mirror of
https://github.com/Atmosphere-NX/Atmosphere-libs.git
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278 lines
11 KiB
C++
278 lines
11 KiB
C++
/*
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* Copyright (c) Atmosphère-NX
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <stratosphere.hpp>
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namespace ams::spl::impl {
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constexpr inline int BitsPerByte = BITSIZEOF(u8);
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/* Nintendo implements CTR_DRBG for their csrng. We will do the same. */
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template<typename BlockCipher, size_t KeySize, bool UseDerivation>
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class CtrDrbg {
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public:
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static constexpr int KeyLen = KeySize * BitsPerByte;
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static constexpr int OutLen = BlockCipher::BlockSize * BitsPerByte;
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static constexpr int SeedLen = KeyLen + OutLen;
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static constexpr int MaxNumberOfBitsPerRequest = (1 << 19);
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static constexpr int ReseedInterval = 0x7FFFFFF0;
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static constexpr size_t OutSize = OutLen / BitsPerByte;
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static constexpr size_t SeedSize = SeedLen / BitsPerByte;
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static constexpr size_t RequestSizeMax = MaxNumberOfBitsPerRequest / BitsPerByte;
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static_assert(SeedSize % OutSize == 0);
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private:
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class Bcc {
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private:
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u8 *m_buffer;
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const BlockCipher *m_cipher;
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size_t m_offset;
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public:
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Bcc(u8 *buffer, const BlockCipher *cipher) : m_buffer(buffer), m_cipher(cipher), m_offset(0) { /* ... */ }
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void Process(const void *data, size_t size) {
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const u8 *data_8 = static_cast<const u8 *>(data);
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size_t remaining = size;
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while (m_offset + remaining >= OutSize) {
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const size_t xor_size = OutSize - m_offset;
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Xor(m_buffer + m_offset, data_8, xor_size);
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m_cipher->EncryptBlock(m_buffer, OutSize, m_buffer, OutSize);
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data_8 += xor_size;
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remaining -= xor_size;
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m_offset = 0;
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}
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Xor(m_buffer + m_offset, data_8, remaining);
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m_offset += remaining;
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}
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void Flush() {
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if (m_offset != 0) {
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m_cipher->EncryptBlock(m_buffer, OutSize, m_buffer, OutSize);
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m_offset = 0;
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}
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}
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};
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private:
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BlockCipher m_block_cipher;
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u8 m_v[OutSize];
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u8 m_key[KeySize];
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u8 m_work1[SeedSize];
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u8 m_work2[SeedSize];
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int m_reseed_counter;
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private:
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static void Xor(void *dst, const void *src, size_t size) {
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const u8 *src_u8 = static_cast<const u8 *>(src);
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u8 *dst_u8 = static_cast<u8 *>(dst);
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for (size_t i = 0; i < size; i++) {
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dst_u8[i] ^= src_u8[i];
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}
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}
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static void Increment(void *v) {
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u8 *v_8 = static_cast<u8 *>(v);
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for (int i = OutSize - 1; i >= 0; --i) {
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if ((++v_8[i]) != 0) {
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break;
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}
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}
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}
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private:
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void DeriveSeed(void *seed, const void *a, size_t a_size, const void *b, size_t b_size, const void *c, size_t c_size) {
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/* Determine sizes. */
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const u32 in_size = a_size + b_size + c_size;
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const u32 out_size = SeedSize;
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/* Create header/footer. */
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u32 header[2];
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util::StoreBigEndian(header + 0, in_size);
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util::StoreBigEndian(header + 1, out_size);
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const u8 footer = 0x80;
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/* Create seed as 000102... */
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u8 *seed_8 = static_cast<u8 *>(seed);
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for (size_t i = 0; i < KeySize; ++i) {
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seed_8[i] = i;
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}
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/* Initialize block cipher. */
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m_block_cipher.Initialize(seed_8, KeySize);
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/* Perform derivation. */
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for (u32 block = 0; block < SeedSize / OutSize; ++block) {
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/* Create the block index value. */
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u32 block_value;
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util::StoreBigEndian(std::addressof(block_value), block);
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/* Get the target block. */
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u8 *target = seed_8 + block * OutSize;
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std::memset(target, 0, OutSize);
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/* Create block processor. */
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Bcc bcc(target, std::addressof(m_block_cipher));
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/* Process block value. */
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bcc.Process(std::addressof(block_value), sizeof(block_value));
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bcc.Flush();
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/* Process header/data. */
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bcc.Process(header, sizeof(header));
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bcc.Process(a, a_size);
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bcc.Process(b, b_size);
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bcc.Process(c, c_size);
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bcc.Process(footer, std::addressof(footer));
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bcc.Flush();
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}
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/* Initialize block cipher. */
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m_block_cipher.Initialize(seed_8, KeySize);
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/* Encrypt seed. */
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m_block_cipher.EncryptBlock(seed_8, OutSize, seed_8 + KeySize, OutSize);
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for (size_t offset = 0; offset < SeedSize - OutSize; offset += OutSize) {
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m_block_cipher.EncryptBlock(seed_8 + offset + OutSize, OutSize, seed_8 + offset, OutSize);
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}
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}
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void UpdateStates(void *key, void *v, const void *provided_data) {
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/* Initialize block cipher. */
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m_block_cipher.Initialize(key, KeySize);
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/* Update work. */
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for (size_t offset = 0; offset < SeedSize; offset += OutSize) {
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Increment(v);
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m_block_cipher.EncryptBlock(std::addressof(m_work2[offset]), OutSize, v, OutSize);
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}
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/* Xor work with provided data. */
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Xor(m_work2, provided_data, SeedSize);
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/* Copy to key/v. */
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std::memcpy(key, m_work2 + 0, KeySize);
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std::memcpy(v, m_work2 + KeySize, OutSize);
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}
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public:
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constexpr CtrDrbg() = default;
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void Initialize(const void *entropy, size_t entropy_size, const void *nonce, size_t nonce_size, const void *personalization, size_t personalization_size) {
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/* Handle init. */
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if constexpr (UseDerivation) {
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this->DeriveSeed(m_work1, entropy, entropy_size, nonce, nonce_size, personalization, personalization_size);
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} else {
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AMS_ASSERT(entropy_size == SeedSize);
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AMS_ASSERT(nonce_size == 0);
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AMS_ASSERT(personalization_size <= SeedSize);
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AMS_UNUSED(entropy_size, nonce, nonce_size);
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std::memcpy(m_work1, entropy, SeedSize);
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Xor(m_work1, personalization, personalization_size);
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}
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/* Clear key/v. */
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std::memset(m_key, 0, sizeof(m_key));
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std::memset(m_v, 0, sizeof(m_v));
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/* Set key/v. */
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this->UpdateStates(m_key, m_v, m_work1);
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/* Set reseed counter. */
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m_reseed_counter = 1;
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}
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void Reseed(const void *entropy, size_t entropy_size, const void *addl, size_t addl_size) {
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/* Handle init. */
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if constexpr (UseDerivation) {
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this->DeriveSeed(m_work1, entropy, entropy_size, addl, addl_size, nullptr, 0);
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} else {
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AMS_ASSERT(entropy_size == SeedSize);
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AMS_ASSERT(addl_size <= SeedSize);
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AMS_UNUSED(entropy_size);
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std::memcpy(m_work1, entropy, SeedSize);
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Xor(m_work1, addl, addl_size);
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}
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/* Set key/v. */
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this->UpdateStates(m_key, m_v, m_work1);
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/* Set reseed counter. */
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m_reseed_counter = 1;
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}
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bool Generate(void *out, size_t size, const void *addl, size_t addl_size) {
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/* Check that the request is small enough. */
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if (size > RequestSizeMax) {
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return false;
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}
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/* Check if we need reseed. */
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if (m_reseed_counter > ReseedInterval) {
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return false;
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}
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/* Clear work buffer. */
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std::memset(m_work1, 0, sizeof(m_work1));
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/* Process additional input, if we have any. */
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if (addl_size > 0) {
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if constexpr (UseDerivation) {
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this->DeriveSeed(m_work1, addl, addl_size, nullptr, 0, nullptr, 0);
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} else {
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AMS_ASSERT(addl_size <= SeedSize);
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std::memcpy(m_work1, addl, addl_size);
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}
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/* Set key/v. */
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this->UpdateStates(m_key, m_v, m_work1);
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}
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/* Get buffer and aligned size. */
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u8 *out_8 = static_cast<u8 *>(out);
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const size_t aligned_size = util::AlignDown(size, OutSize);
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/* Generate ctr bytes. */
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m_block_cipher.Initialize(m_key, KeySize);
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for (size_t offset = 0; offset < aligned_size; offset += OutSize) {
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Increment(m_v);
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m_block_cipher.EncryptBlock(out_8 + offset, OutSize, m_v, OutSize);
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}
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/* Handle any unaligned data. */
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if (size > aligned_size) {
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u8 temp[OutSize];
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Increment(m_v);
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m_block_cipher.EncryptBlock(temp, sizeof(temp), m_v, OutSize);
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std::memcpy(out_8 + aligned_size, temp, size - aligned_size);
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}
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/* Set key/v. */
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this->UpdateStates(m_key, m_v, m_work1);
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/* Increment reseed counter. */
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++m_reseed_counter;
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return true;
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}
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};
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}
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