Expose a low-level Poly1305 API which implements the
ε-almost-∆-universal (εA∆U) hash function underlying the Poly1305 MAC
and supports block-aligned inputs only.

This is needed for Adiantum hashing, which builds an εA∆U hash function
from NH and a polynomial evaluation in GF(2^{130}-5); this polynomial
evaluation is identical to the one the Poly1305 MAC does.  However, the
crypto_shash Poly1305 API isn't very appropriate for this because its
calling convention assumes it is used as a MAC, with a 32-byte "one-time
key" provided for every digest.

But by design, in Adiantum hashing the performance of the polynomial
evaluation isn't nearly as critical as NH.  So it suffices to just have
some C helper functions.  Thus, this patch adds such functions.

Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

In preparation for exposing a low-level Poly1305 API which implements
the ε-almost-∆-universal (εA∆U) hash function underlying the Poly1305
MAC and supports block-aligned inputs only, create structures
poly1305_key and poly1305_state which hold the limbs of the Poly1305
"r" key and accumulator, respectively.

These structures could actually have the same type (e.g. poly1305_val),
but different types are preferable, to prevent misuse.

Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Many shash algorithms set .cra_flags = CRYPTO_ALG_TYPE_SHASH.  But this
is redundant with the C structure type ('struct shash_alg'), and
crypto_register_shash() already sets the type flag automatically,
clearing any type flag that was already there.  Apparently the useless
assignment has just been copy+pasted around.

So, remove the useless assignment from all the shash algorithms.

This patch shouldn't change any actual behavior.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Since Poly1305 requires a nonce per invocation, the Linux kernel
implementations of Poly1305 don't use the crypto API's keying mechanism
and instead expect the key and nonce as the first 32 bytes of the data.
But ->setkey() is still defined as a stub returning an error code.  This
prevents Poly1305 from being used through AF_ALG and will also break it
completely once we start enforcing that all crypto API users (not just
AF_ALG) call ->setkey() if present.

Fix it by removing crypto_poly1305_setkey(), leaving ->setkey as NULL.

Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Now that nothing in poly1305-generic assumes any special alignment,
remove the cra_alignmask so that the crypto API does not have to
unnecessarily align the buffers.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Currently the only part of poly1305-generic which is assuming special
alignment is the part where the final digest is written.  Switch this
over to the unaligned access macros so that we'll be able to remove the
cra_alignmask.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

By using the unaligned access helpers, we drastically improve
performance on small MIPS routers that have to go through the exception
fix-up handler for these unaligned accesses.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

As architecture specific drivers need a software fallback, export Poly1305
init/update/final functions together with some helpers in a header file.

Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

The Poly1305 authenticator requires a unique key for each generated tag. This
implies that we can't set the key per tfm, as multiple users set individual
keys. Instead we pass a desc specific key as the first two blocks of the
message to authenticate in update().

Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Poly1305 is a fast message authenticator designed by Daniel J. Bernstein.
It is further defined in RFC7539 as a building block for the ChaCha20-Poly1305
AEAD for use in IETF protocols.

This is a portable C implementation of the algorithm without architecture
specific optimizations, based on public domain code by Daniel J. Bernstein and
Andrew Moon.

Signed-off-by: Martin Willi <martin@strongswan.org>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>