Add back in Ldt stub impl, so it can be used in chromium

PiperOrigin-RevId: 742808756

presence/implementation/ldt.cc

@@ -23,7 +23,7 @@
 #include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
 #ifdef NEARBY_CHROMIUM
-#include "third_party/beto-core/src/nearby/presence/ldt_np_adv_ffi/c/include/np_ldt.h"
+#include "third_party/nearby/src/presence/implementation/np_ldt.h"
 #else
 #include "np_ldt.h"
 #endif

presence/implementation/ldt_stub.c

@@ -0,0 +1,47 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "presence/implementation/np_ldt.h"
+
+// Placeholder, empty implementations of LDT utilities. They will be replaced
+// with implementations in Rust.
+
+NpLdtEncryptHandle NpLdtEncryptCreate(NpLdtKeySeed key_seed) {
+  NpLdtEncryptHandle handle = {0};
+  return handle;
+}
+
+NpLdtDecryptHandle NpLdtDecryptCreate(NpLdtKeySeed key_seed,
+                                      NpMetadataKeyHmac hmac_tag) {
+  NpLdtDecryptHandle handle = {0};
+  return handle;
+}
+
+NP_LDT_RESULT NpLdtEncryptClose(NpLdtEncryptHandle handle) {
+  return NP_LDT_SUCCESS;
+}
+
+NP_LDT_RESULT NpLdtDecryptClose(NpLdtDecryptHandle handle) {
+  return NP_LDT_SUCCESS;
+}
+
+NP_LDT_RESULT NpLdtEncrypt(NpLdtEncryptHandle handle, uint8_t* buffer,
+                           size_t buffer_len, NpLdtSalt salt) {
+  return NP_LDT_SUCCESS;
+}
+
+NP_LDT_RESULT NpLdtDecryptAndVerify(NpLdtDecryptHandle handle, uint8_t* buffer,
+                                    size_t buffer_len, NpLdtSalt salt) {
+  return NP_LDT_SUCCESS;
+}

presence/implementation/np_ldt.h

@@ -0,0 +1,125 @@
+#ifndef THIRD_PARTY_NEARBY_PRESENCE_IMPLEMENTATION_NP_LDT_H_
+#define THIRD_PARTY_NEARBY_PRESENCE_IMPLEMENTATION_NP_LDT_H_
+
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// C API for Rust implementation of LDT [1], tailored to Nearby Presence's
+// BLE 4.2 legacy format advertisement parsing usecase.
+//
+// [1] https://eprint.iacr.org/2017/841.pdf
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stddef.h>
+#include <stdint.h>
+
+// Individual encrypt/decrypt API, useful when creating advertisements or when
+// decrypting advertisements from a known origin
+
+// The allocated handle to use for encryption
+typedef struct {
+  uint64_t handle;
+} NpLdtEncryptHandle;
+
+// The allocated handle to use for decryption
+typedef struct {
+  uint64_t handle;
+} NpLdtDecryptHandle;
+
+// Key material from the Nearby Presence credential from which keys will be
+// derived.
+typedef struct {
+  uint8_t bytes[32];
+} NpLdtKeySeed;
+
+typedef struct {
+  uint8_t bytes[32];
+} NpMetadataKeyHmac;
+
+typedef struct {
+  uint8_t bytes[2];
+} NpLdtSalt;
+
+// Possible result codes returned from the LDT NP API's
+typedef enum {
+  // Call to api was succesful
+  NP_LDT_SUCCESS = 0,
+  // Payload of invalid length was provided must be >= 16 and <=31 bytes
+  NP_LDT_ERROR_INVALID_LENGTH = -1,
+  // The provided metadata hmac did not match the calculated hmac on call to
+  // decrypt and verify
+  NP_LDT_ERROR_MAC_MISMATCH = -2,
+} NP_LDT_RESULT;
+
+// Allocate an LDT-XTS-AES128 Decryption cipher using the "swap" mix function.
+//
+// `key_seed` is the key material from the Nearby Presence credential from which
+// the LDT key will be derived.
+// 'hmac_tag' is the hmac auth tag calculated on the metadata key used to verify
+// decryption was successful
+//
+// Returns 0 on error, or a non-zero handle on success.
+NpLdtDecryptHandle NpLdtDecryptCreate(NpLdtKeySeed key_seed,
+                                      NpMetadataKeyHmac hmac_tag);
+
+// Allocate an LDT-XTS-AES128 Encryption cipher using the "swap" mix function.
+//
+// `key_seed` is the key material from the Nearby Presence credential from which
+// the LDT key will be derived.
+//
+// Returns 0 on error, or a non-zero handle on success.
+NpLdtEncryptHandle NpLdtEncryptCreate(NpLdtKeySeed key_seed);
+
+// Release allocated resources for an NpLdtEncryptHandle
+//
+// Returns 0 on success or an NP_LDT_RESULT error code on failure
+NP_LDT_RESULT NpLdtEncryptClose(NpLdtEncryptHandle handle);
+
+// Release allocated resources for an NpLdtDecryptHandle
+//
+// Returns 0 on success or an NP_LDT_RESULT error code on failure
+NP_LDT_RESULT NpLdtDecryptClose(NpLdtDecryptHandle handle);
+
+// Encrypt a 16-31 byte buffer in-place.
+//
+// `buffer` is a pointer to a 16-31 byte plaintext, with length in `buffer_len`.
+// `salt` is the big-endian  2 byte salt that will be used in the Nearby
+// Presence advertisement, which will be incorporated into the tweaks LDT uses
+// while encrypting.
+//
+// Returns 0 on success, in which case `buffer` will now contain ciphertext.
+// Returns an NP_LDT_RESULT error code on failure
+NP_LDT_RESULT NpLdtEncrypt(NpLdtEncryptHandle handle, uint8_t* buffer,
+                           size_t buffer_len, NpLdtSalt salt);
+
+// Decrypt a 16-31 byte buffer in-place.
+//
+// `buffer` is a pointer to a 16-31 byte ciphertext, with length in
+// `buffer_len`.
+// `salt` is the big-endian  2 byte salt found in the Nearby Presence
+// advertisement, which will be incorporated into the tweaks LDT uses while
+// decrypting.
+//
+// Returns 0 on success, in which case `buffer` will now contain plaintext.
+// Returns an NP_LDT_RESULT error code on failure
+NP_LDT_RESULT NpLdtDecryptAndVerify(NpLdtDecryptHandle handle, uint8_t* buffer,
+                                    size_t buffer_len, NpLdtSalt salt);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // THIRD_PARTY_NEARBY_PRESENCE_IMPLEMENTATION_NP_LDT_H_