cdrop — 跨 OS 剪贴板与文件传输服务

Commilitia Drop：自托管的跨设备剪贴板同步与点对点文件传输。

- 后端 Go（chi / SQLite WAL / SSE Hub / WebRTC signaling + 状态机 / Relay ring buffer），编译进单个 distroless 镜像（前端 go:embed）。
- 前端 React + TanStack Router + Zustand，自实现 SSE + WebRTC P2P，NAT 受阻时回退服务端中继；聚珍（Juzhen）CJK 综合排版。
- 桌面端 Wails v2（macOS / Windows），瘦客户端复用 web。
- 鉴权 OIDC PKCE（自建 Casdoor 等），refresh_token 信封加密存系统密钥库；iOS Shortcut 用 HS256 scoped token。

架构文档与变更记录见 docs 分支（PROJECT_BRIEF / FRONTEND_DESIGN / CHANGELOG）。

本次为公开发布初始提交：完整开发历史（含部署细节）留存于私有归档，公开仓库自此干净起步。

desktop/platform/identity.go

@@ -0,0 +1,104 @@
+package platform
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// UserInfo is the display identity the WebView store needs (mirrors the web
+// app's User shape: id / name / avatar).
+type UserInfo struct {
+	ID     string `json:"id"`
+	Name   string `json:"name"`
+	Avatar string `json:"avatar"`
+}
+
+// LoginResult is the full result Go keeps internally: tokens + identity. The
+// refresh_token never crosses into the WebView — see SessionView and the
+// credential policy in session.go.
+type LoginResult struct {
+	AccessToken  string   `json:"access_token"`
+	RefreshToken string   `json:"refresh_token"`
+	ExpiresIn    int      `json:"expires_in"`
+	User         UserInfo `json:"user"`
+}
+
+// SessionView is the refresh-token-free projection handed to the WebView (login
+// emit, refresh return, boot injection). The refresh_token — the long-lived
+// secret — is deliberately omitted: it lives only in the Go process and the
+// on-disk session, never in JS or the injected HTML.
+type SessionView struct {
+	AccessToken string   `json:"access_token"`
+	ExpiresIn   int      `json:"expires_in"`
+	User        UserInfo `json:"user"`
+}
+
+// View projects a LoginResult to the refresh-free SessionView.
+func (r LoginResult) View() SessionView {
+	return SessionView{AccessToken: r.AccessToken, ExpiresIn: r.ExpiresIn, User: r.User}
+}
+
+// UserFromToken extracts the display identity from OIDC tokens WITHOUT verifying
+// the signature. This mirrors the backend's extractUser (internal/httpapi/auth.go)
+// exactly: prefer the id_token's richer claims, fall back to the access_token;
+// name priority preferred_username → name → email → sub; avatar avatar → picture.
+//
+// Skipping verification is safe for the same reason it is on the backend: the
+// auth middleware verifies the access_token on every API call via JWKS, so any
+// tamper surfaces there. These claims only drive local display.
+func UserFromToken(idToken, accessToken string) (UserInfo, error) {
+	pick := idToken
+	if pick == "" {
+		pick = accessToken
+	}
+	claims, err := decodeJWTClaims(pick)
+	if err != nil {
+		return UserInfo{}, err
+	}
+
+	u := UserInfo{ID: claimString(claims, "sub")}
+	for _, k := range []string{"preferred_username", "name", "email"} {
+		if v := claimString(claims, k); v != "" {
+			u.Name = v
+			break
+		}
+	}
+	if u.Name == "" {
+		u.Name = u.ID
+	}
+	for _, k := range []string{"avatar", "picture"} {
+		if v := claimString(claims, k); v != "" {
+			u.Avatar = v
+			break
+		}
+	}
+	return u, nil
+}
+
+// decodeJWTClaims base64url-decodes the JWT payload segment and unmarshals it.
+// No signature check (see UserFromToken).
+func decodeJWTClaims(token string) (map[string]any, error) {
+	parts := strings.Split(token, ".")
+	if len(parts) < 2 {
+		return nil, errors.New("oauth: token is not a JWT")
+	}
+	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return nil, fmt.Errorf("oauth: decode jwt payload: %w", err)
+	}
+	var claims map[string]any
+	if err := json.Unmarshal(payload, &claims); err != nil {
+		return nil, fmt.Errorf("oauth: parse jwt claims: %w", err)
+	}
+	return claims, nil
+}
+
+func claimString(m map[string]any, key string) string {
+	if v, ok := m[key].(string); ok {
+		return v
+	}
+	return ""
+}