$Id$ -*- 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.