/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

/*! \file
 * Some portion of this code was derived from universal hash function
 * libraries of Rice University.
\section license UH Universal Hashing Library

Copyright ((c)) 2002, Rice University
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

    * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the following
    disclaimer in the documentation and/or other materials provided
    with the distribution.

    * Neither the name of Rice University (RICE) nor the names of its
    contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.


This software is provided by RICE and the contributors on an "as is"
basis, without any representations or warranties of any kind, express
or implied including, but not limited to, representations or
warranties of non-infringement, merchantability or fitness for a
particular purpose. In no event shall RICE or contributors be liable
for any direct, indirect, incidental, special, exemplary, or
consequential damages (including, but not limited to, procurement of
substitute goods or services; loss of use, data, or profits; or
business interruption) however caused and on any theory of liability,
whether in contract, strict liability, or tort (including negligence
or otherwise) arising in any way out of the use of this software, even
if advised of the possibility of such damage.
*/

#include <config.h>

#include <stdbool.h>

#include <isc/entropy.h>
#include <isc/hash.h>
#include <isc/mem.h>
#include <isc/magic.h>
#include <isc/mutex.h>
#include <isc/once.h>
#include <isc/random.h>
#include <isc/refcount.h>
#include <isc/string.h>
#include <isc/util.h>

#define HASH_MAGIC		ISC_MAGIC('H', 'a', 's', 'h')
#define VALID_HASH(h)		ISC_MAGIC_VALID((h), HASH_MAGIC)

/*%
 * A large 32-bit prime number that specifies the range of the hash output.
 */
#define PRIME32 0xFFFFFFFB              /* 2^32 -  5 */

/*@{*/
/*%
 * Types of random seed and hash accumulator.  Perhaps they can be system
 * dependent.
 */
typedef uint32_t hash_accum_t;
typedef uint16_t hash_random_t;
/*@}*/

/*% isc hash structure */
struct isc_hash {
	unsigned int	magic;
	isc_mem_t	*mctx;
	isc_mutex_t	lock;
	bool	initialized;
	isc_refcount_t	refcnt;
	isc_entropy_t	*entropy; /*%< entropy source */
	size_t		limit;	/*%< upper limit of key length */
	size_t		vectorlen; /*%< size of the vector below */
	hash_random_t	*rndvector; /*%< random vector for universal hashing */
};

static isc_mutex_t createlock;
static isc_once_t once = ISC_ONCE_INIT;

LIBISC_EXTERNAL_DATA isc_hash_t *isc_hashctx = NULL;

static unsigned char maptolower[] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
	0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
	0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
	0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
	0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
	0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
	0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
	0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
	0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
	0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
	0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
	0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
	0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
	0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
	0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
	0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
	0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
	0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
	0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff
};

isc_result_t
isc_hash_ctxcreate(isc_mem_t *mctx, isc_entropy_t *entropy,
		   size_t limit, isc_hash_t **hctxp)
{
	isc_result_t result;
	isc_hash_t *hctx;
	size_t vlen;
	hash_random_t *rv;
	hash_accum_t overflow_limit;

	REQUIRE(mctx != NULL);
	REQUIRE(hctxp != NULL && *hctxp == NULL);

	/*
	 * Overflow check.  Since our implementation only does a modulo
	 * operation at the last stage of hash calculation, the accumulator
	 * must not overflow.
	 */
	overflow_limit =
		1 << (((sizeof(hash_accum_t) - sizeof(hash_random_t))) * 8);
	if (overflow_limit < (limit + 1) * 0xff)
		return (ISC_R_RANGE);

	hctx = isc_mem_get(mctx, sizeof(isc_hash_t));
	if (hctx == NULL)
		return (ISC_R_NOMEMORY);

	vlen = sizeof(hash_random_t) * (limit + 1);
	rv = isc_mem_get(mctx, vlen);
	if (rv == NULL) {
		result = ISC_R_NOMEMORY;
		goto errout;
	}

	/*
	 * We need a lock.
	 */
	result = isc_mutex_init(&hctx->lock);
	if (result != ISC_R_SUCCESS)
		goto errout;

	/*
	 * From here down, no failures will/can occur.
	 */
	hctx->magic = HASH_MAGIC;
	hctx->mctx = NULL;
	isc_mem_attach(mctx, &hctx->mctx);
	hctx->initialized = false;
	result = isc_refcount_init(&hctx->refcnt, 1);
	if (result != ISC_R_SUCCESS)
		goto cleanup_lock;
	hctx->entropy = NULL;
	hctx->limit = limit;
	hctx->vectorlen = vlen;
	hctx->rndvector = rv;

	if (entropy != NULL)
		isc_entropy_attach(entropy, &hctx->entropy);

	*hctxp = hctx;
	return (ISC_R_SUCCESS);

 cleanup_lock:
	DESTROYLOCK(&hctx->lock);
 errout:
	isc_mem_put(mctx, hctx, sizeof(isc_hash_t));
	if (rv != NULL)
		isc_mem_put(mctx, rv, vlen);

	return (result);
}

static void
initialize_lock(void) {
	RUNTIME_CHECK(isc_mutex_init(&createlock) == ISC_R_SUCCESS);
}

isc_result_t
isc_hash_create(isc_mem_t *mctx, isc_entropy_t *entropy, size_t limit) {
	isc_result_t result = ISC_R_SUCCESS;

	REQUIRE(mctx != NULL);
	INSIST(isc_hashctx == NULL);

	RUNTIME_CHECK(isc_once_do(&once, initialize_lock) == ISC_R_SUCCESS);

	LOCK(&createlock);

	if (isc_hashctx == NULL)
		result = isc_hash_ctxcreate(mctx, entropy, limit,
					    &isc_hashctx);

	UNLOCK(&createlock);

	return (result);
}

void
isc_hash_ctxinit(isc_hash_t *hctx) {
	LOCK(&hctx->lock);

	if (hctx->initialized == true)
		goto out;

	if (hctx->entropy != NULL) {
		isc_result_t result;

		result = isc_entropy_getdata(hctx->entropy,
					     hctx->rndvector,
					     (unsigned int)hctx->vectorlen,
					     NULL, 0);
		INSIST(result == ISC_R_SUCCESS);
	} else {
		uint32_t pr;
		size_t i, copylen;
		unsigned char *p;

		p = (unsigned char *)hctx->rndvector;
		for (i = 0; i < hctx->vectorlen; i += copylen, p += copylen) {
			isc_random_get(&pr);
			if (i + sizeof(pr) <= hctx->vectorlen)
				copylen = sizeof(pr);
			else
				copylen = hctx->vectorlen - i;

			memmove(p, &pr, copylen);
		}
		INSIST(p == (unsigned char *)hctx->rndvector +
		       hctx->vectorlen);
	}

	hctx->initialized = true;

 out:
	UNLOCK(&hctx->lock);
}

void
isc_hash_init(void) {
	INSIST(isc_hashctx != NULL && VALID_HASH(isc_hashctx));

	isc_hash_ctxinit(isc_hashctx);
}

void
isc_hash_ctxattach(isc_hash_t *hctx, isc_hash_t **hctxp) {
	REQUIRE(VALID_HASH(hctx));
	REQUIRE(hctxp != NULL && *hctxp == NULL);

	isc_refcount_increment(&hctx->refcnt, NULL);
	*hctxp = hctx;
}

static void
destroy(isc_hash_t **hctxp) {
	isc_hash_t *hctx;
	isc_mem_t *mctx;

	REQUIRE(hctxp != NULL && *hctxp != NULL);
	hctx = *hctxp;
	*hctxp = NULL;

	LOCK(&hctx->lock);

	isc_refcount_destroy(&hctx->refcnt);

	mctx = hctx->mctx;
	if (hctx->entropy != NULL)
		isc_entropy_detach(&hctx->entropy);
	if (hctx->rndvector != NULL)
		isc_mem_put(mctx, hctx->rndvector, hctx->vectorlen);

	UNLOCK(&hctx->lock);

	DESTROYLOCK(&hctx->lock);

	memset(hctx, 0, sizeof(isc_hash_t));
	isc_mem_put(mctx, hctx, sizeof(isc_hash_t));
	isc_mem_detach(&mctx);
}

void
isc_hash_ctxdetach(isc_hash_t **hctxp) {
	isc_hash_t *hctx;
	unsigned int refs;

	REQUIRE(hctxp != NULL && VALID_HASH(*hctxp));
	hctx = *hctxp;

	isc_refcount_decrement(&hctx->refcnt, &refs);
	if (refs == 0)
		destroy(&hctx);

	*hctxp = NULL;
}

void
isc_hash_destroy(void) {
	unsigned int refs;

	INSIST(isc_hashctx != NULL && VALID_HASH(isc_hashctx));

	isc_refcount_decrement(&isc_hashctx->refcnt, &refs);
	INSIST(refs == 0);

	destroy(&isc_hashctx);
}

static inline unsigned int
hash_calc(isc_hash_t *hctx, const unsigned char *key, unsigned int keylen,
	  bool case_sensitive)
{
	hash_accum_t partial_sum = 0;
	hash_random_t *p = hctx->rndvector;
	unsigned int i = 0;

	/* Make it sure that the hash context is initialized. */
	if (hctx->initialized == false)
		isc_hash_ctxinit(hctx);

	if (case_sensitive) {
		for (i = 0; i < keylen; i++)
			partial_sum += key[i] * (hash_accum_t)p[i];
	} else {
		for (i = 0; i < keylen; i++)
			partial_sum += maptolower[key[i]] * (hash_accum_t)p[i];
	}

	partial_sum += p[i];

	return ((unsigned int)(partial_sum % PRIME32));
}

unsigned int
isc_hash_ctxcalc(isc_hash_t *hctx, const unsigned char *key,
		 unsigned int keylen, bool case_sensitive)
{
	REQUIRE(hctx != NULL && VALID_HASH(hctx));
	REQUIRE(keylen <= hctx->limit);

	return (hash_calc(hctx, key, keylen, case_sensitive));
}

unsigned int
isc_hash_calc(const unsigned char *key, unsigned int keylen,
	      bool case_sensitive)
{
	INSIST(isc_hashctx != NULL && VALID_HASH(isc_hashctx));
	REQUIRE(keylen <= isc_hashctx->limit);

	return (hash_calc(isc_hashctx, key, keylen, case_sensitive));
}

void
isc__hash_setvec(const uint16_t *vec) {
	int i;
	hash_random_t *p;

	if (isc_hashctx == NULL)
		return;

	p = isc_hashctx->rndvector;
	for (i = 0; i < 256; i++) {
		p[i] = vec[i];
	}
}

static uint32_t fnv_offset_basis;
static isc_once_t fnv_once = ISC_ONCE_INIT;
static bool fnv_initialized = false;

static void
fnv_initialize(void) {
	/*
	 * This function should not leave fnv_offset_basis set to
	 * 0. Also, after this function has been called, if it is called
	 * again, it should not change fnv_offset_basis.
	 */
	while (fnv_offset_basis == 0) {
		isc_random_get(&fnv_offset_basis);
	}

	fnv_initialized = true;
}

const void *
isc_hash_get_initializer(void) {
	if (ISC_UNLIKELY(!fnv_initialized))
		RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);

	return (&fnv_offset_basis);
}

void
isc_hash_set_initializer(const void *initializer) {
	REQUIRE(initializer != NULL);

	/*
	 * Ensure that fnv_initialize() is not called after
	 * isc_hash_set_initializer() is called.
	 */
	if (ISC_UNLIKELY(!fnv_initialized))
		RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);

	fnv_offset_basis = *((const unsigned int *) initializer);
}

uint32_t
isc_hash_function(const void *data, size_t length,
		  bool case_sensitive,
		  const uint32_t *previous_hashp)
{
	uint32_t hval;
	const unsigned char *bp;
	const unsigned char *be;

	REQUIRE(length == 0 || data != NULL);

	if (ISC_UNLIKELY(!fnv_initialized))
		RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);

	hval = ISC_UNLIKELY(previous_hashp != NULL) ?
		*previous_hashp : fnv_offset_basis;

	if (length == 0)
		return (hval);

	bp = (const unsigned char *) data;
	be = bp + length;

	/*
	 * Fowler-Noll-Vo FNV-1a hash function.
	 *
	 * NOTE: A random FNV offset basis is used by default to avoid
	 * collision attacks as the hash function is reversible. This
	 * makes the mapping non-deterministic, but the distribution in
	 * the domain is still uniform.
	 */

	if (case_sensitive) {
		while (bp <= be - 4) {
			hval ^= bp[0];
			hval *= 16777619;
			hval ^= bp[1];
			hval *= 16777619;
			hval ^= bp[2];
			hval *= 16777619;
			hval ^= bp[3];
			hval *= 16777619;
			bp += 4;
		}
		while (bp < be) {
			hval ^= *bp++;
			hval *= 16777619;
		}
	} else {
		while (bp <= be - 4) {
			hval ^= maptolower[bp[0]];
			hval *= 16777619;
			hval ^= maptolower[bp[1]];
			hval *= 16777619;
			hval ^= maptolower[bp[2]];
			hval *= 16777619;
			hval ^= maptolower[bp[3]];
			hval *= 16777619;
			bp += 4;
		}
		while (bp < be) {
			hval ^= maptolower[*bp++];
			hval *= 16777619;
		}
	}

	return (hval);
}

uint32_t
isc_hash_function_reverse(const void *data, size_t length,
			  bool case_sensitive,
			  const uint32_t *previous_hashp)
{
	uint32_t hval;
	const unsigned char *bp;
	const unsigned char *be;

	REQUIRE(length == 0 || data != NULL);

	if (ISC_UNLIKELY(!fnv_initialized))
		RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);

	hval = ISC_UNLIKELY(previous_hashp != NULL) ?
		*previous_hashp : fnv_offset_basis;

	if (length == 0)
		return (hval);

	bp = (const unsigned char *) data;
	be = bp + length;

	/*
	 * Fowler-Noll-Vo FNV-1a hash function.
	 *
	 * NOTE: A random FNV offset basis is used by default to avoid
	 * collision attacks as the hash function is reversible. This
	 * makes the mapping non-deterministic, but the distribution in
	 * the domain is still uniform.
	 */

	if (case_sensitive) {
		while (be >= bp + 4) {
			be -= 4;
			hval ^= be[3];
			hval *= 16777619;
			hval ^= be[2];
			hval *= 16777619;
			hval ^= be[1];
			hval *= 16777619;
			hval ^= be[0];
			hval *= 16777619;
		}
		while (--be >= bp) {
			hval ^= *be;
			hval *= 16777619;
		}
	} else {
		while (be >= bp + 4) {
			be -= 4;
			hval ^= maptolower[be[3]];
			hval *= 16777619;
			hval ^= maptolower[be[2]];
			hval *= 16777619;
			hval ^= maptolower[be[1]];
			hval *= 16777619;
			hval ^= maptolower[be[0]];
			hval *= 16777619;
		}
		while (--be >= bp) {
			hval ^= maptolower[*be];
			hval *= 16777619;
		}
	}

	return (hval);
}
