1 /*
2 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5
6 /*
7 * lib/krb5/krb/gen_seqnum.c
8 *
9 * Copyright 1991 by the Massachusetts Institute of Technology.
10 * All Rights Reserved.
11 *
12 * Export of this software from the United States of America may
13 * require a specific license from the United States Government.
14 * It is the responsibility of any person or organization contemplating
15 * export to obtain such a license before exporting.
16 *
17 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
18 * distribute this software and its documentation for any purpose and
19 * without fee is hereby granted, provided that the above copyright
20 * notice appear in all copies and that both that copyright notice and
21 * this permission notice appear in supporting documentation, and that
22 * the name of M.I.T. not be used in advertising or publicity pertaining
23 * to distribution of the software without specific, written prior
24 * permission. Furthermore if you modify this software you must label
25 * your software as modified software and not distribute it in such a
26 * fashion that it might be confused with the original M.I.T. software.
27 * M.I.T. makes no representations about the suitability of
28 * this software for any purpose. It is provided "as is" without express
29 * or implied warranty.
30 *
31 *
32 * Routine to automatically generate a starting sequence number.
33 * We do this by getting a random key and encrypting something with it,
34 * then taking the output and slicing it up.
35 */
36
37 #include "k5-int.h"
38
39 #ifndef MIN
40 #define MIN(a,b) ((a) < (b) ? (a) : (b))
41 #endif
42
43 krb5_error_code
krb5_generate_seq_number(krb5_context context,const krb5_keyblock * key,krb5_ui_4 * seqno)44 krb5_generate_seq_number(krb5_context context, const krb5_keyblock *key, krb5_ui_4 *seqno)
45 {
46 krb5_data seed;
47 krb5_error_code retval;
48 #if 0
49 /*
50 * Solaris Kerberos: Don't bother with this PRNG stuff,
51 * we have /dev/random and PKCS#11 to handle Random Numbers.
52 */
53
54
55 seed.length = key->length;
56 seed.data = key->contents;
57 if ((retval = krb5_c_random_add_entropy(context, KRB5_C_RANDSOURCE_TRUSTEDPARTY, &seed)))
58 return(retval);
59 #endif /* 0 */
60
61 seed.length = sizeof(*seqno);
62 seed.data = (char *) seqno;
63 retval = krb5_c_random_make_octets(context, &seed);
64 if (retval)
65 return retval;
66 /*
67 * Work around implementation incompatibilities by not generating
68 * initial sequence numbers greater than 2^30. Previous MIT
69 * implementations use signed sequence numbers, so initial
70 * sequence numbers 2^31 to 2^32-1 inclusive will be rejected.
71 * Letting the maximum initial sequence number be 2^30-1 allows
72 * for about 2^30 messages to be sent before wrapping into
73 * "negative" numbers.
74 */
75 *seqno &= 0x3fffffff;
76 if (*seqno == 0)
77 *seqno = 1;
78 return 0;
79 }
80