hardcoresushi/libgocryptfs
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fusefronted_reverse: fix ino collision between .name and .diriv files

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A directory with a long name has two associated virtual files:
the .name file and the .diriv files.

These used to get the same inode number:

  $ ls -di1  * */*
             33313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw
  1000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw/gocryptfs.diriv
  1000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw.name

With this change we use another prefix (2 instead of 1) for .name files.

  $ ls -di1 * */*
             33313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw
  1000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw/gocryptfs.diriv
  2000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw.name
This commit is contained in:
Jakob Unterwurzacher 2017-07-29 16:13:38 +02:00
parent d5133ca5ac
commit d12aa57715
3 changed files with 26 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
internal/fusefrontend_reverse/reverse_longnames.go
View File

@ -100,5 +100,5 @@ func (rfs *ReverseFS) newNameFile(relPath string) (nodefs.File, fuse.Status) {
}
content := []byte(rfs.nameTransform.EncryptName(pName, dirIV))
parentFile := filepath.Join(rfs.args.Cipherdir, pDir, pName)
return rfs.newVirtualFile(content, parentFile)
return rfs.newVirtualFile(content, parentFile, inoBaseNameFile)
}

4
internal/fusefrontend_reverse/rfs.go
View File

@ -162,9 +162,9 @@ func (rfs *ReverseFS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr
return nil, fuse.ToStatus(err)
}
// Instead of risking an inode number collision, we return an error.
if st.Ino > virtualInoBase {
if st.Ino > inoBaseMin {
tlog.Warn.Printf("GetAttr %q: backing file inode number %d crosses reserved space, max=%d. Returning EOVERFLOW.",
relPath, st.Ino, virtualInoBase)
relPath, st.Ino, inoBaseMin)
return nil, fuse.ToStatus(syscall.EOVERFLOW)
}
var a fuse.Attr

32
internal/fusefrontend_reverse/virtualfile.go
View File

@ -1,6 +1,7 @@
package fusefrontend_reverse
import (
"log"
"syscall"
"github.com/hanwen/go-fuse/fuse"
@ -14,12 +15,19 @@ 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
// virtualInoBase is the start of the inode number range that is used
// for virtual files.
// 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 UINT64_MAX/2.
virtualInoBase = uint64(1000000000000000000)
// 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) {
@ -28,7 +36,7 @@ func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
if err != nil {
return nil, fuse.ToStatus(err)
}
return rfs.newVirtualFile(pathiv.Derive(cDir, pathiv.PurposeDirIV), absDir)
return rfs.newVirtualFile(pathiv.Derive(cDir, pathiv.PurposeDirIV), absDir, inoBaseDirIV)
}
type virtualFile struct {
@ -38,17 +46,23 @@ type virtualFile struct {
content []byte
// absolute path to a parent file
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" (absolute plaintext path). For a "gocryptfs.diriv" file, you
// would use the parent directory as "parentFile".
func (rfs *ReverseFS) newVirtualFile(content []byte, parentFile string) (nodefs.File, fuse.Status) {
func (rfs *ReverseFS) newVirtualFile(content []byte, 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,
parentFile: parentFile,
inoBase: inoBase,
}, fuse.OK
}
@ -72,12 +86,12 @@ func (f *virtualFile) GetAttr(a *fuse.Attr) fuse.Status {
tlog.Debug.Printf("GetAttr: Lstat %q: %v\n", f.parentFile, err)
return fuse.ToStatus(err)
}
if st.Ino > virtualInoBase {
if st.Ino > inoBaseMin {
tlog.Warn.Printf("virtualFile.GetAttr: parent file inode number %d crosses reserved space, max=%d. Returning EOVERFLOW.",
st.Ino, virtualInoBase)
st.Ino, inoBaseMin)
return fuse.ToStatus(syscall.EOVERFLOW)
}
st.Ino = st.Ino + virtualInoBase
st.Ino = st.Ino + f.inoBase
st.Size = int64(len(f.content))
st.Mode = virtualFileMode
st.Nlink = 1