int ssh_make_sessionid(ssh_session session) {
    ssh_string num = NULL;
    ssh_buffer server_hash = NULL;
    ssh_buffer client_hash = NULL;
    ssh_buffer buf = NULL;
    int rc = SSH_ERROR;

    buf = ssh_buffer_new();
    if (buf == NULL) {
        return rc;
    }

    rc = ssh_buffer_pack(buf,
                         "ss",
                         session->clientbanner,
                         session->serverbanner);
    if (rc == SSH_ERROR) {
        goto error;
    }

    if (session->client) {
        server_hash = session->in_hashbuf;
        client_hash = session->out_hashbuf;
    } else {
        server_hash = session->out_hashbuf;
        client_hash = session->in_hashbuf;
    }

    /*
     * Handle the two final fields for the KEXINIT message (RFC 4253 7.1):
     *
     *      boolean      first_kex_packet_follows
     *      uint32       0 (reserved for future extension)
     */
    rc = ssh_buffer_add_u8(server_hash, 0);
    if (rc < 0) {
        goto error;
    }
    rc = ssh_buffer_add_u32(server_hash, 0);
    if (rc < 0) {
        goto error;
    }

    /* These fields are handled for the server case in ssh_packet_kexinit. */
    if (session->client) {
        rc = ssh_buffer_add_u8(client_hash, 0);
        if (rc < 0) {
            goto error;
        }
        rc = ssh_buffer_add_u32(client_hash, 0);
        if (rc < 0) {
            goto error;
        }
    }

    rc = ssh_buffer_pack(buf,
                         "dPdPS",
                         ssh_buffer_get_len(client_hash),
                         ssh_buffer_get_len(client_hash),
                         ssh_buffer_get(client_hash),
                         ssh_buffer_get_len(server_hash),
                         ssh_buffer_get_len(server_hash),
                         ssh_buffer_get(server_hash),
                         session->next_crypto->server_pubkey);

    if(rc != SSH_OK){
        goto error;
    }

    if (session->next_crypto->kex_type == SSH_KEX_DH_GROUP1_SHA1 ||
            session->next_crypto->kex_type == SSH_KEX_DH_GROUP14_SHA1) {
        rc = ssh_buffer_pack(buf,
                             "BB",
                             session->next_crypto->e,
                             session->next_crypto->f);
        if (rc != SSH_OK) {
            goto error;
        }

#ifdef HAVE_ECDH
    } else if (session->next_crypto->kex_type == SSH_KEX_ECDH_SHA2_NISTP256) {
        if (session->next_crypto->ecdh_client_pubkey == NULL ||
            session->next_crypto->ecdh_server_pubkey == NULL) {
            SSH_LOG(SSH_LOG_WARNING, "ECDH parameted missing");
            goto error;
        }
        rc = ssh_buffer_pack(buf,
                             "SS",
                             session->next_crypto->ecdh_client_pubkey,
                             session->next_crypto->ecdh_server_pubkey);
        if (rc != SSH_OK) {
            goto error;
        }
#endif
#ifdef HAVE_CURVE25519
    } else if (session->next_crypto->kex_type == SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG) {
        rc = ssh_buffer_pack(buf,
                             "dPdP",
                             CURVE25519_PUBKEY_SIZE,
                             (size_t)CURVE25519_PUBKEY_SIZE, session->next_crypto->curve25519_client_pubkey,
                             CURVE25519_PUBKEY_SIZE,
                             (size_t)CURVE25519_PUBKEY_SIZE, session->next_crypto->curve25519_server_pubkey);

        if (rc != SSH_OK) {
            goto error;
        }
#endif
    }
    rc = ssh_buffer_pack(buf, "B", session->next_crypto->k);
    if (rc != SSH_OK) {
        goto error;
    }

#ifdef DEBUG_CRYPTO
    ssh_print_hexa("hash buffer", ssh_buffer_get(buf), ssh_buffer_get_len(buf));
#endif

    switch (session->next_crypto->kex_type) {
    case SSH_KEX_DH_GROUP1_SHA1:
    case SSH_KEX_DH_GROUP14_SHA1:
        session->next_crypto->digest_len = SHA_DIGEST_LENGTH;
        session->next_crypto->mac_type = SSH_MAC_SHA1;
        session->next_crypto->secret_hash = malloc(session->next_crypto->digest_len);
        if (session->next_crypto->secret_hash == NULL) {
            ssh_set_error_oom(session);
            goto error;
        }
        sha1(ssh_buffer_get(buf), ssh_buffer_get_len(buf),
                                   session->next_crypto->secret_hash);
        break;
    case SSH_KEX_ECDH_SHA2_NISTP256:
    case SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG:
        session->next_crypto->digest_len = SHA256_DIGEST_LENGTH;
        session->next_crypto->mac_type = SSH_MAC_SHA256;
        session->next_crypto->secret_hash = malloc(session->next_crypto->digest_len);
        if (session->next_crypto->secret_hash == NULL) {
            ssh_set_error_oom(session);
            goto error;
        }
        sha256(ssh_buffer_get(buf), ssh_buffer_get_len(buf),
                                     session->next_crypto->secret_hash);
        break;
    }
    /* During the first kex, secret hash and session ID are equal. However, after
     * a key re-exchange, a new secret hash is calculated. This hash will not replace
     * but complement existing session id.
     */
    if (!session->next_crypto->session_id) {
        session->next_crypto->session_id = malloc(session->next_crypto->digest_len);
        if (session->next_crypto->session_id == NULL) {
            ssh_set_error_oom(session);
            goto error;
        }
        memcpy(session->next_crypto->session_id, session->next_crypto->secret_hash,
                session->next_crypto->digest_len);
    }
#ifdef DEBUG_CRYPTO
    printf("Session hash: \n");
    ssh_print_hexa("secret hash", session->next_crypto->secret_hash, session->next_crypto->digest_len);
    ssh_print_hexa("session id", session->next_crypto->session_id, session->next_crypto->digest_len);
#endif

    rc = SSH_OK;
error:
    ssh_buffer_free(buf);
    ssh_buffer_free(client_hash);
    ssh_buffer_free(server_hash);

    session->in_hashbuf = NULL;
    session->out_hashbuf = NULL;

    ssh_string_free(num);

    return rc;
}