crypto: nhpoly1305 - add NHPoly1305 support

Add a generic implementation of NHPoly1305, an ε-almost-∆-universal hash
function used in the Adiantum encryption mode.

CONFIG_NHPOLY1305 is not selectable by itself since there won't be any
real reason to enable it without also enabling Adiantum support.

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>

1 files changed, 74 insertions, 0 deletions

diff --git a/include/crypto/nhpoly1305.h b/include/crypto/nhpoly1305.h
new file mode 100644
index 000000000000..53c04423c582
--- /dev/null
+++ b/include/crypto/nhpoly1305.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common values and helper functions for the NHPoly1305 hash function.
+ */
+
+#ifndef _NHPOLY1305_H
+#define _NHPOLY1305_H
+
+#include <crypto/hash.h>
+#include <crypto/poly1305.h>
+
+/* NH parameterization: */
+
+/* Endianness: little */
+/* Word size: 32 bits (works well on NEON, SSE2, AVX2) */
+
+/* Stride: 2 words (optimal on ARM32 NEON; works okay on other CPUs too) */
+#define NH_PAIR_STRIDE		2
+#define NH_MESSAGE_UNIT		(NH_PAIR_STRIDE * 2 * sizeof(u32))
+
+/* Num passes (Toeplitz iteration count): 4, to give ε = 2^{-128} */
+#define NH_NUM_PASSES		4
+#define NH_HASH_BYTES		(NH_NUM_PASSES * sizeof(u64))
+
+/* Max message size: 1024 bytes (32x compression factor) */
+#define NH_NUM_STRIDES		64
+#define NH_MESSAGE_WORDS	(NH_PAIR_STRIDE * 2 * NH_NUM_STRIDES)
+#define NH_MESSAGE_BYTES	(NH_MESSAGE_WORDS * sizeof(u32))
+#define NH_KEY_WORDS		(NH_MESSAGE_WORDS + \
+				 NH_PAIR_STRIDE * 2 * (NH_NUM_PASSES - 1))
+#define NH_KEY_BYTES		(NH_KEY_WORDS * sizeof(u32))
+
+#define NHPOLY1305_KEY_SIZE	(POLY1305_BLOCK_SIZE + NH_KEY_BYTES)
+
+struct nhpoly1305_key {
+	struct poly1305_key poly_key;
+	u32 nh_key[NH_KEY_WORDS];
+};
+
+struct nhpoly1305_state {
+
+	/* Running total of polynomial evaluation */
+	struct poly1305_state poly_state;
+
+	/* Partial block buffer */
+	u8 buffer[NH_MESSAGE_UNIT];
+	unsigned int buflen;
+
+	/*
+	 * Number of bytes remaining until the current NH message reaches
+	 * NH_MESSAGE_BYTES.  When nonzero, 'nh_hash' holds the partial NH hash.
+	 */
+	unsigned int nh_remaining;
+
+	__le64 nh_hash[NH_NUM_PASSES];
+};
+
+typedef void (*nh_t)(const u32 *key, const u8 *message, size_t message_len,
+		     __le64 hash[NH_NUM_PASSES]);
+
+int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
+			     const u8 *key, unsigned int keylen);
+
+int crypto_nhpoly1305_init(struct shash_desc *desc);
+int crypto_nhpoly1305_update(struct shash_desc *desc,
+			     const u8 *src, unsigned int srclen);
+int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
+				    const u8 *src, unsigned int srclen,
+				    nh_t nh_fn);
+int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst);
+int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst,
+				   nh_t nh_fn);
+
+#endif /* _NHPOLY1305_H */