For those who don't know what FIPS mode is (like me): https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NS...
FIPS requires that any 'approved' included crypto algorithm implementations are self-tested, and pass a verification program (just a big bunch of somewhat poorly conceived known answer tests).
It also has a list of 'allowed' algorithms, which don't need to be tested but can be offered by a FIPS crypto module.
The CSPRNG used for key generation must be of an approved construction, but there are a number of choices ranging from stupid shit nobody sane would choose (Dual EC DRBG) to ones which are trivial variations on hashes, HMAC or block ciphers in OFB or CTR mode. Sadly, it says nothing about the quality or construction of actual entropy sources.
Naturally, everything not 'approved' or 'allowed' cannot be offered by a FIPS crypto module.
On the plus side, this means vendors can't offer proprietary stupid-shit like LFSR stream ciphers. Unfortunately, the approved and allowed list rarely keeps up with good quality or fixed crypto (you'll not find any eSTREAM finalists, or EdDSA, or deterministic DSA, or curve25519 ECDH, for example).
Also, the rules are pretty poorly enforced: you'll still find new FIPS certificates issued for boxes which do TLS < 1.2. This is a lie: MD5 is not allowed or approved, and is a fundamental (if conservatively used) part of the protocol in those versions.
Source: I used to make FIPS-approved HSMs. AMA? :)
If I understand you correctly, the issue with FIPS is that you would have to be able to disable all but a subset of the features, regardless of these feature being worse or better than what is defined in the FIPS documents?
That's a bit more that one question, but I would like to know. Thanks.
The whole FIPS canister thing in OpenSSL is a HUGE pain in the behind when you are building a library/product using it, and overall doesn't increase security one single bit. Yes your crypto is now FIPS 140 certified, big whoop.
[Note: I am going off the OpenSSL FIPS canister implementation details here...]
Let's differentiate between "FIPS compliant" and "FIPS certified".
FIPS complaint: you could get a FIPS certified product if you wanted, without changing your product.
FIPS certified: you paid NIST and a FIPS test lab some money, the lab tested your module, submitted a test report to NIST, and NIST published certificates saying that a certain version of your product (running on a particular OS and CPU architecture, for software modules) is FIPS certified.
So, yes, you could accidentally come up with a FIPS compliant crypto module. But getting certified costs actual money (last time I did it, as I recall just shy of $100k).
> the issue with FIPS is that you would have to be able to disable > all but a subset of the features, regardless of these feature > being worse or better than what is defined in the FIPS documents?
To some extent it depends what you mean by 'feature' here. If it's a crypto algorithm offered by your module for external use, there is quite little leeway. If it's a fundamental feature of your product that internally uses exotic crypto, you can often convince your test lab to gloss over it.
"FIPS support" also demands configurations that rule out some cryptography, some of it bad, some of it reasonable. FIPS support doesn't require OpenSSL not to implement those algorithms, but it does require a mode of operation that does.
Against that complexity, the only win is the ability to deploy the FIPS-compliant code in FedGov settings, which is something that an OpenBSD fork of OpenSSL doesn't need to do to be successful.
On the other hand, you can't change the source without losing the certification, so it doesn't actually matter.
This is why you might have to use old versions of OpenSSL for FIPS compliance - not all versions might be certified.
Here's the bug I submitted to the chromium project while I beta tested the Cr-48, requesting FIPS support. The closeout comments cite excellent sources. Interesting that this was done right about the time the Heartbleed bug was probably being found as well.
In practice, what this means is that you take one of the fips-openssl-x.y.z releases, and build fipscanister.o from it; that has the fundamental crypto bits in it, it's released as infrequently as possible. Then you build a plain old openssl-x.y.z release with a flag to enable the fips feature. At runtime when you enable FIPS mode, your local openssl library would switch to using crypto functions from fipscanister.o, which might be a year or two old. The idea is that the crypto bits don't generally change, although the rest of libssl/libcrypto might change several times during the year.
Anyway building and using openssl this way is a giant pain in the ass, especially if you statically link. To make matters even more confusing, Redhat took an altogether different tack, and have their own variant of openssl that, when FIPS mode is enabled, switches to using the Linux Kernel crypto functions, which they got independently NIST validated, so if you're deploying the RHEL machines in the .gov space, a different FIPS 140-2 validation applies to you.
It leads to a fair amount of crap in the configure scripts, and macros throughout the code.