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Annotation of src/usr.bin/ssh/kexkemc.c, Revision 1.1

1.1     ! djm         1: /* $OpenBSD: $ */
        !             2: /*
        !             3:  * Copyright (c) 2019 Markus Friedl.  All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  *
        !            14:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
        !            15:  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
        !            16:  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
        !            17:  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
        !            18:  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
        !            19:  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
        !            20:  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
        !            21:  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
        !            22:  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
        !            23:  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
        !            24:  */
        !            25:
        !            26: #include <sys/types.h>
        !            27:
        !            28: #include <stdio.h>
        !            29: #include <string.h>
        !            30: #include <signal.h>
        !            31:
        !            32: #include "sshkey.h"
        !            33: #include "kex.h"
        !            34: #include "log.h"
        !            35: #include "packet.h"
        !            36: #include "ssh2.h"
        !            37: #include "sshbuf.h"
        !            38: #include "digest.h"
        !            39: #include "ssherr.h"
        !            40:
        !            41: static int
        !            42: input_kex_kem_reply(int type, u_int32_t seq, struct ssh *ssh);
        !            43:
        !            44: int
        !            45: kex_kem_client(struct ssh *ssh)
        !            46: {
        !            47:        struct kex *kex = ssh->kex;
        !            48:        int r;
        !            49:
        !            50:        if ((r = kex_kem_sntrup4591761x25519_keypair(kex)) != 0)
        !            51:                return r;
        !            52:        if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
        !            53:            (r = sshpkt_put_stringb(ssh, kex->kem_client_pub)) != 0 ||
        !            54:            (r = sshpkt_send(ssh)) != 0)
        !            55:                return r;
        !            56:        debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
        !            57:        ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_kem_reply);
        !            58:        return 0;
        !            59: }
        !            60:
        !            61: static int
        !            62: input_kex_kem_reply(int type, u_int32_t seq, struct ssh *ssh)
        !            63: {
        !            64:        struct kex *kex = ssh->kex;
        !            65:        struct sshkey *server_host_key = NULL;
        !            66:        struct sshbuf *shared_secret = NULL;
        !            67:        u_char *server_pubkey = NULL;
        !            68:        u_char *server_host_key_blob = NULL, *signature = NULL;
        !            69:        u_char hash[SSH_DIGEST_MAX_LENGTH];
        !            70:        size_t slen, pklen, sbloblen, hashlen;
        !            71:        int r;
        !            72:
        !            73:        /* hostkey */
        !            74:        if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
        !            75:            &sbloblen)) != 0 ||
        !            76:            (r = sshkey_from_blob(server_host_key_blob, sbloblen,
        !            77:            &server_host_key)) != 0)
        !            78:                goto out;
        !            79:        if ((r = kex_verify_host_key(ssh, server_host_key)) != 0)
        !            80:                goto out;
        !            81:
        !            82:        /* Q_S, server public key */
        !            83:        /* signed H */
        !            84:        if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
        !            85:            (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
        !            86:            (r = sshpkt_get_end(ssh)) != 0)
        !            87:                goto out;
        !            88:
        !            89:        /* compute shared secret */
        !            90:        if ((r = kex_kem_sntrup4591761x25519_dec(kex, server_pubkey, pklen,
        !            91:            &shared_secret)) != 0)
        !            92:                goto out;
        !            93:
        !            94:        /* calc and verify H */
        !            95:        hashlen = sizeof(hash);
        !            96:        if ((r = kex_c25519_hash(
        !            97:            kex->hash_alg,
        !            98:            kex->client_version,
        !            99:            kex->server_version,
        !           100:            sshbuf_ptr(kex->my), sshbuf_len(kex->my),
        !           101:            sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
        !           102:            server_host_key_blob, sbloblen,
        !           103:            sshbuf_ptr(kex->kem_client_pub), sshbuf_len(kex->kem_client_pub),
        !           104:            server_pubkey, pklen,
        !           105:            sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
        !           106:            hash, &hashlen)) != 0)
        !           107:                goto out;
        !           108:
        !           109:        if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
        !           110:            kex->hostkey_alg, ssh->compat)) != 0)
        !           111:                goto out;
        !           112:
        !           113:        if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
        !           114:                r = kex_send_newkeys(ssh);
        !           115: out:
        !           116:        explicit_bzero(hash, sizeof(hash));
        !           117:        explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
        !           118:        explicit_bzero(kex->sntrup4591761_client_key,
        !           119:            sizeof(kex->sntrup4591761_client_key));
        !           120:        free(server_host_key_blob);
        !           121:        free(server_pubkey);
        !           122:        free(signature);
        !           123:        sshkey_free(server_host_key);
        !           124:        sshbuf_free(shared_secret);
        !           125:        sshbuf_free(kex->kem_client_pub);
        !           126:        kex->kem_client_pub = NULL;
        !           127:        return r;
        !           128: }