kexecdh.c

   1 /* $OpenBSD: kexecdh.c,v 1.1 2010/08/31 11:54:45 djm Exp $ */
   2 /*
   3  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
   4  * Copyright (c) 2010 Damien Miller.  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 "includes.h"
  28
  29 #include <sys/types.h>
  30
  31 #include <signal.h>
  32 #include <string.h>
  33
  34 #include <openssl/bn.h>
  35 #include <openssl/evp.h>
  36 #include <openssl/ec.h>
  37 #include <openssl/ecdh.h>
  38
  39 #include "buffer.h"
  40 #include "ssh2.h"
  41 #include "key.h"
  42 #include "cipher.h"
  43 #include "kex.h"
  44 #include "log.h"
  45
  46 int
  47 kex_ecdh_name_to_nid(const char *kexname)
  48 {
  49         int ret;
  50
  51         if (strlen(kexname) < sizeof(KEX_ECDH_SHA256) - 1)
  52                 fatal("%s: kexname too short \"%s\"", __func__, kexname);
  53         ret = key_curve_name_to_nid(kexname + sizeof(KEX_ECDH_SHA256) - 1);
  54         if (ret == -1)
  55                 fatal("%s: unsupported curve negotiated \"%s\"", __func__,
  56                     kexname);
  57         return ret;
  58 }
  59
  60 void
  61 kex_ecdh_hash(
  62     const EVP_MD *evp_md,
  63     const EC_GROUP *ec_group,
  64     char *client_version_string,
  65     char *server_version_string,
  66     char *ckexinit, int ckexinitlen,
  67     char *skexinit, int skexinitlen,
  68     u_char *serverhostkeyblob, int sbloblen,
  69     const EC_POINT *client_dh_pub,
  70     const EC_POINT *server_dh_pub,
  71     const BIGNUM *shared_secret,
  72     u_char **hash, u_int *hashlen)
  73 {
  74         Buffer b;
  75         EVP_MD_CTX md;
  76         static u_char digest[EVP_MAX_MD_SIZE];
  77
  78         buffer_init(&b);
  79         buffer_put_cstring(&b, client_version_string);
  80         buffer_put_cstring(&b, server_version_string);
  81
  82         /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
  83         buffer_put_int(&b, ckexinitlen+1);
  84         buffer_put_char(&b, SSH2_MSG_KEXINIT);
  85         buffer_append(&b, ckexinit, ckexinitlen);
  86         buffer_put_int(&b, skexinitlen+1);
  87         buffer_put_char(&b, SSH2_MSG_KEXINIT);
  88         buffer_append(&b, skexinit, skexinitlen);
  89
  90         buffer_put_string(&b, serverhostkeyblob, sbloblen);
  91         buffer_put_ecpoint(&b, ec_group, client_dh_pub);
  92         buffer_put_ecpoint(&b, ec_group, server_dh_pub);
  93         buffer_put_bignum2(&b, shared_secret);
  94
  95 #ifdef DEBUG_KEX
  96         buffer_dump(&b);
  97 #endif
  98         EVP_DigestInit(&md, evp_md);
  99         EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
 100         EVP_DigestFinal(&md, digest, NULL);
 101
 102         buffer_free(&b);
 103
 104 #ifdef DEBUG_KEX
 105         dump_digest("hash", digest, EVP_MD_size(evp_md));
 106 #endif
 107         *hash = digest;
 108         *hashlen = EVP_MD_size(evp_md);
 109 }
 110