/* $OpenBSD: kexdhs.c,v 1.27 2018/04/10 00:10:49 djm Exp $ */ /* * Copyright (c) 2001 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "includes.h" #ifdef WITH_OPENSSL #include #include #include #include #include #include "openbsd-compat/openssl-compat.h" #include "sshkey.h" #include "cipher.h" #include "digest.h" #include "kex.h" #include "log.h" #include "packet.h" #include "dh.h" #include "ssh2.h" #include "dispatch.h" #include "compat.h" #include "ssherr.h" #include "sshbuf.h" static int input_kex_dh_init(int, u_int32_t, struct ssh *); int kexdh_server(struct ssh *ssh) { struct kex *kex = ssh->kex; int r; /* generate server DH public key */ switch (kex->kex_type) { case KEX_DH_GRP1_SHA1: kex->dh = dh_new_group1(); break; case KEX_DH_GRP14_SHA1: case KEX_DH_GRP14_SHA256: kex->dh = dh_new_group14(); break; case KEX_DH_GRP16_SHA512: kex->dh = dh_new_group16(); break; case KEX_DH_GRP18_SHA512: kex->dh = dh_new_group18(); break; default: r = SSH_ERR_INVALID_ARGUMENT; goto out; } if (kex->dh == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) goto out; debug("expecting SSH2_MSG_KEXDH_INIT"); ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init); r = 0; out: return r; } int input_kex_dh_init(int type, u_int32_t seq, struct ssh *ssh) { struct kex *kex = ssh->kex; BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; const BIGNUM *pub_key; struct sshkey *server_host_public, *server_host_private; u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; u_char hash[SSH_DIGEST_MAX_LENGTH]; size_t sbloblen, slen; size_t klen = 0, hashlen; int kout, r; if (kex->load_host_public_key == NULL || kex->load_host_private_key == NULL) { r = SSH_ERR_INVALID_ARGUMENT; goto out; } server_host_public = kex->load_host_public_key(kex->hostkey_type, kex->hostkey_nid, ssh); server_host_private = kex->load_host_private_key(kex->hostkey_type, kex->hostkey_nid, ssh); if (server_host_public == NULL) { r = SSH_ERR_NO_HOSTKEY_LOADED; goto out; } /* key, cert */ if ((dh_client_pub = BN_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } DH_get0_key(kex->dh, &pub_key, NULL); if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 || (r = sshpkt_get_end(ssh)) != 0) goto out; #ifdef DEBUG_KEXDH fprintf(stderr, "dh_client_pub= "); BN_print_fp(stderr, dh_client_pub); fprintf(stderr, "\n"); debug("bits %d", BN_num_bits(dh_client_pub)); DHparams_print_fp(stderr, kex->dh); fprintf(stderr, "pub= "); BN_print_fp(stderr, pub_key); fprintf(stderr, "\n"); #endif if (!dh_pub_is_valid(kex->dh, dh_client_pub)) { sshpkt_disconnect(ssh, "bad client public DH value"); r = SSH_ERR_MESSAGE_INCOMPLETE; goto out; } klen = DH_size(kex->dh); if ((kbuf = malloc(klen)) == NULL || (shared_secret = BN_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 || BN_bin2bn(kbuf, kout, shared_secret) == NULL) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } #ifdef DEBUG_KEXDH dump_digest("shared secret", kbuf, kout); #endif if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob, &sbloblen)) != 0) goto out; /* calc H */ hashlen = sizeof(hash); if ((r = kex_dh_hash( kex->hash_alg, kex->client_version_string, kex->server_version_string, sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), sshbuf_ptr(kex->my), sshbuf_len(kex->my), server_host_key_blob, sbloblen, dh_client_pub, pub_key, shared_secret, hash, &hashlen)) != 0) goto out; /* save session id := H */ if (kex->session_id == NULL) { kex->session_id_len = hashlen; kex->session_id = malloc(kex->session_id_len); if (kex->session_id == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } memcpy(kex->session_id, hash, kex->session_id_len); } /* sign H */ if ((r = kex->sign(server_host_private, server_host_public, &signature, &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0) goto out; /* destroy_sensitive_data(); */ /* send server hostkey, DH pubkey 'f' and signed H */ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 || (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 || (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */ (r = sshpkt_put_string(ssh, signature, slen)) != 0 || (r = sshpkt_send(ssh)) != 0) goto out; if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) r = kex_send_newkeys(ssh); out: explicit_bzero(hash, sizeof(hash)); DH_free(kex->dh); kex->dh = NULL; BN_clear_free(dh_client_pub); if (kbuf) { explicit_bzero(kbuf, klen); free(kbuf); } BN_clear_free(shared_secret); free(server_host_key_blob); free(signature); return r; } #endif /* WITH_OPENSSL */