void kexecdh_client(Kex *kex) { EC_KEY *client_key; EC_POINT *server_public; const EC_GROUP *group; BIGNUM *shared_secret; Key *server_host_key; u_char *server_host_key_blob = NULL, *signature = NULL; u_char *kbuf, *hash; u_int klen, slen, sbloblen, hashlen; if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) fatal("%s: EC_KEY_new_by_curve_name failed", __func__); if (EC_KEY_generate_key(client_key) != 1) fatal("%s: EC_KEY_generate_key failed", __func__); group = EC_KEY_get0_group(client_key); packet_start(SSH2_MSG_KEX_ECDH_INIT); packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key)); packet_send(); debug("sending SSH2_MSG_KEX_ECDH_INIT"); #ifdef DEBUG_KEXECDH fputs("client private key:\n", stderr); key_dump_ec_key(client_key); #endif debug("expecting SSH2_MSG_KEX_ECDH_REPLY"); packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY); /* hostkey */ server_host_key_blob = packet_get_string(&sbloblen); server_host_key = key_from_blob(server_host_key_blob, sbloblen); if (server_host_key == NULL) fatal("cannot decode server_host_key_blob"); if (server_host_key->type != kex->hostkey_type) fatal("type mismatch for decoded server_host_key_blob"); if (kex->verify_host_key == NULL) fatal("cannot verify server_host_key"); if (kex->verify_host_key(server_host_key) == -1) fatal("server_host_key verification failed"); /* Q_S, server public key */ if ((server_public = EC_POINT_new(group)) == NULL) fatal("%s: EC_POINT_new failed", __func__); packet_get_ecpoint(group, server_public); if (key_ec_validate_public(group, server_public) != 0) fatal("%s: invalid server public key", __func__); #ifdef DEBUG_KEXECDH fputs("server public key:\n", stderr); key_dump_ec_point(group, server_public); #endif /* signed H */ signature = packet_get_string(&slen); packet_check_eom(); klen = (EC_GROUP_get_degree(group) + 7) / 8; kbuf = xmalloc(klen); if (ECDH_compute_key(kbuf, klen, server_public, client_key, NULL) != (int)klen) fatal("%s: ECDH_compute_key failed", __func__); #ifdef DEBUG_KEXECDH dump_digest("shared secret", kbuf, klen); #endif if ((shared_secret = BN_new()) == NULL) fatal("%s: BN_new failed", __func__); if (BN_bin2bn(kbuf, klen, shared_secret) == NULL) fatal("%s: BN_bin2bn failed", __func__); memset(kbuf, 0, klen); free(kbuf); /* calc and verify H */ kex_ecdh_hash( kex->evp_md, group, kex->client_version_string, kex->server_version_string, buffer_ptr(&kex->my), buffer_len(&kex->my), buffer_ptr(&kex->peer), buffer_len(&kex->peer), server_host_key_blob, sbloblen, EC_KEY_get0_public_key(client_key), server_public, shared_secret, &hash, &hashlen ); free(server_host_key_blob); EC_POINT_clear_free(server_public); EC_KEY_free(client_key); if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) fatal("key_verify failed for server_host_key"); key_free(server_host_key); free(signature); /* save session id */ if (kex->session_id == NULL) { kex->session_id_len = hashlen; kex->session_id = xmalloc(kex->session_id_len); memcpy(kex->session_id, hash, kex->session_id_len); } kex_derive_keys(kex, hash, hashlen, shared_secret); BN_clear_free(shared_secret); kex_finish(kex); }
void kexecdh_server(Kex *kex) { EC_POINT *client_public; EC_KEY *server_key; const EC_GROUP *group; BIGNUM *shared_secret; Key *server_host_private, *server_host_public; u_char *server_host_key_blob = NULL, *signature = NULL; u_char *kbuf, *hash; u_int klen, slen, sbloblen, hashlen; int curve_nid; if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1) fatal("%s: unsupported ECDH curve \"%s\"", __func__, kex->name); if ((server_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL) fatal("%s: EC_KEY_new_by_curve_name failed", __func__); if (EC_KEY_generate_key(server_key) != 1) fatal("%s: EC_KEY_generate_key failed", __func__); group = EC_KEY_get0_group(server_key); #ifdef DEBUG_KEXECDH fputs("server private key:\n", stderr); key_dump_ec_key(server_key); #endif if (kex->load_host_public_key == NULL || kex->load_host_private_key == NULL) fatal("Cannot load hostkey"); server_host_public = kex->load_host_public_key(kex->hostkey_type); if (server_host_public == NULL) fatal("Unsupported hostkey type %d", kex->hostkey_type); server_host_private = kex->load_host_private_key(kex->hostkey_type); if (server_host_private == NULL) fatal("Missing private key for hostkey type %d", kex->hostkey_type); debug("expecting SSH2_MSG_KEX_ECDH_INIT"); packet_read_expect(SSH2_MSG_KEX_ECDH_INIT); if ((client_public = EC_POINT_new(group)) == NULL) fatal("%s: EC_POINT_new failed", __func__); packet_get_ecpoint(group, client_public); packet_check_eom(); if (key_ec_validate_public(group, client_public) != 0) fatal("%s: invalid client public key", __func__); #ifdef DEBUG_KEXECDH fputs("client public key:\n", stderr); key_dump_ec_point(group, client_public); #endif /* Calculate shared_secret */ klen = (EC_GROUP_get_degree(group) + 7) / 8; kbuf = xmalloc(klen); if (ECDH_compute_key(kbuf, klen, client_public, server_key, NULL) != (int)klen) fatal("%s: ECDH_compute_key failed", __func__); #ifdef DEBUG_KEXDH dump_digest("shared secret", kbuf, klen); #endif if ((shared_secret = BN_new()) == NULL) fatal("%s: BN_new failed", __func__); if (BN_bin2bn(kbuf, klen, shared_secret) == NULL) fatal("%s: BN_bin2bn failed", __func__); memset(kbuf, 0, klen); xfree(kbuf); /* calc H */ key_to_blob(server_host_public, &server_host_key_blob, &sbloblen); kex_ecdh_hash( kex->evp_md, group, kex->client_version_string, kex->server_version_string, buffer_ptr(&kex->peer), buffer_len(&kex->peer), buffer_ptr(&kex->my), buffer_len(&kex->my), server_host_key_blob, sbloblen, client_public, EC_KEY_get0_public_key(server_key), shared_secret, &hash, &hashlen ); EC_POINT_clear_free(client_public); /* save session id := H */ if (kex->session_id == NULL) { kex->session_id_len = hashlen; kex->session_id = xmalloc(kex->session_id_len); memcpy(kex->session_id, hash, kex->session_id_len); } /* sign H */ if (PRIVSEP(key_sign(server_host_private, &signature, &slen, hash, hashlen)) < 0) fatal("kexdh_server: key_sign failed"); /* destroy_sensitive_data(); */ /* send server hostkey, ECDH pubkey 'Q_S' and signed H */ packet_start(SSH2_MSG_KEX_ECDH_REPLY); packet_put_string(server_host_key_blob, sbloblen); packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key)); packet_put_string(signature, slen); packet_send(); xfree(signature); xfree(server_host_key_blob); /* have keys, free server key */ EC_KEY_free(server_key); kex_derive_keys(kex, hash, hashlen, shared_secret); BN_clear_free(shared_secret); kex_finish(kex); }