diff options
Diffstat (limited to 'kexdh.c')
| -rw-r--r-- | kexdh.c | 203 |
1 files changed, 203 insertions, 0 deletions
@@ -0,0 +1,203 @@ +/* $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" + +#ifdef WITH_OPENSSL + +#include <sys/types.h> + +#include <stdio.h> +#include <string.h> +#include <signal.h> + +#include "openbsd-compat/openssl-compat.h" +#include <openssl/dh.h> + +#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; +} +#endif /* WITH_OPENSSL */ |