feat: wip update checker

app/internal/utils/update.go

@@ -0,0 +1,92 @@
+package utils
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/apernet/hysteria/core/client"
+)
+
+const (
+	updateCheckEndpoint = "https://api.hy2.io/v1/update"
+	updateCheckTimeout  = 10 * time.Second
+)
+
+type UpdateChecker struct {
+	CurrentVersion string
+	Platform       string
+	Architecture   string
+	Channel        string
+	Client         *http.Client
+}
+
+func NewServerUpdateChecker(currentVersion, platform, architecture, channel string) *UpdateChecker {
+	return &UpdateChecker{
+		CurrentVersion: currentVersion,
+		Platform:       platform,
+		Architecture:   architecture,
+		Channel:        channel,
+		Client: &http.Client{
+			Timeout: updateCheckTimeout,
+		},
+	}
+}
+
+// NewClientUpdateChecker ensures that update checks are routed through a HyClient,
+// not being sent directly. This safeguard is CRITICAL, especially in scenarios where
+// users use Hysteria to bypass censorship. Making direct HTTPS requests to the API
+// endpoint could be easily spotted by censors (through SNI, for example), and could
+// serve as a signal to identify and penalize Hysteria users.
+func NewClientUpdateChecker(currentVersion, platform, architecture, channel string, hyClient client.Client) *UpdateChecker {
+	return &UpdateChecker{
+		CurrentVersion: currentVersion,
+		Platform:       platform,
+		Architecture:   architecture,
+		Channel:        channel,
+		Client: &http.Client{
+			Timeout: updateCheckTimeout,
+			Transport: &http.Transport{
+				DialContext: func(_ context.Context, network, addr string) (net.Conn, error) {
+					// Unfortunately HyClient doesn't support context for now
+					return hyClient.TCP(addr)
+				},
+			},
+		},
+	}
+}
+
+type UpdateResponse struct {
+	HasUpdate     bool   `json:"update"`
+	LatestVersion string `json:"lver"`
+	URL           string `json:"url"`
+	Urgent        bool   `json:"urgent"`
+}
+
+func (uc *UpdateChecker) Check() (*UpdateResponse, error) {
+	url := fmt.Sprintf("%s?cver=%s&plat=%s&arch=%s&chan=%s",
+		updateCheckEndpoint,
+		uc.CurrentVersion,
+		uc.Platform,
+		uc.Architecture,
+		uc.Channel,
+	)
+	resp, err := uc.Client.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+	var uResp UpdateResponse
+	decoder := json.NewDecoder(resp.Body)
+	if err := decoder.Decode(&uResp); err != nil {
+		return nil, err
+	}
+	return &uResp, nil
+}