ttssh2/ttxssh/hostkey.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 "hostkey.h"
#include "kex.h"


struct ssh2_host_key_t {
        ssh_keyalgo algo;
        ssh_keytype type;
        int digest_type;
        char *name;
};

static const struct ssh2_host_key_t ssh2_host_key[] = {
        {KEY_ALGO_RSA1,     KEY_RSA1,     NID_sha1,   "ssh-rsa1"},            // for SSH1 only
        {KEY_ALGO_RSA,      KEY_RSA,      NID_sha1,   "ssh-rsa"},             // RFC4253
        {KEY_ALGO_DSA,      KEY_DSA,      NID_sha1,   "ssh-dss"},             // RFC4253
        {KEY_ALGO_ECDSA256, KEY_ECDSA256, NID_sha256, "ecdsa-sha2-nistp256"}, // RFC5656
        {KEY_ALGO_ECDSA384, KEY_ECDSA384, NID_sha384, "ecdsa-sha2-nistp384"}, // RFC5656
        {KEY_ALGO_ECDSA521, KEY_ECDSA521, NID_sha512, "ecdsa-sha2-nistp521"}, // RFC5656
        {KEY_ALGO_ED25519,  KEY_ED25519,  NID_sha512, "ssh-ed25519"},         // RDC8709
        {KEY_ALGO_RSASHA256,KEY_RSA,      NID_sha256, "rsa-sha2-256"},        // RFC8332
        {KEY_ALGO_RSASHA512,KEY_RSA,      NID_sha512, "rsa-sha2-512"},        // RFC8332
        {KEY_ALGO_UNSPEC,   KEY_UNSPEC,   NID_undef,  "ssh-unknown"},
        {KEY_ALGO_NONE,     KEY_NONE,     NID_undef,  NULL},
};

struct ssh_digest_t {
        digest_algorithm id;
        char *name;
};

/* NB. Indexed directly by algorithm number */
static const struct ssh_digest_t ssh_digests[] = {
        { SSH_DIGEST_MD5,       "MD5" },
        { SSH_DIGEST_RIPEMD160, "RIPEMD160" },
        { SSH_DIGEST_SHA1,      "SHA1" },
        { SSH_DIGEST_SHA256,    "SHA256" },
        { SSH_DIGEST_SHA384,    "SHA384" },
        { SSH_DIGEST_SHA512,    "SHA512" },
        { SSH_DIGEST_MAX,       NULL },
};


ssh_keytype get_hostkey_type_from_name(char *name)
{
        if (strcmp(name, "rsa1") == 0) {
                return KEY_RSA1;
        } else if (strcmp(name, "rsa") == 0) {
                return KEY_RSA;
        } else if (strcmp(name, "dsa") == 0) {
                return KEY_DSA;
        } else if (strcmp(name, "ssh-rsa") == 0) {
                return KEY_RSA;
        } else if (strcmp(name, "ssh-dss") == 0) {
                return KEY_DSA;
        } else if (strcmp(name, "ecdsa-sha2-nistp256") == 0) {
                return KEY_ECDSA256;
        } else if (strcmp(name, "ecdsa-sha2-nistp384") == 0) {
                return KEY_ECDSA384;
        } else if (strcmp(name, "ecdsa-sha2-nistp521") == 0) {
                return KEY_ECDSA521;
        } else if (strcmp(name, "ssh-ed25519") == 0) {
                return KEY_ED25519;
        }
        return KEY_UNSPEC;
}

char* get_ssh2_hostkey_type_name(ssh_keytype type)
{
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

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

        // not found.
        return "ssh-unknown";
}

char *get_ssh2_hostkey_type_name_from_key(Key *key)
{
        return get_ssh2_hostkey_type_name(key->type);
}

char* get_ssh2_keyalgo_name(ssh_keyalgo algo)
{
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

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

        // not found.
        return "ssh-unknown";
}

ssh_keyalgo get_ssh2_keyalgo_from_name(const char *name)
{
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

        while (ptr->name != NULL) {
                if (strcmp(name, ptr->name) == 0) {
                        return ptr->algo;
                }
                ptr++;
        }

        // not found.
        return KEY_ALGO_UNSPEC;
}

int get_ssh2_key_hashtype(ssh_keyalgo algo)
{
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

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

        // not found.
        return NID_sha1;
}

ssh_keytype get_ssh2_keytype_from_keyalgo(ssh_keyalgo algo)
{
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

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

        // not found.
        return KEY_UNSPEC;
}

const char* get_ssh2_keytype_name_from_keyalgo(ssh_keyalgo algo)
{
        return get_ssh2_hostkey_type_name(get_ssh2_keytype_from_keyalgo(algo));
}

char* get_digest_algorithm_name(digest_algorithm id)
{
        const struct ssh_digest_t *ptr = ssh_digests;

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

        // not found.
        return "unknown";
}

void normalize_host_key_order(char *buf)
{
        static char default_strings[] = {
                KEY_ALGO_ECDSA256,
                KEY_ALGO_ECDSA384,
                KEY_ALGO_ECDSA521,
                KEY_ALGO_ED25519,
                KEY_ALGO_RSASHA256,
                KEY_ALGO_RSASHA512,
                KEY_ALGO_RSA,
                KEY_ALGO_DSA,
                KEY_ALGO_NONE,
        };

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

ssh_keyalgo choose_SSH2_host_key_algorithm(char *server_proposal, char *my_proposal)
{
        ssh_keytype type = KEY_UNSPEC;
        char str_keytype[20];
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

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

        return get_ssh2_keyalgo_from_name(str_keytype);
}

// Host Key�A���S���Y���D���������������Amyproposal[]�������������B
// (2011.2.28 yutaka)
void SSH2_update_host_key_myproposal(PTInstVar pvar)
{
        static char buf[256]; // TODO: malloc()��������
        int index;
        int len, i;

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

        buf[0] = '\0';
        for (i = 0 ; pvar->settings.HostKeyOrder[i] != 0 ; i++) {
                index = pvar->settings.HostKeyOrder[i] - '0';
                if (index == KEY_NONE) // disabled line
                        break;
                strncat_s(buf, sizeof(buf), get_ssh2_keyalgo_name(index), _TRUNCATE);
                strncat_s(buf, sizeof(buf), ",", _TRUNCATE);
        }
        len = strlen(buf);
        if (len > 0)
                buf[len - 1] = '\0';  // get rid of comma
        myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = buf; 
}

ssh_keyalgo choose_SSH2_keysign_algorithm(char *server_proposal, ssh_keytype keytype)
{
        char buff[128];
        const struct ssh2_host_key_t *ptr = ssh2_host_key;

        if (keytype == KEY_RSA) {
                if (server_proposal == NULL) {
                        logprintf(LOG_LEVEL_VERBOSE, "%s: no server_sig_algs, ssh-rsa is selected.", __FUNCTION__);
                        return KEY_ALGO_RSA;
                }
                else {
                        choose_SSH2_proposal(server_proposal, "rsa-sha2-512,rsa-sha2-256,ssh-rsa", buff, sizeof(buff));
                        if (strlen(buff) == 0) {
                                // not found.
                                logprintf(LOG_LEVEL_WARNING, "%s: no match sign algorithm.", __FUNCTION__);
                                return KEY_ALGO_UNSPEC;
                        }
                        else {
                                logprintf(LOG_LEVEL_VERBOSE, "%s: %s is selected.", __FUNCTION__, buff);
                                return get_ssh2_keyalgo_from_name(buff);
                        }
                }
        }
        else {
                while (ptr->type != KEY_UNSPEC && ptr->type != keytype) {
                        ptr++;
                }

                return ptr->algo;
        }

        // not reached
        return KEY_ALGO_UNSPEC;
}