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passt/siphash.c
David Gibson 5cc843521d siphash: Fix bug in state initialisation 
The SipHash algorithm starts with initializing the 32 bytes of internal
state with some magic numbers XORed with the hash key.  However, our
implementation has a bug - rather than XORing the hash key, it *sets* the
initial state to copies of the key.

I don't know if that affects any of the cryptographic properties of SipHash
but it's not what we should be doing.  Fix it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2023-09-30 12:40:43 +02:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* 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/ 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.
* --
*
*/
#include <stddef.h>
#include <stdint.h>
#include "siphash.h"
#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
#define PREAMBLE \
uint64_t v[4] = { 0x736f6d6570736575ULL, 0x646f72616e646f6dULL, \
0x6c7967656e657261ULL, 0x7465646279746573ULL }; \
int __i; \
\
do { \
for (__i = sizeof(v) / sizeof(v[0]) - 1; __i >= 0; __i--) \
v[__i] ^= k[__i % 2]; \
} while (0)
/**
* sipround() - Perform rounds of SipHash scrambling
* @v: siphash state (4 x 64-bit integers)
* @n: Number of rounds to apply
*/
static inline void sipround(uint64_t *v, int n)
{
int i;
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);
}
}
/**
* 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(uint64_t *v, uint64_t in)
{
v[3] ^= in;
sipround(v, 2);
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(uint64_t *v, size_t len, uint64_t tail)
{
uint64_t b = (uint64_t)(len) << 56 | tail;
siphash_feed(v, b);
v[2] ^= 0xff;
sipround(v, 4);
return v[0] ^ v[1] ^ v[2] ^ v[3];
}
/**
* 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
*/
/* Type-Based Alias Analysis (TBAA) optimisation in gcc 11 and 12 (-flto -O2)
* makes these functions essentially useless by allowing reordering of stores of
* input data across function calls. Not even declaring @in as char pointer is
* enough: disable gcc's interpretation of strict aliasing altogether. See also:
*
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106706
* https://stackoverflow.com/questions/2958633/gcc-strict-aliasing-and-horror-stories
* https://lore.kernel.org/all/alpine.LFD.2.00.0901121128080.6528__33422.5328093909$1232291247$gmane$org@localhost.localdomain/
*/
/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
__attribute__((optimize("-fno-strict-aliasing")))
/* cppcheck-suppress unusedFunction */
uint64_t siphash_8b(const uint8_t *in, const uint64_t *k)
{
PREAMBLE;
siphash_feed(v, *(uint64_t *)in);
return siphash_final(v, 8, 0);
}
/**
* 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: the 64-bit hash output
*/
/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
__attribute__((optimize("-fno-strict-aliasing"))) /* See siphash_8b() */
/* cppcheck-suppress unusedFunction */
uint64_t siphash_12b(const uint8_t *in, const uint64_t *k)
{
uint32_t *in32 = (uint32_t *)in;
PREAMBLE;
siphash_feed(v, (uint64_t)(*(in32 + 1)) << 32 | *in32);
return siphash_final(v, 12, *(in32 + 2));
}
/**
* 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
*/
/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
__attribute__((optimize("-fno-strict-aliasing"))) /* See siphash_8b() */
uint64_t siphash_20b(const uint8_t *in, const uint64_t *k)
{
uint32_t *in32 = (uint32_t *)in;
int i;
PREAMBLE;
for (i = 0; i < 2; i++, in32 += 2)
siphash_feed(v, (uint64_t)(*(in32 + 1)) << 32 | *in32);
return siphash_final(v, 20, *in32);
}
/**
* 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
*/
/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
__attribute__((optimize("-fno-strict-aliasing"))) /* See siphash_8b() */
/* cppcheck-suppress unusedFunction */
uint64_t siphash_32b(const uint8_t *in, const uint64_t *k)
{
uint64_t *in64 = (uint64_t *)in;
int i;
PREAMBLE;
for (i = 0; i < 4; i++, in64++)
siphash_feed(v, *in64);
return siphash_final(v, 32, 0);
}
/**
* 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: the 64-bit hash output
*/
/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
__attribute__((optimize("-fno-strict-aliasing"))) /* See siphash_8b() */
uint64_t siphash_36b(const uint8_t *in, const uint64_t *k)
{
uint32_t *in32 = (uint32_t *)in;
int i;
PREAMBLE;
for (i = 0; i < 4; i++, in32 += 2)
siphash_feed(v, (uint64_t)(*(in32 + 1)) << 32 | *in32);
return siphash_final(v, 36, *in32);
}
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