feat(loadtest): sync add real 500-session capacity harness

internal/loadharness/storage.go

@@ -0,0 +1,165 @@
+package loadharness
+
+import (
+	"context"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+
+	"github.com/iamxvbaba/td/session"
+)
+
+const encryptedSessionMagic = "TLSLOAD1"
+
+// EncryptedFileStorage encrypts gotd's complete session blob with AES-256-GCM.
+// A unique random nonce is generated on every replacement and the file is
+// written with owner-only permissions.
+type EncryptedFileStorage struct {
+	Path string
+	Key  [32]byte
+	mu   sync.Mutex
+}
+
+func (s *EncryptedFileStorage) LoadSession(context.Context) ([]byte, error) {
+	if s == nil || strings.TrimSpace(s.Path) == "" {
+		return nil, errors.New("invalid encrypted session storage")
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	data, err := os.ReadFile(s.Path)
+	if os.IsNotExist(err) {
+		return nil, session.ErrNotFound
+	}
+	if err != nil {
+		return nil, fmt.Errorf("read encrypted session: %w", err)
+	}
+	block, err := aes.NewCipher(s.Key[:])
+	if err != nil {
+		return nil, err
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+	header := len(encryptedSessionMagic) + gcm.NonceSize()
+	if len(data) < header || string(data[:len(encryptedSessionMagic)]) != encryptedSessionMagic {
+		return nil, errors.New("encrypted session has an invalid header")
+	}
+	nonce := data[len(encryptedSessionMagic):header]
+	plain, err := gcm.Open(nil, nonce, data[header:], []byte(encryptedSessionMagic))
+	if err != nil {
+		return nil, errors.New("encrypted session authentication failed")
+	}
+	return plain, nil
+}
+
+func (s *EncryptedFileStorage) StoreSession(_ context.Context, plain []byte) error {
+	if s == nil || strings.TrimSpace(s.Path) == "" {
+		return errors.New("invalid encrypted session storage")
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	block, err := aes.NewCipher(s.Key[:])
+	if err != nil {
+		return err
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return err
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return fmt.Errorf("generate session nonce: %w", err)
+	}
+	data := make([]byte, 0, len(encryptedSessionMagic)+len(nonce)+len(plain)+gcm.Overhead())
+	data = append(data, encryptedSessionMagic...)
+	data = append(data, nonce...)
+	data = gcm.Seal(data, nonce, plain, []byte(encryptedSessionMagic))
+	return writeFileAtomic(s.Path, data, 0o600)
+}
+
+func GenerateSessionKey(path string) error {
+	if _, err := os.Stat(path); err == nil {
+		return fmt.Errorf("refusing to overwrite existing session key %q", path)
+	} else if !os.IsNotExist(err) {
+		return err
+	}
+	var key [32]byte
+	if _, err := io.ReadFull(rand.Reader, key[:]); err != nil {
+		return err
+	}
+	encoded := base64.StdEncoding.EncodeToString(key[:]) + "\n"
+	return writeFileAtomic(path, []byte(encoded), 0o600)
+}
+
+func LoadSessionKey(path string) ([32]byte, error) {
+	var key [32]byte
+	info, err := os.Stat(path)
+	if err != nil {
+		return key, fmt.Errorf("stat session key: %w", err)
+	}
+	if runtime.GOOS != "windows" && info.Mode().Perm()&0o077 != 0 {
+		return key, fmt.Errorf("session key %q must not be group/world accessible (mode %o)", path, info.Mode().Perm())
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return key, err
+	}
+	decoded, err := base64.StdEncoding.DecodeString(strings.TrimSpace(string(data)))
+	if err != nil || len(decoded) != len(key) {
+		return key, errors.New("session key must be base64-encoded 32 bytes")
+	}
+	copy(key[:], decoded)
+	return key, nil
+}
+
+func writeFileAtomic(path string, data []byte, mode os.FileMode) (retErr error) {
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		return err
+	}
+	tmp, err := os.CreateTemp(dir, ".telesrv-load-*")
+	if err != nil {
+		return err
+	}
+	tmpName := tmp.Name()
+	defer func() {
+		_ = tmp.Close()
+		if retErr != nil {
+			_ = os.Remove(tmpName)
+		}
+	}()
+	if err := tmp.Chmod(mode); err != nil {
+		return err
+	}
+	if _, err := tmp.Write(data); err != nil {
+		return err
+	}
+	if err := tmp.Sync(); err != nil {
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+	// On Unix rename atomically replaces. Windows requires removing the old
+	// destination first; session files remain recoverable from the complete temp
+	// file if that narrow replacement fails.
+	if runtime.GOOS == "windows" {
+		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+			return err
+		}
+	}
+	if err := os.Rename(tmpName, path); err != nil {
+		return err
+	}
+	return nil
+}