tcp: Add siphash implementation for initial sequence numbers

Implement siphash routines for initial TCP sequence numbers (12 bytes
input for IPv4, 36 bytes input for IPv6), and while at it, also
functions we'll use later on for hash table indices and TCP timestamp
offsets (with 8, 20, 32 bytes of input).

Use these to set the initial sequence number, according to RFC 6528,
for connections originating either from the tap device or from
sockets.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 217 insertions, 0 deletions

diff --git a/siphash.c b/siphash.c
new file mode 100644
index 0000000..910c718
--- /dev/null
+++ b/siphash.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+/* PASST - Plug A Simple Socket Transport
+ *
+ * siphash.c - SipHash routines
+ *
+ * Copyright (c) 2020-2021 Red Hat GmbH
+ * Author: Stefano Brivio <sbrivio@redhat.com>
+ *
+ * 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/ 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), 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.
+ * --
+ *
+ */
+
+#include <stdint.h>
+
+#include "siphash.h"
+
+#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
+
+#define PREAMBLE(len)							  \
+	uint64_t v[4] = { 0x736f6d6570736575ULL, 0x646f72616e646f6dULL,	  \
+			  0x6c7967656e657261ULL, 0x7465646279746573ULL }; \
+	uint64_t b = (uint64_t)(len) << 56;				  \
+	uint32_t ret;							  \
+	int __i;							  \
+									  \
+	do {								  \
+		for (__i = sizeof(v) / sizeof(v[0]); __i >= 0; __i--)	  \
+			v[__i] = k[__i % 2];				  \
+	} while (0)
+
+#define SIPROUND(n)							  \
+	do {								  \
+		for (__i = 0; __i < (n); __i++) {			  \
+			v[0] += v[1];					  \
+			v[1] = ROTL(v[1], 13) ^ v[0];			  \
+			v[0] = ROTL(v[0], 32);				  \
+			v[2] += v[3];					  \
+			v[3] = ROTL(v[3], 16) ^ v[2];			  \
+			v[0] += v[3];					  \
+			v[3] = ROTL(v[3], 21) ^ v[0];			  \
+			v[2] += v[1];					  \
+			v[1] = ROTL(v[1], 17) ^ v[2];			  \
+			v[2] = ROTL(v[2], 32);				  \
+		}							  \
+	} while (0)
+
+#define POSTAMBLE							  \
+	do {								  \
+		v[3] ^= b;						  \
+		SIPROUND(2);						  \
+		v[0] ^= b;						  \
+		v[2] ^= 0xff;						  \
+		SIPROUND(4);						  \
+		b = (v[0] ^ v[1]) ^ (v[2] ^ v[3]);			  \
+		ret = (uint32_t)(b >> 32) ^ (uint32_t)b;		  \
+		(void)ret;						  \
+	} while (0)
+
+/**
+ * siphash_8b() - Table index or timestamp offset for TCP over IPv4 (8 bytes in)
+ * @in:		Input data (remote address and two ports, or two addresses)
+ * @k:		Hash function key, 128 bits
+ *
+ * Return: the 64-bit hash output
+ */
+uint64_t siphash_8b(const uint8_t *in, const uint64_t *k)
+{
+	PREAMBLE(8);
+	v[3] ^= *(uint64_t *)in;
+	SIPROUND(2);
+	v[0] ^= *(uint64_t *)in;
+	POSTAMBLE;
+
+	return b;
+}
+
+/**
+ * siphash_12b() - Initial sequence number for TCP over IPv4 (12 bytes in)
+ * @in:		Input data (two addresses, two ports)
+ * @k:		Hash function key, 128 bits
+ *
+ * Return: 32 bits obtained by XORing the two halves of the 64-bit hash output
+ */
+uint32_t siphash_12b(const uint8_t *in, const uint64_t *k)
+{
+	uint32_t *in32 = (uint32_t *)in;
+	uint64_t combined;
+
+	combined = (uint64_t)(*(in32 + 1)) << 32 | *in32;
+
+	PREAMBLE(12);
+	v[3] ^= combined;
+	SIPROUND(2);
+	v[0] ^= combined;
+	b |= *(in32 + 2);
+	POSTAMBLE;
+
+	return ret;
+}
+
+/**
+ * siphash_20b() - Table index for TCP over IPv6 (20 bytes in)
+ * @in:		Input data (remote address, two ports)
+ * @k:		Hash function key, 128 bits
+ *
+ * Return: the 64-bit hash output
+ */
+uint64_t siphash_20b(const uint8_t *in, const uint64_t *k)
+{
+	uint32_t *in32 = (uint32_t *)in;
+	uint64_t combined;
+	int i;
+
+	PREAMBLE(20);
+
+	for (i = 0; i < 2; i++, in32 += 2) {
+		combined = (uint64_t)(*(in32 + 1)) << 32 | *in32;
+		v[3] ^= combined;
+		SIPROUND(2);
+		v[0] ^= combined;
+	}
+
+	b |= *in32;
+	POSTAMBLE;
+
+	return b;
+}
+
+/**
+ * siphash_32b() - Timestamp offset for TCP over IPv6 (32 bytes in)
+ * @in:		Input data (two addresses)
+ * @k:		Hash function key, 128 bits
+ *
+ * Return: the 64-bit hash output
+ */
+uint32_t siphash_32b(const uint8_t *in, const uint64_t *k)
+{
+	uint64_t *in64 = (uint64_t *)in;
+	int i;
+
+	PREAMBLE(32);
+
+	for (i = 0; i < 4; i++, in64++) {
+		v[3] ^= *in64;
+		SIPROUND(2);
+		v[0] ^= *in64;
+	}
+
+	POSTAMBLE;
+
+	return b;
+}
+
+/**
+ * siphash_36b() - Initial sequence number for TCP over IPv6 (36 bytes in)
+ * @in:		Input data (two addresses, two ports)
+ * @k:		Hash function key, 128 bits
+ *
+ * Return: 32 bits obtained by XORing the two halves of the 64-bit hash output
+ */
+uint32_t siphash_36b(const uint8_t *in, const uint64_t *k)
+{
+	uint32_t *in32 = (uint32_t *)in;
+	uint64_t combined;
+	int i;
+
+	PREAMBLE(36);
+
+	for (i = 0; i < 4; i++, in32 += 2) {
+		combined = (uint64_t)(*(in32 + 1)) << 32 | *in32;
+		v[3] ^= combined;
+		SIPROUND(2);
+		v[0] ^= combined;
+	}
+
+	b |= *in32;
+	POSTAMBLE;
+
+	return ret;
+}