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package nametransform
import (
"fmt"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/v2/internal/tlog"
)
// xattr names are encrypted like file names, but with a fixed IV.
// Padded with "_xx" for length 16.
var xattrNameIV = []byte("xattr_name_iv_xx")
func isValidXattrName(name string) error {
if name == "" {
return fmt.Errorf("empty input")
}
if strings.Contains(name, "\000") {
return fmt.Errorf("contains forbidden null byte")
}
return nil
}
// EncryptXattrName encrypts an extended attribute (xattr) name.
// xattr names are encrypted like file names, but with a fixed IV, and fewer
// naming restriction.
func (n *NameTransform) EncryptXattrName(plainName string) (cipherName64 string, err error) {
if err := isValidXattrName(plainName); err != nil {
tlog.Warn.Printf("EncryptXattrName %q: invalid plainName: %v", plainName, err)
return "", syscall.EBADMSG
}
return n.encryptName(plainName, xattrNameIV), nil
}
// DecryptXattrName calls decryptName to try and decrypt a base64-encoded encrypted
// filename "cipherName", and failing that checks if it can be bypassed
func (n *NameTransform) DecryptXattrName(cipherName string) (plainName string, err error) {
if plainName, err = n.decryptName(cipherName, xattrNameIV); err != nil {
return "", err
}
if err := isValidXattrName(plainName); err != nil {
tlog.Warn.Printf("DecryptXattrName %q: invalid name after decryption: %v", cipherName, err)
return "", syscall.EBADMSG
}
return plainName, err
}
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