1/*
2 * Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include "../ssl_local.h"
11#include "record_local.h"
12
13/* mod 128 saturating subtract of two 64-bit values in big-endian order */
14static int satsub64be(const unsigned char *v1, const unsigned char *v2)
15{
16    int64_t ret;
17    uint64_t l1, l2;
18
19    n2l8(v1, l1);
20    n2l8(v2, l2);
21
22    ret = l1 - l2;
23
24    /* We do not permit wrap-around */
25    if (l1 > l2 && ret < 0)
26        return 128;
27    else if (l2 > l1 && ret > 0)
28        return -128;
29
30    if (ret > 128)
31        return 128;
32    else if (ret < -128)
33        return -128;
34    else
35        return (int)ret;
36}
37
38int dtls1_record_replay_check(SSL *s, DTLS1_BITMAP *bitmap)
39{
40    int cmp;
41    unsigned int shift;
42    const unsigned char *seq = s->rlayer.read_sequence;
43
44    cmp = satsub64be(seq, bitmap->max_seq_num);
45    if (cmp > 0) {
46        SSL3_RECORD_set_seq_num(RECORD_LAYER_get_rrec(&s->rlayer), seq);
47        return 1;               /* this record in new */
48    }
49    shift = -cmp;
50    if (shift >= sizeof(bitmap->map) * 8)
51        return 0;               /* stale, outside the window */
52    else if (bitmap->map & (1UL << shift))
53        return 0;               /* record previously received */
54
55    SSL3_RECORD_set_seq_num(RECORD_LAYER_get_rrec(&s->rlayer), seq);
56    return 1;
57}
58
59void dtls1_record_bitmap_update(SSL *s, DTLS1_BITMAP *bitmap)
60{
61    int cmp;
62    unsigned int shift;
63    const unsigned char *seq = RECORD_LAYER_get_read_sequence(&s->rlayer);
64
65    cmp = satsub64be(seq, bitmap->max_seq_num);
66    if (cmp > 0) {
67        shift = cmp;
68        if (shift < sizeof(bitmap->map) * 8)
69            bitmap->map <<= shift, bitmap->map |= 1UL;
70        else
71            bitmap->map = 1UL;
72        memcpy(bitmap->max_seq_num, seq, SEQ_NUM_SIZE);
73    } else {
74        shift = -cmp;
75        if (shift < sizeof(bitmap->map) * 8)
76            bitmap->map |= 1UL << shift;
77    }
78}
79