hardcoresushi/libgocryptfs
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reverse: derive file ID and block IVs from file paths

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This commit is contained in:
Jakob Unterwurzacher 2016-09-25 11:20:10 +02:00
parent 3a9bd92754
commit 7bbf6ad6ea
6 changed files with 41 additions and 37 deletions
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19
internal/contentenc/content.go
View File

@ -19,9 +19,9 @@ const (
// We always use 128-bit IVs for file content encryption
IVBitLen = 128
_ = iota // skip zero
RandomNonce NonceMode = iota
ReverseDummyNonce NonceMode = iota
_ = iota // skip zero
RandomNonce NonceMode = iota
ReverseDeterministicNonce NonceMode = iota
)
type ContentEnc struct {
@ -147,12 +147,17 @@ func (be *ContentEnc) EncryptBlock(plaintext []byte, blockNo uint64, fileID []by
var nonce []byte
switch nMode {
case ReverseDummyNonce:
case ReverseDeterministicNonce:
if be.cryptoCore.AEADBackend != cryptocore.BackendGCMSIV {
panic("MUST NOT use dummy nonces unless in GCMSIV mode!")
panic("MUST NOT use deterministic nonces unless in GCMSIV mode!")
}
nonce = make([]byte, IVBitLen/8)
binary.BigEndian.PutUint64(nonce, blockNo)
l := IVBitLen / 8
nonce = make([]byte, l)
copy(nonce, fileID)
// Add the block number to the last 8 byte. Plus one so the block-zero
// IV is distinct from the fileID.
counter := binary.BigEndian.Uint64(nonce[l-8 : l])
binary.BigEndian.PutUint64(nonce[l-8:l], counter+blockNo+1)
case RandomNonce:
// Get a fresh random nonce
nonce = be.cryptoCore.IVGenerator.Get()

9
internal/fusefrontend_reverse/reverse_diriv.go
View File

@ -9,10 +9,9 @@ import (
"github.com/rfjakob/gocryptfs/internal/nametransform"
)
// deriveDirIV derives the DirIV from the encrypted directory path by
// hashing it
func deriveDirIV(dirPath string) []byte {
hash := sha256.Sum256([]byte(dirPath))
// derivePathIV derives an IV from an encrypted path by hashing it
func derivePathIV(path string) []byte {
hash := sha256.Sum256([]byte(path))
return hash[:nametransform.DirIVLen]
}
@ -22,5 +21,5 @@ func (rfs *reverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
if err != nil {
return nil, fuse.ToStatus(err)
}
return rfs.NewVirtualFile(deriveDirIV(cDir), absDir)
return rfs.NewVirtualFile(derivePathIV(cDir), absDir)
}

2
internal/fusefrontend_reverse/reverse_longnames.go
View File

@ -89,7 +89,7 @@ func (rfs *reverseFS) newNameFile(relPath string) (nodefs.File, fuse.Status) {
if err != nil {
return nil, fuse.ToStatus(err)
}
dirIV := deriveDirIV(cDir)
dirIV := derivePathIV(cDir)
e, err := rfs.findLongnameParent(pDir, dirIV, longname)
if err != nil {
return nil, fuse.ToStatus(err)

34
internal/fusefrontend_reverse/rfile.go
View File

@ -13,29 +13,32 @@ import (
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// File header that contains an all-zero File ID
var zeroFileHeader *contentenc.FileHeader
func init() {
zeroFileHeader = contentenc.RandomHeader()
// Overwrite with zeros
zeroFileHeader.Id = make([]byte, contentenc.HEADER_ID_LEN)
}
type reverseFile struct {
// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
nodefs.File
// Backing FD
fd *os.File
// File header (contains the IV)
header contentenc.FileHeader
// Content encryption helper
contentEnc *contentenc.ContentEnc
}
func NewFile(fd *os.File, contentEnc *contentenc.ContentEnc) (nodefs.File, fuse.Status) {
func (rfs *reverseFS) NewFile(relPath string, flags uint32) (nodefs.File, fuse.Status) {
absPath, err := rfs.abs(rfs.decryptPath(relPath))
if err != nil {
return nil, fuse.ToStatus(err)
}
fd, err := os.OpenFile(absPath, int(flags), 0666)
if err != nil {
return nil, fuse.ToStatus(err)
}
id := derivePathIV(relPath)
return &reverseFile{
File: nodefs.NewDefaultFile(),
fd: fd,
contentEnc: contentEnc,
header: contentenc.FileHeader{contentenc.CurrentVersion, id},
contentEnc: rfs.contentEnc,
}, fuse.OK
}
@ -64,7 +67,7 @@ func (rf *reverseFile) readBackingFile(off uint64, length uint64) (out []byte, e
plaintext = plaintext[0:n]
// Encrypt blocks
ciphertext := rf.contentEnc.EncryptBlocks(plaintext, blocks[0].BlockNo, zeroFileHeader.Id, contentenc.ReverseDummyNonce)
ciphertext := rf.contentEnc.EncryptBlocks(plaintext, blocks[0].BlockNo, rf.header.Id, contentenc.ReverseDeterministicNonce)
// Crop down to the relevant part
lenHave := len(ciphertext)
@ -88,7 +91,7 @@ func (rf *reverseFile) Read(buf []byte, ioff int64) (resultData fuse.ReadResult,
// Synthesize file header
if off < contentenc.HEADER_LEN {
header = zeroFileHeader.Pack()
header = rf.header.Pack()
// Truncate to requested part
end := int(off) + len(buf)
if end > len(header) {
@ -119,3 +122,8 @@ func (rf *reverseFile) Read(buf []byte, ioff int64) (resultData fuse.ReadResult,
return fuse.ReadResultData(out.Bytes()), fuse.OK
}
// Release - FUSE call, close file
func (rf *reverseFile) Release() {
rf.fd.Close()
}

12
internal/fusefrontend_reverse/rfs.go
View File

@ -226,15 +226,7 @@ func (rfs *reverseFS) Open(relPath string, flags uint32, context *fuse.Context)
if rfs.isFiltered(relPath) {
return nil, fuse.EPERM
}
absPath, err := rfs.abs(rfs.decryptPath(relPath))
if err != nil {
return nil, fuse.ToStatus(err)
}
f, err := os.OpenFile(absPath, int(flags), 0666)
if err != nil {
return nil, fuse.ToStatus(err)
}
return NewFile(f, rfs.contentEnc)
return rfs.NewFile(relPath, flags)
}
// OpenDir - FUSE readdir call
@ -258,7 +250,7 @@ func (rfs *reverseFS) OpenDir(cipherPath string, context *fuse.Context) ([]fuse.
nVirtual := 1
// Encrypt names
dirIV := deriveDirIV(cipherPath)
dirIV := derivePathIV(cipherPath)
for i := range entries {
var cName string
// ".gocryptfs.reverse.conf" in the root directory is mapped to "gocryptfs.conf"

2
internal/fusefrontend_reverse/rpath.go
View File

@ -36,7 +36,7 @@ func (rfs *reverseFS) decryptPath(relPath string) (string, error) {
// Start at the top and recurse
currentDir := filepath.Join(parts[:i]...)
nameType := nametransform.NameType(part)
dirIV := deriveDirIV(currentDir)
dirIV := derivePathIV(currentDir)
var transformedPart string
if nameType == nametransform.LongNameNone {
transformedPart, err = rfs.nameTransform.DecryptName(part, dirIV)