| /* $OpenBSD: kexgen.c,v 1.3 2019/09/06 05:23:55 djm Exp $ */ |
| /* |
| * Copyright (c) 2019 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" |
| |
| #include <sys/types.h> |
| |
| #include <stdarg.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <signal.h> |
| |
| #include "sshkey.h" |
| #include "kex.h" |
| #include "log.h" |
| #include "packet.h" |
| #include "ssh2.h" |
| #include "sshbuf.h" |
| #include "digest.h" |
| #include "ssherr.h" |
| |
| static int input_kex_gen_init(int, u_int32_t, struct ssh *); |
| static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh); |
| |
| static int |
| kex_gen_hash( |
| int hash_alg, |
| const struct sshbuf *client_version, |
| const struct sshbuf *server_version, |
| const struct sshbuf *client_kexinit, |
| const struct sshbuf *server_kexinit, |
| const struct sshbuf *server_host_key_blob, |
| const struct sshbuf *client_pub, |
| const struct sshbuf *server_pub, |
| const struct sshbuf *shared_secret, |
| u_char *hash, size_t *hashlen) |
| { |
| struct sshbuf *b; |
| int r; |
| |
| if (*hashlen < ssh_digest_bytes(hash_alg)) |
| return SSH_ERR_INVALID_ARGUMENT; |
| if ((b = sshbuf_new()) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| if ((r = sshbuf_put_stringb(b, client_version)) != 0 || |
| (r = sshbuf_put_stringb(b, server_version)) != 0 || |
| /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ |
| (r = sshbuf_put_u32(b, sshbuf_len(client_kexinit) + 1)) != 0 || |
| (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 || |
| (r = sshbuf_putb(b, client_kexinit)) != 0 || |
| (r = sshbuf_put_u32(b, sshbuf_len(server_kexinit) + 1)) != 0 || |
| (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 || |
| (r = sshbuf_putb(b, server_kexinit)) != 0 || |
| (r = sshbuf_put_stringb(b, server_host_key_blob)) != 0 || |
| (r = sshbuf_put_stringb(b, client_pub)) != 0 || |
| (r = sshbuf_put_stringb(b, server_pub)) != 0 || |
| (r = sshbuf_putb(b, shared_secret)) != 0) { |
| sshbuf_free(b); |
| return r; |
| } |
| #ifdef DEBUG_KEX |
| sshbuf_dump(b, stderr); |
| #endif |
| if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) { |
| sshbuf_free(b); |
| return SSH_ERR_LIBCRYPTO_ERROR; |
| } |
| sshbuf_free(b); |
| *hashlen = ssh_digest_bytes(hash_alg); |
| #ifdef DEBUG_KEX |
| dump_digest("hash", hash, *hashlen); |
| #endif |
| return 0; |
| } |
| |
| int |
| kex_gen_client(struct ssh *ssh) |
| { |
| struct kex *kex = ssh->kex; |
| int r; |
| |
| switch (kex->kex_type) { |
| #ifdef WITH_OPENSSL |
| case KEX_DH_GRP1_SHA1: |
| case KEX_DH_GRP14_SHA1: |
| case KEX_DH_GRP14_SHA256: |
| case KEX_DH_GRP16_SHA512: |
| case KEX_DH_GRP18_SHA512: |
| r = kex_dh_keypair(kex); |
| break; |
| case KEX_ECDH_SHA2: |
| r = kex_ecdh_keypair(kex); |
| break; |
| #endif |
| case KEX_C25519_SHA256: |
| r = kex_c25519_keypair(kex); |
| break; |
| case KEX_KEM_SNTRUP4591761X25519_SHA512: |
| r = kex_kem_sntrup4591761x25519_keypair(kex); |
| break; |
| default: |
| r = SSH_ERR_INVALID_ARGUMENT; |
| break; |
| } |
| if (r != 0) |
| return r; |
| if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 || |
| (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0 || |
| (r = sshpkt_send(ssh)) != 0) |
| return r; |
| debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); |
| ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_gen_reply); |
| return 0; |
| } |
| |
| static int |
| input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh) |
| { |
| struct kex *kex = ssh->kex; |
| struct sshkey *server_host_key = NULL; |
| struct sshbuf *shared_secret = NULL; |
| struct sshbuf *server_blob = NULL; |
| struct sshbuf *tmp = NULL, *server_host_key_blob = NULL; |
| u_char *signature = NULL; |
| u_char hash[SSH_DIGEST_MAX_LENGTH]; |
| size_t slen, hashlen; |
| int r; |
| |
| /* hostkey */ |
| if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0) |
| goto out; |
| /* sshkey_fromb() consumes its buffer, so make a copy */ |
| if ((tmp = sshbuf_fromb(server_host_key_blob)) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| if ((r = sshkey_fromb(tmp, &server_host_key)) != 0) |
| goto out; |
| if ((r = kex_verify_host_key(ssh, server_host_key)) != 0) |
| goto out; |
| |
| /* Q_S, server public key */ |
| /* signed H */ |
| if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 || |
| (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || |
| (r = sshpkt_get_end(ssh)) != 0) |
| goto out; |
| |
| /* compute shared secret */ |
| switch (kex->kex_type) { |
| #ifdef WITH_OPENSSL |
| case KEX_DH_GRP1_SHA1: |
| case KEX_DH_GRP14_SHA1: |
| case KEX_DH_GRP14_SHA256: |
| case KEX_DH_GRP16_SHA512: |
| case KEX_DH_GRP18_SHA512: |
| r = kex_dh_dec(kex, server_blob, &shared_secret); |
| break; |
| case KEX_ECDH_SHA2: |
| r = kex_ecdh_dec(kex, server_blob, &shared_secret); |
| break; |
| #endif |
| case KEX_C25519_SHA256: |
| r = kex_c25519_dec(kex, server_blob, &shared_secret); |
| break; |
| case KEX_KEM_SNTRUP4591761X25519_SHA512: |
| r = kex_kem_sntrup4591761x25519_dec(kex, server_blob, |
| &shared_secret); |
| break; |
| default: |
| r = SSH_ERR_INVALID_ARGUMENT; |
| break; |
| } |
| if (r !=0 ) |
| goto out; |
| |
| /* calc and verify H */ |
| hashlen = sizeof(hash); |
| if ((r = kex_gen_hash( |
| kex->hash_alg, |
| kex->client_version, |
| kex->server_version, |
| kex->my, |
| kex->peer, |
| server_host_key_blob, |
| kex->client_pub, |
| server_blob, |
| shared_secret, |
| hash, &hashlen)) != 0) |
| goto out; |
| |
| if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen, |
| kex->hostkey_alg, ssh->compat)) != 0) |
| goto out; |
| |
| if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0) |
| r = kex_send_newkeys(ssh); |
| out: |
| explicit_bzero(hash, sizeof(hash)); |
| explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key)); |
| explicit_bzero(kex->sntrup4591761_client_key, |
| sizeof(kex->sntrup4591761_client_key)); |
| sshbuf_free(server_host_key_blob); |
| free(signature); |
| sshbuf_free(tmp); |
| sshkey_free(server_host_key); |
| sshbuf_free(server_blob); |
| sshbuf_free(shared_secret); |
| sshbuf_free(kex->client_pub); |
| kex->client_pub = NULL; |
| return r; |
| } |
| |
| int |
| kex_gen_server(struct ssh *ssh) |
| { |
| debug("expecting SSH2_MSG_KEX_ECDH_INIT"); |
| ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_gen_init); |
| return 0; |
| } |
| |
| static int |
| input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh) |
| { |
| struct kex *kex = ssh->kex; |
| struct sshkey *server_host_private, *server_host_public; |
| struct sshbuf *shared_secret = NULL; |
| struct sshbuf *server_pubkey = NULL; |
| struct sshbuf *client_pubkey = NULL; |
| struct sshbuf *server_host_key_blob = NULL; |
| u_char *signature = NULL, hash[SSH_DIGEST_MAX_LENGTH]; |
| size_t slen, hashlen; |
| int r; |
| |
| if ((r = kex_load_hostkey(ssh, &server_host_private, |
| &server_host_public)) != 0) |
| goto out; |
| |
| if ((r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 || |
| (r = sshpkt_get_end(ssh)) != 0) |
| goto out; |
| |
| /* compute shared secret */ |
| switch (kex->kex_type) { |
| #ifdef WITH_OPENSSL |
| case KEX_DH_GRP1_SHA1: |
| case KEX_DH_GRP14_SHA1: |
| case KEX_DH_GRP14_SHA256: |
| case KEX_DH_GRP16_SHA512: |
| case KEX_DH_GRP18_SHA512: |
| r = kex_dh_enc(kex, client_pubkey, &server_pubkey, |
| &shared_secret); |
| break; |
| case KEX_ECDH_SHA2: |
| r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey, |
| &shared_secret); |
| break; |
| #endif |
| case KEX_C25519_SHA256: |
| r = kex_c25519_enc(kex, client_pubkey, &server_pubkey, |
| &shared_secret); |
| break; |
| case KEX_KEM_SNTRUP4591761X25519_SHA512: |
| r = kex_kem_sntrup4591761x25519_enc(kex, client_pubkey, |
| &server_pubkey, &shared_secret); |
| break; |
| default: |
| r = SSH_ERR_INVALID_ARGUMENT; |
| break; |
| } |
| if (r !=0 ) |
| goto out; |
| |
| /* calc H */ |
| if ((server_host_key_blob = sshbuf_new()) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0) |
| goto out; |
| hashlen = sizeof(hash); |
| if ((r = kex_gen_hash( |
| kex->hash_alg, |
| kex->client_version, |
| kex->server_version, |
| kex->peer, |
| kex->my, |
| server_host_key_blob, |
| client_pubkey, |
| server_pubkey, |
| shared_secret, |
| hash, &hashlen)) != 0) |
| goto out; |
| |
| /* sign H */ |
| if ((r = kex->sign(ssh, server_host_private, server_host_public, |
| &signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0) |
| goto out; |
| |
| /* send server hostkey, ECDH pubkey 'Q_S' and signed H */ |
| if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 || |
| (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 || |
| (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 || |
| (r = sshpkt_put_string(ssh, signature, slen)) != 0 || |
| (r = sshpkt_send(ssh)) != 0) |
| goto out; |
| |
| if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0) |
| r = kex_send_newkeys(ssh); |
| out: |
| explicit_bzero(hash, sizeof(hash)); |
| sshbuf_free(server_host_key_blob); |
| free(signature); |
| sshbuf_free(shared_secret); |
| sshbuf_free(client_pubkey); |
| sshbuf_free(server_pubkey); |
| return r; |
| } |