crypto/openssh/kexc25519s.c

   1 /* $OpenBSD: kexc25519s.c,v 1.10 2015/12/04 16:41:28 markus Exp $ */
   2 /*
   3  * Copyright (c) 2001 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  * 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 #include <stdio.h>
  31 #include <string.h>
  32 #include <signal.h>
  33
  34 #include "sshkey.h"
  35 #include "cipher.h"
  36 #include "digest.h"
  37 #include "kex.h"
  38 #include "log.h"
  39 #include "packet.h"
  40 #include "ssh2.h"
  41 #include "sshbuf.h"
  42 #include "ssherr.h"
  43
  44 static int input_kex_c25519_init(int, u_int32_t, void *);
  45
  46 int
  47 kexc25519_server(struct ssh *ssh)
  48 {
  49         debug("expecting SSH2_MSG_KEX_ECDH_INIT");
  50         ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_c25519_init);
  51         return 0;
  52 }
  53
  54 static int
  55 input_kex_c25519_init(int type, u_int32_t seq, void *ctxt)
  56 {
  57         struct ssh *ssh = ctxt;
  58         struct kex *kex = ssh->kex;
  59         struct sshkey *server_host_private, *server_host_public;
  60         struct sshbuf *shared_secret = NULL;
  61         u_char *server_host_key_blob = NULL, *signature = NULL;
  62         u_char server_key[CURVE25519_SIZE];
  63         u_char *client_pubkey = NULL;
  64         u_char server_pubkey[CURVE25519_SIZE];
  65         u_char hash[SSH_DIGEST_MAX_LENGTH];
  66         size_t slen, pklen, sbloblen, hashlen;
  67         int r;
  68
  69         /* generate private key */
  70         kexc25519_keygen(server_key, server_pubkey);
  71 #ifdef DEBUG_KEXECDH
  72         dump_digest("server private key:", server_key, sizeof(server_key));
  73 #endif
  74         if (kex->load_host_public_key == NULL ||
  75             kex->load_host_private_key == NULL) {
  76                 r = SSH_ERR_INVALID_ARGUMENT;
  77                 goto out;
  78         }
  79         server_host_public = kex->load_host_public_key(kex->hostkey_type,
  80             kex->hostkey_nid, ssh);
  81         server_host_private = kex->load_host_private_key(kex->hostkey_type,
  82             kex->hostkey_nid, ssh);
  83         if (server_host_public == NULL) {
  84                 r = SSH_ERR_NO_HOSTKEY_LOADED;
  85                 goto out;
  86         }
  87
  88         if ((r = sshpkt_get_string(ssh, &client_pubkey, &pklen)) != 0 ||
  89             (r = sshpkt_get_end(ssh)) != 0)
  90                 goto out;
  91         if (pklen != CURVE25519_SIZE) {
  92                 r = SSH_ERR_SIGNATURE_INVALID;
  93                 goto out;
  94         }
  95 #ifdef DEBUG_KEXECDH
  96         dump_digest("client public key:", client_pubkey, CURVE25519_SIZE);
  97 #endif
  98
  99         if ((shared_secret = sshbuf_new()) == NULL) {
 100                 r = SSH_ERR_ALLOC_FAIL;
 101                 goto out;
 102         }
 103         if ((r = kexc25519_shared_key(server_key, client_pubkey,
 104             shared_secret)) < 0)
 105                 goto out;
 106
 107         /* calc H */
 108         if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
 109             &sbloblen)) != 0)
 110                 goto out;
 111         hashlen = sizeof(hash);
 112         if ((r = kex_c25519_hash(
 113             kex->hash_alg,
 114             kex->client_version_string,
 115             kex->server_version_string,
 116             sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 117             sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 118             server_host_key_blob, sbloblen,
 119             client_pubkey,
 120             server_pubkey,
 121             sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
 122             hash, &hashlen)) < 0)
 123                 goto out;
 124
 125         /* save session id := H */
 126         if (kex->session_id == NULL) {
 127                 kex->session_id_len = hashlen;
 128                 kex->session_id = malloc(kex->session_id_len);
 129                 if (kex->session_id == NULL) {
 130                         r = SSH_ERR_ALLOC_FAIL;
 131                         goto out;
 132                 }
 133                 memcpy(kex->session_id, hash, kex->session_id_len);
 134         }
 135
 136         /* sign H */
 137         if ((r = kex->sign(server_host_private, server_host_public, &signature,
 138              &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
 139                 goto out;
 140
 141         /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
 142         if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
 143             (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
 144             (r = sshpkt_put_string(ssh, server_pubkey, sizeof(server_pubkey))) != 0 ||
 145             (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
 146             (r = sshpkt_send(ssh)) != 0)
 147                 goto out;
 148
 149         if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
 150                 r = kex_send_newkeys(ssh);
 151 out:
 152         explicit_bzero(hash, sizeof(hash));
 153         explicit_bzero(server_key, sizeof(server_key));
 154         free(server_host_key_blob);
 155         free(signature);
 156         free(client_pubkey);
 157         sshbuf_free(shared_secret);
 158         return r;
 159 }