kexecdh.c

   1 /* $OpenBSD: kexecdh.c,v 1.3 2010/09/22 05:01:29 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 #ifdef OPENSSL_HAS_ECC
  30
  31 #include <sys/types.h>
  32
  33 #include <signal.h>
  34 #include <string.h>
  35
  36 #include <openssl/bn.h>
  37 #include <openssl/evp.h>
  38 #include <openssl/ec.h>
  39 #include <openssl/ecdh.h>
  40
  41 #include "buffer.h"
  42 #include "ssh2.h"
  43 #include "key.h"
  44 #include "cipher.h"
  45 #include "kex.h"
  46 #include "log.h"
  47
  48 int
  49 kex_ecdh_name_to_nid(const char *kexname)
  50 {
  51         if (strlen(kexname) < sizeof(KEX_ECDH_SHA2_STEM) - 1)
  52                 fatal("%s: kexname too short \"%s\"", __func__, kexname);
  53         return key_curve_name_to_nid(kexname + sizeof(KEX_ECDH_SHA2_STEM) - 1);
  54 }
  55
  56 const EVP_MD *
  57 kex_ecdh_name_to_evpmd(const char *kexname)
  58 {
  59         int nid = kex_ecdh_name_to_nid(kexname);
  60
  61         if (nid == -1)
  62                 fatal("%s: unsupported ECDH curve \"%s\"", __func__, kexname);
  63         return key_ec_nid_to_evpmd(nid);
  64 }
  65
  66 void
  67 kex_ecdh_hash(
  68     const EVP_MD *evp_md,
  69     const EC_GROUP *ec_group,
  70     char *client_version_string,
  71     char *server_version_string,
  72     char *ckexinit, int ckexinitlen,
  73     char *skexinit, int skexinitlen,
  74     u_char *serverhostkeyblob, int sbloblen,
  75     const EC_POINT *client_dh_pub,
  76     const EC_POINT *server_dh_pub,
  77     const BIGNUM *shared_secret,
  78     u_char **hash, u_int *hashlen)
  79 {
  80         Buffer b;
  81         EVP_MD_CTX md;
  82         static u_char digest[EVP_MAX_MD_SIZE];
  83
  84         buffer_init(&b);
  85         buffer_put_cstring(&b, client_version_string);
  86         buffer_put_cstring(&b, server_version_string);
  87
  88         /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
  89         buffer_put_int(&b, ckexinitlen+1);
  90         buffer_put_char(&b, SSH2_MSG_KEXINIT);
  91         buffer_append(&b, ckexinit, ckexinitlen);
  92         buffer_put_int(&b, skexinitlen+1);
  93         buffer_put_char(&b, SSH2_MSG_KEXINIT);
  94         buffer_append(&b, skexinit, skexinitlen);
  95
  96         buffer_put_string(&b, serverhostkeyblob, sbloblen);
  97         buffer_put_ecpoint(&b, ec_group, client_dh_pub);
  98         buffer_put_ecpoint(&b, ec_group, server_dh_pub);
  99         buffer_put_bignum2(&b, shared_secret);
 100
 101 #ifdef DEBUG_KEX
 102         buffer_dump(&b);
 103 #endif
 104         EVP_DigestInit(&md, evp_md);
 105         EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
 106         EVP_DigestFinal(&md, digest, NULL);
 107
 108         buffer_free(&b);
 109
 110 #ifdef DEBUG_KEX
 111         dump_digest("hash", digest, EVP_MD_size(evp_md));
 112 #endif
 113         *hash = digest;
 114         *hashlen = EVP_MD_size(evp_md);
 115 }
 116
 117 #endif /* OPENSSL_HAS_ECC */