98 lines
2.8 KiB
Go
98 lines
2.8 KiB
Go
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// Package security provides the security primitives used across the backend:
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// symmetric encryption for secrets at rest, hashing for access tokens and
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// passwords, and the prompt-injection / least-privilege controls applied by
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// the agent runtime.
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package security
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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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"encoding/hex"
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"errors"
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"fmt"
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"io"
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"golang.org/x/crypto/bcrypt"
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)
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// Crypto wraps an AES-GCM cipher derived from a master key. It is used to
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// encrypt model API keys at rest.
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type Crypto struct {
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aead cipher.AEAD
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}
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// NewCrypto initialises an AES-GCM cipher from a 32-byte master key.
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func NewCrypto(masterKey string) (*Crypto, error) {
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if len(masterKey) != 32 {
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return nil, fmt.Errorf("master key must be 32 bytes, got %d", len(masterKey))
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}
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block, err := aes.NewCipher([]byte(masterKey))
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if err != nil {
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return nil, fmt.Errorf("create aes 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("create gcm: %w", err)
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}
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return &Crypto{aead: aead}, nil
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}
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// Encrypt returns a base64-encoded ciphertext of the plaintext. A random
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// nonce is prepended to the ciphertext.
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func (c *Crypto) Encrypt(plaintext string) (string, error) {
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if plaintext == "" {
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return "", nil
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}
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nonce := make([]byte, c.aead.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return "", fmt.Errorf("read nonce: %w", err)
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}
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ct := c.aead.Seal(nonce, nonce, []byte(plaintext), nil)
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return base64.StdEncoding.EncodeToString(ct), nil
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}
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// Decrypt reverses Encrypt. An empty input yields an empty output.
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func (c *Crypto) Decrypt(b64 string) (string, error) {
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if b64 == "" {
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return "", nil
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}
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raw, err := base64.StdEncoding.DecodeString(b64)
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if err != nil {
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return "", fmt.Errorf("base64 decode: %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 "", errors.New("ciphertext too short")
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}
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pt, err := c.aead.Open(nil, raw[:ns], raw[ns:], nil)
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if err != nil {
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return "", fmt.Errorf("gcm open: %w", err)
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}
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return string(pt), nil
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}
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// HashToken returns a hex SHA-256 digest of an app access token. Tokens are
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// random and high-entropy, so a plain hash (no salt) is sufficient and keeps
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// lookups O(1) on the unique index.
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func HashToken(token string) string {
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sum := sha256.Sum256([]byte(token))
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return hex.EncodeToString(sum[:])
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}
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// HashPassword returns a bcrypt hash of a password.
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func HashPassword(password string) (string, error) {
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b, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
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if err != nil {
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return "", fmt.Errorf("bcrypt: %w", err)
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}
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return string(b), nil
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}
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// VerifyPassword checks a bcrypt hash against a plaintext password.
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func VerifyPassword(hash, password string) bool {
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return bcrypt.CompareHashAndPassword([]byte(hash), []byte(password)) == nil
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}
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