heicode-mananger/heicode/common/crypto.go

package common

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/ed25519"
	"crypto/hmac"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"io"

	"golang.org/x/crypto/bcrypt"
)

func GenerateHMACWithKey(key []byte, data string) string {
	h := hmac.New(sha256.New, key)
	h.Write([]byte(data))
	return hex.EncodeToString(h.Sum(nil))
}

func GenerateHMAC(data string) string {
	h := hmac.New(sha256.New, []byte(CryptoSecret))
	h.Write([]byte(data))
	return hex.EncodeToString(h.Sum(nil))
}

func Password2Hash(password string) (string, error) {
	passwordBytes := []byte(password)
	hashedPassword, err := bcrypt.GenerateFromPassword(passwordBytes, bcrypt.DefaultCost)
	return string(hashedPassword), err
}

func ValidatePasswordAndHash(password string, hash string) bool {
	err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
	return err == nil
}

// VerifyEd25519Signature validates a base64-encoded Ed25519 signature over
// the given message bytes, using a base64-encoded 32-byte public key.
// Returns nil if valid, otherwise an error describing what failed.
//
// Used by the device-signature middleware to authenticate per-request
// signatures from device-bound Heicode clients. The client signs the
// SHA-256 hash of a canonical request string; this helper just does the
// raw Ed25519 verify and surface-level decode.
func VerifyEd25519Signature(pubkeyB64 string, message []byte, signatureB64 string) error {
	if pubkeyB64 == "" {
		return errors.New("empty public key")
	}
	if signatureB64 == "" {
		return errors.New("empty signature")
	}
	pubkey, err := base64.StdEncoding.DecodeString(pubkeyB64)
	if err != nil {
		return errors.New("public key is not valid base64")
	}
	if len(pubkey) != ed25519.PublicKeySize {
		return errors.New("public key has wrong length")
	}
	sig, err := base64.StdEncoding.DecodeString(signatureB64)
	if err != nil {
		return errors.New("signature is not valid base64")
	}
	if len(sig) != ed25519.SignatureSize {
		return errors.New("signature has wrong length")
	}
	if !ed25519.Verify(ed25519.PublicKey(pubkey), message, sig) {
		return errors.New("signature did not verify")
	}
	return nil
}

// SealWithCryptoSecret wraps plaintext bytes with AES-256-GCM using a
// key derived from CryptoSecret (SHA-256). Returns base64(nonce || ct
// || tag). Used by ServerKey to keep the long-lived X25519 private key
// encrypted at rest — the env-var CryptoSecret is required to decrypt,
// so a SQL dump alone doesn't expose the private key.
func SealWithCryptoSecret(plaintext []byte) (string, error) {
	if CryptoSecret == "" {
		return "", errors.New("CRYPTO_SECRET is empty; refusing to seal")
	}
	keyHash := sha256.Sum256([]byte(CryptoSecret))
	block, err := aes.NewCipher(keyHash[:])
	if err != nil {
		return "", err
	}
	aead, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	nonce := make([]byte, aead.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	out := aead.Seal(nonce, nonce, plaintext, nil)
	return base64.StdEncoding.EncodeToString(out), nil
}

// SafeWipe overwrites a byte slice with zeros. Best-effort defense
// against secrets lingering in heap memory after use. Not a guarantee
// (Go GC may relocate, compiler may elide), but cheap insurance for
// short-lived secrets like a ChaCha20 key after the AEAD is built.
func SafeWipe(b []byte) {
	for i := range b {
		b[i] = 0
	}
}

// UnsealWithCryptoSecret reverses SealWithCryptoSecret.
func UnsealWithCryptoSecret(sealedB64 string) ([]byte, error) {
	if CryptoSecret == "" {
		return nil, errors.New("CRYPTO_SECRET is empty; refusing to unseal")
	}
	keyHash := sha256.Sum256([]byte(CryptoSecret))
	block, err := aes.NewCipher(keyHash[:])
	if err != nil {
		return nil, err
	}
	aead, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	raw, err := base64.StdEncoding.DecodeString(sealedB64)
	if err != nil {
		return nil, errors.New("sealed payload is not valid base64")
	}
	if len(raw) < aead.NonceSize() {
		return nil, errors.New("sealed payload too short")
	}
	nonce, ct := raw[:aead.NonceSize()], raw[aead.NonceSize():]
	return aead.Open(nil, nonce, ct, nil)
}