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package fusefrontend_reverse
import (
"crypto/sha256"
"encoding/base64"
"path/filepath"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// saneDir is like filepath.Dir but returns "" instead of "."
func saneDir(path string) string {
d := filepath.Dir(path)
if d == "." {
return ""
}
return d
}
type ivPurposeType string
const (
ivPurposeDirIV ivPurposeType = "DIRIV"
ivPurposeFileID ivPurposeType = "FILEID"
ivPurposeSymlinkIV ivPurposeType = "SYMLINKIV"
ivPurposeBlock0IV ivPurposeType = "BLOCK0IV"
)
// derivePathIV derives an IV from an encrypted path by hashing it with sha256
func derivePathIV(path string, purpose ivPurposeType) []byte {
// Use null byte as separator as it cannot occur in the path
extended := []byte(path + "\000" + string(purpose))
hash := sha256.Sum256(extended)
return hash[:nametransform.DirIVLen]
}
func (rfs *ReverseFS) abs(relPath string, err error) (string, error) {
if err != nil {
return "", err
}
return filepath.Join(rfs.args.Cipherdir, relPath), nil
}
func (rfs *ReverseFS) rDecryptName(cName string, dirIV []byte, pDir string) (pName string, err error) {
nameType := nametransform.NameType(cName)
if nameType == nametransform.LongNameNone {
pName, err = rfs.nameTransform.DecryptName(cName, dirIV)
if err != nil {
// We get lots of decrypt requests for names like ".Trash" that
// are invalid base64. Convert them to ENOENT so the correct
// error gets returned to the user.
if _, ok := err.(base64.CorruptInputError); ok {
return "", syscall.ENOENT
}
// Stat attempts on the link target of encrypted symlinks.
// These are always valid base64 but the length is not a
// multiple of 16.
if err == syscall.EINVAL {
return "", syscall.ENOENT
}
return "", err
}
} else if nameType == nametransform.LongNameContent {
pName, err = rfs.findLongnameParent(pDir, dirIV, cName)
if err != nil {
return "", err
}
} else {
// It makes no sense to decrypt a ".name" file. This is a virtual file
// that has no represantation in the plaintext filesystem. ".name"
// files should have already been handled in virtualfile.go.
tlog.Warn.Printf("decryptPath: tried to decrypt %q!? Returning EINVAL.", cName)
return "", syscall.EINVAL
}
return pName, nil
}
func (rfs *ReverseFS) decryptPath(relPath string) (string, error) {
if rfs.args.PlaintextNames || relPath == "" {
return relPath, nil
}
parts := strings.Split(relPath, "/")
var transformedParts []string
for i := range parts {
// Start at the top and recurse
currentCipherDir := filepath.Join(parts[:i]...)
currentPlainDir := filepath.Join(transformedParts[:i]...)
dirIV := derivePathIV(currentCipherDir, ivPurposeDirIV)
transformedPart, err := rfs.rDecryptName(parts[i], dirIV, currentPlainDir)
if err != nil {
return "", err
}
transformedParts = append(transformedParts, transformedPart)
}
return filepath.Join(transformedParts...), nil
}
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