61 lines
1.6 KiB
Go
61 lines
1.6 KiB
Go
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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"crypto/sha256"
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"encoding/base64"
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"fmt"
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)
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// Cipher 用主密钥派生的 AES-256-GCM 做敏感字段加解密。
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type Cipher struct {
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aead cipher.AEAD
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}
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// NewCipher 以 SHA-256 从主密钥字符串派生 32 字节密钥，
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// 允许 DATA_KEY 是任意长度的强随机字符串。
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func NewCipher(masterKey string) (*Cipher, error) {
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if masterKey == "" {
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return nil, fmt.Errorf("new cipher: empty master key")
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}
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sum := sha256.Sum256([]byte(masterKey))
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block, err := aes.NewCipher(sum[:])
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if err != nil {
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return nil, fmt.Errorf("new cipher: %w", 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, fmt.Errorf("new cipher: %w", err)
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}
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return &Cipher{aead: aead}, nil
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}
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// EncryptString 加密明文，返回 base64(nonce | ciphertext)。
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func (c *Cipher) EncryptString(plaintext string) (string, error) {
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nonce := make([]byte, c.aead.NonceSize())
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if _, err := rand.Read(nonce); err != nil {
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return "", fmt.Errorf("encrypt: %w", err)
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}
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out := c.aead.Seal(nonce, nonce, []byte(plaintext), nil)
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return base64.StdEncoding.EncodeToString(out), nil
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}
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// DecryptString 解密 EncryptString 的输出。
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func (c *Cipher) DecryptString(encoded string) (string, error) {
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raw, err := base64.StdEncoding.DecodeString(encoded)
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if err != nil {
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return "", fmt.Errorf("decrypt: %w", err)
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}
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ns := c.aead.NonceSize()
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if len(raw) < ns {
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return "", fmt.Errorf("decrypt: ciphertext too short")
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}
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plain, err := c.aead.Open(nil, raw[:ns], raw[ns:], nil)
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if err != nil {
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return "", fmt.Errorf("decrypt: %w", err)
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}
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return string(plain), nil
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}
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