diff options
Diffstat (limited to 'kexecdh.c')
| -rw-r--r-- | kexecdh.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/kexecdh.c b/kexecdh.c new file mode 100644 index 0000000..efb2e55 --- /dev/null +++ b/kexecdh.c @@ -0,0 +1,239 @@ +/* $OpenBSD: kexecdh.c,v 1.10 2019/01/21 10:40:11 djm Exp $ */ +/* + * Copyright (c) 2010 Damien Miller. All rights reserved. + * 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" + +#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) + +#include <sys/types.h> + +#include <stdio.h> +#include <string.h> +#include <signal.h> + +#include <openssl/ecdh.h> + +#include "sshkey.h" +#include "kex.h" +#include "sshbuf.h" +#include "digest.h" +#include "ssherr.h" + +static int +kex_ecdh_dec_key_group(struct kex *, const struct sshbuf *, EC_KEY *key, + const EC_GROUP *, struct sshbuf **); + +int +kex_ecdh_keypair(struct kex *kex) +{ + EC_KEY *client_key = NULL; + const EC_GROUP *group; + const EC_POINT *public_key; + struct sshbuf *buf = NULL; + int r; + + if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (EC_KEY_generate_key(client_key) != 1) { + r = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } + group = EC_KEY_get0_group(client_key); + public_key = EC_KEY_get0_public_key(client_key); + + if ((buf = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = sshbuf_put_ec(buf, public_key, group)) != 0 || + (r = sshbuf_get_u32(buf, NULL)) != 0) + goto out; +#ifdef DEBUG_KEXECDH + fputs("client private key:\n", stderr); + sshkey_dump_ec_key(client_key); +#endif + kex->ec_client_key = client_key; + kex->ec_group = group; + client_key = NULL; /* owned by the kex */ + kex->client_pub = buf; + buf = NULL; + out: + EC_KEY_free(client_key); + sshbuf_free(buf); + return r; +} + +int +kex_ecdh_enc(struct kex *kex, const struct sshbuf *client_blob, + struct sshbuf **server_blobp, struct sshbuf **shared_secretp) +{ + const EC_GROUP *group; + const EC_POINT *pub_key; + EC_KEY *server_key = NULL; + struct sshbuf *server_blob = NULL; + int r; + + *server_blobp = NULL; + *shared_secretp = NULL; + + if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (EC_KEY_generate_key(server_key) != 1) { + r = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } + group = EC_KEY_get0_group(server_key); + +#ifdef DEBUG_KEXECDH + fputs("server private key:\n", stderr); + sshkey_dump_ec_key(server_key); +#endif + pub_key = EC_KEY_get0_public_key(server_key); + if ((server_blob = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = sshbuf_put_ec(server_blob, pub_key, group)) != 0 || + (r = sshbuf_get_u32(server_blob, NULL)) != 0) + goto out; + if ((r = kex_ecdh_dec_key_group(kex, client_blob, server_key, group, + shared_secretp)) != 0) + goto out; + *server_blobp = server_blob; + server_blob = NULL; + out: + EC_KEY_free(server_key); + sshbuf_free(server_blob); + return r; +} + +static int +kex_ecdh_dec_key_group(struct kex *kex, const struct sshbuf *ec_blob, + EC_KEY *key, const EC_GROUP *group, struct sshbuf **shared_secretp) +{ + struct sshbuf *buf = NULL; + BIGNUM *shared_secret = NULL; + EC_POINT *dh_pub = NULL; + u_char *kbuf = NULL; + size_t klen = 0; + int r; + + *shared_secretp = NULL; + + if ((buf = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = sshbuf_put_stringb(buf, ec_blob)) != 0) + goto out; + if ((dh_pub = EC_POINT_new(group)) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if ((r = sshbuf_get_ec(buf, dh_pub, group)) != 0) { + goto out; + } + sshbuf_reset(buf); + +#ifdef DEBUG_KEXECDH + fputs("public key:\n", stderr); + sshkey_dump_ec_point(group, dh_pub); +#endif + if (sshkey_ec_validate_public(group, dh_pub) != 0) { + r = SSH_ERR_MESSAGE_INCOMPLETE; + goto out; + } + klen = (EC_GROUP_get_degree(group) + 7) / 8; + if ((kbuf = malloc(klen)) == NULL || + (shared_secret = BN_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (ECDH_compute_key(kbuf, klen, dh_pub, key, NULL) != (int)klen || + BN_bin2bn(kbuf, klen, shared_secret) == NULL) { + r = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } +#ifdef DEBUG_KEXECDH + dump_digest("shared secret", kbuf, klen); +#endif + if ((r = sshbuf_put_bignum2(buf, shared_secret)) != 0) + goto out; + *shared_secretp = buf; + buf = NULL; + out: + EC_POINT_clear_free(dh_pub); + BN_clear_free(shared_secret); + freezero(kbuf, klen); + sshbuf_free(buf); + return r; +} + +int +kex_ecdh_dec(struct kex *kex, const struct sshbuf *server_blob, + struct sshbuf **shared_secretp) +{ + int r; + + r = kex_ecdh_dec_key_group(kex, server_blob, kex->ec_client_key, + kex->ec_group, shared_secretp); + EC_KEY_free(kex->ec_client_key); + kex->ec_client_key = NULL; + return r; +} + +#else + +#include "ssherr.h" + +struct kex; +struct sshbuf; +struct sshkey; + +int +kex_ecdh_keypair(struct kex *kex) +{ + return SSH_ERR_SIGN_ALG_UNSUPPORTED; +} + +int +kex_ecdh_enc(struct kex *kex, const struct sshbuf *client_blob, + struct sshbuf **server_blobp, struct sshbuf **shared_secretp) +{ + return SSH_ERR_SIGN_ALG_UNSUPPORTED; +} + +int +kex_ecdh_dec(struct kex *kex, const struct sshbuf *server_blob, + struct sshbuf **shared_secretp) +{ + return SSH_ERR_SIGN_ALG_UNSUPPORTED; +} +#endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */ |