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blockstorage: allow reading partial block data from storage

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It will allow fetching specific transactions using an external index,
following https://github.com/bitcoin/bitcoin/pull/32541#issuecomment-3267485313.

No logging takes place in case of an invalid offset/size (to avoid spamming the log),
by using a new `ReadRawError::BadPartRange` error variant.

Co-authored-by: Hodlinator <172445034+hodlinator@users.noreply.github.com>
Co-authored-by: Lőrinc <pap.lorinc@gmail.com>
This commit is contained in:
Roman Zeyde
2025-12-06 15:02:29 +01:00
parent f2fd1aa21c
commit 4e2af1c065
4 changed files with 75 additions and 2 deletions
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11
src/node/blockstorage.cpp
View File

@@ -1048,7 +1048,7 @@ bool BlockManager::ReadBlock(CBlock& block, const CBlockIndex& index) const
return ReadBlock(block, block_pos, index.GetBlockHash());
}
BlockManager::ReadRawBlockResult BlockManager::ReadRawBlock(const FlatFilePos& pos) const
BlockManager::ReadRawBlockResult BlockManager::ReadRawBlock(const FlatFilePos& pos, std::optional<std::pair<size_t, size_t>> block_part) const
{
if (pos.nPos < STORAGE_HEADER_BYTES) {
// If nPos is less than STORAGE_HEADER_BYTES, we can't read the header that precedes the block data
@@ -1081,6 +1081,15 @@ BlockManager::ReadRawBlockResult BlockManager::ReadRawBlock(const FlatFilePos& p
return util::Unexpected{ReadRawError::IO};
}
if (block_part) {
const auto [offset, size]{*block_part};
if (size == 0 || offset >= blk_size || size > blk_size - offset) {
return util::Unexpected{ReadRawError::BadPartRange}; // Avoid logging - offset/size come from untrusted REST input
}
filein.seek(offset, SEEK_CUR);
blk_size = size;
}
std::vector<std::byte> data(blk_size); // Zeroing of memory is intentional here
filein.read(data);
return data;

3
src/node/blockstorage.h
View File

@@ -172,6 +172,7 @@ std::ostream& operator<<(std::ostream& os, const BlockfileCursor& cursor);
enum class ReadRawError {
IO,
BadPartRange,
};
/**
@@ -460,7 +461,7 @@ public:
/** Functions for disk access for blocks */
bool ReadBlock(CBlock& block, const FlatFilePos& pos, const std::optional<uint256>& expected_hash) const;
bool ReadBlock(CBlock& block, const CBlockIndex& index) const;
ReadRawBlockResult ReadRawBlock(const FlatFilePos& pos) const;
ReadRawBlockResult ReadRawBlock(const FlatFilePos& pos, std::optional<std::pair<size_t, size_t>> block_part = std::nullopt) const;
bool ReadBlockUndo(CBlockUndo& blockundo, const CBlockIndex& index) const;