siphash: Make internal helpers public

Move a bunch of code from siphash.c to siphash.h, making it available to
other modules.  This will allow places which need hashes of more complex
objects to construct them incrementally.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 111 insertions, 2 deletions

diff --git a/siphash.h b/siphash.h
index de04c56..f966cdb 100644
--- a/siphash.h
+++ b/siphash.h
@@ -1,11 +1,120 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later
- * Copyright (c) 2021 Red Hat GmbH
+ * Copyright Red Hat
  * Author: Stefano Brivio <sbrivio@redhat.com>
- */
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ *
+ * This is an implementation of the SipHash-2-4-64 functions needed for TCP
+ * initial sequence numbers and socket lookup table hash for IPv4 and IPv6, see:
+ *
+ *	Aumasson, J.P. and Bernstein, D.J., 2012, December. SipHash: a fast
+ *	short-input PRF. In International Conference on Cryptology in India
+ *	(pp. 489-508). Springer, Berlin, Heidelberg.
+ *
+ *	http://cr.yp.to/siphash/siphash-20120918.pdf
+ *
+ * This includes code from the reference SipHash implementation at
+ * https://github.com/veorq/SipHash/ originally licensed as follows:
+ *
+ * --
+ *  SipHash reference C implementation
+ *
+ * Copyright (c) 2012-2021 Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
+ * Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>
+ *
+ * To the extent possible under law, the author(s) have dedicated all copyright
+ * and related and neighboring rights to this software to the public domain
+ * worldwide. This software is distributed without any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication along
+ * with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ * --
+ *
+ * and from the Linux kernel implementation (lib/siphash.c), originally licensed
+ * as follows:
+ *
+ * --
+ * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This file is provided under a dual BSD/GPLv2 license.
+ * --
+ *
+*/
 
 #ifndef SIPHASH_H
 #define SIPHASH_H
 
+/**
+ * struct siphash_state - Internal state of siphash calculation
+ */
+struct siphash_state {
+	uint64_t v[4];
+};
+
+#define SIPHASH_INIT(k) { {						\
+		0x736f6d6570736575ULL ^ (k)[0],				\
+		0x646f72616e646f6dULL ^ (k)[1],				\
+		0x6c7967656e657261ULL ^ (k)[0],				\
+		0x7465646279746573ULL ^ (k)[1]				\
+	} }
+
+/**
+ * sipround() - Perform rounds of SipHash scrambling
+ * @v:		siphash state (4 x 64-bit integers)
+ * @n:		Number of rounds to apply
+ */
+static inline void sipround(struct siphash_state *state, int n)
+{
+	int i;
+
+#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
+
+	for (i = 0; i < n; i++) {
+
+		state->v[0] += state->v[1];
+		state->v[1] = ROTL(state->v[1], 13) ^ state->v[0];
+		state->v[0] = ROTL(state->v[0], 32);
+		state->v[2] += state->v[3];
+		state->v[3] = ROTL(state->v[3], 16) ^ state->v[2];
+		state->v[0] += state->v[3];
+		state->v[3] = ROTL(state->v[3], 21) ^ state->v[0];
+		state->v[2] += state->v[1];
+		state->v[1] = ROTL(state->v[1], 17) ^ state->v[2];
+		state->v[2] = ROTL(state->v[2], 32);
+	}
+
+#undef ROTL
+}
+
+/**
+ * siphash_feed() - Fold 64-bits of data into the hash state
+ * @v:		siphash state (4 x 64-bit integers)
+ * @in:		New value to fold into hash
+ */
+static inline void siphash_feed(struct siphash_state *state, uint64_t in)
+{
+	state->v[3] ^= in;
+	sipround(state, 2);
+	state->v[0] ^= in;
+}
+
+/**
+ * siphash_final - Finalize SipHash calculations
+ * @v:		siphash state (4 x 64-bit integers)
+ * @len:	Total length of input data
+ * @tail:	Final data for the hash (<= 7 bytes)
+ */
+static inline uint64_t siphash_final(struct siphash_state *state,
+				     size_t len, uint64_t tail)
+{
+	uint64_t b = (uint64_t)(len) << 56 | tail;
+
+	siphash_feed(state, b);
+	state->v[2] ^= 0xff;
+	sipround(state, 4);
+	return state->v[0] ^ state->v[1] ^ state->v[2] ^ state->v[3];
+}
+
 uint64_t siphash_8b(const uint8_t *in, const uint64_t *k);
 uint64_t siphash_12b(const uint8_t *in, const uint64_t *k);
 uint64_t siphash_20b(const uint8_t *in, const uint64_t *k);