Re: [RFC PATCH v3 10/15] crypto: poly1305 - use structures for key and accumulator

From: Ard Biesheuvel
Date: Tue Nov 06 2018 - 09:28:28 EST

On 6 November 2018 at 00:25, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> In preparation for exposing a low-level Poly1305 API which implements
> the Î-almost-â-universal (ÎAâU) 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.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> arch/x86/crypto/poly1305_glue.c | 20 +++++++------
> crypto/poly1305_generic.c | 52 ++++++++++++++++-----------------
> include/crypto/poly1305.h | 12 ++++++--
> 3 files changed, 47 insertions(+), 37 deletions(-)
>
> diff --git a/arch/x86/crypto/poly1305_glue.c b/arch/x86/crypto/poly1305_glue.c
> index f012b7e28ad1..88cc01506c84 100644
> --- a/arch/x86/crypto/poly1305_glue.c
> +++ b/arch/x86/crypto/poly1305_glue.c
> @@ -83,35 +83,37 @@ static unsigned int poly1305_simd_blocks(struct poly1305_desc_ctx *dctx,
> if (poly1305_use_avx2 && srclen >= POLY1305_BLOCK_SIZE * 4) {
> if (unlikely(!sctx->wset)) {
> if (!sctx->uset) {
> - memcpy(sctx->u, dctx->r, sizeof(sctx->u));
> - poly1305_simd_mult(sctx->u, dctx->r);
> + memcpy(sctx->u, dctx->r.r, sizeof(sctx->u));
> + poly1305_simd_mult(sctx->u, dctx->r.r);
> sctx->uset = true;
> }
> memcpy(sctx->u + 5, sctx->u, sizeof(sctx->u));
> - poly1305_simd_mult(sctx->u + 5, dctx->r);
> + poly1305_simd_mult(sctx->u + 5, dctx->r.r);
> memcpy(sctx->u + 10, sctx->u + 5, sizeof(sctx->u));
> - poly1305_simd_mult(sctx->u + 10, dctx->r);
> + poly1305_simd_mult(sctx->u + 10, dctx->r.r);
> sctx->wset = true;
> }
> blocks = srclen / (POLY1305_BLOCK_SIZE * 4);
> - poly1305_4block_avx2(dctx->h, src, dctx->r, blocks, sctx->u);
> + poly1305_4block_avx2(dctx->h.h, src, dctx->r.r, blocks,
> + sctx->u);
> src += POLY1305_BLOCK_SIZE * 4 * blocks;
> srclen -= POLY1305_BLOCK_SIZE * 4 * blocks;
> }
> #endif
> if (likely(srclen >= POLY1305_BLOCK_SIZE * 2)) {
> if (unlikely(!sctx->uset)) {
> - memcpy(sctx->u, dctx->r, sizeof(sctx->u));
> - poly1305_simd_mult(sctx->u, dctx->r);
> + memcpy(sctx->u, dctx->r.r, sizeof(sctx->u));
> + poly1305_simd_mult(sctx->u, dctx->r.r);
> sctx->uset = true;
> }
> blocks = srclen / (POLY1305_BLOCK_SIZE * 2);
> - poly1305_2block_sse2(dctx->h, src, dctx->r, blocks, sctx->u);
> + poly1305_2block_sse2(dctx->h.h, src, dctx->r.r, blocks,
> + sctx->u);
> src += POLY1305_BLOCK_SIZE * 2 * blocks;
> srclen -= POLY1305_BLOCK_SIZE * 2 * blocks;
> }
> if (srclen >= POLY1305_BLOCK_SIZE) {
> - poly1305_block_sse2(dctx->h, src, dctx->r, 1);
> + poly1305_block_sse2(dctx->h.h, src, dctx->r.r, 1);
> srclen -= POLY1305_BLOCK_SIZE;
> }
> return srclen;
> diff --git a/crypto/poly1305_generic.c b/crypto/poly1305_generic.c
> index 47d3a6b83931..a23173f351b7 100644
> --- a/crypto/poly1305_generic.c
> +++ b/crypto/poly1305_generic.c
> @@ -38,7 +38,7 @@ int crypto_poly1305_init(struct shash_desc *desc)
> {
> struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
>
> - memset(dctx->h, 0, sizeof(dctx->h));
> + memset(dctx->h.h, 0, sizeof(dctx->h.h));
> dctx->buflen = 0;
> dctx->rset = false;
> dctx->sset = false;
> @@ -50,11 +50,11 @@ EXPORT_SYMBOL_GPL(crypto_poly1305_init);
> static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key)
> {
> /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
> - dctx->r[0] = (get_unaligned_le32(key + 0) >> 0) & 0x3ffffff;
> - dctx->r[1] = (get_unaligned_le32(key + 3) >> 2) & 0x3ffff03;
> - dctx->r[2] = (get_unaligned_le32(key + 6) >> 4) & 0x3ffc0ff;
> - dctx->r[3] = (get_unaligned_le32(key + 9) >> 6) & 0x3f03fff;
> - dctx->r[4] = (get_unaligned_le32(key + 12) >> 8) & 0x00fffff;
> + dctx->r.r[0] = (get_unaligned_le32(key + 0) >> 0) & 0x3ffffff;
> + dctx->r.r[1] = (get_unaligned_le32(key + 3) >> 2) & 0x3ffff03;
> + dctx->r.r[2] = (get_unaligned_le32(key + 6) >> 4) & 0x3ffc0ff;
> + dctx->r.r[3] = (get_unaligned_le32(key + 9) >> 6) & 0x3f03fff;
> + dctx->r.r[4] = (get_unaligned_le32(key + 12) >> 8) & 0x00fffff;
> }
>
> static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key)
> @@ -107,22 +107,22 @@ static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx,
> srclen = datalen;
> }
>
> - r0 = dctx->r[0];
> - r1 = dctx->r[1];
> - r2 = dctx->r[2];
> - r3 = dctx->r[3];
> - r4 = dctx->r[4];
> + r0 = dctx->r.r[0];
> + r1 = dctx->r.r[1];
> + r2 = dctx->r.r[2];
> + r3 = dctx->r.r[3];
> + r4 = dctx->r.r[4];
>
> s1 = r1 * 5;
> s2 = r2 * 5;
> s3 = r3 * 5;
> s4 = r4 * 5;
>
> - h0 = dctx->h[0];
> - h1 = dctx->h[1];
> - h2 = dctx->h[2];
> - h3 = dctx->h[3];
> - h4 = dctx->h[4];
> + h0 = dctx->h.h[0];
> + h1 = dctx->h.h[1];
> + h2 = dctx->h.h[2];
> + h3 = dctx->h.h[3];
> + h4 = dctx->h.h[4];
>
> while (likely(srclen >= POLY1305_BLOCK_SIZE)) {
>
> @@ -157,11 +157,11 @@ static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx,
> srclen -= POLY1305_BLOCK_SIZE;
> }
>
> - dctx->h[0] = h0;
> - dctx->h[1] = h1;
> - dctx->h[2] = h2;
> - dctx->h[3] = h3;
> - dctx->h[4] = h4;
> + dctx->h.h[0] = h0;
> + dctx->h.h[1] = h1;
> + dctx->h.h[2] = h2;
> + dctx->h.h[3] = h3;
> + dctx->h.h[4] = h4;
>
> return srclen;
> }
> @@ -220,11 +220,11 @@ int crypto_poly1305_final(struct shash_desc *desc, u8 *dst)
> }
>
> /* fully carry h */
> - h0 = dctx->h[0];
> - h1 = dctx->h[1];
> - h2 = dctx->h[2];
> - h3 = dctx->h[3];
> - h4 = dctx->h[4];
> + h0 = dctx->h.h[0];
> + h1 = dctx->h.h[1];
> + h2 = dctx->h.h[2];
> + h3 = dctx->h.h[3];
> + h4 = dctx->h.h[4];
>
> h2 += (h1 >> 26); h1 = h1 & 0x3ffffff;
> h3 += (h2 >> 26); h2 = h2 & 0x3ffffff;
> diff --git a/include/crypto/poly1305.h b/include/crypto/poly1305.h
> index f718a19da82f..493244c46664 100644
> --- a/include/crypto/poly1305.h
> +++ b/include/crypto/poly1305.h
> @@ -13,13 +13,21 @@
> #define POLY1305_KEY_SIZE 32
> #define POLY1305_DIGEST_SIZE 16
>
> +struct poly1305_key {
> + u32 r[5]; /* key, base 2^26 */
> +};
> +
> +struct poly1305_state {
> + u32 h[5]; /* accumulator, base 2^26 */
> +};
> +

Sorry to bikeshed, but wouldn't it make more sense to have single definition

struct poly1305_val {
u32 v[5]; /* base 2^26 */
};

and have 'key' and 'accum[ulator]' fields of type struct poly1305_val
in the struct below?

> struct poly1305_desc_ctx {
> /* key */
> - u32 r[5];
> + struct poly1305_key r;
> /* finalize key */
> u32 s[4];
> /* accumulator */
> - u32 h[5];
> + struct poly1305_state h;
> /* partial buffer */
> u8 buf[POLY1305_BLOCK_SIZE];
> /* bytes used in partial buffer */
> --
> 2.19.1.930.g4563a0d9d0-goog
>