169 lines
5.2 KiB
C
169 lines
5.2 KiB
C
/* $OpenBSD: kexecdhc.c,v 1.2 2010/09/22 05:01:29 djm Exp $ */
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/*
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* Copyright (c) 2001 Markus Friedl. All rights reserved.
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* Copyright (c) 2010 Damien Miller. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <stdio.h>
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#include <string.h>
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#include <signal.h>
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#include "xmalloc.h"
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#include "buffer.h"
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#include "key.h"
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#include "cipher.h"
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#include "kex.h"
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#include "log.h"
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#include "packet.h"
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#include "dh.h"
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#include "ssh2.h"
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#ifdef OPENSSL_HAS_ECC
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#include <openssl/ecdh.h>
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void
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kexecdh_client(Kex *kex)
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{
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EC_KEY *client_key;
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EC_POINT *server_public;
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const EC_GROUP *group;
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BIGNUM *shared_secret;
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Key *server_host_key;
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u_char *server_host_key_blob = NULL, *signature = NULL;
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u_char *kbuf, *hash;
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u_int klen, slen, sbloblen, hashlen;
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int curve_nid;
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if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1)
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fatal("%s: unsupported ECDH curve \"%s\"", __func__, kex->name);
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if ((client_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL)
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fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
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if (EC_KEY_generate_key(client_key) != 1)
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fatal("%s: EC_KEY_generate_key failed", __func__);
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group = EC_KEY_get0_group(client_key);
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packet_start(SSH2_MSG_KEX_ECDH_INIT);
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packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key));
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packet_send();
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debug("sending SSH2_MSG_KEX_ECDH_INIT");
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#ifdef DEBUG_KEXECDH
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fputs("client private key:\n", stderr);
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key_dump_ec_key(client_key);
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#endif
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debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
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packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
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/* hostkey */
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server_host_key_blob = packet_get_string(&sbloblen);
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server_host_key = key_from_blob(server_host_key_blob, sbloblen);
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if (server_host_key == NULL)
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fatal("cannot decode server_host_key_blob");
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if (server_host_key->type != kex->hostkey_type)
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fatal("type mismatch for decoded server_host_key_blob");
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if (kex->verify_host_key == NULL)
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fatal("cannot verify server_host_key");
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if (kex->verify_host_key(server_host_key) == -1)
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fatal("server_host_key verification failed");
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/* Q_S, server public key */
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if ((server_public = EC_POINT_new(group)) == NULL)
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fatal("%s: EC_POINT_new failed", __func__);
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packet_get_ecpoint(group, server_public);
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if (key_ec_validate_public(group, server_public) != 0)
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fatal("%s: invalid server public key", __func__);
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#ifdef DEBUG_KEXECDH
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fputs("server public key:\n", stderr);
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key_dump_ec_point(group, server_public);
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#endif
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/* signed H */
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signature = packet_get_string(&slen);
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packet_check_eom();
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klen = (EC_GROUP_get_degree(group) + 7) / 8;
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kbuf = xmalloc(klen);
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if (ECDH_compute_key(kbuf, klen, server_public,
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client_key, NULL) != (int)klen)
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fatal("%s: ECDH_compute_key failed", __func__);
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#ifdef DEBUG_KEXECDH
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dump_digest("shared secret", kbuf, klen);
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#endif
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if ((shared_secret = BN_new()) == NULL)
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fatal("%s: BN_new failed", __func__);
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if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
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fatal("%s: BN_bin2bn failed", __func__);
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memset(kbuf, 0, klen);
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xfree(kbuf);
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/* calc and verify H */
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kex_ecdh_hash(
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kex->evp_md,
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group,
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kex->client_version_string,
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kex->server_version_string,
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buffer_ptr(&kex->my), buffer_len(&kex->my),
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buffer_ptr(&kex->peer), buffer_len(&kex->peer),
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server_host_key_blob, sbloblen,
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EC_KEY_get0_public_key(client_key),
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server_public,
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shared_secret,
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&hash, &hashlen
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);
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xfree(server_host_key_blob);
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EC_POINT_clear_free(server_public);
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EC_KEY_free(client_key);
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if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
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fatal("key_verify failed for server_host_key");
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key_free(server_host_key);
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xfree(signature);
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/* save session id */
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if (kex->session_id == NULL) {
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kex->session_id_len = hashlen;
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kex->session_id = xmalloc(kex->session_id_len);
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memcpy(kex->session_id, hash, kex->session_id_len);
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}
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kex_derive_keys(kex, hash, hashlen, shared_secret);
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BN_clear_free(shared_secret);
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kex_finish(kex);
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}
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#else /* OPENSSL_HAS_ECC */
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void
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kexecdh_client(Kex *kex)
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{
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fatal("ECC support is not enabled");
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}
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#endif /* OPENSSL_HAS_ECC */
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