1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* lib/crypto/krb/prf_dk.c - RFC 3961 simplified profile PRF */
3 /*
4 * Copyright (C) 2004 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 krb5_error_code
krb5int_dk_prf(const struct krb5_keytypes * ktp,krb5_key key,const krb5_data * in,krb5_data * out)30 krb5int_dk_prf(const struct krb5_keytypes *ktp, krb5_key key,
31 const krb5_data *in, krb5_data *out)
32 {
33 const struct krb5_enc_provider *enc = ktp->enc;
34 const struct krb5_hash_provider *hash = ktp->hash;
35 krb5_crypto_iov iov;
36 krb5_data cksum = empty_data(), prfconst = make_data("prf", 3);
37 krb5_key kp = NULL;
38 krb5_error_code ret;
39
40 /* Hash the input data into an allocated buffer. */
41 ret = alloc_data(&cksum, hash->hashsize);
42 if (ret != 0)
43 goto cleanup;
44 iov.flags = KRB5_CRYPTO_TYPE_DATA;
45 iov.data = *in;
46 ret = hash->hash(&iov, 1, &cksum);
47 if (ret != 0)
48 goto cleanup;
49
50 /* Derive a key using the PRF constant. */
51 ret = krb5int_derive_key(ktp->enc, NULL, key, &kp, &prfconst,
52 DERIVE_RFC3961);
53 if (ret != 0)
54 goto cleanup;
55
56 /* Truncate the hash to the closest multiple of the block size. */
57 iov.data.data = cksum.data;
58 iov.data.length = (hash->hashsize / enc->block_size) * enc->block_size;
59
60 /* Encrypt the truncated hash in the derived key to get the output. */
61 ret = ktp->enc->encrypt(kp, NULL, &iov, 1);
62 if (ret != 0)
63 goto cleanup;
64 memcpy(out->data, iov.data.data, out->length);
65
66 cleanup:
67 zapfree(cksum.data, hash->hashsize);
68 krb5_k_free_key(NULL, kp);
69 return ret;
70 }
71