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    SubjectRe: [PATCH 5/6] crypto: hkdf - add known answer tests
    On Mon, Jan 14, 2019 at 10:25:16AM +0100, Stephan Müller wrote:
    > Am Samstag, 12. Januar 2019, 06:19:15 CET schrieb Eric Biggers:
    >
    > Hi Eric,
    >
    > [...]
    > >
    > > > + }
    > > > + }
    > > > + }, {
    > > > + .alg = "hkdf(hmac(sha224))",
    > > > + .test = alg_test_null,
    > > > + .fips_allowed = 1,
    > >
    > > I think it is dumb to add algorithms to the testmgr with no tests just so
    > > the 'fips_allowed' flag can be set.
    >
    > Currently it is the only way. But I agree that it could be done better.
    >
    > > And doesn't FIPS sometimes require
    > > tests anyway? I don't think the "null test" should count as a test :-)
    >
    > Yes, it DOES count as a test (as strange as it may sound)! :-)
    >
    > The FIPS requirements are as follows:
    >
    > - raw ciphers must be subject to a FIPS test with one block chaining mode to
    > cover that cipher with all block chaining modes (e.g. you can test ecb(aes) to
    > cover AES with *all* existing block chaining modes).
    >
    > - for compound crypto algorithm (like RSA with respect to hashes, KDF with
    > respect to the keyed message digest, HMAC with respect to hashes), the
    > wrapping crypto algorithm needs to be tested with *one* wrapped cipher at
    > least (but also not more. E.g. if you have a self test for, say, all SHA-1 and
    > SHA-2, you only need one HMAC SHA test or one KDF HMAC SHA test.
    >
    > - in some circumstances, it is even permissible to test wrapping crypto
    > algorithms where the underlying algo is implicitly tested. E.g. if you have a
    > HMAC SHA-256 test, you do not need an individual SHA-256 test.
    >
    >
    > >
    > > Perhaps just include sha256 and sha512, and have tests for them?
    >
    > Do you happen to have an official SHA-512 HKDF test vector? RFC5869 only has
    > SHA-1 and SHA-256 tests.
    > >
    >

    No, I don't know of any official HKDF-SHA512 test vectors.

    > [...]
    > > >
    > > > +/* Test vectors from RFC 5869 appendix A */
    > > > +static struct kdf_testvec hkdf_hmac_sha256_tv_template[] = {
    > >
    > > const
    > >
    > > Likewise for all other kdf_testvecs.
    >
    > const does not work with __VECS :-(
    >
    > I leave it without const at the moment. I think the __VECS should be updated
    > along with all test vectors.
    >
    > [...]

    I don't see why. kdf_testvec just needs to be made const everywhere.

    - Eric

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