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//===--- SipHash.cpp - An ABI-stable string hash --------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements an ABI-stable string hash based on SipHash, used to
// compute ptrauth discriminators.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/SipHash.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include <cstdint>
using namespace llvm;
using namespace support;
#define DEBUG_TYPE "llvm-siphash"
// Lightly adapted from the SipHash reference C implementation:
// https://github.com/veorq/SipHash
// by Jean-Philippe Aumasson and Daniel J. Bernstein
#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
#define SIPROUND \
do { \
v0 += v1; \
v1 = ROTL(v1, 13); \
v1 ^= v0; \
v0 = ROTL(v0, 32); \
v2 += v3; \
v3 = ROTL(v3, 16); \
v3 ^= v2; \
v0 += v3; \
v3 = ROTL(v3, 21); \
v3 ^= v0; \
v2 += v1; \
v1 = ROTL(v1, 17); \
v1 ^= v2; \
v2 = ROTL(v2, 32); \
} while (0)
namespace {
/// Computes a SipHash value
///
/// \param in: pointer to input data (read-only)
/// \param inlen: input data length in bytes (any size_t value)
/// \param k: reference to the key data 16-byte array (read-only)
/// \returns output data, must be 8 or 16 bytes
///
template <int cROUNDS, int dROUNDS, size_t outlen>
void siphash(const unsigned char *in, uint64_t inlen,
const unsigned char (&k)[16], unsigned char (&out)[outlen]) {
const unsigned char *ni = (const unsigned char *)in;
const unsigned char *kk = (const unsigned char *)k;
static_assert(outlen == 8 || outlen == 16, "result should be 8 or 16 bytes");
uint64_t v0 = UINT64_C(0x736f6d6570736575);
uint64_t v1 = UINT64_C(0x646f72616e646f6d);
uint64_t v2 = UINT64_C(0x6c7967656e657261);
uint64_t v3 = UINT64_C(0x7465646279746573);
uint64_t k0 = endian::read64le(kk);
uint64_t k1 = endian::read64le(kk + 8);
uint64_t m;
int i;
const unsigned char *end = ni + inlen - (inlen % sizeof(uint64_t));
const int left = inlen & 7;
uint64_t b = ((uint64_t)inlen) << 56;
v3 ^= k1;
v2 ^= k0;
v1 ^= k1;
v0 ^= k0;
if (outlen == 16)
v1 ^= 0xee;
for (; ni != end; ni += 8) {
m = endian::read64le(ni);
v3 ^= m;
for (i = 0; i < cROUNDS; ++i)
SIPROUND;
v0 ^= m;
}
switch (left) {
case 7:
b |= ((uint64_t)ni[6]) << 48;
LLVM_FALLTHROUGH;
case 6:
b |= ((uint64_t)ni[5]) << 40;
LLVM_FALLTHROUGH;
case 5:
b |= ((uint64_t)ni[4]) << 32;
LLVM_FALLTHROUGH;
case 4:
b |= ((uint64_t)ni[3]) << 24;
LLVM_FALLTHROUGH;
case 3:
b |= ((uint64_t)ni[2]) << 16;
LLVM_FALLTHROUGH;
case 2:
b |= ((uint64_t)ni[1]) << 8;
LLVM_FALLTHROUGH;
case 1:
b |= ((uint64_t)ni[0]);
break;
case 0:
break;
}
v3 ^= b;
for (i = 0; i < cROUNDS; ++i)
SIPROUND;
v0 ^= b;
if (outlen == 16)
v2 ^= 0xee;
else
v2 ^= 0xff;
for (i = 0; i < dROUNDS; ++i)
SIPROUND;
b = v0 ^ v1 ^ v2 ^ v3;
endian::write64le(out, b);
if (outlen == 8)
return;
v1 ^= 0xdd;
for (i = 0; i < dROUNDS; ++i)
SIPROUND;
b = v0 ^ v1 ^ v2 ^ v3;
endian::write64le(out + 8, b);
}
} // end anonymous namespace
void llvm::getSipHash_2_4_64(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
uint8_t (&Out)[8]) {
siphash<2, 4>(In.data(), In.size(), K, Out);
}
void llvm::getSipHash_2_4_128(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
uint8_t (&Out)[16]) {
siphash<2, 4>(In.data(), In.size(), K, Out);
}
/// Compute an ABI-stable 16-bit hash of the given string.
uint16_t llvm::getPointerAuthStableSipHash(StringRef Str) {
static const uint8_t K[16] = {0xb5, 0xd4, 0xc9, 0xeb, 0x79, 0x10, 0x4a, 0x79,
0x6f, 0xec, 0x8b, 0x1b, 0x42, 0x87, 0x81, 0xd4};
uint8_t RawHashBytes[8];
getSipHash_2_4_64(arrayRefFromStringRef(Str), K, RawHashBytes);
uint64_t RawHash = endian::read64le(RawHashBytes);
// Produce a non-zero 16-bit discriminator.
uint16_t Discriminator = (RawHash % 0xFFFF) + 1;
LLVM_DEBUG(
dbgs() << "ptrauth stable hash discriminator: " << utostr(Discriminator)
<< " (0x"
<< utohexstr(Discriminator, /*Lowercase=*/false, /*Width=*/4)
<< ")"
<< " of: " << Str << "\n");
return Discriminator;
}
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