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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 "k5-int.h"
#include "aead.h"
/*
* Because our built-in HMAC implementation doesn't need to invoke any
* encryption or keyed hash functions, it is simplest to define it in
* terms of keyblocks, and then supply a simple wrapper for the
* "normal" krb5_key-using interfaces. The keyblock interfaces are
* useful for the built-in arcfour code which constructs a lot of
* intermediate HMAC keys. For other back ends, it should not be
* necessary to supply the _keyblock versions of the hmac functions if
* the back end code doesn't make use of them.
*/
/*
* the HMAC transform looks like:
*
* H(K XOR opad, H(K XOR ipad, text))
*
* where H is a cryptographic hash
* K is an n byte key
* ipad is the byte 0x36 repeated blocksize times
* opad is the byte 0x5c repeated blocksize times
* and text is the data being protected
*/
krb5_error_code
krb5int_hmac_keyblock(const struct krb5_hash_provider *hash,
const krb5_keyblock *key, unsigned int icount,
const krb5_data *input, krb5_data *output)
{
size_t hashsize, blocksize;
unsigned char *xorkey, *ihash;
unsigned int i;
krb5_data *hashin, hashout;
krb5_error_code ret;
hashsize = hash->hashsize;
blocksize = hash->blocksize;
if (key->length > blocksize)
return(KRB5_CRYPTO_INTERNAL);
if (output->length < hashsize)
return(KRB5_BAD_MSIZE);
/* if this isn't > 0, then there won't be enough space in this
array to compute the outer hash */
if (icount == 0)
return(KRB5_CRYPTO_INTERNAL);
/* allocate space for the xor key, hash input vector, and inner hash */
if ((xorkey = (unsigned char *) malloc(blocksize)) == NULL)
return(ENOMEM);
if ((ihash = (unsigned char *) malloc(hashsize)) == NULL) {
free(xorkey);
return(ENOMEM);
}
if ((hashin = (krb5_data *)malloc(sizeof(krb5_data)*(icount+1))) == NULL) {
free(ihash);
free(xorkey);
return(ENOMEM);
}
/* create the inner padded key */
memset(xorkey, 0x36, blocksize);
for (i=0; i<key->length; i++)
xorkey[i] ^= key->contents[i];
/* compute the inner hash */
hashin[0].length = blocksize;
hashin[0].data = (char *) xorkey;
for (i=0; i<icount; i++)
hashin[i+1] = input[i];
hashout.length = hashsize;
hashout.data = (char *) ihash;
if ((ret = ((*(hash->hash))(icount+1, hashin, &hashout))))
goto cleanup;
/* create the outer padded key */
memset(xorkey, 0x5c, blocksize);
for (i=0; i<key->length; i++)
xorkey[i] ^= key->contents[i];
/* compute the outer hash */
hashin[0].length = blocksize;
hashin[0].data = (char *) xorkey;
hashin[1] = hashout;
output->length = hashsize;
if ((ret = ((*(hash->hash))(2, hashin, output))))
memset(output->data, 0, output->length);
/* ret is set correctly by the prior call */
cleanup:
memset(xorkey, 0, blocksize);
memset(ihash, 0, hashsize);
free(hashin);
free(ihash);
free(xorkey);
return(ret);
}
krb5_error_code
krb5int_hmac_iov_keyblock(const struct krb5_hash_provider *hash,
const krb5_keyblock *key,
const krb5_crypto_iov *data, size_t num_data,
krb5_data *output)
{
krb5_data *sign_data;
size_t num_sign_data;
krb5_error_code ret;
size_t i, j;
/* Create a checksum over all the data to be signed */
for (i = 0, num_sign_data = 0; i < num_data; i++) {
const krb5_crypto_iov *iov = &data[i];
if (SIGN_IOV(iov))
num_sign_data++;
}
/* XXX cleanup to avoid alloc */
sign_data = (krb5_data *)calloc(num_sign_data, sizeof(krb5_data));
if (sign_data == NULL)
return ENOMEM;
for (i = 0, j = 0; i < num_data; i++) {
const krb5_crypto_iov *iov = &data[i];
if (SIGN_IOV(iov))
sign_data[j++] = iov->data;
}
/* caller must store checksum in iov as it may be TYPE_TRAILER or TYPE_CHECKSUM */
ret = krb5int_hmac_keyblock(hash, key, num_sign_data, sign_data, output);
free(sign_data);
return ret;
}
krb5_error_code
krb5int_hmac(const struct krb5_hash_provider *hash, krb5_key key,
unsigned int icount, const krb5_data *input, krb5_data *output)
{
return krb5int_hmac_keyblock(hash, &key->keyblock, icount, input, output);
}
krb5_error_code
krb5int_hmac_iov(const struct krb5_hash_provider *hash, krb5_key key,
const krb5_crypto_iov *data, size_t num_data,
krb5_data *output)
{
return krb5int_hmac_iov_keyblock(hash, &key->keyblock, data, num_data,
output);
}
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