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package nametransform
// Filename encryption / decryption functions
import (
"crypto/aes"
"crypto/cipher"
"encoding/base64"
"fmt"
"github.com/rfjakob/eme"
)
// DecryptName - decrypt base64-encoded encrypted filename "cipherName"
// The used encryption is either CBC or EME, depending on "useEME".
//
// This function is exported because it allows for a very efficient readdir
// implementation (read IV once, decrypt all names using this function).
func (n *NameTransform) DecryptName(cipherName string, iv []byte) (string, error) {
bin, err := base64.URLEncoding.DecodeString(cipherName)
if err != nil {
return "", err
}
if len(bin)%aes.BlockSize != 0 {
return "", fmt.Errorf("Decoded length %d is not a multiple of the AES block size", len(bin))
}
if n.useEME {
bin = eme.Transform(n.cryptoCore.BlockCipher, iv, bin, eme.DirectionDecrypt)
} else {
cbc := cipher.NewCBCDecrypter(n.cryptoCore.BlockCipher, iv)
cbc.CryptBlocks(bin, bin)
}
bin, err = unPad16(bin)
if err != nil {
return "", err
}
plain := string(bin)
return plain, err
}
// encryptName - encrypt "plainName", return base64-encoded "cipherName64"
// The used encryption is either CBC or EME, depending on "useEME".
func (n *NameTransform) encryptName(plainName string, iv []byte) (cipherName64 string) {
bin := []byte(plainName)
bin = pad16(bin)
if n.useEME {
bin = eme.Transform(n.cryptoCore.BlockCipher, iv, bin, eme.DirectionEncrypt)
} else {
cbc := cipher.NewCBCEncrypter(n.cryptoCore.BlockCipher, iv)
cbc.CryptBlocks(bin, bin)
}
cipherName64 = base64.URLEncoding.EncodeToString(bin)
return cipherName64
}
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