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derive.c
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derive.c
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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* Copyright (C) 1998 by the FundsXpress, INC.
*
* All rights reserved.
*
* Export of this software from the United States of America may require
* a specific license from the United States Government. It is the
* responsibility of any person or organization contemplating export to
* obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of FundsXpress. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. FundsXpress makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#include "sanon_locl.h"
extern krb5_error_code
krb5int_hmac(const struct krb5_hash_provider *hash,
krb5_key key, const krb5_crypto_iov *data,
size_t num_data, krb5_data *output);
/*
* NIST SP800-108 KDF in counter mode (section 5.1).
* Parameters:
* - HMAC (with hash as the hash provider) is the PRF.
* - A block counter of four bytes is used.
* - Four bytes are used to encode the output length in the PRF input.
*
* There are no uses requiring more than a single PRF invocation.
*/
krb5_error_code
SP800_108_HMAC(const struct krb5_hash_provider *hash,
krb5_key inkey, krb5_data *outrnd,
const krb5_data *label, const krb5_data *context)
{
krb5_crypto_iov iov[5];
krb5_error_code ret;
krb5_data prf;
unsigned char ibuf[4], lbuf[4];
if (hash == NULL || outrnd->length > hash->hashsize)
return KRB5_CRYPTO_INTERNAL;
/* Allocate encryption data buffer. */
ret = alloc_data(&prf, hash->hashsize);
if (ret)
return ret;
/* [i]2: four-byte big-endian binary string giving the block counter (1) */
iov[0].flags = KRB5_CRYPTO_TYPE_DATA;
iov[0].data = make_data(ibuf, sizeof(ibuf));
encode_be_uint32(1, ibuf);
/* Label */
iov[1].flags = KRB5_CRYPTO_TYPE_DATA;
iov[1].data = *label;
/* 0x00: separator byte */
iov[2].flags = KRB5_CRYPTO_TYPE_DATA;
iov[2].data = make_data((uint8_t *)"", 1);
/* Context */
iov[3].flags = KRB5_CRYPTO_TYPE_DATA;
iov[3].data = *context;
/* [L]2: four-byte big-endian binary string giving the output length */
iov[4].flags = KRB5_CRYPTO_TYPE_DATA;
iov[4].data = make_data(lbuf, sizeof(lbuf));
encode_be_uint32(outrnd->length * 8, lbuf);
ret = krb5int_hmac(hash, inkey, iov, 5, &prf);
if (ret == 0)
memcpy(outrnd->data, prf.data, outrnd->length);
secure_zero_memory(prf.data, prf.length);
free(prf.data);
return ret;
}