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package fusefrontend_reverse
import (
"log"
"path/filepath"
"syscall"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/fuse"
"github.com/hanwen/go-fuse/fuse/nodefs"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/pathiv"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
// virtualFileMode is the mode to use for virtual files (gocryptfs.diriv and
// *.name). They are always readable, as stated in func Access
virtualFileMode = syscall.S_IFREG | 0444
// inoBaseDirIV is the start of the inode number range that is used
// for virtual gocryptfs.diriv files. inoBaseNameFile is the thing for
// *.name files.
// The value 10^19 is just below 2^60. A power of 10 has been chosen so the
// "ls -li" output (which is base-10) is easy to read.
// 10^19 is the largest power of 10 that is smaller than
// INT64_MAX (=UINT64_MAX/2). This avoids signedness issues.
inoBaseDirIV = uint64(1000000000000000000)
inoBaseNameFile = uint64(2000000000000000000)
// inoBaseMin marks the start of the inode number space that is
// reserved for virtual files. It is the lowest of the inoBaseXXX values
// above.
inoBaseMin = inoBaseDirIV
)
func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
cDir := nametransform.Dir(cRelPath)
dir, err := rfs.decryptPath(cDir)
if err != nil {
return nil, fuse.ToStatus(err)
}
iv := pathiv.Derive(cDir, pathiv.PurposeDirIV)
return rfs.newVirtualFile(iv, rfs.args.Cipherdir, dir, inoBaseDirIV)
}
type virtualFile struct {
// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
nodefs.File
// file content
content []byte
// backing directory
cipherdir string
// path to a parent file (relative to cipherdir)
parentFile string
// inode number of a virtual file is inode of parent file plus inoBase
inoBase uint64
}
// newVirtualFile creates a new in-memory file that does not have a representation
// on disk. "content" is the file content. Timestamps and file owner are copied
// from "parentFile" (plaintext path relative to "cipherdir").
// For a "gocryptfs.diriv" file, you would use the parent directory as
// "parentFile".
func (rfs *ReverseFS) newVirtualFile(content []byte, cipherdir string, parentFile string, inoBase uint64) (nodefs.File, fuse.Status) {
if inoBase < inoBaseMin {
log.Panicf("BUG: virtual inode number base %d is below reserved space", inoBase)
}
return &virtualFile{
File: nodefs.NewDefaultFile(),
content: content,
cipherdir: cipherdir,
parentFile: parentFile,
inoBase: inoBase,
}, fuse.OK
}
// Read - FUSE call
func (f *virtualFile) Read(buf []byte, off int64) (resultData fuse.ReadResult, status fuse.Status) {
if off >= int64(len(f.content)) {
return nil, fuse.OK
}
end := int(off) + len(buf)
if end > len(f.content) {
end = len(f.content)
}
return fuse.ReadResultData(f.content[off:end]), fuse.OK
}
// GetAttr - FUSE call
func (f *virtualFile) GetAttr(a *fuse.Attr) fuse.Status {
dir := filepath.Dir(f.parentFile)
dirfd, err := syscallcompat.OpenNofollow(f.cipherdir, dir, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
if err != nil {
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
name := filepath.Base(f.parentFile)
var st unix.Stat_t
err = syscallcompat.Fstatat(dirfd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
tlog.Debug.Printf("GetAttr: Fstatat %q: %v\n", f.parentFile, err)
return fuse.ToStatus(err)
}
if st.Ino > inoBaseMin {
tlog.Warn.Printf("virtualFile.GetAttr: parent file inode number %d crosses reserved space, max=%d. Returning EOVERFLOW.",
st.Ino, inoBaseMin)
return fuse.ToStatus(syscall.EOVERFLOW)
}
st.Ino = st.Ino + f.inoBase
st.Size = int64(len(f.content))
st.Mode = virtualFileMode
st.Nlink = 1
st2 := syscallcompat.Unix2syscall(st)
a.FromStat(&st2)
return fuse.OK
}
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