dev_agent
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Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com> Co-committed-by: dev_agent <dev_agent@cubecraftlabs.com>
82 lines
2.5 KiB
Go
82 lines
2.5 KiB
Go
// Package secretbox encrypts secrets at rest with AES-256-GCM. It is the only
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// owner of secret encryption: every _ct column holds a token produced by
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// Box.Encrypt, laid out as nonce ‖ ciphertext.
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//
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// Errors from this package never contain plaintext, ciphertext or key
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// material.
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package secretbox
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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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"fmt"
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)
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// KeySize is the decoded key length in bytes (AES-256).
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const KeySize = 32
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var (
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// ErrKeyEncoding means the key is not valid standard base64.
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ErrKeyEncoding = errors.New("secretbox: key is not valid standard base64")
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// ErrKeyLength means the decoded key is not exactly KeySize bytes.
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ErrKeyLength = errors.New("secretbox: key must decode to exactly 32 bytes")
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// ErrMalformed means a token is too short to hold a nonce and tag.
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ErrMalformed = errors.New("secretbox: token is too short")
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// ErrDecrypt means a token failed authentication: it was corrupted or
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// sealed under a different key.
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ErrDecrypt = errors.New("secretbox: token failed authentication")
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)
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// Box seals and opens secrets under one key. It is safe for concurrent use.
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type Box struct {
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aead cipher.AEAD
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}
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// New returns a Box for encodedKey, the standard-base64 encoding of a
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// KeySize-byte key.
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func New(encodedKey string) (*Box, error) {
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key, err := base64.StdEncoding.Strict().DecodeString(encodedKey)
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if err != nil {
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// The decoder's error is not wrapped: it describes the key's content.
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return nil, ErrKeyEncoding
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}
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if len(key) != KeySize {
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return nil, fmt.Errorf("%w, got %d", ErrKeyLength, 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("secretbox: %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("secretbox: %w", err)
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}
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return &Box{aead: aead}, nil
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}
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// Encrypt seals plaintext under a fresh random nonce and returns
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// nonce ‖ ciphertext.
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func (b *Box) Encrypt(plaintext []byte) ([]byte, error) {
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nonce := make([]byte, b.aead.NonceSize(), b.aead.NonceSize()+len(plaintext)+b.aead.Overhead())
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if _, err := rand.Read(nonce); err != nil {
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return nil, fmt.Errorf("secretbox: generate nonce: %w", err)
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}
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return b.aead.Seal(nonce, nonce, plaintext, nil), nil
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}
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// Decrypt authenticates and opens a token produced by Encrypt.
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func (b *Box) Decrypt(token []byte) ([]byte, error) {
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n := b.aead.NonceSize()
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if len(token) < n+b.aead.Overhead() {
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return nil, ErrMalformed
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}
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plaintext, err := b.aead.Open(nil, token[:n], token[n:], nil)
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if err != nil {
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return nil, ErrDecrypt
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}
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return plaintext, nil
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}
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