ttssh2/ttxssh/comp.c

/*
 * (C) 2021- TeraTerm Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "ttxssh.h"
#include "comp.h"
#include "kex.h"


struct ssh2_comp_t {
        compression_type type;
        char *name;
};

static const struct ssh2_comp_t ssh2_comps[] = {
        {COMP_NOCOMP,  "none"},             // RFC4253
        {COMP_ZLIB,    "zlib"},             // RFC4253
        {COMP_DELAYED, "zlib@openssh.com"},
        {COMP_NONE,    NULL},
};


char* get_ssh2_comp_name(compression_type type)
{
        const struct ssh2_comp_t *ptr = ssh2_comps;

        while (ptr->name != NULL) {
                if (type == ptr->type) {
                        return ptr->name;
                }
                ptr++;
        }

        // not found.
        return "unknown";
}

void normalize_comp_order(char *buf)
{
        static char default_strings[] = {
                COMP_DELAYED,
                COMP_ZLIB,
                COMP_NOCOMP,
                COMP_NONE,
        };

        normalize_generic_order(buf, default_strings, NUM_ELEM(default_strings));
}

compression_type choose_SSH2_compression_algorithm(char *server_proposal, char *my_proposal)
{
        compression_type type = COMP_UNKNOWN;
        char str_comp[20];
        const struct ssh2_comp_t *ptr = ssh2_comps;

        choose_SSH2_proposal(server_proposal, my_proposal, str_comp, sizeof(str_comp));

        while (ptr->name != NULL) {
                if (strcmp(ptr->name, str_comp) == 0) {
                        type = ptr->type;
                        break;
                }
                ptr++;
        }

        return (type);
}

void SSH2_update_compression_myproposal(PTInstVar pvar)
{
        static char buf[128]; // TODO: malloc()��������
        int index;
        int len, i;

        // ���M�������������������������A�O�������B(2006.6.26 maya)
        if (pvar->socket != INVALID_SOCKET) {
                return;
        }

        // ���k���x�����������Amyproposal[]�������������B(2005.7.9 yutaka)
        buf[0] = '\0';
        for (i = 0 ; pvar->settings.CompOrder[i] != 0 ; i++) {
                index = pvar->settings.CompOrder[i] - '0';
                if (index == COMP_NONE) // disabled line
                        break;
                strncat_s(buf, sizeof(buf), get_ssh2_comp_name(index), _TRUNCATE);
                strncat_s(buf, sizeof(buf), ",", _TRUNCATE);
        }
        len = strlen(buf);
        if (len > 0)
                buf[len - 1] = '\0';  // get rid of comma

        // ���k�w���������������A���k���x�������������[���������B
        if (buf[0] == '\0') {
                pvar->settings.CompressionLevel = 0;
        }

        if (pvar->settings.CompressionLevel == 0) {
                _snprintf_s(buf, sizeof(buf), _TRUNCATE, get_ssh2_comp_name(COMP_NOCOMP));
        }
        if (buf[0] != '\0') {
                myproposal[PROPOSAL_COMP_ALGS_CTOS] = buf;  // Client To Server
                myproposal[PROPOSAL_COMP_ALGS_STOC] = buf;  // Server To Client
        }
}