/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/crypto/krb/checksum_hmac_md5.c */
/*
* Copyright (C) 2009 by the Massachusetts Institute of Technology.
* 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 M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
/*
* Microsoft HMAC-MD5 and MD5-HMAC checksums (see RFC 4757):
* HMAC(KS, hash(msusage || input))
* KS is HMAC(key, "signaturekey\0") for HMAC-MD5, or just the key for
* MD5-HMAC.
*/
#include "crypto_int.h"
krb5_error_code krb5int_hmacmd5_checksum(const struct krb5_cksumtypes *ctp,
krb5_key key, krb5_keyusage usage,
const krb5_crypto_iov *data,
size_t num_data,
krb5_data *output)
{
krb5_keyusage ms_usage;
krb5_error_code ret;
krb5_keyblock ks, *keyblock;
krb5_crypto_iov *hash_iov = NULL, iov;
krb5_data ds = empty_data(), hashval = empty_data();
char t[4];
if (key == NULL || key->keyblock.length > ctp->hash->blocksize)
return KRB5_BAD_ENCTYPE;
if (ctp->ctype == CKSUMTYPE_HMAC_MD5_ARCFOUR) {
/* Compute HMAC(key, "signaturekey\0") to get the signing key ks. */
ret = alloc_data(&ds, ctp->hash->hashsize);
if (ret != 0)
goto cleanup;
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = make_data("signaturekey", 13);
ret = krb5int_hmac(ctp->hash, key, &iov, 1, &ds);
if (ret)
goto cleanup;
ks.length = ds.length;
ks.contents = (krb5_octet *) ds.data;
keyblock = &ks;
} else /* For md5-hmac, just use the key. */
keyblock = &key->keyblock;
/* Compute the MD5 value of the input. */
ms_usage = krb5int_arcfour_translate_usage(usage);
store_32_le(ms_usage, t);
hash_iov = k5calloc(num_data + 1, sizeof(krb5_crypto_iov), &ret);
if (hash_iov == NULL)
goto cleanup;
hash_iov[0].flags = KRB5_CRYPTO_TYPE_DATA;
hash_iov[0].data = make_data(t, 4);
memcpy(hash_iov + 1, data, num_data * sizeof(krb5_crypto_iov));
ret = alloc_data(&hashval, ctp->hash->hashsize);
if (ret != 0)
goto cleanup;
ret = ctp->hash->hash(hash_iov, num_data + 1, &hashval);
if (ret != 0)
goto cleanup;
/* Compute HMAC(ks, md5value). */
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = hashval;
ret = krb5int_hmac_keyblock(ctp->hash, keyblock, &iov, 1, output);
cleanup:
zapfree(ds.data, ds.length);
zapfree(hashval.data, hashval.length);
free(hash_iov);
return ret;
}