package frontend // frontend sits between FUSE and ClueFS // and uses cryptfs for all crypto operations // // cryptfs // ^ // | // v // FUSE <-> frontend <-> ClueFS // // This file handles files access import ( "fmt" "github.com/rfjakob/gocryptfs/cryptfs" "github.com/rfjakob/cluefs/lib/cluefs" "bazil.org/fuse" fusefs "bazil.org/fuse/fs" "golang.org/x/net/context" ) func fixFlags(flags fuse.OpenFlags) (fuse.OpenFlags, bool) { cryptfs.Debug.Printf("fixFlags: Before: %s\n", flags.String()) var writeOnly bool // We always need read access to do read-modify-write cycles if flags & fuse.OpenWriteOnly > 0 { flags = flags &^ fuse.OpenWriteOnly flags = flags | fuse.OpenReadWrite writeOnly = true } // We also cannot open the file in append mode, we need to seek back for RMW flags = flags &^ fuse.OpenAppend cryptfs.Debug.Printf("fixFlags: After: %s\n", flags.String()) return flags, writeOnly } func max(x int, y int) int { if x > y { return x } return y } type File struct { *cluefs.File crfs *cryptfs.CryptFS // Remember if the file is supposed to be write-only writeOnly bool } func (f *File) Open(ctx context.Context, req *fuse.OpenRequest, resp *fuse.OpenResponse) (fusefs.Handle, error) { cryptfs.Debug.Printf("File.Open\n") req.Flags, f.writeOnly = fixFlags(req.Flags) h, err := f.File.Open(ctx, req, resp) if err != nil { return nil, err } clueFile := h.(*cluefs.File) return &File { File: clueFile, crfs: f.crfs, }, nil } func (f *File) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) error { cryptfs.Debug.Printf("Read: o=%d l=%d\n", req.Offset, req.Size) // Read the backing ciphertext in one go iblocks := f.crfs.SplitRange(uint64(req.Offset), uint64(req.Size)) var cipherReq fuse.ReadRequest var cipherResp fuse.ReadResponse o, l := f.crfs.JoinCiphertextRange(iblocks) cipherResp.Data = make([]byte, int(l)) cipherReq.Offset = int64(o) cipherReq.Size = int(l) cryptfs.Debug.Printf("Read: cipherReq o=%d l=%d\n", o, l) err := f.File.Read(ctx, &cipherReq, &cipherResp) if err != nil { return err } // Decrypt it plaintext, err := f.crfs.DecryptBlocks(cipherResp.Data) if err != nil { resp.Data = plaintext return err } // Crop down to relevant part resp.Data = f.crfs.CropPlaintext(plaintext, iblocks) return nil } func (f *File) Write(ctx context.Context, req *fuse.WriteRequest, resp *fuse.WriteResponse) error { cryptfs.Debug.Printf("File.Write\n") resp.Size = 0 iblocks := f.crfs.SplitRange(uint64(req.Offset), uint64(len(req.Data))) var blockData []byte for _, ib := range iblocks { if ib.IsPartial() { // RMW cryptfs.Debug.Printf("RMW\n") blockData = make([]byte, f.crfs.PlainBS()) var readReq fuse.ReadRequest var readResp fuse.ReadResponse o, l := ib.PlaintextRange() readReq.Offset = int64(o) readReq.Size = int(l) err := f.Read(ctx, &readReq, &readResp) if err != nil { return err } copy(blockData, readResp.Data) copy(blockData[ib.Offset:ib.Offset+ib.Length], req.Data) blockLen := max(len(readResp.Data), int(ib.Offset+ib.Length)) blockData = blockData[0:blockLen] } else { blockData = req.Data[0:f.crfs.PlainBS()] } ciphertext := f.crfs.EncryptBlock(blockData) var partReq fuse.WriteRequest var partResp fuse.WriteResponse o, _ := ib.CiphertextRange() partReq.Data = ciphertext partReq.Offset = int64(o) err := f.File.Write(ctx, &partReq, &partResp) if err != nil { fmt.Printf("Write failure: %s\n", err.Error()) return err } // Remove written data from the front of the request cryptfs.Debug.Printf("req.Data[%d:%d]\n", int(ib.Length), len(req.Data)) req.Data = req.Data[int(ib.Length):len(req.Data)] resp.Size += int(ib.Length) } return nil } func (f *File) Attr(ctx context.Context, attr *fuse.Attr) error { cryptfs.Debug.Printf("Attr\n") err := f.File.Node.Attr(ctx, attr) if err != nil { return err } attr.Size = f.crfs.PlainSize(attr.Size) return nil }