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| 1 | +package blockfilter |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "crypto/sha256" |
| 6 | + "encoding/hex" |
| 7 | + "encoding/json" |
| 8 | + "fmt" |
| 9 | + "io" |
| 10 | + "net/http" |
| 11 | + "os" |
| 12 | + "path/filepath" |
| 13 | + "sync" |
| 14 | + "time" |
| 15 | + |
| 16 | + "github.com/benbjohnson/clock" |
| 17 | + "github.com/ipfs/go-cid" |
| 18 | + logging "github.com/ipfs/go-log/v2" |
| 19 | + "github.com/multiformats/go-multibase" |
| 20 | +) |
| 21 | + |
| 22 | +var log = logging.Logger("booster-bitswap") |
| 23 | + |
| 24 | +// BadBitsDenyList is the URL for well known bad bits list |
| 25 | +const BadBitsDenyList string = "https://badbits.dwebops.pub/denylist.json" |
| 26 | + |
| 27 | +// UpdateInterval is the default interval at which the public list is refected and updated |
| 28 | +const UpdateInterval = 5 * time.Minute |
| 29 | + |
| 30 | +// DenyListFetcher is a function that fetches a deny list in the json style of the BadBits list |
| 31 | +// The first return value indicates whether any update has occurred since the last fetch time |
| 32 | +// The second return is a stream of data if an update has occurred |
| 33 | +// The third is any error |
| 34 | +type DenyListFetcher func(lastFetchTime time.Time) (bool, io.ReadCloser, error) |
| 35 | + |
| 36 | +const expectedListGrowth = 128 |
| 37 | + |
| 38 | +// FetchBadBitsList is the default function used to get the BadBits list |
| 39 | +func FetchBadBitsList(ifModifiedSince time.Time) (bool, io.ReadCloser, error) { |
| 40 | + req, err := http.NewRequest("GET", BadBitsDenyList, nil) |
| 41 | + if err != nil { |
| 42 | + return false, nil, err |
| 43 | + } |
| 44 | + // set the modification sync header, assuming we are not given time zero |
| 45 | + if !ifModifiedSince.IsZero() { |
| 46 | + req.Header.Set("If-Modified-Since", ifModifiedSince.Format(http.TimeFormat)) |
| 47 | + } |
| 48 | + response, err := http.DefaultClient.Do(req) |
| 49 | + if err != nil { |
| 50 | + return false, nil, err |
| 51 | + } |
| 52 | + if response.StatusCode == http.StatusNotModified { |
| 53 | + return false, nil, nil |
| 54 | + } |
| 55 | + if response.StatusCode < 200 && response.StatusCode > 299 { |
| 56 | + bodyText, _ := io.ReadAll(response.Body) |
| 57 | + return false, nil, fmt.Errorf("expected HTTP success code, got: %s, response body: %s", http.StatusText(response.StatusCode), string(bodyText)) |
| 58 | + } |
| 59 | + return true, response.Body, nil |
| 60 | +} |
| 61 | + |
| 62 | +// BlockFilter manages updating a deny list and checking for CID inclusion in that list |
| 63 | +type BlockFilter struct { |
| 64 | + cacheFile string |
| 65 | + lastUpdated time.Time |
| 66 | + denyListFetcher DenyListFetcher |
| 67 | + filteredHashesLk sync.RWMutex |
| 68 | + filteredHashes map[string]struct{} |
| 69 | + ctx context.Context |
| 70 | + cancel context.CancelFunc |
| 71 | + clock clock.Clock |
| 72 | + onTimerSet func() |
| 73 | +} |
| 74 | + |
| 75 | +func newBlockFilter(cfgDir string, denyListFetcher DenyListFetcher, clock clock.Clock, onTimerSet func()) *BlockFilter { |
| 76 | + return &BlockFilter{ |
| 77 | + cacheFile: filepath.Join(cfgDir, "denylist.json"), |
| 78 | + denyListFetcher: denyListFetcher, |
| 79 | + filteredHashes: make(map[string]struct{}), |
| 80 | + clock: clock, |
| 81 | + onTimerSet: onTimerSet, |
| 82 | + } |
| 83 | +} |
| 84 | + |
| 85 | +// NewBlockFilter returns a block filter |
| 86 | +func NewBlockFilter(cfgDir string) *BlockFilter { |
| 87 | + return newBlockFilter(cfgDir, FetchBadBitsList, clock.New(), nil) |
| 88 | +} |
| 89 | + |
| 90 | +// Start initializes asynchronous updates to the deny list filter |
| 91 | +// It blocks to confirm at least one synchronous update of the denylist |
| 92 | +func (bf *BlockFilter) Start(ctx context.Context) error { |
| 93 | + bf.ctx, bf.cancel = context.WithCancel(ctx) |
| 94 | + // open the cache file if it eixsts |
| 95 | + cache, err := os.Open(bf.cacheFile) |
| 96 | + var cachedCopy bool |
| 97 | + // if the file does not exist, synchronously fetch the list |
| 98 | + if err != nil { |
| 99 | + if !os.IsNotExist(err) { |
| 100 | + return fmt.Errorf("fetching badbits list: %w", err) |
| 101 | + } |
| 102 | + bf.updateDenyList() |
| 103 | + } else { |
| 104 | + defer cache.Close() |
| 105 | + // otherwise, read the file and fetch the list asynchronously |
| 106 | + cachedCopy = true |
| 107 | + bf.filteredHashes, err = bf.parseDenyList(cache, len(bf.filteredHashes)+expectedListGrowth) |
| 108 | + if err != nil { |
| 109 | + return err |
| 110 | + } |
| 111 | + } |
| 112 | + go bf.run(cachedCopy) |
| 113 | + return nil |
| 114 | +} |
| 115 | + |
| 116 | +// Close shuts down asynchronous updating |
| 117 | +func (bf *BlockFilter) Close() { |
| 118 | + bf.cancel() |
| 119 | +} |
| 120 | + |
| 121 | +// IsFiltered checks if a given CID is in the deny list, per the rules |
| 122 | +// of hashing cids (convert to base32, add "/" to path, then sha256 hash) |
| 123 | +func (bf *BlockFilter) IsFiltered(c cid.Cid) (bool, error) { |
| 124 | + // convert CIDv0 to CIDv1 |
| 125 | + if c.Version() == 0 { |
| 126 | + c = cid.NewCidV1(cid.DagProtobuf, c.Hash()) |
| 127 | + } |
| 128 | + // get base32 string |
| 129 | + cidStr, err := c.StringOfBase(multibase.Base32) |
| 130 | + if err != nil { |
| 131 | + return false, err |
| 132 | + } |
| 133 | + // add "/" |
| 134 | + cidStr += "/" |
| 135 | + // sha256 sum the bytes |
| 136 | + shaBytes := sha256.Sum256([]byte(cidStr)) |
| 137 | + // encode to a hex string |
| 138 | + shaString := hex.EncodeToString(shaBytes[:]) |
| 139 | + |
| 140 | + // check for set inclusion |
| 141 | + bf.filteredHashesLk.RLock() |
| 142 | + _, has := bf.filteredHashes[shaString] |
| 143 | + bf.filteredHashesLk.RUnlock() |
| 144 | + return has, nil |
| 145 | +} |
| 146 | + |
| 147 | +// fetch deny list fetches and parses a deny list to get a new set of filtered hashes |
| 148 | +// it uses streaming JSON decoding to avoid an intermediate copy of the entire response |
| 149 | +// lenSuggestion is used to avoid a large number of allocations as the list grows |
| 150 | +func (bf *BlockFilter) parseDenyList(denyListStream io.Reader, lenSuggestion int) (map[string]struct{}, error) { |
| 151 | + // first fetch the reading for the deny list |
| 152 | + type blockedCid struct { |
| 153 | + Anchor string `json:"anchor"` |
| 154 | + } |
| 155 | + // initialize a json decoder |
| 156 | + jsonDenyList := json.NewDecoder(denyListStream) |
| 157 | + |
| 158 | + // read open bracket |
| 159 | + _, err := jsonDenyList.Token() |
| 160 | + if err != nil { |
| 161 | + return nil, fmt.Errorf("parsing denylist: %w", err) |
| 162 | + } |
| 163 | + |
| 164 | + filteredHashes := make(map[string]struct{}, lenSuggestion) |
| 165 | + // while the array contains values |
| 166 | + for jsonDenyList.More() { |
| 167 | + var b blockedCid |
| 168 | + // decode an array value (Message) |
| 169 | + err = jsonDenyList.Decode(&b) |
| 170 | + if err != nil { |
| 171 | + return nil, fmt.Errorf("parsing denylist: %w", err) |
| 172 | + } |
| 173 | + // save it in the filtered hash set |
| 174 | + filteredHashes[b.Anchor] = struct{}{} |
| 175 | + } |
| 176 | + |
| 177 | + // read closing bracket |
| 178 | + _, err = jsonDenyList.Token() |
| 179 | + if err != nil { |
| 180 | + return nil, fmt.Errorf("parsing denylist: %w", err) |
| 181 | + } |
| 182 | + |
| 183 | + return filteredHashes, nil |
| 184 | +} |
| 185 | + |
| 186 | +// updateDenyList replaces the current filtered hashes after successfully |
| 187 | +// fetching and parsing the latest deny list |
| 188 | +func (bf *BlockFilter) updateDenyList() { |
| 189 | + fetchTime := time.Now() |
| 190 | + updated, denyListStream, err := bf.denyListFetcher(bf.lastUpdated) |
| 191 | + if err != nil { |
| 192 | + log.Errorf("fetching deny list: %s", err) |
| 193 | + return |
| 194 | + } |
| 195 | + if !updated { |
| 196 | + return |
| 197 | + } |
| 198 | + defer denyListStream.Close() |
| 199 | + // open the cache file |
| 200 | + cache, err := os.OpenFile(bf.cacheFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600) |
| 201 | + if err != nil { |
| 202 | + log.Errorf("opening cache file: %s", err) |
| 203 | + } |
| 204 | + defer cache.Close() |
| 205 | + forkedStream := io.TeeReader(denyListStream, cache) |
| 206 | + bf.lastUpdated = fetchTime |
| 207 | + filteredHashes, err := bf.parseDenyList(forkedStream, len(bf.filteredHashes)+expectedListGrowth) |
| 208 | + if err != nil { |
| 209 | + log.Errorf("parsing deny list: %s", err) |
| 210 | + return |
| 211 | + } |
| 212 | + bf.filteredHashesLk.Lock() |
| 213 | + bf.filteredHashes = filteredHashes |
| 214 | + bf.filteredHashesLk.Unlock() |
| 215 | +} |
| 216 | + |
| 217 | +// run periodically updates the deny list asynchronously |
| 218 | +func (bf *BlockFilter) run(cachedCopy bool) { |
| 219 | + // if there was a cached copy, immediately asynchornously fetch an update |
| 220 | + if cachedCopy { |
| 221 | + bf.updateDenyList() |
| 222 | + } |
| 223 | + updater := bf.clock.Ticker(UpdateInterval) |
| 224 | + // call the callback if set |
| 225 | + if bf.onTimerSet != nil { |
| 226 | + bf.onTimerSet() |
| 227 | + } |
| 228 | + for { |
| 229 | + select { |
| 230 | + case <-bf.ctx.Done(): |
| 231 | + return |
| 232 | + case <-updater.C: |
| 233 | + // when timer expires, update deny list |
| 234 | + bf.updateDenyList() |
| 235 | + // call the callback if set |
| 236 | + if bf.onTimerSet != nil { |
| 237 | + bf.onTimerSet() |
| 238 | + } |
| 239 | + } |
| 240 | + } |
| 241 | +} |
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