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 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