1 files changed, 152 insertions, 0 deletions
diff --git a/cluefs_frontend/fe_file.go b/cluefs_frontend/fe_file.go
new file mode 100644
index 0000000..4c4e38a
--- /dev/null
+++ b/cluefs_frontend/fe_file.go
@@ -0,0 +1,152 @@
+package cluefs_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
+}