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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 {
fmt.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
}
|
