crypto/openssh/kexc25519c.c

   1 /* $OpenBSD: kexc25519c.c,v 1.8 2017/05/31 04:17:12 djm 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  * 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 "includes.h"
  29
  30 #include <sys/types.h>
  31
  32 #include <stdio.h>
  33 #include <string.h>
  34 #include <signal.h>
  35
  36 #include "sshkey.h"
  37 #include "cipher.h"
  38 #include "kex.h"
  39 #include "log.h"
  40 #include "packet.h"
  41 #include "ssh2.h"
  42 #include "sshbuf.h"
  43 #include "digest.h"
  44 #include "ssherr.h"
  45
  46 static int
  47 input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh);
  48
  49 int
  50 kexc25519_client(struct ssh *ssh)
  51 {
  52         struct kex *kex = ssh->kex;
  53         int r;
  54
  55         kexc25519_keygen(kex->c25519_client_key, kex->c25519_client_pubkey);
  56 #ifdef DEBUG_KEXECDH
  57         dump_digest("client private key:", kex->c25519_client_key,
  58             sizeof(kex->c25519_client_key));
  59 #endif
  60         if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
  61             (r = sshpkt_put_string(ssh, kex->c25519_client_pubkey,
  62             sizeof(kex->c25519_client_pubkey))) != 0 ||
  63             (r = sshpkt_send(ssh)) != 0)
  64                 return r;
  65
  66         debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
  67         ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_c25519_reply);
  68         return 0;
  69 }
  70
  71 static int
  72 input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh)
  73 {
  74         struct kex *kex = ssh->kex;
  75         struct sshkey *server_host_key = NULL;
  76         struct sshbuf *shared_secret = NULL;
  77         u_char *server_pubkey = NULL;
  78         u_char *server_host_key_blob = NULL, *signature = NULL;
  79         u_char hash[SSH_DIGEST_MAX_LENGTH];
  80         size_t slen, pklen, sbloblen, hashlen;
  81         int r;
  82
  83         if (kex->verify_host_key == NULL) {
  84                 r = SSH_ERR_INVALID_ARGUMENT;
  85                 goto out;
  86         }
  87
  88         /* hostkey */
  89         if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
  90             &sbloblen)) != 0 ||
  91             (r = sshkey_from_blob(server_host_key_blob, sbloblen,
  92             &server_host_key)) != 0)
  93                 goto out;
  94         if (server_host_key->type != kex->hostkey_type ||
  95             (kex->hostkey_type == KEY_ECDSA &&
  96             server_host_key->ecdsa_nid != kex->hostkey_nid)) {
  97                 r = SSH_ERR_KEY_TYPE_MISMATCH;
  98                 goto out;
  99         }
 100         if (kex->verify_host_key(server_host_key, ssh) == -1) {
 101                 r = SSH_ERR_SIGNATURE_INVALID;
 102                 goto out;
 103         }
 104
 105         /* Q_S, server public key */
 106         /* signed H */
 107         if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
 108             (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
 109             (r = sshpkt_get_end(ssh)) != 0)
 110                 goto out;
 111         if (pklen != CURVE25519_SIZE) {
 112                 r = SSH_ERR_SIGNATURE_INVALID;
 113                 goto out;
 114         }
 115
 116 #ifdef DEBUG_KEXECDH
 117         dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
 118 #endif
 119
 120         if ((shared_secret = sshbuf_new()) == NULL) {
 121                 r = SSH_ERR_ALLOC_FAIL;
 122                 goto out;
 123         }
 124         if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey,
 125             shared_secret)) < 0)
 126                 goto out;
 127
 128         /* calc and verify H */
 129         hashlen = sizeof(hash);
 130         if ((r = kex_c25519_hash(
 131             kex->hash_alg,
 132             kex->client_version_string,
 133             kex->server_version_string,
 134             sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 135             sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 136             server_host_key_blob, sbloblen,
 137             kex->c25519_client_pubkey,
 138             server_pubkey,
 139             sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
 140             hash, &hashlen)) < 0)
 141                 goto out;
 142
 143         if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
 144             ssh->compat)) != 0)
 145                 goto out;
 146
 147         /* save session id */
 148         if (kex->session_id == NULL) {
 149                 kex->session_id_len = hashlen;
 150                 kex->session_id = malloc(kex->session_id_len);
 151                 if (kex->session_id == NULL) {
 152                         r = SSH_ERR_ALLOC_FAIL;
 153                         goto out;
 154                 }
 155                 memcpy(kex->session_id, hash, kex->session_id_len);
 156         }
 157
 158         if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
 159                 r = kex_send_newkeys(ssh);
 160 out:
 161         explicit_bzero(hash, sizeof(hash));
 162         explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
 163         free(server_host_key_blob);
 164         free(server_pubkey);
 165         free(signature);
 166         sshkey_free(server_host_key);
 167         sshbuf_free(shared_secret);
 168         return r;
 169 }