github.com/google/trillian-examples@v0.0.0-20240520080811-0d40d35cef0e/binary_transparency/firmware/cmd/ft_witness/internal/http/witness.go (about)

     1  // Copyright 2021 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 http contains private implementation details for the FirmwareTransparency witness.
    16  package http
    17  
    18  import (
    19  	"context"
    20  	"fmt"
    21  	"net/http"
    22  	"net/url"
    23  	"sync"
    24  	"time"
    25  
    26  	"github.com/golang/glog"
    27  	"github.com/google/trillian-examples/binary_transparency/firmware/api"
    28  	"github.com/google/trillian-examples/binary_transparency/firmware/internal/client"
    29  	"github.com/gorilla/mux"
    30  	"golang.org/x/mod/sumdb/note"
    31  )
    32  
    33  // WitnessStore is the interface to the  Witness Store, for storage of latest checkpoint
    34  type WitnessStore interface {
    35  	// Store puts the checkpoint into Witness Store
    36  	StoreCP([]byte) error
    37  
    38  	// Retrieve gets the stored checkpoint.
    39  	RetrieveCP() ([]byte, error)
    40  }
    41  
    42  // Witness is the core state & handler implementation of the FT Witness
    43  type Witness struct {
    44  	ws             WitnessStore
    45  	gcp            api.LogCheckpoint
    46  	logURL         string
    47  	logSigVerifier note.Verifier
    48  	pollInterval   time.Duration
    49  	witnessLock    sync.Mutex
    50  }
    51  
    52  // NewWitness creates a new Witness.
    53  func NewWitness(ws WitnessStore, logURL string, logSigVerifier note.Verifier, pollInterval time.Duration) (*Witness, error) {
    54  	gcpRaw, err := ws.RetrieveCP()
    55  	if err != nil {
    56  		return nil, fmt.Errorf("new witness failed due to storage retrieval: %w", err)
    57  	}
    58  	gcp := api.LogCheckpoint{
    59  		Envelope: gcpRaw,
    60  	}
    61  	if len(gcpRaw) > 0 {
    62  		cp, err := api.ParseCheckpoint(gcpRaw, logSigVerifier)
    63  		if err != nil {
    64  			return nil, fmt.Errorf("failed to open stored checkpoint: %w", err)
    65  		}
    66  		gcp = *cp
    67  	}
    68  
    69  	return &Witness{
    70  		ws:             ws,
    71  		gcp:            gcp,
    72  		logURL:         logURL,
    73  		logSigVerifier: logSigVerifier,
    74  		pollInterval:   pollInterval,
    75  	}, nil
    76  }
    77  
    78  // getCheckpoint returns a checkpoint which is registered with witness
    79  func (s *Witness) getCheckpoint(w http.ResponseWriter, r *http.Request) {
    80  	s.witnessLock.Lock()
    81  	w.Header().Set("Content-Type", "text/plain")
    82  	if _, err := w.Write(s.gcp.Envelope); err != nil {
    83  		glog.Errorf("w.Write(): %v", err)
    84  	}
    85  }
    86  
    87  // RegisterHandlers registers HTTP handlers for firmware transparency endpoints.
    88  func (s *Witness) RegisterHandlers(r *mux.Router) {
    89  	r.HandleFunc(fmt.Sprintf("/%s", api.WitnessGetCheckpoint), s.getCheckpoint).Methods("GET")
    90  }
    91  
    92  // Poll periodically polls the FT log for updating the witness checkpoint.
    93  // It only returns on error (when it doesn't start its own polling thread)
    94  func (s *Witness) Poll(ctx context.Context) error {
    95  	ftURL, err := url.Parse(s.logURL)
    96  	if err != nil {
    97  		return fmt.Errorf("failed to parse FT log URL: %w", err)
    98  	}
    99  	c := client.ReadonlyClient{
   100  		LogURL:         ftURL,
   101  		LogSigVerifier: s.logSigVerifier,
   102  	}
   103  	follow := client.NewLogFollower(c)
   104  
   105  	glog.Infof("Polling FT log %q...", ftURL)
   106  	cpc, cperrc := follow.Checkpoints(ctx, s.pollInterval, s.gcp)
   107  
   108  	for {
   109  		var cp api.LogCheckpoint
   110  		select {
   111  		case err = <-cperrc:
   112  			return err
   113  		case <-ctx.Done():
   114  			return ctx.Err()
   115  		case cp = <-cpc:
   116  		}
   117  
   118  		s.witnessLock.Lock()
   119  		if err = s.ws.StoreCP(cp.Envelope); err != nil {
   120  			glog.Warningf("Failed to save new logcheckpoint into store: %q", err)
   121  			s.witnessLock.Unlock()
   122  			continue
   123  		}
   124  		s.gcp = cp
   125  		s.witnessLock.Unlock()
   126  	}
   127  }