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Annotation of src/usr.bin/ssh/kexc25519.c, Revision 1.1

1.1     ! markus      1: /*
        !             2:  * Copyright (c) 2001, 2013 Markus Friedl.  All rights reserved.
        !             3:  * Copyright (c) 2010 Damien Miller.  All rights reserved.
        !             4:  * Copyright (c) 2013 Aris Adamantiadis.  All rights reserved.
        !             5:  *
        !             6:  * Redistribution and use in source and binary forms, with or without
        !             7:  * modification, are permitted provided that the following conditions
        !             8:  * are met:
        !             9:  * 1. Redistributions of source code must retain the above copyright
        !            10:  *    notice, this list of conditions and the following disclaimer.
        !            11:  * 2. Redistributions in binary form must reproduce the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer in the
        !            13:  *    documentation and/or other materials provided with the distribution.
        !            14:  *
        !            15:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
        !            16:  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
        !            17:  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
        !            18:  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
        !            19:  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
        !            20:  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
        !            21:  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
        !            22:  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
        !            23:  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
        !            24:  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
        !            25:  */
        !            26:
        !            27: #include <sys/types.h>
        !            28:
        !            29: #include <signal.h>
        !            30: #include <string.h>
        !            31:
        !            32: #include <openssl/bn.h>
        !            33: #include <openssl/evp.h>
        !            34:
        !            35: #include "buffer.h"
        !            36: #include "ssh2.h"
        !            37: #include "key.h"
        !            38: #include "cipher.h"
        !            39: #include "kex.h"
        !            40: #include "log.h"
        !            41:
        !            42: extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
        !            43:     const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
        !            44:        __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
        !            45:        __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)))
        !            46:        __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE)));
        !            47:
        !            48: void
        !            49: kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
        !            50: {
        !            51:        static const u_char basepoint[CURVE25519_SIZE] = {9};
        !            52:
        !            53:        arc4random_buf(key, CURVE25519_SIZE);
        !            54:        crypto_scalarmult_curve25519(pub, key, basepoint);
        !            55: }
        !            56:
        !            57: BIGNUM *
        !            58: kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
        !            59:     const u_char pub[CURVE25519_SIZE])
        !            60: {
        !            61:        u_char shared_key[CURVE25519_SIZE];
        !            62:        BIGNUM *shared_secret;
        !            63:
        !            64:        crypto_scalarmult_curve25519(shared_key, key, pub);
        !            65: #ifdef DEBUG_KEXECDH
        !            66:        dump_digest("shared secret", shared_key, CURVE25519_SIZE);
        !            67: #endif
        !            68:        if ((shared_secret = BN_new()) == NULL)
        !            69:                fatal("%s: BN_new failed", __func__);
        !            70:        if (BN_bin2bn(shared_key, sizeof(shared_key), shared_secret) == NULL)
        !            71:                fatal("%s: BN_bin2bn failed", __func__);
        !            72:        memset(shared_key, 0, CURVE25519_SIZE); /* XXX explicit_bzero() */
        !            73:        return (shared_secret);
        !            74: }
        !            75:
        !            76: void
        !            77: kex_c25519_hash(
        !            78:     const EVP_MD *evp_md,
        !            79:     char *client_version_string,
        !            80:     char *server_version_string,
        !            81:     char *ckexinit, int ckexinitlen,
        !            82:     char *skexinit, int skexinitlen,
        !            83:     u_char *serverhostkeyblob, int sbloblen,
        !            84:     const u_char client_dh_pub[CURVE25519_SIZE],
        !            85:     const u_char server_dh_pub[CURVE25519_SIZE],
        !            86:     const BIGNUM *shared_secret,
        !            87:     u_char **hash, u_int *hashlen)
        !            88: {
        !            89:        Buffer b;
        !            90:        EVP_MD_CTX md;
        !            91:        static u_char digest[EVP_MAX_MD_SIZE];
        !            92:
        !            93:        buffer_init(&b);
        !            94:        buffer_put_cstring(&b, client_version_string);
        !            95:        buffer_put_cstring(&b, server_version_string);
        !            96:
        !            97:        /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
        !            98:        buffer_put_int(&b, ckexinitlen+1);
        !            99:        buffer_put_char(&b, SSH2_MSG_KEXINIT);
        !           100:        buffer_append(&b, ckexinit, ckexinitlen);
        !           101:        buffer_put_int(&b, skexinitlen+1);
        !           102:        buffer_put_char(&b, SSH2_MSG_KEXINIT);
        !           103:        buffer_append(&b, skexinit, skexinitlen);
        !           104:
        !           105:        buffer_put_string(&b, serverhostkeyblob, sbloblen);
        !           106:        buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE);
        !           107:        buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE);
        !           108:        buffer_put_bignum2(&b, shared_secret);
        !           109:
        !           110: #ifdef DEBUG_KEX
        !           111:        buffer_dump(&b);
        !           112: #endif
        !           113:        EVP_DigestInit(&md, evp_md);
        !           114:        EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
        !           115:        EVP_DigestFinal(&md, digest, NULL);
        !           116:
        !           117:        buffer_free(&b);
        !           118:
        !           119: #ifdef DEBUG_KEX
        !           120:        dump_digest("hash", digest, EVP_MD_size(evp_md));
        !           121: #endif
        !           122:        *hash = digest;
        !           123:        *hashlen = EVP_MD_size(evp_md);
        !           124: }