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修雨 1637ae16c7 fix(keychain): add DWS_DISABLE_KEYCHAIN fallback for macOS sandbox (#214) (#267)
In sandboxed macOS runtimes (e.g. Codex App), `security` / Keychain APIs
are blocked, so `keyring.Get`/`Set` for the DEK fails on every token
read/write. Add an opt-in env var that switches the macOS implementation
to the same file-based DEK scheme already used on Linux. Default
behavior is unchanged.

- Extract shared `fileDEK(service)` into `file_dek.go` (darwin || linux)
- Linux `getDEK` now delegates to `fileDEK`
- Darwin `getDEK` short-circuits to `fileDEK` when DWS_DISABLE_KEYCHAIN=1
- Document the tradeoff in reference.md (DEK and ciphertext co-located)
- Add darwin-only tests covering fallback path + overwrite
2026-05-12 14:57:00 +08:00

66 lines
1.9 KiB
Go

// Copyright 2026 Alibaba Group
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build darwin || linux
package keychain
import (
"crypto/rand"
"fmt"
"os"
"path/filepath"
"github.com/google/uuid"
)
// fileDEK retrieves or generates a Data Encryption Key stored as a plain
// file under the platform storage directory. Shared by Linux (default) and
// the macOS sandbox fallback path (DWS_DISABLE_KEYCHAIN=1).
func fileDEK(service string) ([]byte, error) {
dir := StorageDir(service)
keyPath := filepath.Join(dir, "dek")
key, err := os.ReadFile(keyPath)
if err == nil && len(key) == dekBytes {
return key, nil
}
if err := os.MkdirAll(dir, 0700); err != nil {
return nil, fmt.Errorf("create keychain dir: %w", err)
}
key = make([]byte, dekBytes)
if _, err := rand.Read(key); err != nil {
return nil, fmt.Errorf("generate dek: %w", err)
}
tmpKeyPath := filepath.Join(dir, "dek."+uuid.New().String()+".tmp")
defer os.Remove(tmpKeyPath)
if err := os.WriteFile(tmpKeyPath, key, 0600); err != nil {
return nil, fmt.Errorf("write dek: %w", err)
}
if err := os.Rename(tmpKeyPath, keyPath); err != nil {
// If rename fails, another process might have created it. Try reading again.
existingKey, readErr := os.ReadFile(keyPath)
if readErr == nil && len(existingKey) == dekBytes {
return existingKey, nil
}
return nil, fmt.Errorf("save dek: %w", err)
}
return key, nil
}