1 files changed, 276 insertions, 0 deletions
diff --git a/include/crypto/gf128hash.h b/include/crypto/gf128hash.h
new file mode 100644
index 000000000..41c557d55
--- /dev/null
+++ b/include/crypto/gf128hash.h
@@ -0,0 +1,276 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * GF(2^128) polynomial hashing: GHASH and POLYVAL
+ *
+ * Copyright 2025 Google LLC
+ */
+
+#ifndef _CRYPTO_GF128HASH_H
+#define _CRYPTO_GF128HASH_H
+
+#include <crypto/ghash.h>
+#include <linux/string.h>
+#include <linux/types.h>
+
+#define POLYVAL_BLOCK_SIZE	16
+#define POLYVAL_DIGEST_SIZE	16
+
+/**
+ * struct polyval_elem - An element of the POLYVAL finite field
+ * @bytes: View of the element as a byte array (unioned with @lo and @hi)
+ * @lo: The low 64 terms of the element's polynomial
+ * @hi: The high 64 terms of the element's polynomial
+ *
+ * This represents an element of the finite field GF(2^128), using the POLYVAL
+ * convention: little-endian byte order and natural bit order.
+ */
+struct polyval_elem {
+	union {
+		u8 bytes[POLYVAL_BLOCK_SIZE];
+		struct {
+			__le64 lo;
+			__le64 hi;
+		};
+	};
+};
+
+/**
+ * struct ghash_key - Prepared key for GHASH
+ *
+ * Use ghash_preparekey() to initialize this.
+ */
+struct ghash_key {
+#if defined(CONFIG_CRYPTO_LIB_GF128HASH_ARCH) && defined(CONFIG_PPC64)
+	/** @htable: GHASH key format used by the POWER8 assembly code */
+	u64 htable[4][2];
+#elif defined(CONFIG_CRYPTO_LIB_GF128HASH_ARCH) && \
+	(defined(CONFIG_RISCV) || defined(CONFIG_S390))
+	/** @h_raw: The hash key H, in GHASH format */
+	u8 h_raw[GHASH_BLOCK_SIZE];
+#endif
+	/** @h: The hash key H, in POLYVAL format */
+	struct polyval_elem h;
+};
+
+/**
+ * struct polyval_key - Prepared key for POLYVAL
+ *
+ * This may contain just the raw key H, or it may contain precomputed key
+ * powers, depending on the platform's POLYVAL implementation.  Use
+ * polyval_preparekey() to initialize this.
+ *
+ * By H^i we mean H^(i-1) * H * x^-128, with base case H^1 = H.  I.e. the
+ * exponentiation repeats the POLYVAL dot operation, with its "extra" x^-128.
+ */
+struct polyval_key {
+#if defined(CONFIG_CRYPTO_LIB_GF128HASH_ARCH) && \
+	(defined(CONFIG_ARM64) || defined(CONFIG_X86))
+	/** @h_powers: Powers of the hash key H^8 through H^1 */
+	struct polyval_elem h_powers[8];
+#else
+	/** @h: The hash key H */
+	struct polyval_elem h;
+#endif
+};
+
+/**
+ * struct ghash_ctx - Context for computing a GHASH value
+ * @key: Pointer to the prepared GHASH key.  The user of the API is
+ *	 responsible for ensuring that the key lives as long as the context.
+ * @acc: The accumulator.  It is stored in POLYVAL format rather than GHASH
+ *	 format, since most implementations want it in POLYVAL format.
+ * @partial: Number of data bytes processed so far modulo GHASH_BLOCK_SIZE
+ */
+struct ghash_ctx {
+	const struct ghash_key *key;
+	struct polyval_elem acc;
+	size_t partial;
+};
+
+/**
+ * struct polyval_ctx - Context for computing a POLYVAL value
+ * @key: Pointer to the prepared POLYVAL key.  The user of the API is
+ *	 responsible for ensuring that the key lives as long as the context.
+ * @acc: The accumulator
+ * @partial: Number of data bytes processed so far modulo POLYVAL_BLOCK_SIZE
+ */
+struct polyval_ctx {
+	const struct polyval_key *key;
+	struct polyval_elem acc;
+	size_t partial;
+};
+
+/**
+ * ghash_preparekey() - Prepare a GHASH key
+ * @key: (output) The key structure to initialize
+ * @raw_key: The raw hash key
+ *
+ * Initialize a GHASH key structure from a raw key.
+ *
+ * Context: Any context.
+ */
+void ghash_preparekey(struct ghash_key *key,
+		      const u8 raw_key[GHASH_BLOCK_SIZE]);
+
+/**
+ * polyval_preparekey() - Prepare a POLYVAL key
+ * @key: (output) The key structure to initialize
+ * @raw_key: The raw hash key
+ *
+ * Initialize a POLYVAL key structure from a raw key.  This may be a simple
+ * copy, or it may involve precomputing powers of the key, depending on the
+ * platform's POLYVAL implementation.
+ *
+ * Context: Any context.
+ */
+void polyval_preparekey(struct polyval_key *key,
+			const u8 raw_key[POLYVAL_BLOCK_SIZE]);
+
+/**
+ * ghash_init() - Initialize a GHASH context for a new message
+ * @ctx: The context to initialize
+ * @key: The key to use.  Note that a pointer to the key is saved in the
+ *	 context, so the key must live at least as long as the context.
+ */
+static inline void ghash_init(struct ghash_ctx *ctx,
+			      const struct ghash_key *key)
+{
+	*ctx = (struct ghash_ctx){ .key = key };
+}
+
+/**
+ * polyval_init() - Initialize a POLYVAL context for a new message
+ * @ctx: The context to initialize
+ * @key: The key to use.  Note that a pointer to the key is saved in the
+ *	 context, so the key must live at least as long as the context.
+ */
+static inline void polyval_init(struct polyval_ctx *ctx,
+				const struct polyval_key *key)
+{
+	*ctx = (struct polyval_ctx){ .key = key };
+}
+
+/**
+ * polyval_import_blkaligned() - Import a POLYVAL accumulator value
+ * @ctx: The context to initialize
+ * @key: The key to import.  Note that a pointer to the key is saved in the
+ *	 context, so the key must live at least as long as the context.
+ * @acc: The accumulator value to import.
+ *
+ * This imports an accumulator that was saved by polyval_export_blkaligned().
+ * The same key must be used.
+ */
+static inline void
+polyval_import_blkaligned(struct polyval_ctx *ctx,
+			  const struct polyval_key *key,
+			  const struct polyval_elem *acc)
+{
+	*ctx = (struct polyval_ctx){ .key = key, .acc = *acc };
+}
+
+/**
+ * polyval_export_blkaligned() - Export a POLYVAL accumulator value
+ * @ctx: The context to export the accumulator value from
+ * @acc: (output) The exported accumulator value
+ *
+ * This exports the accumulator from a POLYVAL context.  The number of data
+ * bytes processed so far must be a multiple of POLYVAL_BLOCK_SIZE.
+ */
+static inline void polyval_export_blkaligned(const struct polyval_ctx *ctx,
+					     struct polyval_elem *acc)
+{
+	*acc = ctx->acc;
+}
+
+/**
+ * ghash_update() - Update a GHASH context with message data
+ * @ctx: The context to update; must have been initialized
+ * @data: The message data
+ * @len: The data length in bytes.  Doesn't need to be block-aligned.
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+void ghash_update(struct ghash_ctx *ctx, const u8 *data, size_t len);
+
+/**
+ * polyval_update() - Update a POLYVAL context with message data
+ * @ctx: The context to update; must have been initialized
+ * @data: The message data
+ * @len: The data length in bytes.  Doesn't need to be block-aligned.
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+void polyval_update(struct polyval_ctx *ctx, const u8 *data, size_t len);
+
+/**
+ * ghash_final() - Finish computing a GHASH value
+ * @ctx: The context to finalize
+ * @out: The output value
+ *
+ * If the total data length isn't a multiple of GHASH_BLOCK_SIZE, then the
+ * final block is automatically zero-padded.
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void ghash_final(struct ghash_ctx *ctx, u8 out[GHASH_BLOCK_SIZE]);
+
+/**
+ * polyval_final() - Finish computing a POLYVAL value
+ * @ctx: The context to finalize
+ * @out: The output value
+ *
+ * If the total data length isn't a multiple of POLYVAL_BLOCK_SIZE, then the
+ * final block is automatically zero-padded.
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void polyval_final(struct polyval_ctx *ctx, u8 out[POLYVAL_BLOCK_SIZE]);
+
+/**
+ * ghash() - Compute a GHASH value
+ * @key: The prepared key
+ * @data: The message data
+ * @len: The data length in bytes.  Doesn't need to be block-aligned.
+ * @out: The output value
+ *
+ * Context: Any context.
+ */
+static inline void ghash(const struct ghash_key *key, const u8 *data,
+			 size_t len, u8 out[GHASH_BLOCK_SIZE])
+{
+	struct ghash_ctx ctx;
+
+	ghash_init(&ctx, key);
+	ghash_update(&ctx, data, len);
+	ghash_final(&ctx, out);
+}
+
+/**
+ * polyval() - Compute a POLYVAL value
+ * @key: The prepared key
+ * @data: The message data
+ * @len: The data length in bytes.  Doesn't need to be block-aligned.
+ * @out: The output value
+ *
+ * Context: Any context.
+ */
+static inline void polyval(const struct polyval_key *key,
+			   const u8 *data, size_t len,
+			   u8 out[POLYVAL_BLOCK_SIZE])
+{
+	struct polyval_ctx ctx;
+
+	polyval_init(&ctx, key);
+	polyval_update(&ctx, data, len);
+	polyval_final(&ctx, out);
+}
+
+#endif /* _CRYPTO_GF128HASH_H */