/* $NetBSD: kexdh.c,v 1.8.2.1 2023/12/25 12:31:04 martin Exp $ */ /* $OpenBSD: kexdh.c,v 1.34 2020/12/04 02:29:25 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" __RCSID("$NetBSD: kexdh.c,v 1.8.2.1 2023/12/25 12:31:04 martin Exp $"); #include #include #include #include #include "sshkey.h" #include "kex.h" #include "sshbuf.h" #include "digest.h" #include "ssherr.h" #include "dh.h" #include "log.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->client_pub = buf; buf = NULL; out: sshbuf_free(buf); return r; } int kex_dh_enc(struct kex *kex, const struct sshbuf *client_blob, 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, client_blob, 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 struct sshbuf *dh_blob, 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_stringb(buf, dh_blob)) != 0 || (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: BN_free(dh_pub); DH_free(kex->dh); kex->dh = NULL; sshbuf_free(buf); return r; }