1 /* $OpenBSD: kexc25519c.c,v 1.7 2015/01/26 06:10:03 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, void *ctxt); 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, void *ctxt) 73 { 74 struct ssh *ssh = ctxt; 75 struct kex *kex = ssh->kex; 76 struct sshkey *server_host_key = NULL; 77 struct sshbuf *shared_secret = NULL; 78 u_char *server_pubkey = NULL; 79 u_char *server_host_key_blob = NULL, *signature = NULL; 80 u_char hash[SSH_DIGEST_MAX_LENGTH]; 81 size_t slen, pklen, sbloblen, hashlen; 82 int r; 83 84 if (kex->verify_host_key == NULL) { 85 r = SSH_ERR_INVALID_ARGUMENT; 86 goto out; 87 } 88 89 /* hostkey */ 90 if ((r = sshpkt_get_string(ssh, &server_host_key_blob, 91 &sbloblen)) != 0 || 92 (r = sshkey_from_blob(server_host_key_blob, sbloblen, 93 &server_host_key)) != 0) 94 goto out; 95 if (server_host_key->type != kex->hostkey_type || 96 (kex->hostkey_type == KEY_ECDSA && 97 server_host_key->ecdsa_nid != kex->hostkey_nid)) { 98 r = SSH_ERR_KEY_TYPE_MISMATCH; 99 goto out; 100 } 101 if (kex->verify_host_key(server_host_key, ssh) == -1) { 102 r = SSH_ERR_SIGNATURE_INVALID; 103 goto out; 104 } 105 106 /* Q_S, server public key */ 107 /* signed H */ 108 if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 || 109 (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || 110 (r = sshpkt_get_end(ssh)) != 0) 111 goto out; 112 if (pklen != CURVE25519_SIZE) { 113 r = SSH_ERR_SIGNATURE_INVALID; 114 goto out; 115 } 116 117 #ifdef DEBUG_KEXECDH 118 dump_digest("server public key:", server_pubkey, CURVE25519_SIZE); 119 #endif 120 121 if ((shared_secret = sshbuf_new()) == NULL) { 122 r = SSH_ERR_ALLOC_FAIL; 123 goto out; 124 } 125 if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey, 126 shared_secret)) < 0) 127 goto out; 128 129 /* calc and verify H */ 130 hashlen = sizeof(hash); 131 if ((r = kex_c25519_hash( 132 kex->hash_alg, 133 kex->client_version_string, 134 kex->server_version_string, 135 sshbuf_ptr(kex->my), sshbuf_len(kex->my), 136 sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), 137 server_host_key_blob, sbloblen, 138 kex->c25519_client_pubkey, 139 server_pubkey, 140 sshbuf_ptr(shared_secret), sshbuf_len(shared_secret), 141 hash, &hashlen)) < 0) 142 goto out; 143 144 if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen, 145 ssh->compat)) != 0) 146 goto out; 147 148 /* save session id */ 149 if (kex->session_id == NULL) { 150 kex->session_id_len = hashlen; 151 kex->session_id = malloc(kex->session_id_len); 152 if (kex->session_id == NULL) { 153 r = SSH_ERR_ALLOC_FAIL; 154 goto out; 155 } 156 memcpy(kex->session_id, hash, kex->session_id_len); 157 } 158 159 if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0) 160 r = kex_send_newkeys(ssh); 161 out: 162 explicit_bzero(hash, sizeof(hash)); 163 explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key)); 164 free(server_host_key_blob); 165 free(server_pubkey); 166 free(signature); 167 sshkey_free(server_host_key); 168 sshbuf_free(shared_secret); 169 return r; 170 } 171
