1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* lib/crypto/krb/checksum_dk_cmac.c */
3 /*
4 * Copyright 2010 by the Massachusetts Institute of Technology.
5 * All Rights Reserved.
6 *
7 * Export of this software from the United States of America may
8 * require a specific license from the United States Government.
9 * It is the responsibility of any person or organization contemplating
10 * export to obtain such a license before exporting.
11 *
12 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
13 * distribute this software and its documentation for any purpose and
14 * without fee is hereby granted, provided that the above copyright
15 * notice appear in all copies and that both that copyright notice and
16 * this permission notice appear in supporting documentation, and that
17 * the name of M.I.T. not be used in advertising or publicity pertaining
18 * to distribution of the software without specific, written prior
19 * permission. Furthermore if you modify this software you must label
20 * your software as modified software and not distribute it in such a
21 * fashion that it might be confused with the original M.I.T. software.
22 * M.I.T. makes no representations about the suitability of
23 * this software for any purpose. It is provided "as is" without express
24 * or implied warranty.
25 */
26
27 #include "crypto_int.h"
28
29 #define K5CLENGTH 5 /* 32 bit net byte order integer + one byte seed */
30
31 krb5_error_code
krb5int_dk_cmac_checksum(const struct krb5_cksumtypes * ctp,krb5_key key,krb5_keyusage usage,const krb5_crypto_iov * data,size_t num_data,krb5_data * output)32 krb5int_dk_cmac_checksum(const struct krb5_cksumtypes *ctp,
33 krb5_key key, krb5_keyusage usage,
34 const krb5_crypto_iov *data, size_t num_data,
35 krb5_data *output)
36 {
37 const struct krb5_enc_provider *enc = ctp->enc;
38 krb5_error_code ret;
39 unsigned char constantdata[K5CLENGTH];
40 krb5_data datain;
41 krb5_key kc;
42
43 /* Derive the key. */
44 datain = make_data(constantdata, K5CLENGTH);
45 store_32_be(usage, constantdata);
46 constantdata[4] = (char) 0x99;
47 ret = krb5int_derive_key(enc, NULL, key, &kc, &datain,
48 DERIVE_SP800_108_CMAC);
49 if (ret != 0)
50 return ret;
51
52 /* Hash the data. */
53 ret = krb5int_cmac_checksum(enc, kc, data, num_data, output);
54 if (ret != 0)
55 memset(output->data, 0, output->length);
56
57 krb5_k_free_key(NULL, kc);
58 return ret;
59 }
60