loglist_refresher.go

Documentation: github.com/google/certificate-transparency-go/submission

     1  // Copyright 2019 Google LLC. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package submission
    16  
    17  import (
    18  	"bytes"
    19  	"fmt"
    20  	"net/http"
    21  	"sync"
    22  	"time"
    23  
    24  	"github.com/google/certificate-transparency-go/loglist3"
    25  	"github.com/google/certificate-transparency-go/x509util"
    26  )
    27  
    28  const (
    29  	// HttpClientTimeout timeout for Log list reader http client.
    30  	httpClientTimeout = 10 * time.Second
    31  )
    32  
    33  // LogListData wraps info on external LogList, keeping its JSON source and time
    34  // of download.
    35  type LogListData struct {
    36  	JSON         []byte
    37  	List         *loglist3.LogList
    38  	DownloadTime time.Time
    39  }
    40  
    41  // LogListRefresher is interface for Log List updates watcher.
    42  type LogListRefresher interface {
    43  	Refresh() (*LogListData, error)
    44  	LastJSON() []byte
    45  	Source() string
    46  }
    47  
    48  // logListRefresherImpl regularly reads Log-list and emits notifications when
    49  // updates/errors observed. Implements LogListRefresher interface.
    50  type logListRefresherImpl struct {
    51  	// updateMu limits LogListRefresherImpl to a single Refresh() at a time.
    52  	updateMu sync.RWMutex
    53  	lastJSON []byte
    54  	path     string
    55  	client   *http.Client
    56  }
    57  
    58  // NewCustomLogListRefresher creates and inits a LogListRefresherImpl instance.
    59  func NewCustomLogListRefresher(client *http.Client, llPath string) LogListRefresher {
    60  	return &logListRefresherImpl{
    61  		path:   llPath,
    62  		client: client,
    63  	}
    64  }
    65  
    66  // NewLogListRefresher creates and inits a LogListRefresherImpl instance using
    67  // default http.Client
    68  func NewLogListRefresher(llPath string) LogListRefresher {
    69  	return NewCustomLogListRefresher(&http.Client{Timeout: httpClientTimeout}, llPath)
    70  }
    71  
    72  // Refresh fetches the log list and returns its source, formed LogList and
    73  // timestamp if source has changed compared to previous Refresh.
    74  func (llr *logListRefresherImpl) Refresh() (*LogListData, error) {
    75  	llr.updateMu.Lock()
    76  	defer llr.updateMu.Unlock()
    77  
    78  	t := time.Now()
    79  	json, err := x509util.ReadFileOrURL(llr.path, llr.client)
    80  	if err != nil {
    81  		return nil, fmt.Errorf("failed to read %q: %v", llr.path, err)
    82  	}
    83  
    84  	if bytes.Equal(json, llr.lastJSON) {
    85  		return nil, nil
    86  	}
    87  
    88  	ll, err := loglist3.NewFromJSON(json)
    89  	if err != nil {
    90  		return nil, fmt.Errorf("failed to parse %q: %v", llr.path, err)
    91  	}
    92  	llr.lastJSON = json
    93  	return &LogListData{JSON: json, List: ll, DownloadTime: t}, nil
    94  }
    95  
    96  // LastJSON returns last version of Log list in JSON.
    97  func (llr *logListRefresherImpl) LastJSON() []byte {
    98  	llr.updateMu.Lock()
    99  	defer llr.updateMu.Unlock()
   100  	if llr.lastJSON == nil {
   101  		return []byte{}
   102  	}
   103  	return llr.lastJSON
   104  }
   105  
   106  // Source exposes internal Log list path.
   107  func (llr *logListRefresherImpl) Source() string {
   108  	return llr.path
   109  }
   110
View as plain text