76 lines
2.3 KiB
Go
76 lines
2.3 KiB
Go
// Package nametransform encrypts and decrypts filenames.
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package nametransform
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import (
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"crypto/aes"
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"encoding/base64"
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"syscall"
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"github.com/rfjakob/eme"
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"github.com/rfjakob/gocryptfs/internal/cryptocore"
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"github.com/rfjakob/gocryptfs/internal/tlog"
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)
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// NameTransform is used to transform filenames.
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type NameTransform struct {
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cryptoCore *cryptocore.CryptoCore
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longNames bool
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DirIVCache dirIVCache
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// b64 = either base64.URLEncoding or base64.RawURLEncoding
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b64 *base64.Encoding
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}
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// New returns a new NameTransform instance.
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func New(c *cryptocore.CryptoCore, longNames bool, raw64 bool) *NameTransform {
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b64 := base64.URLEncoding
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if raw64 {
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b64 = getRaw64Encoding()
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}
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return &NameTransform{
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cryptoCore: c,
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longNames: longNames,
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b64: b64,
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}
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}
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// DecryptName - decrypt base64-encoded encrypted filename "cipherName"
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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 := n.b64.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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tlog.Debug.Printf("DecryptName %q: decoded length %d is not a multiple of 16", cipherName, len(bin))
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return "", syscall.EINVAL
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}
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bin = eme.Transform(n.cryptoCore.BlockCipher, iv, bin, eme.DirectionDecrypt)
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bin, err = unPad16(bin)
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if err != nil {
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tlog.Debug.Printf("pad16 error detail: %v", err)
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// unPad16 returns detailed errors including the position of the
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// incorrect bytes. Kill the padding oracle by lumping everything into
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// a generic error.
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return "", syscall.EINVAL
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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 encrypts "plainName", returns a 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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bin = eme.Transform(n.cryptoCore.BlockCipher, iv, bin, eme.DirectionEncrypt)
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cipherName64 = n.b64.EncodeToString(bin)
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return cipherName64
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}
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