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Diffstat (limited to 'pkg/merkletree/merkletree.go')
| -rw-r--r-- | pkg/merkletree/merkletree.go | 314 |
1 files changed, 0 insertions, 314 deletions
diff --git a/pkg/merkletree/merkletree.go b/pkg/merkletree/merkletree.go deleted file mode 100644 index 955c9c473..000000000 --- a/pkg/merkletree/merkletree.go +++ /dev/null @@ -1,314 +0,0 @@ -// Copyright 2020 The gVisor Authors. -// -// 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. - -// Package merkletree implements Merkle tree generating and verification. -package merkletree - -import ( - "bytes" - "crypto/sha256" - "fmt" - "io" - - "gvisor.dev/gvisor/pkg/usermem" -) - -const ( - // sha256DigestSize specifies the digest size of a SHA256 hash. - sha256DigestSize = 32 -) - -// Layout defines the scale of a Merkle tree. -type Layout struct { - // blockSize is the size of a data block to be hashed. - blockSize int64 - // digestSize is the size of a generated hash. - digestSize int64 - // levelOffset contains the offset of the begnning of each level in - // bytes. The number of levels in the tree is the length of the slice. - // The leaf nodes (level 0) contain hashes of blocks of the input data. - // Each level N contains hashes of the blocks in level N-1. The highest - // level is the root hash. - levelOffset []int64 -} - -// InitLayout initializes and returns a new Layout object describing the structure -// of a tree. dataSize specifies the size of input data in bytes. -func InitLayout(dataSize int64) Layout { - layout := Layout{ - blockSize: usermem.PageSize, - // TODO(b/156980949): Allow config other hash methods (SHA384/SHA512). - digestSize: sha256DigestSize, - } - numBlocks := (dataSize + layout.blockSize - 1) / layout.blockSize - level := 0 - offset := int64(0) - - // Calculate the number of levels in the Merkle tree and the beginning - // offset of each level. Level 0 consists of the leaf nodes that - // contain the hashes of the data blocks, while level numLevels - 1 is - // the root. - for numBlocks > 1 { - layout.levelOffset = append(layout.levelOffset, offset*layout.blockSize) - // Round numBlocks up to fill up a block. - numBlocks += (layout.hashesPerBlock() - numBlocks%layout.hashesPerBlock()) % layout.hashesPerBlock() - offset += numBlocks / layout.hashesPerBlock() - numBlocks = numBlocks / layout.hashesPerBlock() - level++ - } - layout.levelOffset = append(layout.levelOffset, offset*layout.blockSize) - return layout -} - -// hashesPerBlock() returns the number of digests in each block. For example, -// if blockSize is 4096 bytes, and digestSize is 32 bytes, there will be 128 -// hashesPerBlock. Therefore 128 hashes in one level will be combined in one -// hash in the level above. -func (layout Layout) hashesPerBlock() int64 { - return layout.blockSize / layout.digestSize -} - -// numLevels returns the total number of levels in the Merkle tree. -func (layout Layout) numLevels() int { - return len(layout.levelOffset) -} - -// rootLevel returns the level of the root hash. -func (layout Layout) rootLevel() int { - return layout.numLevels() - 1 -} - -// digestOffset finds the offset of a digest from the beginning of the tree. -// The target digest is at level of the tree, with index from the beginning of -// the current level. -func (layout Layout) digestOffset(level int, index int64) int64 { - return layout.levelOffset[level] + index*layout.digestSize -} - -// blockOffset finds the offset of a block from the beginning of the tree. The -// target block is at level of the tree, with index from the beginning of the -// current level. -func (layout Layout) blockOffset(level int, index int64) int64 { - return layout.levelOffset[level] + index*layout.blockSize -} - -// Generate constructs a Merkle tree for the contents of data. The output is -// written to treeWriter. The treeReader should be able to read the tree after -// it has been written. That is, treeWriter and treeReader should point to the -// same underlying data but have separate cursors. -func Generate(data io.Reader, dataSize int64, treeReader io.Reader, treeWriter io.Writer) ([]byte, error) { - layout := InitLayout(dataSize) - - numBlocks := (dataSize + layout.blockSize - 1) / layout.blockSize - - var root []byte - for level := 0; level < layout.numLevels(); level++ { - for i := int64(0); i < numBlocks; i++ { - buf := make([]byte, layout.blockSize) - var ( - n int - err error - ) - if level == 0 { - // Read data block from the target file since level 0 includes hashes - // of blocks in the input data. - n, err = data.Read(buf) - } else { - // Read data block from the tree file since levels higher than 0 are - // hashing the lower level hashes. - n, err = treeReader.Read(buf) - } - - // err is populated as long as the bytes read is smaller than the buffer - // size. This could be the case if we are reading the last block, and - // break in that case. If this is the last block, the end of the block - // will be zero-padded. - if n == 0 && err == io.EOF { - break - } else if err != nil && err != io.EOF { - return nil, err - } - // Hash the bytes in buf. - digest := sha256.Sum256(buf) - - if level == layout.rootLevel() { - root = digest[:] - } - - // Write the generated hash to the end of the tree file. - if _, err = treeWriter.Write(digest[:]); err != nil { - return nil, err - } - } - // If the generated digests do not round up to a block, zero-padding the - // remaining of the last block. But no need to do so for root. - if level != layout.rootLevel() && numBlocks%layout.hashesPerBlock() != 0 { - zeroBuf := make([]byte, layout.blockSize-(numBlocks%layout.hashesPerBlock())*layout.digestSize) - if _, err := treeWriter.Write(zeroBuf[:]); err != nil { - return nil, err - } - } - numBlocks = (numBlocks + layout.hashesPerBlock() - 1) / layout.hashesPerBlock() - } - return root, nil -} - -// Verify verifies the content read from data with offset. The content is -// verified against tree. If content spans across multiple blocks, each block is -// verified. Verification fails if the hash of the data does not match the tree -// at any level, or if the final root hash does not match expectedRoot. -// Once the data is verified, it will be written using w. -// Verify will modify the cursor for data, but always restores it to its -// original position upon exit. The cursor for tree is modified and not -// restored. -func Verify(w io.Writer, data, tree io.ReadSeeker, dataSize int64, readOffset int64, readSize int64, expectedRoot []byte) error { - if readSize <= 0 { - return fmt.Errorf("Unexpected read size: %d", readSize) - } - layout := InitLayout(int64(dataSize)) - - // Calculate the index of blocks that includes the target range in input - // data. - firstDataBlock := readOffset / layout.blockSize - lastDataBlock := (readOffset + readSize - 1) / layout.blockSize - - // Store the current offset, so we can set it back once verification - // finishes. - origOffset, err := data.Seek(0, io.SeekCurrent) - if err != nil { - return fmt.Errorf("Find current data offset failed: %v", err) - } - defer data.Seek(origOffset, io.SeekStart) - - // Move to the first block that contains target data. - if _, err := data.Seek(firstDataBlock*layout.blockSize, io.SeekStart); err != nil { - return fmt.Errorf("Seek to datablock start failed: %v", err) - } - - buf := make([]byte, layout.blockSize) - var readErr error - bytesRead := 0 - for i := firstDataBlock; i <= lastDataBlock; i++ { - // Read a block that includes all or part of target range in - // input data. - bytesRead, readErr = data.Read(buf) - // If at the end of input data and all previous blocks are - // verified, return the verified input data and EOF. - if readErr == io.EOF && bytesRead == 0 { - break - } - if readErr != nil && readErr != io.EOF { - return fmt.Errorf("Read from data failed: %v", err) - } - // If this is the end of file, zero the remaining bytes in buf, - // otherwise they are still from the previous block. - // TODO(b/162908070): Investigate possible issues with zero - // padding the data. - if bytesRead < len(buf) { - for j := bytesRead; j < len(buf); j++ { - buf[j] = 0 - } - } - if err := verifyBlock(tree, layout, buf, i, expectedRoot); err != nil { - return err - } - // startOff is the beginning of the read range within the - // current data block. Note that for all blocks other than the - // first, startOff should be 0. - startOff := int64(0) - if i == firstDataBlock { - startOff = readOffset % layout.blockSize - } - // endOff is the end of the read range within the current data - // block. Note that for all blocks other than the last, endOff - // should be the block size. - endOff := layout.blockSize - if i == lastDataBlock { - endOff = (readOffset+readSize-1)%layout.blockSize + 1 - } - // If the provided size exceeds the end of input data, we should - // only copy the parts in buf that's part of input data. - if startOff > int64(bytesRead) { - startOff = int64(bytesRead) - } - if endOff > int64(bytesRead) { - endOff = int64(bytesRead) - } - w.Write(buf[startOff:endOff]) - - } - return readErr -} - -// verifyBlock verifies a block against tree. index is the number of block in -// original data. The block is verified through each level of the tree. It -// fails if the calculated hash from block is different from any level of -// hashes stored in tree. And the final root hash is compared with -// expectedRoot. verifyBlock modifies the cursor for tree. Users needs to -// maintain the cursor if intended. -func verifyBlock(tree io.ReadSeeker, layout Layout, dataBlock []byte, blockIndex int64, expectedRoot []byte) error { - if len(dataBlock) != int(layout.blockSize) { - return fmt.Errorf("incorrect block size") - } - - expectedDigest := make([]byte, layout.digestSize) - treeBlock := make([]byte, layout.blockSize) - var digest []byte - for level := 0; level < layout.numLevels(); level++ { - // Calculate hash. - if level == 0 { - digestArray := sha256.Sum256(dataBlock) - digest = digestArray[:] - } else { - // Read a block in previous level that contains the - // hash we just generated, and generate a next level - // hash from it. - if _, err := tree.Seek(layout.blockOffset(level-1, blockIndex), io.SeekStart); err != nil { - return err - } - if _, err := tree.Read(treeBlock); err != nil { - return err - } - digestArray := sha256.Sum256(treeBlock) - digest = digestArray[:] - } - - // Move to stored hash for the current block, read the digest - // and store in expectedDigest. - if _, err := tree.Seek(layout.digestOffset(level, blockIndex), io.SeekStart); err != nil { - return err - } - if _, err := tree.Read(expectedDigest); err != nil { - return err - } - - if !bytes.Equal(digest, expectedDigest) { - return fmt.Errorf("Verification failed") - } - - // If this is the root layer, no need to generate next level - // hash. - if level == layout.rootLevel() { - break - } - blockIndex = blockIndex / layout.hashesPerBlock() - } - - // Verification for the tree succeeded. Now compare the root hash in the - // tree with expectedRoot. - if !bytes.Equal(digest[:], expectedRoot) { - return fmt.Errorf("Verification failed") - } - return nil -} |