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package fusefrontend_reverse
import (
"encoding/base64"
"path/filepath"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/pathiv"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// abs basically returns storage dir + "/" + relPath.
// It takes an error parameter so it can directly wrap decryptPath like this:
// a, err := rfs.abs(rfs.decryptPath(relPath))
// abs never generates an error on its own. In other words, abs(p, nil) never
// fails.
func (rfs *ReverseFS) abs(relPath string, err error) (string, error) {
if err != nil {
return "", err
}
return filepath.Join(rfs.args.Cipherdir, relPath), nil
}
// rDecryptName decrypts the ciphertext name "cName", given the dirIV of the
// directory "cName" lies in. The relative plaintext path to the directory
// "pDir" is used if a "gocryptfs.longname.XYZ.name" must be resolved.
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.EBADMSG {
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 representation in the plaintext filesystem. ".name"
// files should have already been handled in virtualfile.go.
tlog.Warn.Printf("rDecryptName: cannot decrypt virtual file %q", cName)
return "", syscall.EINVAL
}
return pName, nil
}
// decryptPath decrypts a relative ciphertext path to a relative plaintext
// path.
func (rfs *ReverseFS) decryptPath(relPath string) (string, error) {
if rfs.args.PlaintextNames || relPath == "" {
return relPath, nil
}
// Check if the parent dir is in the cache
cDir := nametransform.Dir(relPath)
dirIV, pDir := rPathCache.lookup(cDir)
if dirIV != nil {
cName := filepath.Base(relPath)
pName, err := rfs.rDecryptName(cName, dirIV, pDir)
if err != nil {
return "", err
}
return filepath.Join(pDir, pName), 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 = pathiv.Derive(currentCipherDir, pathiv.PurposeDirIV)
transformedPart, err := rfs.rDecryptName(parts[i], dirIV, currentPlainDir)
if err != nil {
return "", err
}
transformedParts = append(transformedParts, transformedPart)
}
pRelPath := filepath.Join(transformedParts...)
rPathCache.store(cDir, dirIV, nametransform.Dir(pRelPath))
return pRelPath, nil
}
// openBackingDir decrypt the relative ciphertext path "cRelPath", opens
// the directory that contains the target file/dir and returns the fd to
// the directory and the decrypted name of the target file.
// The fd/name pair is intended for use with fchownat and friends.
func (rfs *ReverseFS) openBackingDir(cRelPath string) (dirfd int, pName string, err error) {
// Decrypt relative path
pRelPath, err := rfs.decryptPath(cRelPath)
if err != nil {
return -1, "", err
}
// Open directory, safe against symlink races
pDir := filepath.Dir(pRelPath)
dirfd, err = syscallcompat.OpenDirNofollow(rfs.args.Cipherdir, pDir)
if err != nil {
return -1, "", err
}
pName = filepath.Base(pRelPath)
return dirfd, pName, nil
}
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