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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,44 @@ | ||
| // This is an alternate to cmd/torrent which has become bloated with awful argument parsing. Since | ||
| // this is my most complicated binary, I will try to build something that satisfies only what I need | ||
| // here. | ||
| package main | ||
|
|
||
| import ( | ||
| "github.com/anacrolix/torrent/metainfo" | ||
| "os" | ||
| ) | ||
|
|
||
| type argError struct { | ||
| err error | ||
| } | ||
|
|
||
| func assertOk(err error) { | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| } | ||
|
|
||
| func bail(str string) { | ||
| panic(str) | ||
| } | ||
|
|
||
| func main() { | ||
| args := os.Args[1:] | ||
| map[string]func(){ | ||
| "metainfo": func() { | ||
| map[string]func(){ | ||
| "validate-v2": func() { | ||
| mi, err := metainfo.LoadFromFile(args[2]) | ||
| assertOk(err) | ||
| info, err := mi.UnmarshalInfo() | ||
| assertOk(err) | ||
| if !info.HasV2() { | ||
| bail("not a v2 torrent") | ||
| } | ||
| err = metainfo.ValidatePieceLayers(mi.PieceLayers, &info.FileTree, info.PieceLength) | ||
| assertOk(err) | ||
| }, | ||
| }[args[1]]() | ||
| }, | ||
| }[args[0]]() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,42 @@ | ||
| package merkle | ||
|
|
||
| import ( | ||
| "crypto/sha256" | ||
| "fmt" | ||
| g "github.com/anacrolix/generics" | ||
| "math/bits" | ||
| ) | ||
|
|
||
| func Root(hashes [][sha256.Size]byte) [sha256.Size]byte { | ||
| if len(hashes) <= 1 { | ||
| return hashes[0] | ||
| } | ||
| numHashes := uint(len(hashes)) | ||
| if numHashes != RoundUpToPowerOfTwo(uint(len(hashes))) { | ||
| panic(fmt.Sprintf("expected power of two number of hashes, got %d", numHashes)) | ||
| } | ||
| var next [][sha256.Size]byte | ||
| for i := 0; i < len(hashes); i += 2 { | ||
| left := hashes[i] | ||
| right := hashes[i+1] | ||
| h := sha256.Sum256(append(left[:], right[:]...)) | ||
| next = append(next, h) | ||
| } | ||
| return Root(next) | ||
| } | ||
|
|
||
| func CompactLayerToSliceHashes(compactLayer string) (hashes [][sha256.Size]byte, err error) { | ||
| g.MakeSliceWithLength(&hashes, len(compactLayer)/sha256.Size) | ||
| for i := range hashes { | ||
| n := copy(hashes[i][:], compactLayer[i*sha256.Size:]) | ||
| if n != sha256.Size { | ||
| err = fmt.Errorf("compact layer has incomplete hash at index %d", i) | ||
| return | ||
| } | ||
| } | ||
| return | ||
| } | ||
|
|
||
| func RoundUpToPowerOfTwo(n uint) (ret uint) { | ||
| return 1 << bits.Len(n-1) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,58 @@ | ||
| package metainfo | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "github.com/anacrolix/torrent/merkle" | ||
| ) | ||
|
|
||
| func ValidatePieceLayers( | ||
| pieceLayers map[string]string, | ||
| fileTree *FileTree, | ||
| pieceLength int64, | ||
| ) (err error) { | ||
| fileTree.Walk(nil, func(path []string, ft *FileTree) { | ||
| if err != nil { | ||
| return | ||
| } | ||
| if ft.IsDir() { | ||
| return | ||
| } | ||
| piecesRoot := ft.PiecesRootAsByteArray() | ||
| if !piecesRoot.Ok { | ||
| return | ||
| } | ||
| filePieceLayers, ok := pieceLayers[string(piecesRoot.Value[:])] | ||
| if !ok { | ||
| // BEP 52: "For each file in the file tree that is larger than the piece size it | ||
| // contains one string value.". The reference torrent creator in | ||
| // https://blog.libtorrent.org/2020/09/bittorrent-v2/ also has this. I'm not sure what | ||
| // harm it causes if it's present anyway, possibly it won't be useful to us. | ||
| if ft.File.Length > pieceLength { | ||
| err = fmt.Errorf("no piece layers for file %q", path) | ||
| } | ||
| return | ||
| } | ||
| var layerHashes [][32]byte | ||
| layerHashes, err = merkle.CompactLayerToSliceHashes(filePieceLayers) | ||
| padHash := HashForPiecePad(pieceLength) | ||
| for uint(len(layerHashes)) < merkle.RoundUpToPowerOfTwo(uint(len(layerHashes))) { | ||
| layerHashes = append(layerHashes, padHash) | ||
| } | ||
| var root [32]byte | ||
| root = merkle.Root(layerHashes) | ||
| if root != piecesRoot.Value { | ||
| err = fmt.Errorf("file %q: expected hash %x got %x", path, piecesRoot.Value, root) | ||
| return | ||
| } | ||
| }) | ||
| return | ||
| } | ||
|
|
||
| // Returns the padding hash for the hash layer corresponding to a piece. It can't be zero because | ||
| // that's the bottom-most layer (the hashes for the smallest blocks). | ||
| func HashForPiecePad(pieceLength int64) (hash [32]byte) { | ||
| // This should be a power of two, and probably checked elsewhere. | ||
| blocksPerPiece := pieceLength / (1 << 14) | ||
| blockHashes := make([][32]byte, blocksPerPiece) | ||
| return merkle.Root(blockHashes) | ||
| } |
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