ssl/record/dtls1_bitmap.c

/*
 * Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#include "../ssl_local.h"
#include "record_local.h"

/* mod 128 saturating subtract of two 64-bit values in big-endian order */
static int satsub64be(const unsigned char *v1, const unsigned char *v2)
{
    int64_t ret;
    uint64_t l1, l2;

    n2l8(v1, l1);
    n2l8(v2, l2);

    ret = l1 - l2;

    /* We do not permit wrap-around */
    if (l1 > l2 && ret < 0)
        return 128;
    else if (l2 > l1 && ret > 0)
        return -128;

    if (ret > 128)
        return 128;
    else if (ret < -128)
        return -128;
    else
        return (int)ret;
}

int dtls1_record_replay_check(SSL *s, DTLS1_BITMAP *bitmap)
{
    int cmp;
    unsigned int shift;
    const unsigned char *seq = s->rlayer.read_sequence;

    cmp = satsub64be(seq, bitmap->max_seq_num);
    if (cmp > 0) {
        SSL3_RECORD_set_seq_num(RECORD_LAYER_get_rrec(&s->rlayer), seq);
        return 1;               /* this record in new */
    }
    shift = -cmp;
    if (shift >= sizeof(bitmap->map) * 8)
        return 0;               /* stale, outside the window */
    else if (bitmap->map & (1UL << shift))
        return 0;               /* record previously received */

    SSL3_RECORD_set_seq_num(RECORD_LAYER_get_rrec(&s->rlayer), seq);
    return 1;
}

void dtls1_record_bitmap_update(SSL *s, DTLS1_BITMAP *bitmap)
{
    int cmp;
    unsigned int shift;
    const unsigned char *seq = RECORD_LAYER_get_read_sequence(&s->rlayer);

    cmp = satsub64be(seq, bitmap->max_seq_num);
    if (cmp > 0) {
        shift = cmp;
        if (shift < sizeof(bitmap->map) * 8)
            bitmap->map <<= shift, bitmap->map |= 1UL;
        else
            bitmap->map = 1UL;
        memcpy(bitmap->max_seq_num, seq, SEQ_NUM_SIZE);
    } else {
        shift = -cmp;
        if (shift < sizeof(bitmap->map) * 8)
            bitmap->map |= 1UL << shift;
    }
}