54 lines
1.1 KiB
Go
54 lines
1.1 KiB
Go
package seal
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/base64"
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"errors"
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)
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const keySize = 32
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var ErrKey = errors.New("seal: key must be 32 random bytes in base64")
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type Box struct {
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aead cipher.AEAD
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}
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func New(encodedKey string) (*Box, error) {
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key, err := base64.StdEncoding.DecodeString(encodedKey)
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if err != nil || len(key) != keySize {
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return nil, ErrKey
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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aead, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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return &Box{aead: aead}, nil
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}
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func (b *Box) Seal(plain, purpose string) []byte {
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nonce := make([]byte, b.aead.NonceSize())
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if _, err := rand.Read(nonce); err != nil {
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panic(err)
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}
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return b.aead.Seal(nonce, nonce, []byte(plain), []byte(purpose))
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}
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func (b *Box) Open(sealed []byte, purpose string) (string, error) {
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size := b.aead.NonceSize()
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if len(sealed) < size {
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return "", errors.New("seal: ciphertext too short")
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}
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plain, err := b.aead.Open(nil, sealed[:size], sealed[size:], []byte(purpose))
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if err != nil {
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return "", errors.New("seal: cannot decrypt")
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}
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return string(plain), nil
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}
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