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// Package cryptocore wraps OpenSSL and Go GCM crypto and provides
// a nonce generator.
package cryptocore
import (
"crypto/aes"
"crypto/cipher"
"fmt"
"github.com/rfjakob/gocryptfs/internal/stupidgcm"
)
const (
KeyLen = 32 // AES-256
AuthTagLen = 16
)
type CryptoCore struct {
BlockCipher cipher.Block
Gcm cipher.AEAD
GcmIVGen *nonceGenerator
IVLen int
}
// "New" returns a new CryptoCore object or panics.
//
// Even though the "GCMIV128" feature flag is now mandatory, we must still
// support 96-bit IVs here because they are used for encrypting the master
// key in gocryptfs.conf.
func New(key []byte, useOpenssl bool, GCMIV128 bool) *CryptoCore {
if len(key) != KeyLen {
panic(fmt.Sprintf("Unsupported key length %d", len(key)))
}
// We want the IV size in bytes
IVLen := 96 / 8
if GCMIV128 {
IVLen = 128 / 8
}
// Name encryption always uses built-in Go AES through BlockCipher.
// Content encryption uses BlockCipher only if useOpenssl=false.
blockCipher, err := aes.NewCipher(key)
if err != nil {
panic(err)
}
var gcm cipher.AEAD
if useOpenssl && GCMIV128 {
// stupidgcm only supports 128-bit IVs
gcm = stupidgcm.New(key)
} else {
gcm, err = goGCMWrapper(blockCipher, IVLen)
if err != nil {
panic(err)
}
}
return &CryptoCore{
BlockCipher: blockCipher,
Gcm: gcm,
GcmIVGen: &nonceGenerator{nonceLen: IVLen},
IVLen: IVLen,
}
}
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