Add hadamard utilities to encode keys
Add the utility functions to encode & decode 32 bytes keys. The
hadamard encoding will expand a 2 bytes word to 2^15 bits. And thus the
32 byte key will expand to 64KiB in space. The encoded value is more
robust and we will be able to recover the key even if there is some
corruption.
Test: unittest pass
Change-Id: Iae8a28a8c7c1699f8641f9250f0eccde5c2ff138
diff --git a/rebootescrow/aidl/default/HadamardUtilsTest.cpp b/rebootescrow/aidl/default/HadamardUtilsTest.cpp
new file mode 100644
index 0000000..e397e76
--- /dev/null
+++ b/rebootescrow/aidl/default/HadamardUtilsTest.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * 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
+ *
+ * http://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 <stdint.h>
+#include <random>
+
+#include <bitset>
+#include <utility>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include <HadamardUtils.h>
+
+using namespace aidl::android::hardware::rebootescrow::hadamard;
+
+class HadamardTest : public testing::Test {
+ protected:
+ void SetUp() override {
+ auto ones = std::bitset<ENCODE_LENGTH>{}.set();
+ // Expects 0x4000 to encode as top half as ones, and lower half as zeros. i.e.
+ // [1, 1 .. 1, 0, 0 .. 0]
+ expected_half_size_ = ones << half_size_;
+
+ // Expects 0x1 to encode as interleaved 1 and 0s i.e. [1, 0, 1, 0 ..]
+ expected_one_ = ones;
+ for (uint32_t i = ENCODE_LENGTH / 2; i >= 1; i /= 2) {
+ expected_one_ ^= (expected_one_ >> i);
+ }
+ }
+
+ uint16_t half_size_ = ENCODE_LENGTH / 2;
+ std::bitset<ENCODE_LENGTH> expected_one_;
+ std::bitset<ENCODE_LENGTH> expected_half_size_;
+};
+
+static void AddError(std::bitset<ENCODE_LENGTH>* corrupted_bits) {
+ // The hadamard code has a hamming distance of ENCODE_LENGTH/2. So we should always be able to
+ // correct the data if less than a quarter of the encoded bits are corrupted.
+ auto corrupted_max = 0.24f * corrupted_bits->size();
+ auto corrupted_num = 0;
+ for (size_t i = 0; i < corrupted_bits->size() && corrupted_num < corrupted_max; i++) {
+ if (random() % 2 == 0) {
+ (*corrupted_bits)[i] = !(*corrupted_bits)[i];
+ corrupted_num += 1;
+ }
+ }
+}
+
+static void EncodeAndDecodeKeys(const std::vector<uint8_t>& key) {
+ auto encoded = EncodeKey(key);
+ ASSERT_EQ(64 * 1024, encoded.size());
+ auto decoded = DecodeKey(encoded);
+ ASSERT_EQ(key, std::vector<uint8_t>(decoded.begin(), decoded.begin() + key.size()));
+}
+
+TEST_F(HadamardTest, Encode_smoke) {
+ ASSERT_EQ(expected_half_size_, EncodeWord(half_size_));
+ ASSERT_EQ(expected_one_, EncodeWord(1));
+ // Check the complement of 1.
+ ASSERT_EQ(~expected_one_, EncodeWord(1u << CODE_K | 1u));
+}
+
+TEST_F(HadamardTest, Decode_smoke) {
+ auto candidate = DecodeWord(expected_half_size_);
+ auto expected = std::pair<int32_t, uint16_t>{ENCODE_LENGTH, half_size_};
+ ASSERT_EQ(expected, candidate.top());
+
+ candidate = DecodeWord(expected_one_);
+ expected = std::pair<int32_t, uint16_t>{ENCODE_LENGTH, 1};
+ ASSERT_EQ(expected, candidate.top());
+}
+
+TEST_F(HadamardTest, Decode_error_correction) {
+ constexpr auto iteration = 10;
+ for (int i = 0; i < iteration; i++) {
+ uint16_t word = random() % (ENCODE_LENGTH * 2);
+ auto corrupted_bits = EncodeWord(word);
+ AddError(&corrupted_bits);
+
+ auto candidate = DecodeWord(corrupted_bits);
+ ASSERT_EQ(word, candidate.top().second);
+ }
+}
+
+TEST_F(HadamardTest, BytesToBitset_smoke) {
+ auto bytes = BitsetToBytes(expected_one_);
+
+ auto read_back = BytesToBitset(bytes);
+ ASSERT_EQ(expected_one_, read_back);
+}
+
+TEST_F(HadamardTest, EncodeAndDecodeKey) {
+ std::vector<uint8_t> KEY_1{
+ 0xA5, 0x00, 0xFF, 0x01, 0xA5, 0x5a, 0xAA, 0x55, 0x00, 0xD3, 0x2A,
+ 0x8C, 0x2E, 0x83, 0x0E, 0x65, 0x9E, 0x8D, 0xC6, 0xAC, 0x1E, 0x83,
+ 0x21, 0xB3, 0x95, 0x02, 0x89, 0x64, 0x64, 0x92, 0x12, 0x1F,
+ };
+ std::vector<uint8_t> KEY_2{
+ 0xFF, 0x00, 0x00, 0xAA, 0x5A, 0x19, 0x20, 0x71, 0x9F, 0xFB, 0xDA,
+ 0xB6, 0x2D, 0x06, 0xD5, 0x49, 0x7E, 0xEF, 0x63, 0xAC, 0x18, 0xFF,
+ 0x5A, 0xA3, 0x40, 0xBB, 0x64, 0xFA, 0x67, 0xC1, 0x10, 0x18,
+ };
+
+ EncodeAndDecodeKeys(KEY_1);
+ EncodeAndDecodeKeys(KEY_2);
+
+ std::vector<uint8_t> key;
+ for (uint8_t i = 0; i < KEY_SIZE_IN_BYTES; i++) {
+ key.push_back(i);
+ };
+ EncodeAndDecodeKeys(key);
+}