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opaque.go
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opaque.go
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package google_oauth_handler
import (
"crypto/rand"
"encoding/base64"
"errors"
"io"
"golang.org/x/crypto/nacl/secretbox"
)
func newNonce() *[24]byte {
nonce := new([24]byte)
if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
panic(err)
}
return nonce
}
func opaqueByte(b []byte, secretKey *[32]byte) string {
nonce := newNonce()
encrypted := secretbox.Seal(nonce[:], b, nonce, secretKey)
return base64.URLEncoding.EncodeToString(encrypted)
}
var errTooShort = errors.New("google_oauth_handler: Encrypted string is too short")
var errInvalidInput = errors.New("google_oauth_handler: Could not decrypt invalid input")
func unopaqueByte(compressed string, secretKey *[32]byte) ([]byte, error) {
encrypted, err := base64.URLEncoding.DecodeString(compressed)
if err != nil {
return nil, err
}
if len(encrypted) < 24 {
return nil, errTooShort
}
decryptNonce := new([24]byte)
copy(decryptNonce[:], encrypted[:24])
decrypted, ok := secretbox.Open([]byte{}, encrypted[24:], decryptNonce, secretKey)
if !ok {
return nil, errInvalidInput
}
return decrypted, nil
}