generates a resource certificate -
   I'm not sure I understand what the inputs are to be here - perhaps
   a data structure of the fields and values, but this should be
   confirmed. the output is a DER object (or pem, or either
   selectable?)

   Status: Done, for some definition of done.

8. generate a certificate request (previous note on which certificate
   request format to use is on the table)

   Status: Done, for some definition of done.

9. process a certificate request and say yes / no on whether the
   request is well formed.

   Status: Mostly done -- code exists but is not yet organized in a
   way that allows it to be called except as part of path validation.

10. process a certificate request and generate a certificate in
    response.

   Status: done, for some definition of done.

Wishy-washy answers to some of the above are not attempting to be
evasive, they're a reflection of the fact that much of this work was
adding support for particular extensions to an existing package, so
the question of whether the package supports the desired functionality
now with the extensions depends on whether one believes that the
package supported the desired functionality without the extensions
before.  Eg, are the OpenSSL CLI tools "ca", "x509", "req", etc
sufficient?  Yes for some purposes, no for others.