Don't change the state of the ETM flags until CCS processing

Changing the ciphersuite during a renegotiation can result in a crash
leading to a DoS attack. ETM has not been implemented in 1.1.0 for DTLS
so this is TLS only.

The problem is caused by changing the flag indicating whether to use ETM
or not immediately on negotiation of ETM, rather than at CCS. Therefore,
during a renegotiation, if the ETM state is changing (usually due to a
change of ciphersuite), then an error/crash will occur.

Due to the fact that there are separate CCS messages for read and write
we actually now need two flags to determine whether to use ETM or not.

CVE-2017-3733

Reviewed-by: Richard Levitte <levitte@openssl.org>
int dtls1_get_record(SSL *s)
{
    int ssl_major, ssl_minor;
    int i, n;
    SSL3_RECORD *rr;
    unsigned char *p = NULL;
    unsigned short version;
    DTLS1_BITMAP *bitmap;
    unsigned int is_next_epoch;

    rr = RECORD_LAYER_get_rrec(&s->rlayer);

 again:
    /*
     * The epoch may have changed.  If so, process all the pending records.
     * This is a non-blocking operation.
     */
    if (!dtls1_process_buffered_records(s))
        return -1;

    /* if we're renegotiating, then there may be buffered records */
    if (dtls1_get_processed_record(s))
        return 1;

    /* get something from the wire */

    /* check if we have the header */
    if ((RECORD_LAYER_get_rstate(&s->rlayer) != SSL_ST_READ_BODY) ||
        (RECORD_LAYER_get_packet_length(&s->rlayer) < DTLS1_RT_HEADER_LENGTH)) {
        n = ssl3_read_n(s, DTLS1_RT_HEADER_LENGTH,
                        SSL3_BUFFER_get_len(&s->rlayer.rbuf), 0, 1);
        /* read timeout is handled by dtls1_read_bytes */
        if (n <= 0)
            return (n);         /* error or non-blocking */

        /* this packet contained a partial record, dump it */
        if (RECORD_LAYER_get_packet_length(&s->rlayer) !=
            DTLS1_RT_HEADER_LENGTH) {
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_BODY);

        p = RECORD_LAYER_get_packet(&s->rlayer);

        if (s->msg_callback)
            s->msg_callback(0, 0, SSL3_RT_HEADER, p, DTLS1_RT_HEADER_LENGTH,
                            s, s->msg_callback_arg);

        /* Pull apart the header into the DTLS1_RECORD */
        rr->type = *(p++);
        ssl_major = *(p++);
        ssl_minor = *(p++);
        version = (ssl_major << 8) | ssl_minor;

        /* sequence number is 64 bits, with top 2 bytes = epoch */
        n2s(p, rr->epoch);

        memcpy(&(RECORD_LAYER_get_read_sequence(&s->rlayer)[2]), p, 6);
        p += 6;

        n2s(p, rr->length);

        /* Lets check version */
        if (!s->first_packet) {
            if (version != s->version) {
                /* unexpected version, silently discard */
                rr->length = 0;
                RECORD_LAYER_reset_packet_length(&s->rlayer);
                goto again;
            }
        }

        if ((version & 0xff00) != (s->version & 0xff00)) {
            /* wrong version, silently discard record */
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        if (rr->length > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
            /* record too long, silently discard it */
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        /* now s->rlayer.rstate == SSL_ST_READ_BODY */
    }

    /* s->rlayer.rstate == SSL_ST_READ_BODY, get and decode the data */

    if (rr->length >
        RECORD_LAYER_get_packet_length(&s->rlayer) - DTLS1_RT_HEADER_LENGTH) {
        /* now s->packet_length == DTLS1_RT_HEADER_LENGTH */
        i = rr->length;
        n = ssl3_read_n(s, i, i, 1, 1);
        /* this packet contained a partial record, dump it */
        if (n != i) {
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        /*
         * now n == rr->length, and s->packet_length ==
         * DTLS1_RT_HEADER_LENGTH + rr->length
         */
    }
    /* set state for later operations */
    RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_HEADER);

    /* match epochs.  NULL means the packet is dropped on the floor */
    bitmap = dtls1_get_bitmap(s, rr, &is_next_epoch);
    if (bitmap == NULL) {
        rr->length = 0;
        RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
        goto again;             /* get another record */
    }
#ifndef OPENSSL_NO_SCTP
    /* Only do replay check if no SCTP bio */
    if (!BIO_dgram_is_sctp(SSL_get_rbio(s))) {
#endif
        /* Check whether this is a repeat, or aged record. */
        /*
         * TODO: Does it make sense to have replay protection in epoch 0 where
         * we have no integrity negotiated yet?
         */
        if (!dtls1_record_replay_check(s, bitmap)) {
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
            goto again;         /* get another record */
        }
#ifndef OPENSSL_NO_SCTP
    }
#endif

    /* just read a 0 length packet */
    if (rr->length == 0)
        goto again;

    /*
     * If this record is from the next epoch (either HM or ALERT), and a
     * handshake is currently in progress, buffer it since it cannot be
     * processed at this time.
     */
    if (is_next_epoch) {
        if ((SSL_in_init(s) || ossl_statem_get_in_handshake(s))) {
            if (dtls1_buffer_record
                (s, &(DTLS_RECORD_LAYER_get_unprocessed_rcds(&s->rlayer)),
                 rr->seq_num) < 0)
                return -1;
        }
        rr->length = 0;
        RECORD_LAYER_reset_packet_length(&s->rlayer);
        goto again;
    }

    if (!dtls1_process_record(s, bitmap)) {
        rr->length = 0;
        RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
        goto again;             /* get another record */
    }

    return (1);

}

int dtls1_get_record(SSL *s)
{
    int ssl_major, ssl_minor;
    int i, n;
    SSL3_RECORD *rr;
    unsigned char *p = NULL;
    unsigned short version;
    DTLS1_BITMAP *bitmap;
    unsigned int is_next_epoch;

    rr = RECORD_LAYER_get_rrec(&s->rlayer);

 again:
    /*
     * The epoch may have changed.  If so, process all the pending records.
     * This is a non-blocking operation.
     */
    if (!dtls1_process_buffered_records(s))
        return -1;

    /* if we're renegotiating, then there may be buffered records */
    if (dtls1_get_processed_record(s))
        return 1;

    /* get something from the wire */

    /* check if we have the header */
    if ((RECORD_LAYER_get_rstate(&s->rlayer) != SSL_ST_READ_BODY) ||
        (RECORD_LAYER_get_packet_length(&s->rlayer) < DTLS1_RT_HEADER_LENGTH)) {
        n = ssl3_read_n(s, DTLS1_RT_HEADER_LENGTH,
                        SSL3_BUFFER_get_len(&s->rlayer.rbuf), 0, 1);
        /* read timeout is handled by dtls1_read_bytes */
        if (n <= 0)
            return (n);         /* error or non-blocking */

        /* this packet contained a partial record, dump it */
        if (RECORD_LAYER_get_packet_length(&s->rlayer) !=
            DTLS1_RT_HEADER_LENGTH) {
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_BODY);

        p = RECORD_LAYER_get_packet(&s->rlayer);

        if (s->msg_callback)
            s->msg_callback(0, 0, SSL3_RT_HEADER, p, DTLS1_RT_HEADER_LENGTH,
                            s, s->msg_callback_arg);

        /* Pull apart the header into the DTLS1_RECORD */
        rr->type = *(p++);
        ssl_major = *(p++);
        ssl_minor = *(p++);
        version = (ssl_major << 8) | ssl_minor;

        /* sequence number is 64 bits, with top 2 bytes = epoch */
        n2s(p, rr->epoch);

        memcpy(&(RECORD_LAYER_get_read_sequence(&s->rlayer)[2]), p, 6);
        p += 6;

        n2s(p, rr->length);

        /* Lets check version */
        if (!s->first_packet) {
            if (version != s->version) {
                /* unexpected version, silently discard */
                rr->length = 0;
                RECORD_LAYER_reset_packet_length(&s->rlayer);
                goto again;
            }
        }

        if ((version & 0xff00) != (s->version & 0xff00)) {
            /* wrong version, silently discard record */
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        if (rr->length > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
            /* record too long, silently discard it */
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        /* now s->rlayer.rstate == SSL_ST_READ_BODY */
    }

    /* s->rlayer.rstate == SSL_ST_READ_BODY, get and decode the data */

    if (rr->length >
        RECORD_LAYER_get_packet_length(&s->rlayer) - DTLS1_RT_HEADER_LENGTH) {
        /* now s->packet_length == DTLS1_RT_HEADER_LENGTH */
        i = rr->length;
        n = ssl3_read_n(s, i, i, 1, 1);
        /* this packet contained a partial record, dump it */
        if (n != i) {
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer);
            goto again;
        }

        /*
         * now n == rr->length, and s->packet_length ==
         * DTLS1_RT_HEADER_LENGTH + rr->length
         */
    }
    /* set state for later operations */
    RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_HEADER);

    /* match epochs.  NULL means the packet is dropped on the floor */
    bitmap = dtls1_get_bitmap(s, rr, &is_next_epoch);
    if (bitmap == NULL) {
        rr->length = 0;
        RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
        goto again;             /* get another record */
    }
#ifndef OPENSSL_NO_SCTP
    /* Only do replay check if no SCTP bio */
    if (!BIO_dgram_is_sctp(SSL_get_rbio(s))) {
#endif
        /* Check whether this is a repeat, or aged record. */
        /*
         * TODO: Does it make sense to have replay protection in epoch 0 where
         * we have no integrity negotiated yet?
         */
        if (!dtls1_record_replay_check(s, bitmap)) {
            rr->length = 0;
            RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
            goto again;         /* get another record */
        }
#ifndef OPENSSL_NO_SCTP
    }
#endif

    /* just read a 0 length packet */
    if (rr->length == 0)
        goto again;

    /*
     * If this record is from the next epoch (either HM or ALERT), and a
     * handshake is currently in progress, buffer it since it cannot be
     * processed at this time.
     */
    if (is_next_epoch) {
        if ((SSL_in_init(s) || ossl_statem_get_in_handshake(s))) {
            if (dtls1_buffer_record
                (s, &(DTLS_RECORD_LAYER_get_unprocessed_rcds(&s->rlayer)),
                 rr->seq_num) < 0)
                return -1;
        }
        rr->length = 0;
        RECORD_LAYER_reset_packet_length(&s->rlayer);
        goto again;
    }

    if (!dtls1_process_record(s, bitmap)) {
        rr->length = 0;
        RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
        goto again;             /* get another record */
    }

    return (1);

}
