| /* $OpenBSD: kexdh.c,v 1.30 2019/01/21 10:28:01 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" |
| |
| #ifdef WITH_OPENSSL |
| |
| #include <sys/types.h> |
| |
| #include <signal.h> |
| #include <stdio.h> |
| #include <string.h> |
| |
| #include "sshkey.h" |
| #include "kex.h" |
| #include "sshbuf.h" |
| #include "digest.h" |
| #include "ssherr.h" |
| #include "dh.h" |
| |
| int |
| kex_dh_keygen(struct kex *kex) |
| { |
| 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: |
| return SSH_ERR_INVALID_ARGUMENT; |
| } |
| if (kex->dh == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| return (dh_gen_key(kex->dh, kex->we_need * 8)); |
| } |
| |
| int |
| kex_dh_compute_key(struct kex *kex, BIGNUM *dh_pub, struct sshbuf *out) |
| { |
| BIGNUM *shared_secret = NULL; |
| u_char *kbuf = NULL; |
| size_t klen = 0; |
| int kout, r; |
| |
| #ifdef DEBUG_KEXDH |
| fprintf(stderr, "dh_pub= "); |
| BN_print_fp(stderr, dh_pub); |
| fprintf(stderr, "\n"); |
| debug("bits %d", BN_num_bits(dh_pub)); |
| DHparams_print_fp(stderr, kex->dh); |
| fprintf(stderr, "\n"); |
| #endif |
| |
| if (!dh_pub_is_valid(kex->dh, dh_pub)) { |
| 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_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 |
| r = sshbuf_put_bignum2(out, shared_secret); |
| out: |
| freezero(kbuf, klen); |
| BN_clear_free(shared_secret); |
| return r; |
| } |
| |
| int |
| kex_dh_keypair(struct kex *kex) |
| { |
| const BIGNUM *pub_key; |
| struct sshbuf *buf = NULL; |
| int r; |
| |
| if ((r = kex_dh_keygen(kex)) != 0) |
| return r; |
| DH_get0_key(kex->dh, &pub_key, NULL); |
| if ((buf = sshbuf_new()) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| if ((r = sshbuf_put_bignum2(buf, pub_key)) != 0 || |
| (r = sshbuf_get_u32(buf, NULL)) != 0) |
| goto out; |
| #ifdef DEBUG_KEXDH |
| DHparams_print_fp(stderr, kex->dh); |
| fprintf(stderr, "pub= "); |
| BN_print_fp(stderr, pub_key); |
| fprintf(stderr, "\n"); |
| #endif |
| kex->kem_client_pub = buf; |
| buf = NULL; |
| out: |
| sshbuf_free(buf); |
| return r; |
| } |
| |
| int |
| kex_dh_enc(struct kex *kex, const u_char *pkblob, size_t pklen, |
| struct sshbuf **server_blobp, struct sshbuf **shared_secretp) |
| { |
| const BIGNUM *pub_key; |
| struct sshbuf *server_blob = NULL; |
| int r; |
| |
| *server_blobp = NULL; |
| *shared_secretp = NULL; |
| |
| if ((r = kex_dh_keygen(kex)) != 0) |
| goto out; |
| DH_get0_key(kex->dh, &pub_key, NULL); |
| if ((server_blob = sshbuf_new()) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| if ((r = sshbuf_put_bignum2(server_blob, pub_key)) != 0 || |
| (r = sshbuf_get_u32(server_blob, NULL)) != 0) |
| goto out; |
| if ((r = kex_dh_dec(kex, pkblob, pklen, shared_secretp)) != 0) |
| goto out; |
| *server_blobp = server_blob; |
| server_blob = NULL; |
| out: |
| DH_free(kex->dh); |
| kex->dh = NULL; |
| sshbuf_free(server_blob); |
| return r; |
| } |
| |
| int |
| kex_dh_dec(struct kex *kex, const u_char *pkblob, size_t pklen, |
| struct sshbuf **shared_secretp) |
| { |
| struct sshbuf *buf = NULL; |
| BIGNUM *dh_pub = NULL; |
| int r; |
| |
| *shared_secretp = NULL; |
| |
| if ((buf = sshbuf_new()) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| if ((r = sshbuf_put_u32(buf, pklen)) != 0 || |
| (r = sshbuf_put(buf, pkblob, pklen)) != 0) { |
| goto out; |
| } |
| if ((r = sshbuf_get_bignum2(buf, &dh_pub)) != 0) { |
| goto out; |
| } |
| sshbuf_reset(buf); |
| if ((r = kex_dh_compute_key(kex, dh_pub, buf)) != 0) |
| goto out; |
| *shared_secretp = buf; |
| buf = NULL; |
| out: |
| DH_free(kex->dh); |
| kex->dh = NULL; |
| sshbuf_free(buf); |
| return r; |
| } |
| #endif /* WITH_OPENSSL */ |