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Annotation of src/usr.bin/ssh/kexc25519.c, Revision 1.2

1.2     ! markus      1: /* $OpenBSD: myproposal.h,v 1.33 2013/11/02 21:59:15 markus Exp $ */
1.1       markus      2: /*
                      3:  * Copyright (c) 2001, 2013 Markus Friedl.  All rights reserved.
                      4:  * Copyright (c) 2010 Damien Miller.  All rights reserved.
                      5:  * Copyright (c) 2013 Aris Adamantiadis.  All rights reserved.
                      6:  *
                      7:  * Redistribution and use in source and binary forms, with or without
                      8:  * modification, are permitted provided that the following conditions
                      9:  * are met:
                     10:  * 1. Redistributions of source code must retain the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
                     15:  *
                     16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
                     17:  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
                     18:  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
                     19:  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
                     20:  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
                     21:  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
                     22:  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
                     23:  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
                     24:  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
                     25:  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
                     26:  */
                     27:
                     28: #include <sys/types.h>
                     29:
                     30: #include <signal.h>
                     31: #include <string.h>
                     32:
                     33: #include <openssl/bn.h>
                     34: #include <openssl/evp.h>
                     35:
                     36: #include "buffer.h"
                     37: #include "ssh2.h"
                     38: #include "key.h"
                     39: #include "cipher.h"
                     40: #include "kex.h"
                     41: #include "log.h"
                     42:
                     43: extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
                     44:     const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
                     45:        __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
                     46:        __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)))
                     47:        __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE)));
                     48:
                     49: void
                     50: kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
                     51: {
                     52:        static const u_char basepoint[CURVE25519_SIZE] = {9};
                     53:
                     54:        arc4random_buf(key, CURVE25519_SIZE);
                     55:        crypto_scalarmult_curve25519(pub, key, basepoint);
                     56: }
                     57:
                     58: BIGNUM *
                     59: kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
                     60:     const u_char pub[CURVE25519_SIZE])
                     61: {
                     62:        u_char shared_key[CURVE25519_SIZE];
                     63:        BIGNUM *shared_secret;
                     64:
                     65:        crypto_scalarmult_curve25519(shared_key, key, pub);
                     66: #ifdef DEBUG_KEXECDH
                     67:        dump_digest("shared secret", shared_key, CURVE25519_SIZE);
                     68: #endif
                     69:        if ((shared_secret = BN_new()) == NULL)
                     70:                fatal("%s: BN_new failed", __func__);
                     71:        if (BN_bin2bn(shared_key, sizeof(shared_key), shared_secret) == NULL)
                     72:                fatal("%s: BN_bin2bn failed", __func__);
                     73:        memset(shared_key, 0, CURVE25519_SIZE); /* XXX explicit_bzero() */
                     74:        return (shared_secret);
                     75: }
                     76:
                     77: void
                     78: kex_c25519_hash(
                     79:     const EVP_MD *evp_md,
                     80:     char *client_version_string,
                     81:     char *server_version_string,
                     82:     char *ckexinit, int ckexinitlen,
                     83:     char *skexinit, int skexinitlen,
                     84:     u_char *serverhostkeyblob, int sbloblen,
                     85:     const u_char client_dh_pub[CURVE25519_SIZE],
                     86:     const u_char server_dh_pub[CURVE25519_SIZE],
                     87:     const BIGNUM *shared_secret,
                     88:     u_char **hash, u_int *hashlen)
                     89: {
                     90:        Buffer b;
                     91:        EVP_MD_CTX md;
                     92:        static u_char digest[EVP_MAX_MD_SIZE];
                     93:
                     94:        buffer_init(&b);
                     95:        buffer_put_cstring(&b, client_version_string);
                     96:        buffer_put_cstring(&b, server_version_string);
                     97:
                     98:        /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
                     99:        buffer_put_int(&b, ckexinitlen+1);
                    100:        buffer_put_char(&b, SSH2_MSG_KEXINIT);
                    101:        buffer_append(&b, ckexinit, ckexinitlen);
                    102:        buffer_put_int(&b, skexinitlen+1);
                    103:        buffer_put_char(&b, SSH2_MSG_KEXINIT);
                    104:        buffer_append(&b, skexinit, skexinitlen);
                    105:
                    106:        buffer_put_string(&b, serverhostkeyblob, sbloblen);
                    107:        buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE);
                    108:        buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE);
                    109:        buffer_put_bignum2(&b, shared_secret);
                    110:
                    111: #ifdef DEBUG_KEX
                    112:        buffer_dump(&b);
                    113: #endif
                    114:        EVP_DigestInit(&md, evp_md);
                    115:        EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
                    116:        EVP_DigestFinal(&md, digest, NULL);
                    117:
                    118:        buffer_free(&b);
                    119:
                    120: #ifdef DEBUG_KEX
                    121:        dump_digest("hash", digest, EVP_MD_size(evp_md));
                    122: #endif
                    123:        *hash = digest;
                    124:        *hashlen = EVP_MD_size(evp_md);
                    125: }