diff options
| -rw-r--r-- | internal/cryptocore/cryptocore.go | 46 |
1 files changed, 33 insertions, 13 deletions
diff --git a/internal/cryptocore/cryptocore.go b/internal/cryptocore/cryptocore.go index e427350..09bab53 100644 --- a/internal/cryptocore/cryptocore.go +++ b/internal/cryptocore/cryptocore.go @@ -65,12 +65,18 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec // Initialize EME for filename encryption. var emeCipher *eme.EMECipher + var err error { - emeKey := key + var emeBlockCipher cipher.Block if useHKDF { - emeKey = hkdfDerive(key, hkdfInfoEMENames, KeyLen) + emeKey := hkdfDerive(key, hkdfInfoEMENames, KeyLen) + emeBlockCipher, err = aes.NewCipher(emeKey) + for i := range emeKey { + emeKey[i] = 0 + } + } else { + emeBlockCipher, err = aes.NewCipher(key) } - emeBlockCipher, err := aes.NewCipher(emeKey) if err != nil { log.Panic(err) } @@ -80,9 +86,11 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec // Initialize an AEAD cipher for file content encryption. var aeadCipher cipher.AEAD if aeadType == BackendOpenSSL || aeadType == BackendGoGCM { - gcmKey := key + var gcmKey []byte if useHKDF { gcmKey = hkdfDerive(key, hkdfInfoGCMContent, KeyLen) + } else { + gcmKey = append([]byte{}, key...) } switch aeadType { case BackendOpenSSL: @@ -100,22 +108,29 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec log.Panic(err) } } + for i := range gcmKey { + gcmKey[i] = 0 + } } else if aeadType == BackendAESSIV { if IVLen != 16 { // SIV supports any nonce size, but we only use 16. log.Panic("AES-SIV must use 16-byte nonces") } + // AES-SIV uses 1/2 of the key for authentication, 1/2 for + // encryption, so we need a 64-bytes key for AES-256. Derive it from + // the 32-byte master key using HKDF, or, for older filesystems, with + // SHA256. var key64 []byte if useHKDF { key64 = hkdfDerive(key, hkdfInfoSIVContent, siv_aead.KeyLen) } else { - // AES-SIV uses 1/2 of the key for authentication, 1/2 for - // encryption, so we need a 64-bytes key for AES-256. Derive it from - // the master key by hashing it with SHA-512. s := sha512.Sum512(key) key64 = s[:] } aeadCipher = siv_aead.New(key64) + for i := range key64 { + key64[i] = 0 + } } else { log.Panic("unknown backend cipher") } @@ -129,20 +144,25 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec } } +type wiper interface { + Wipe() +} + // Wipe tries to wipe secret keys from memory by overwriting them with zeros // and/or setting references to nil. // // This is not bulletproof due to possible GC copies, but // still raises to bar for extracting the key. func (c *CryptoCore) Wipe() { - if c.AEADBackend == BackendOpenSSL { - tlog.Debug.Print("CryptoCore.Wipe: Wiping stupidgcm key") + be := c.AEADBackend + if be == BackendOpenSSL || be == BackendAESSIV { + tlog.Debug.Printf("CryptoCore.Wipe: Wiping AEADBackend %d key", be) // We don't use "x, ok :=" because we *want* to crash loudly if the - // type assertion fails (it should never fail). - sgcm := c.AEADCipher.(*stupidgcm.StupidGCM) - sgcm.Wipe() + // type assertion fails. + w := c.AEADCipher.(wiper) + w.Wipe() } else { - tlog.Debug.Print("CryptoCore.Wipe: niling stdlib refs") + tlog.Debug.Print("CryptoCore.Wipe: Only nil'ing stdlib refs") } // We have no access to the keys (or key-equivalents) stored inside the // Go stdlib. Best we can is to nil the references and force a GC. |