diff --git a/src/core/crypto/ctr_encryption_layer.cpp b/src/core/crypto/ctr_encryption_layer.cpp index 6769754413..82473f57d7 100644 --- a/src/core/crypto/ctr_encryption_layer.cpp +++ b/src/core/crypto/ctr_encryption_layer.cpp @@ -5,6 +5,7 @@ // SPDX-License-Identifier: GPL-2.0-or-later #include +#include #include #include "core/crypto/ctr_encryption_layer.h" @@ -18,35 +19,84 @@ std::size_t CTREncryptionLayer::Read(u8* data, std::size_t length, std::size_t o if (length == 0) return 0; + constexpr std::size_t BlockSize = 0x10; + constexpr std::size_t MaxChunkSize = 0x10000; + std::size_t total_read = 0; - // Handle an initial misaligned portion if needed. - if (auto const sector_offset = offset & 0xF; sector_offset != 0) { - const std::size_t aligned_off = offset - sector_offset; - std::array block{}; - if (auto const got = base->Read(block.data(), block.size(), aligned_off); got != 0) { - UpdateIV(base_offset + aligned_off); - cipher.Transcode(block.data(), got, block.data(), Op::Decrypt); - auto const to_copy = std::min(length, got > sector_offset ? got - sector_offset : 0); - if (to_copy > 0) { - std::memcpy(data, block.data() + sector_offset, to_copy); - data += to_copy; - offset += to_copy; - length -= to_copy; - total_read += to_copy; - } - } else { - return 0; + auto* out = data; + std::size_t remaining = length; + std::size_t current_offset = offset; + + const auto read_exact = [this](u8* dst, std::size_t bytes, std::size_t src_offset) { + std::size_t filled = 0; + while (filled < bytes) { + const std::size_t got = base->Read(dst + filled, bytes - filled, src_offset + filled); + if (got == 0) + break; + filled += got; } + return filled; + }; + + if (const std::size_t intra_block = current_offset & (BlockSize - 1); intra_block != 0) { + std::array block{}; + const std::size_t aligned_offset = current_offset - intra_block; + const std::size_t got = read_exact(block.data(), BlockSize, aligned_offset); + if (got <= intra_block) + return total_read; + + UpdateIV(base_offset + aligned_offset); + cipher.Transcode(block.data(), got, block.data(), Op::Decrypt); + + const std::size_t available = got - intra_block; + const std::size_t to_copy = std::min(remaining, available); + std::memcpy(out, block.data() + intra_block, to_copy); + + out += to_copy; + current_offset += to_copy; + remaining -= to_copy; + total_read += to_copy; + + if (to_copy != available) + return total_read; } - if (length > 0) { - // Now aligned to 0x10 - UpdateIV(base_offset + offset); - const std::size_t got = base->Read(data, length, offset); - if (got > 0) { - cipher.Transcode(data, got, data, Op::Decrypt); - total_read += got; - } + + while (remaining >= BlockSize) { + const std::size_t chunk_request = std::min(remaining, MaxChunkSize); + const std::size_t aligned_request = chunk_request - (chunk_request % BlockSize); + if (aligned_request == 0) + break; + + const std::size_t got = read_exact(out, aligned_request, current_offset); + if (got == 0) + break; + + UpdateIV(base_offset + current_offset); + cipher.Transcode(out, got, out, Op::Decrypt); + + out += got; + current_offset += got; + remaining -= got; + total_read += got; + + if (got < aligned_request) + return total_read; } + + if (remaining > 0) { + std::array block{}; + const std::size_t got = read_exact(block.data(), BlockSize, current_offset); + if (got == 0) + return total_read; + + UpdateIV(base_offset + current_offset); + cipher.Transcode(block.data(), got, block.data(), Op::Decrypt); + + const std::size_t to_copy = std::min(remaining, got); + std::memcpy(out, block.data(), to_copy); + total_read += to_copy; + } + return total_read; }