diff options
| -rw-r--r-- | pkg/merkletree/merkletree.go | 64 | ||||
| -rw-r--r-- | pkg/merkletree/merkletree_test.go | 60 |
2 files changed, 124 insertions, 0 deletions
diff --git a/pkg/merkletree/merkletree.go b/pkg/merkletree/merkletree.go index 965f3670b..906f67943 100644 --- a/pkg/merkletree/merkletree.go +++ b/pkg/merkletree/merkletree.go @@ -16,6 +16,9 @@ package merkletree import ( + "crypto/sha256" + "io" + "gvisor.dev/gvisor/pkg/usermem" ) @@ -69,3 +72,64 @@ func MakeSize(dataSize int64) Size { size.levelStart = append(size.levelStart, offset) return size } + +// 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) { + size := MakeSize(dataSize) + + numBlocks := (dataSize + size.blockSize - 1) / size.blockSize + + var root []byte + for level := 0; level < len(size.levelStart); level++ { + for i := int64(0); i < numBlocks; i++ { + buf := make([]byte, size.blockSize) + var ( + n int + err error + ) + if level == 0 { + // Read data block from the target file since level 0 is directly above + // the raw data block. + 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 == len(size.levelStart)-1 { + 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 genereated 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 != len(size.levelStart)-1 && numBlocks%size.hashesPerBlock != 0 { + zeroBuf := make([]byte, size.blockSize-(numBlocks%size.hashesPerBlock)*size.digestSize) + if _, err := treeWriter.Write(zeroBuf[:]); err != nil { + return nil, err + } + } + numBlocks = (numBlocks + size.hashesPerBlock - 1) / size.hashesPerBlock + } + return root, nil +} diff --git a/pkg/merkletree/merkletree_test.go b/pkg/merkletree/merkletree_test.go index 6221eec07..7344db0b6 100644 --- a/pkg/merkletree/merkletree_test.go +++ b/pkg/merkletree/merkletree_test.go @@ -15,6 +15,7 @@ package merkletree import ( + "bytes" "fmt" "testing" @@ -60,3 +61,62 @@ func TestSize(t *testing.T) { }) } } + +func TestGenerate(t *testing.T) { + // The input data has size dataSize. It starts with the data in startWith, + // and all other bytes are zeroes. + testCases := []struct { + dataSize int + startWith []byte + expectedRoot []byte + }{ + { + dataSize: usermem.PageSize, + startWith: nil, + expectedRoot: []byte{173, 127, 172, 178, 88, 111, 198, 233, 102, 192, 4, 215, 209, 209, 107, 2, 79, 88, 5, 255, 124, 180, 124, 122, 133, 218, 189, 139, 72, 137, 44, 167}, + }, + { + dataSize: 128*usermem.PageSize + 1, + startWith: nil, + expectedRoot: []byte{62, 93, 40, 92, 161, 241, 30, 223, 202, 99, 39, 2, 132, 113, 240, 139, 117, 99, 79, 243, 54, 18, 100, 184, 141, 121, 238, 46, 149, 202, 203, 132}, + }, + { + dataSize: 1, + startWith: []byte{'a'}, + expectedRoot: []byte{52, 75, 204, 142, 172, 129, 37, 14, 145, 137, 103, 203, 11, 162, 209, 205, 30, 169, 213, 72, 20, 28, 243, 24, 242, 2, 92, 43, 169, 59, 110, 210}, + }, + { + dataSize: 1, + startWith: []byte{'1'}, + expectedRoot: []byte{74, 35, 103, 179, 176, 149, 254, 112, 42, 65, 104, 66, 119, 56, 133, 124, 228, 15, 65, 161, 150, 0, 117, 174, 242, 34, 115, 115, 218, 37, 3, 105}, + }, + } + + for _, tc := range testCases { + t.Run(fmt.Sprintf("%d", tc.dataSize), func(t *testing.T) { + var ( + data bytes.Buffer + tree bytes.Buffer + ) + + startSize := len(tc.startWith) + _, err := data.Write(tc.startWith) + if err != nil { + t.Fatalf("Failed to write to data: %v", err) + } + _, err = data.Write(make([]byte, tc.dataSize-startSize)) + if err != nil { + t.Fatalf("Failed to write to data: %v", err) + } + + root, err := Generate(&data, int64(tc.dataSize), &tree, &tree) + if err != nil { + t.Fatalf("Generate failed: %v", err) + } + + if !bytes.Equal(root, tc.expectedRoot) { + t.Errorf("Unexpected root") + } + }) + } +} |