85 lines
2.2 KiB
Go
85 lines
2.2 KiB
Go
package nametransform
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// Filename encryption / decryption functions
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import (
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"crypto/aes"
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"crypto/cipher"
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"encoding/base64"
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"fmt"
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"github.com/rfjakob/eme"
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"github.com/rfjakob/gocryptfs/internal/cryptocore"
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)
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type NameTransform struct {
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cryptoCore *cryptocore.CryptoCore
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useEME bool
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longNames bool
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DirIVCache dirIVCache
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}
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func New(c *cryptocore.CryptoCore, useEME bool, longNames bool) *NameTransform {
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return &NameTransform{
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cryptoCore: c,
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longNames: longNames,
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useEME: useEME,
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}
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}
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// DecryptName - decrypt base64-encoded encrypted filename "cipherName"
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// Used by DecryptPathDirIV().
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// The encryption is either CBC or EME, depending on "useEME".
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//
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// This function is exported because it allows for a very efficient readdir
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// implementation (read IV once, decrypt all names using this function).
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func (n *NameTransform) DecryptName(cipherName string, iv []byte) (string, error) {
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bin, err := base64.URLEncoding.DecodeString(cipherName)
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if err != nil {
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return "", err
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}
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if len(bin)%aes.BlockSize != 0 {
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return "", fmt.Errorf("Decoded length %d is not a multiple of the AES block size", len(bin))
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}
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if n.useEME {
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bin = eme.Transform(n.cryptoCore.BlockCipher, iv, bin, eme.DirectionDecrypt)
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} else {
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cbc := cipher.NewCBCDecrypter(n.cryptoCore.BlockCipher, iv)
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cbc.CryptBlocks(bin, bin)
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}
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bin, err = unPad16(bin)
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if err != nil {
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return "", err
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}
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plain := string(bin)
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return plain, err
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}
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// encryptName - encrypt "plainName", return base64-encoded "cipherName64".
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// Used internally by EncryptPathDirIV().
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// The encryption is either CBC or EME, depending on "useEME".
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//
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// This function is exported because fusefrontend needs access to the full (not hashed)
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// name if longname is used. Otherwise you should use EncryptPathDirIV()
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func (n *NameTransform) EncryptName(plainName string, iv []byte) (cipherName64 string) {
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bin := []byte(plainName)
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bin = pad16(bin)
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if n.useEME {
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bin = eme.Transform(n.cryptoCore.BlockCipher, iv, bin, eme.DirectionEncrypt)
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} else {
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cbc := cipher.NewCBCEncrypter(n.cryptoCore.BlockCipher, iv)
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cbc.CryptBlocks(bin, bin)
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}
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cipherName64 = base64.URLEncoding.EncodeToString(bin)
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return cipherName64
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}
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