1/* $OpenBSD: kexc25519c.c,v 1.9 2017/12/18 02:25:15 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 46static int 47input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh); 48 49int 50kexc25519_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 71static int 72input_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 kex->hostkey_alg, 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); 160out: 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} 170