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/*
* 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"
/*
* 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
krb5_hmac(hash, key, icount, input, output)
krb5_const struct krb5_hash_provider *hash;
krb5_const krb5_keyblock *key;
unsigned int icount;
krb5_const krb5_data *input;
krb5_data *output;
{
size_t hashsize, blocksize;
unsigned char *xorkey, *ihash;
int i;
krb5_data *hashin, hashout;
krb5_error_code ret;
(*(hash->hash_size))(&hashsize);
(*(hash->block_size))(&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 */
for (i=0; i<icount; i++) {
hashin[0].length = blocksize;
hashin[0].data = xorkey;
hashin[i+1] = input[i];
}
hashout.length = hashsize;
hashout.data = 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 = 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);
}
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