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64 lines
1.9 KiB
Go
64 lines
1.9 KiB
Go
// Package crypto provides AES-256-GCM symmetric encryption for sensitive
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// secret fields persisted to the database (e.g. git credentials, LLM API keys).
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//
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// The master key is supplied by the caller (see config.MasterKey) and never
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// stored alongside the ciphertext.
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package crypto
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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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"errors"
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"fmt"
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"io"
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)
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// Encryptor 用 AES-256-GCM 加解密 secret。
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// 密文格式：nonce(12) || ciphertext || tag。
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type Encryptor struct {
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gcm cipher.AEAD
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}
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// NewEncryptor constructs an Encryptor from a 32-byte (AES-256) key.
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// Any other key length yields an error rather than silently downgrading.
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func NewEncryptor(key []byte) (*Encryptor, error) {
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if len(key) != 32 {
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return nil, fmt.Errorf("key must be 32 bytes (got %d)", len(key))
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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, fmt.Errorf("aes new cipher: %w", err)
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, fmt.Errorf("new gcm: %w", err)
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}
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return &Encryptor{gcm: gcm}, nil
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}
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// Encrypt seals plaintext with a fresh random nonce and returns
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// nonce || ciphertext || tag.
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func (e *Encryptor) Encrypt(plaintext []byte) ([]byte, error) {
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nonce := make([]byte, e.gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return nil, fmt.Errorf("rand nonce: %w", err)
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}
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// Seal 把 nonce 作为 dst 前缀写入
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return e.gcm.Seal(nonce, nonce, plaintext, nil), nil
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}
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// Decrypt verifies and opens a ciphertext produced by Encrypt.
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// It returns an error if the input is too short or authentication fails.
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func (e *Encryptor) Decrypt(ciphertext []byte) ([]byte, error) {
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if len(ciphertext) < e.gcm.NonceSize() {
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return nil, errors.New("ciphertext too short")
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}
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nonce, ct := ciphertext[:e.gcm.NonceSize()], ciphertext[e.gcm.NonceSize():]
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pt, err := e.gcm.Open(nil, nonce, ct, nil)
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if err != nil {
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return nil, fmt.Errorf("gcm open: %w", err)
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}
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return pt, nil
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}
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