80 lines
2.4 KiB
Go
80 lines
2.4 KiB
Go
// Copyright 2021 Google LLC. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package log provides basic support for the common log checkpoint and proof
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// format described by the README in this directory.
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package log
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import (
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"bytes"
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"encoding/base64"
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"errors"
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"fmt"
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"strconv"
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)
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// Checkpoint represents a minimal log checkpoint (STH).
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type Checkpoint struct {
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// Origin is the string identifying the log which issued this checkpoint.
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Origin string
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// Size is the number of entries in the log at this checkpoint.
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Size uint64
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// Hash is the hash which commits to the contents of the entire log.
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Hash []byte
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}
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// Marshal returns the common format representation of this Checkpoint.
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func (c Checkpoint) Marshal() []byte {
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return []byte(fmt.Sprintf("%s\n%d\n%s\n", c.Origin, c.Size, base64.StdEncoding.EncodeToString(c.Hash)))
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}
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// Unmarshal parses the common formatted checkpoint data and stores the result
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// in the Checkpoint.
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//
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// The supplied data is expected to begin with the following 3 lines of text,
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// each followed by a newline:
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// - <origin string>
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// - <decimal representation of log size>
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// - <base64 representation of root hash>
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//
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// Any trailing data after this will be returned.
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func (c *Checkpoint) Unmarshal(data []byte) ([]byte, error) {
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l := bytes.SplitN(data, []byte("\n"), 4)
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if len(l) < 4 {
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return nil, errors.New("invalid checkpoint - too few newlines")
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}
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origin := string(l[0])
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if len(origin) == 0 {
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return nil, errors.New("invalid checkpoint - empty origin")
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}
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size, err := strconv.ParseUint(string(l[1]), 10, 64)
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if err != nil {
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return nil, fmt.Errorf("invalid checkpoint - size invalid: %w", err)
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}
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h, err := base64.StdEncoding.DecodeString(string(l[2]))
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if err != nil {
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return nil, fmt.Errorf("invalid checkpoint - invalid hash: %w", err)
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}
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var rest []byte
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if len(l[3]) > 0 {
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rest = l[3]
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}
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*c = Checkpoint{
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Origin: origin,
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Size: size,
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Hash: h,
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}
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return rest, nil
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}
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