154 lines
3.7 KiB
Go
154 lines
3.7 KiB
Go
package lib
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"errors"
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"io"
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"github.com/klauspost/compress/zstd"
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"golang.org/x/crypto/hkdf"
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)
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var (
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ErrDecryptionFailed = errors.New("decryption failed")
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ErrInvalidCiphertext = errors.New("invalid ciphertext")
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)
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// NormalizeKey doubles an 8-byte key to 16 bytes for AES-128.
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// Mirrors normalize_key() in crypto/crypto.js.
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// 16 and 32 byte keys pass through unchanged.
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func NormalizeKey(key []byte) []byte {
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if len(key) == 8 {
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doubled := make([]byte, 16)
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copy(doubled[:8], key)
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copy(doubled[8:], key)
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return doubled
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}
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return key
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}
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// DeriveEntryKey derives a per-entry AES key from the L1 key using HKDF-SHA256.
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// L1 (8 bytes) is normalized to 16 → derives 16-byte key → AES-128-GCM.
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func DeriveEntryKey(l1Key []byte, entryID int64) ([]byte, error) {
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normalized := NormalizeKey(l1Key)
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info := []byte("clavitor-entry-" + IDToHex(entryID))
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reader := hkdf.New(sha256.New, normalized, nil, info)
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key := make([]byte, len(normalized)) // 16 bytes for AES-128
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if _, err := io.ReadFull(reader, key); err != nil {
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return nil, err
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}
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return key, nil
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}
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// DeriveHMACKey derives a separate HMAC key for blind indexes from L1.
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func DeriveHMACKey(l1Key []byte) ([]byte, error) {
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normalized := NormalizeKey(l1Key)
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info := []byte("clavitor-hmac-index")
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reader := hkdf.New(sha256.New, normalized, nil, info)
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key := make([]byte, 32)
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if _, err := io.ReadFull(reader, key); err != nil {
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return nil, err
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}
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return key, nil
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}
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// BlindIndex computes an HMAC-SHA256 blind index for searchable encrypted fields.
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// Returns truncated hash (16 bytes) for storage efficiency.
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func BlindIndex(hmacKey []byte, plaintext string) []byte {
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h := hmac.New(sha256.New, hmacKey)
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h.Write([]byte(plaintext))
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return h.Sum(nil)[:16] // truncate to 16 bytes
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}
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// Pack compresses with zstd then encrypts with AES-GCM (random nonce).
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// Key size determines AES variant: 16=AES-128, 32=AES-256.
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func Pack(key []byte, plaintext string) ([]byte, error) {
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compressed, err := zstdCompress([]byte(plaintext))
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if err != nil {
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return nil, err
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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, 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, err
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}
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nonce := make([]byte, gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return nil, err
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}
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return gcm.Seal(nonce, nonce, compressed, nil), nil
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}
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// Unpack decrypts AES-GCM then decompresses zstd.
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func Unpack(key []byte, ciphertext []byte) (string, error) {
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if len(ciphertext) == 0 {
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return "", nil
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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 "", 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 "", err
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}
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nonceSize := gcm.NonceSize()
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if len(ciphertext) < nonceSize {
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return "", ErrInvalidCiphertext
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}
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nonce, ct := ciphertext[:nonceSize], ciphertext[nonceSize:]
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compressed, err := gcm.Open(nil, nonce, ct, nil)
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if err != nil {
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return "", ErrDecryptionFailed
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}
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decompressed, err := zstdDecompress(compressed)
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if err != nil {
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return "", err
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}
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return string(decompressed), nil
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}
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// zstd encoder/decoder (reusable, goroutine-safe)
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var (
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zstdEncoder, _ = zstd.NewWriter(nil, zstd.WithEncoderLevel(zstd.SpeedDefault))
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zstdDecoder, _ = zstd.NewReader(nil)
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)
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func zstdCompress(data []byte) ([]byte, error) {
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return zstdEncoder.EncodeAll(data, nil), nil
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}
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func zstdDecompress(data []byte) ([]byte, error) {
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return zstdDecoder.DecodeAll(data, nil)
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}
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// GenerateToken generates a random hex token (32 bytes = 64 hex chars).
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func GenerateToken() string {
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b := make([]byte, 32)
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rand.Read(b)
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const hex = "0123456789abcdef"
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result := make([]byte, 64)
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for i, v := range b {
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result[i*2] = hex[v>>4]
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result[i*2+1] = hex[v&0x0f]
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}
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return string(result)
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}
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