Simplify erasure code by separating bitrot from erasure code (#5959)

cmd/bitrot.go

@@ -0,0 +1,192 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * 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 cmd
+
+import (
+	"context"
+	"crypto/sha256"
+	"errors"
+	"hash"
+
+	"github.com/minio/highwayhash"
+	"github.com/minio/minio/cmd/logger"
+	"golang.org/x/crypto/blake2b"
+)
+
+// magic HH-256 key as HH-256 hash of the first 100 decimals of π as utf-8 string with a zero key.
+var magicHighwayHash256Key = []byte("\x4b\xe7\x34\xfa\x8e\x23\x8a\xcd\x26\x3e\x83\xe6\xbb\x96\x85\x52\x04\x0f\x93\x5d\xa3\x9f\x44\x14\x97\xe0\x9d\x13\x22\xde\x36\xa0")
+
+// BitrotAlgorithm specifies a algorithm used for bitrot protection.
+type BitrotAlgorithm uint
+
+const (
+	// SHA256 represents the SHA-256 hash function
+	SHA256 BitrotAlgorithm = 1 + iota
+	// HighwayHash256 represents the HighwayHash-256 hash function
+	HighwayHash256
+	// BLAKE2b512 represents the BLAKE2b-512 hash function
+	BLAKE2b512
+)
+
+// DefaultBitrotAlgorithm is the default algorithm used for bitrot protection.
+const (
+	DefaultBitrotAlgorithm = HighwayHash256
+)
+
+var bitrotAlgorithms = map[BitrotAlgorithm]string{
+	SHA256:         "sha256",
+	BLAKE2b512:     "blake2b",
+	HighwayHash256: "highwayhash256",
+}
+
+// New returns a new hash.Hash calculating the given bitrot algorithm.
+func (a BitrotAlgorithm) New() hash.Hash {
+	switch a {
+	case SHA256:
+		return sha256.New()
+	case BLAKE2b512:
+		b2, _ := blake2b.New512(nil) // New512 never returns an error if the key is nil
+		return b2
+	case HighwayHash256:
+		hh, _ := highwayhash.New(magicHighwayHash256Key) // New will never return error since key is 256 bit
+		return hh
+	default:
+		logger.CriticalIf(context.Background(), errors.New("Unsupported bitrot algorithm"))
+		return nil
+	}
+}
+
+// Available reports whether the given algorihm is available.
+func (a BitrotAlgorithm) Available() bool {
+	_, ok := bitrotAlgorithms[a]
+	return ok
+}
+
+// String returns the string identifier for a given bitrot algorithm.
+// If the algorithm is not supported String panics.
+func (a BitrotAlgorithm) String() string {
+	name, ok := bitrotAlgorithms[a]
+	if !ok {
+		logger.CriticalIf(context.Background(), errors.New("Unsupported bitrot algorithm"))
+	}
+	return name
+}
+
+// NewBitrotVerifier returns a new BitrotVerifier implementing the given algorithm.
+func NewBitrotVerifier(algorithm BitrotAlgorithm, checksum []byte) *BitrotVerifier {
+	return &BitrotVerifier{algorithm, checksum}
+}
+
+// BitrotVerifier can be used to verify protected data.
+type BitrotVerifier struct {
+	algorithm BitrotAlgorithm
+	sum       []byte
+}
+
+// BitrotAlgorithmFromString returns a bitrot algorithm from the given string representation.
+// It returns 0 if the string representation does not match any supported algorithm.
+// The zero value of a bitrot algorithm is never supported.
+func BitrotAlgorithmFromString(s string) (a BitrotAlgorithm) {
+	for alg, name := range bitrotAlgorithms {
+		if name == s {
+			return alg
+		}
+	}
+	return
+}
+
+// To read bit-rot verified data.
+type bitrotReader struct {
+	disk      StorageAPI
+	volume    string
+	filePath  string
+	verifier  *BitrotVerifier // Holds the bit-rot info
+	endOffset int64           // Affects the length of data requested in disk.ReadFile depending on Read()'s offset
+	buf       []byte          // Holds bit-rot verified data
+}
+
+// newBitrotReader returns bitrotReader.
+// Note that the buffer is allocated later in Read(). This is because we will know the buffer length only
+// during the bitrotReader.Read(). Depending on when parallelReader fails-over, the buffer length can be different.
+func newBitrotReader(disk StorageAPI, volume, filePath string, algo BitrotAlgorithm, endOffset int64, sum []byte) *bitrotReader {
+	return &bitrotReader{
+		disk:      disk,
+		volume:    volume,
+		filePath:  filePath,
+		verifier:  &BitrotVerifier{algo, sum},
+		endOffset: endOffset,
+		buf:       nil,
+	}
+}
+
+// ReadChunk returns requested data.
+func (b *bitrotReader) ReadChunk(offset int64, length int64) ([]byte, error) {
+	if b.buf == nil {
+		b.buf = make([]byte, b.endOffset-offset)
+		if _, err := b.disk.ReadFile(b.volume, b.filePath, offset, b.buf, b.verifier); err != nil {
+			logger.LogIf(context.Background(), err)
+			return nil, err
+		}
+	}
+	if int64(len(b.buf)) < length {
+		logger.LogIf(context.Background(), errLessData)
+		return nil, errLessData
+	}
+	retBuf := b.buf[:length]
+	b.buf = b.buf[length:]
+	return retBuf, nil
+}
+
+// To calculate the bit-rot of the written data.
+type bitrotWriter struct {
+	disk     StorageAPI
+	volume   string
+	filePath string
+	h        hash.Hash
+}
+
+// newBitrotWriter returns bitrotWriter.
+func newBitrotWriter(disk StorageAPI, volume, filePath string, algo BitrotAlgorithm) *bitrotWriter {
+	return &bitrotWriter{
+		disk:     disk,
+		volume:   volume,
+		filePath: filePath,
+		h:        algo.New(),
+	}
+}
+
+// Append appends the data and while calculating the hash.
+func (b *bitrotWriter) Append(buf []byte) error {
+	n, err := b.h.Write(buf)
+	if err != nil {
+		return err
+	}
+	if n != len(buf) {
+		logger.LogIf(context.Background(), errUnexpected)
+		return errUnexpected
+	}
+	if err = b.disk.AppendFile(b.volume, b.filePath, buf); err != nil {
+		logger.LogIf(context.Background(), err)
+		return err
+	}
+	return nil
+}
+
+// Sum returns bit-rot sum.
+func (b *bitrotWriter) Sum() []byte {
+	return b.h.Sum(nil)
+}