libgocryptfs/cryptfs/cryptfs.go

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package cryptfs
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// CryptFS is the crypto backend of GoCryptFS
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import (
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"crypto/aes"
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"crypto/cipher"
"fmt"
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)
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const (
DEFAULT_PLAINBS = 4096
KEY_LEN = 32 // AES-256
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NONCE_LEN = 12
AUTH_TAG_LEN = 16
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)
type CryptFS struct {
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blockCipher cipher.Block
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gcm cipher.AEAD
plainBS uint64
cipherBS uint64
// Stores an all-zero block of size cipherBS
allZeroBlock []byte
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}
func NewCryptFS(key []byte, useOpenssl bool) *CryptFS {
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if len(key) != KEY_LEN {
panic(fmt.Sprintf("Unsupported key length %d", len(key)))
}
b, err := aes.NewCipher(key)
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if err != nil {
panic(err)
}
var gcm cipher.AEAD
if useOpenssl {
gcm = opensslGCM{key}
} else {
gcm, err = cipher.NewGCM(b)
if err != nil {
panic(err)
}
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}
cipherBS := DEFAULT_PLAINBS + NONCE_LEN + AUTH_TAG_LEN
return &CryptFS{
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blockCipher: b,
gcm: gcm,
plainBS: DEFAULT_PLAINBS,
cipherBS: uint64(cipherBS),
allZeroBlock: make([]byte, cipherBS),
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}
}
// Get plaintext block size
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func (be *CryptFS) PlainBS() uint64 {
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return be.plainBS
}
// Get ciphertext block size
func (be *CryptFS) CipherBS() uint64 {
return be.cipherBS
}