On Tue, Feb 25, 2020 at 9:45 PM Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> On Tue, Feb 25, 2020 at 05:48:33PM +0200, Gilad Ben-Yossef wrote:
> > Use generic algs to produce inauthentic AEAD messages,
> > otherwise we are running the risk of using an untested
> > code to produce the test messages.
> >
> > As this code is only used in developer only extended tests
> > any cycles/runtime costs are negligible.
> >
> > Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>
> > Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> It's intentional to use the same implementation to generate the inauthentic AEAD
> messages, because it allows the inauthentic AEAD input tests to run even if the
> generic implementation is unavailable.
That is a good.
We can simply revert to the same implementation if the generic one is
not available.
>
> > @@ -2337,8 +2338,42 @@ static int test_aead_inauthentic_inputs(struct aead_extra_tests_ctx *ctx)
> > {
> > unsigned int i;
> > int err;
> > + struct crypto_aead *tfm = ctx->tfm;
> > + const char *algname = crypto_aead_alg(tfm)->base.cra_name;
> > + const char *driver = ctx->driver;
> > + const char *generic_driver = ctx->test_desc->generic_driver;
> > + char _generic_driver[CRYPTO_MAX_ALG_NAME];
> > + struct crypto_aead *generic_tfm = NULL;
> > + struct aead_request *generic_req = NULL;
> > +
> > + if (!generic_driver) {
> > + err = build_generic_driver_name(algname, _generic_driver);
> > + if (err)
> > + return err;
> > + generic_driver = _generic_driver;
> > + }
> > +
> > + if (!strcmp(generic_driver, driver) == 0) {
> > + /* Already the generic impl? */
> > +
> > + generic_tfm = crypto_alloc_aead(generic_driver, 0, 0);
>
> I think you meant the condition to be 'if (strcmp(generic_driver, driver) != 0)'
> and for the comment to be "Not already the generic impl?".
Yes, of course. Silly me,
>
> > + if (IS_ERR(generic_tfm)) {
> > + err = PTR_ERR(generic_tfm);
> > + pr_err("alg: aead: error allocating %s (generic impl of %s): %d\n",
> > + generic_driver, algname, err);
> > + return err;
> > + }
>
> This means the test won't run if the generic implementation is unavailable.
> Is there any particular reason to impose that requirement?
>
> You mentioned a concern about the implementation being "untested", but it
> actually already passed test_aead() before getting to test_aead_extra().
>
The impetus to write this patch came from my experience debugging a
test failure with the ccree driver.
At some point while tweaking around I got into a situation where the
test was succeeding (that is, declaring the message inauthentic) not
because the mutation was being detected but because the generation of
the origin was producing a bogus ICV.
At that point it seemed to me that it would be safer to "isolate" the
original AEAD messages generation from the code that was being teste.
> We could also just move test_aead_inauthentic_inputs() to below
> test_aead_vs_generic_impl() so that it runs last.
This would probably be better, although I think that this stage also
generates inauthentic messages from time to time, no?
At any rate, I don't have strong feelings about it either way. I defer
to your judgment whether it is worth it to add a fallback to use the
same implementation and fix what needs fixing or drop the patch
altogether if you think this isn't worth the trouble - just let me
know.
Thanks,
Gilad
--
Gilad Ben-Yossef
Chief Coffee Drinker
values of β will give rise to dom!
