feat: update agent button on server page

agent/internal/sync/sync.go

@@ -2,10 +2,15 @@ package agentsync
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"fmt"
+	"io"
 	"log"
 	"net"
+	"net/http"
 	"os"
+	"os/exec"
 	"runtime"
 	"strings"
 	"time"
@@ -16,7 +21,7 @@ import (
 	"github.com/mrhid6/keymanager/agent/internal/keys"
 )
 
-func Run(ctx context.Context, cfg *config.Config) error {
+func Run(ctx context.Context, cfg *config.Config, version string) error {
 	client, err := grpcclient.New(cfg.ServerURL, cfg.TLS)
 	if err != nil {
 		return fmt.Errorf("dial grpc: %w", err)
@@ -60,7 +65,7 @@ func Run(ctx context.Context, cfg *config.Config) error {
 	defer ticker.Stop()
 
 	// Run immediately on startup
-	if err := poll(client, cfg); err != nil {
+	if err := poll(client, cfg, version); err != nil {
 		log.Printf("poll error: %v", err)
 	}
 
@@ -69,15 +74,15 @@ func Run(ctx context.Context, cfg *config.Config) error {
 		case <-ctx.Done():
 			return nil
 		case <-ticker.C:
-			if err := poll(client, cfg); err != nil {
+			if err := poll(client, cfg, version); err != nil {
 				log.Printf("poll error: %v", err)
 			}
 		}
 	}
 }
 
-func poll(client *grpcclient.Client, cfg *config.Config) error {
-	desired, err := client.SyncKeys(cfg.ServerID, cfg.AgentToken)
+func poll(client *grpcclient.Client, cfg *config.Config, version string) error {
+	desired, err := client.SyncKeys(cfg.ServerID, cfg.AgentToken, version)
 	if err != nil {
 		return fmt.Errorf("SyncKeys: %w", err)
 	}
@@ -165,6 +170,9 @@ func connectAndHandleStream(ctx context.Context, cfg *config.Config) error {
 		if cmd.DeleteKey != nil {
 			go handleDeleteKey(cmd)
 		}
+		if cmd.UpdateAgent != nil {
+			go handleUpdateAgent(cmd)
+		}
 	}
 }
 
@@ -184,6 +192,101 @@ func handleDeleteKey(cmd *pb.ServerCommand) {
 	log.Printf("deleted local key files for %q (cmd=%s)", label, cmd.CommandId)
 }
 
+func handleUpdateAgent(cmd *pb.ServerCommand) {
+	u := cmd.UpdateAgent
+	arch := runtime.GOARCH // "amd64" or "arm64"
+	tag := "agent%2Fv" + u.Version
+	binaryURL := fmt.Sprintf("%s/mrhid6/keymanager/releases/download/%s/keymanager-agent-linux-%s", u.GiteaBaseURL, tag, arch)
+	checksumURL := fmt.Sprintf("%s/mrhid6/keymanager/releases/download/%s/checksums.txt", u.GiteaBaseURL, tag)
+
+	log.Printf("updating agent to v%s from %s (cmd=%s)", u.Version, u.GiteaBaseURL, cmd.CommandId)
+
+	// Download binary
+	tmpBin := "/tmp/keymanager-agent-update"
+	if err := downloadFile(binaryURL, tmpBin); err != nil {
+		log.Printf("update download failed (cmd=%s): %v", cmd.CommandId, err)
+		return
+	}
+
+	// Download and verify checksum
+	checksumData, err := httpGetBytes(checksumURL)
+	if err != nil {
+		log.Printf("update checksum fetch failed (cmd=%s): %v", cmd.CommandId, err)
+		return
+	}
+	if err := verifyChecksum(tmpBin, fmt.Sprintf("keymanager-agent-linux-%s", arch), checksumData); err != nil {
+		log.Printf("update checksum mismatch (cmd=%s): %v", cmd.CommandId, err)
+		os.Remove(tmpBin)
+		return
+	}
+
+	if err := os.Chmod(tmpBin, 0755); err != nil {
+		log.Printf("update chmod failed (cmd=%s): %v", cmd.CommandId, err)
+		return
+	}
+	if err := os.Rename(tmpBin, "/usr/local/bin/keymanager-agent"); err != nil {
+		log.Printf("update replace binary failed (cmd=%s): %v", cmd.CommandId, err)
+		return
+	}
+
+	log.Printf("agent binary replaced, restarting service (cmd=%s)", cmd.CommandId)
+	exec.Command("systemctl", "restart", "keymanager-agent").Run()
+}
+
+func downloadFile(url, dest string) error {
+	resp, err := http.Get(url) //nolint:gosec
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("HTTP %d from %s", resp.StatusCode, url)
+	}
+	f, err := os.Create(dest)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = io.Copy(f, resp.Body)
+	return err
+}
+
+func httpGetBytes(url string) ([]byte, error) {
+	resp, err := http.Get(url) //nolint:gosec
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP %d from %s", resp.StatusCode, url)
+	}
+	return io.ReadAll(resp.Body)
+}
+
+func verifyChecksum(filePath, filename string, checksumData []byte) error {
+	f, err := os.Open(filePath)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return err
+	}
+	actual := hex.EncodeToString(h.Sum(nil))
+
+	for _, line := range strings.Split(string(checksumData), "\n") {
+		fields := strings.Fields(line)
+		if len(fields) == 2 && fields[1] == filename {
+			if fields[0] != actual {
+				return fmt.Errorf("expected %s got %s", fields[0], actual)
+			}
+			return nil
+		}
+	}
+	return fmt.Errorf("no checksum entry found for %s", filename)
+}
+
 func handleGenerateKey(cfg *config.Config, cmd *pb.ServerCommand) {
 	g := cmd.GenerateKey
 	label := g.Label