mirror of git://anongit.mindrot.org/openssh.git
385 lines
11 KiB
C
385 lines
11 KiB
C
/* $OpenBSD: kexgen.c,v 1.10 2024/09/09 02:39:57 djm Exp $ */
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/*
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* Copyright (c) 2019 Markus Friedl. 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 <stdarg.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 "sshkey.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 "ssh2.h"
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#include "sshbuf.h"
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#include "digest.h"
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#include "ssherr.h"
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static int input_kex_gen_init(int, u_int32_t, struct ssh *);
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static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh);
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static int
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kex_gen_hash(
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int hash_alg,
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const struct sshbuf *client_version,
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const struct sshbuf *server_version,
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const struct sshbuf *client_kexinit,
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const struct sshbuf *server_kexinit,
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const struct sshbuf *server_host_key_blob,
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const struct sshbuf *client_pub,
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const struct sshbuf *server_pub,
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const struct sshbuf *shared_secret,
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u_char *hash, size_t *hashlen)
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{
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struct sshbuf *b;
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int r;
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if (*hashlen < ssh_digest_bytes(hash_alg))
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return SSH_ERR_INVALID_ARGUMENT;
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if ((b = sshbuf_new()) == NULL)
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return SSH_ERR_ALLOC_FAIL;
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if ((r = sshbuf_put_stringb(b, client_version)) != 0 ||
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(r = sshbuf_put_stringb(b, server_version)) != 0 ||
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/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
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(r = sshbuf_put_u32(b, sshbuf_len(client_kexinit) + 1)) != 0 ||
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(r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
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(r = sshbuf_putb(b, client_kexinit)) != 0 ||
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(r = sshbuf_put_u32(b, sshbuf_len(server_kexinit) + 1)) != 0 ||
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(r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
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(r = sshbuf_putb(b, server_kexinit)) != 0 ||
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(r = sshbuf_put_stringb(b, server_host_key_blob)) != 0 ||
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(r = sshbuf_put_stringb(b, client_pub)) != 0 ||
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(r = sshbuf_put_stringb(b, server_pub)) != 0 ||
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(r = sshbuf_putb(b, shared_secret)) != 0) {
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sshbuf_free(b);
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return r;
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}
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#ifdef DEBUG_KEX
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sshbuf_dump(b, stderr);
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#endif
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if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
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sshbuf_free(b);
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return SSH_ERR_LIBCRYPTO_ERROR;
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}
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sshbuf_free(b);
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*hashlen = ssh_digest_bytes(hash_alg);
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#ifdef DEBUG_KEX
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dump_digest("hash", hash, *hashlen);
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#endif
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return 0;
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}
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int
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kex_gen_client(struct ssh *ssh)
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{
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struct kex *kex = ssh->kex;
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int r;
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switch (kex->kex_type) {
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#ifdef WITH_OPENSSL
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case KEX_DH_GRP1_SHA1:
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case KEX_DH_GRP14_SHA1:
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case KEX_DH_GRP14_SHA256:
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case KEX_DH_GRP16_SHA512:
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case KEX_DH_GRP18_SHA512:
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r = kex_dh_keypair(kex);
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break;
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case KEX_ECDH_SHA2:
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r = kex_ecdh_keypair(kex);
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break;
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#endif
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case KEX_C25519_SHA256:
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r = kex_c25519_keypair(kex);
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break;
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case KEX_KEM_SNTRUP761X25519_SHA512:
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r = kex_kem_sntrup761x25519_keypair(kex);
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break;
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case KEX_KEM_MLKEM768X25519_SHA256:
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r = kex_kem_mlkem768x25519_keypair(kex);
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break;
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default:
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r = SSH_ERR_INVALID_ARGUMENT;
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break;
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}
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if (r != 0)
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return r;
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
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(r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0 ||
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(r = sshpkt_send(ssh)) != 0)
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return r;
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debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_gen_reply);
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return 0;
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}
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static int
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input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
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{
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struct kex *kex = ssh->kex;
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struct sshkey *server_host_key = NULL;
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struct sshbuf *shared_secret = NULL;
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struct sshbuf *server_blob = NULL;
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struct sshbuf *tmp = NULL, *server_host_key_blob = NULL;
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u_char *signature = NULL;
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u_char hash[SSH_DIGEST_MAX_LENGTH];
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size_t slen, hashlen;
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int r;
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debug("SSH2_MSG_KEX_ECDH_REPLY received");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &kex_protocol_error);
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/* hostkey */
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if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
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goto out;
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/* sshkey_fromb() consumes its buffer, so make a copy */
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if ((tmp = sshbuf_fromb(server_host_key_blob)) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshkey_fromb(tmp, &server_host_key)) != 0)
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goto out;
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if ((r = kex_verify_host_key(ssh, server_host_key)) != 0)
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goto out;
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/* Q_S, server public key */
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/* signed H */
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if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
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(r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
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(r = sshpkt_get_end(ssh)) != 0)
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goto out;
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/* compute shared secret */
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switch (kex->kex_type) {
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#ifdef WITH_OPENSSL
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case KEX_DH_GRP1_SHA1:
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case KEX_DH_GRP14_SHA1:
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case KEX_DH_GRP14_SHA256:
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case KEX_DH_GRP16_SHA512:
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case KEX_DH_GRP18_SHA512:
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r = kex_dh_dec(kex, server_blob, &shared_secret);
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break;
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case KEX_ECDH_SHA2:
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r = kex_ecdh_dec(kex, server_blob, &shared_secret);
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break;
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#endif
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case KEX_C25519_SHA256:
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r = kex_c25519_dec(kex, server_blob, &shared_secret);
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break;
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case KEX_KEM_SNTRUP761X25519_SHA512:
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r = kex_kem_sntrup761x25519_dec(kex, server_blob,
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&shared_secret);
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break;
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case KEX_KEM_MLKEM768X25519_SHA256:
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r = kex_kem_mlkem768x25519_dec(kex, server_blob,
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&shared_secret);
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break;
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default:
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r = SSH_ERR_INVALID_ARGUMENT;
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break;
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}
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if (r !=0 )
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goto out;
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/* calc and verify H */
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hashlen = sizeof(hash);
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if ((r = kex_gen_hash(
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kex->hash_alg,
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kex->client_version,
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kex->server_version,
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kex->my,
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kex->peer,
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server_host_key_blob,
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kex->client_pub,
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server_blob,
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shared_secret,
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hash, &hashlen)) != 0)
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goto out;
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if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
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kex->hostkey_alg, ssh->compat, NULL)) != 0)
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goto out;
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if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
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(r = kex_send_newkeys(ssh)) != 0)
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goto out;
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/* save initial signature and hostkey */
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if ((kex->flags & KEX_INITIAL) != 0) {
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if (kex->initial_hostkey != NULL || kex->initial_sig != NULL) {
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r = SSH_ERR_INTERNAL_ERROR;
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goto out;
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}
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if ((kex->initial_sig = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshbuf_put(kex->initial_sig, signature, slen)) != 0)
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goto out;
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kex->initial_hostkey = server_host_key;
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server_host_key = NULL;
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}
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/* success */
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out:
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explicit_bzero(hash, sizeof(hash));
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explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
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explicit_bzero(kex->sntrup761_client_key,
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sizeof(kex->sntrup761_client_key));
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explicit_bzero(kex->mlkem768_client_key,
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sizeof(kex->mlkem768_client_key));
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sshbuf_free(server_host_key_blob);
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free(signature);
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sshbuf_free(tmp);
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sshkey_free(server_host_key);
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sshbuf_free(server_blob);
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sshbuf_free(shared_secret);
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sshbuf_free(kex->client_pub);
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kex->client_pub = NULL;
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return r;
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}
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int
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kex_gen_server(struct ssh *ssh)
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{
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debug("expecting SSH2_MSG_KEX_ECDH_INIT");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_gen_init);
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return 0;
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}
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static int
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input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh)
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{
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struct kex *kex = ssh->kex;
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struct sshkey *server_host_private, *server_host_public;
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struct sshbuf *shared_secret = NULL;
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struct sshbuf *server_pubkey = NULL;
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struct sshbuf *client_pubkey = NULL;
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struct sshbuf *server_host_key_blob = NULL;
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u_char *signature = NULL, hash[SSH_DIGEST_MAX_LENGTH];
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size_t slen, hashlen;
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int r;
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debug("SSH2_MSG_KEX_ECDH_INIT received");
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &kex_protocol_error);
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if ((r = kex_load_hostkey(ssh, &server_host_private,
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&server_host_public)) != 0)
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goto out;
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if ((r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
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(r = sshpkt_get_end(ssh)) != 0)
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goto out;
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/* compute shared secret */
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switch (kex->kex_type) {
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#ifdef WITH_OPENSSL
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case KEX_DH_GRP1_SHA1:
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case KEX_DH_GRP14_SHA1:
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case KEX_DH_GRP14_SHA256:
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case KEX_DH_GRP16_SHA512:
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case KEX_DH_GRP18_SHA512:
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r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
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&shared_secret);
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break;
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case KEX_ECDH_SHA2:
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r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
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&shared_secret);
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break;
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#endif
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case KEX_C25519_SHA256:
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r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
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&shared_secret);
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break;
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case KEX_KEM_SNTRUP761X25519_SHA512:
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r = kex_kem_sntrup761x25519_enc(kex, client_pubkey,
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&server_pubkey, &shared_secret);
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break;
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case KEX_KEM_MLKEM768X25519_SHA256:
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r = kex_kem_mlkem768x25519_enc(kex, client_pubkey,
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&server_pubkey, &shared_secret);
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break;
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default:
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r = SSH_ERR_INVALID_ARGUMENT;
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break;
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}
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if (r !=0 )
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goto out;
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/* calc H */
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if ((server_host_key_blob = sshbuf_new()) == NULL) {
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r = SSH_ERR_ALLOC_FAIL;
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goto out;
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}
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if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
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goto out;
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hashlen = sizeof(hash);
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if ((r = kex_gen_hash(
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kex->hash_alg,
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kex->client_version,
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kex->server_version,
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kex->peer,
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kex->my,
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server_host_key_blob,
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client_pubkey,
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server_pubkey,
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shared_secret,
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hash, &hashlen)) != 0)
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goto out;
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/* sign H */
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if ((r = kex->sign(ssh, server_host_private, server_host_public,
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&signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
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goto out;
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/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
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(r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
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(r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
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(r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
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(r = sshpkt_send(ssh)) != 0)
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goto out;
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if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
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(r = kex_send_newkeys(ssh)) != 0)
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goto out;
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/* retain copy of hostkey used at initial KEX */
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if (kex->initial_hostkey == NULL &&
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(r = sshkey_from_private(server_host_public,
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&kex->initial_hostkey)) != 0)
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goto out;
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/* success */
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out:
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explicit_bzero(hash, sizeof(hash));
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sshbuf_free(server_host_key_blob);
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free(signature);
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sshbuf_free(shared_secret);
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sshbuf_free(client_pubkey);
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sshbuf_free(server_pubkey);
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return r;
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}
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