mirror of
https://github.com/kidfromjupiter/nearby.git
synced 2026-09-16 15:36:12 -04:00
Janusz Sobczak
f643f7a466
New features: * Smart Audio Source Switching. * Fast Pair for BLE-only devices. * Two byte salt size for improved security. Other changes: * Added optional encryption modules based on mbedtls. * Fixed build issues. * More verbose and readable logs.
109 lines
3.2 KiB
C
109 lines
3.2 KiB
C
// Copyright 2022 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// gen_secret module
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//
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// Implements the nearby_platform_GenSec256r1Secret() function, using the
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// MBEDTLS package developed by ARM.
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//
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// To use the package, uncomment the NEARBY_PLATFORM_USE_MBEDTLS define in
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// config.mk.
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//
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// This routine was separated from the mbedtls.c code because an implementation
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// may need to implement the shared secret function using a hardware embedded
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// key. In such an implementation, the actual private key is not directly
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// accessable, but rather the shared secret is generated using the public key
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// and the sequestered private key without ever revealing the private key in
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// code.
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//
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#define MBEDTLS_ALLOW_PRIVATE_ACCESS
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#include <mbedtls/aes.h>
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#include <mbedtls/ecdh.h>
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#include <mbedtls/ecp.h>
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#include <mbedtls/error.h>
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#include <mbedtls/md.h> /* generic interface */
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#include <mbedtls/sha256.h>
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#if (MBEDTLS_VERSION_NUMBER >= 0x03000000)
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#include <mbedtls/compat-2.x.h>
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#endif
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#include <nearby_platform_se.h>
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#include <stdlib.h>
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#ifndef NEARBY_PLATFORM_HAS_SE
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static int crypto_rand(void* const seed, uint8_t* const out,
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size_t const size) {
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(void)seed;
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for (size_t i = 0; i < size; i++) {
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out[i] = rand() % UINT8_MAX;
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}
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return 0;
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}
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/**
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* Generates a shared sec256p1 secret using remote party public key and this
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* device's private key.
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*/
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nearby_platform_status nearby_platform_GenSec256r1Secret(
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const uint8_t remote_party_public_key[64], uint8_t shared_secret[32]) {
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nearby_platform_status status = kNearbyStatusError;
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mbedtls_ecp_group grp;
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mbedtls_ecp_point pub;
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mbedtls_mpi prv;
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mbedtls_mpi secret;
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mbedtls_ecp_group_init(&grp);
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mbedtls_ecp_point_init(&pub);
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mbedtls_mpi_init(&prv);
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mbedtls_mpi_init(&secret);
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mbedtls_mpi_uint p = 1;
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pub.Z.p = &p;
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pub.Z.n = 1;
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const uint8_t* pkp;
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pkp = nearby_platform_GetAntiSpoofingPrivateKey();
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if (!pkp) {
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goto exit;
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}
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if (mbedtls_ecp_group_load(&grp, MBEDTLS_ECP_DP_SECP256R1) != 0) goto exit;
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if (mbedtls_mpi_read_binary(&pub.X, remote_party_public_key, 32) != 0)
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goto exit;
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if (mbedtls_mpi_read_binary(&pub.Y, remote_party_public_key + 32, 32) != 0)
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goto exit;
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if (mbedtls_mpi_read_binary(&prv, pkp, 32) != 0) goto exit;
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if ((mbedtls_ecdh_compute_shared(&grp, &secret, &pub, &prv, crypto_rand,
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NULL)) != 0)
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goto exit;
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if (mbedtls_mpi_write_binary(&secret, shared_secret, 32) != 0) goto exit;
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status = kNearbyStatusOK;
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exit:
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pub.Z.p = NULL;
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pub.Z.n = 0;
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mbedtls_ecp_group_free(&grp);
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mbedtls_ecp_point_free(&pub);
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mbedtls_mpi_free(&prv);
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mbedtls_mpi_free(&secret);
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return status;
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}
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#endif /* NEARBY_PLATFORM_HAS_SE */
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