Improved update flow

Using the previously added new API endpoint, the update flow can now skip updates if the latest version is already installed. This also improves the output by making it so update can print the version. Also improved the error handling.

client/lib/lib.go

@@ -40,6 +40,8 @@ var ConfigShContents string
 //go:embed test_config.sh
 var TestConfigShContents string
 
+var Version string = "Unknown"
+
 func getCwd() (string, error) {
 	cwd, err := os.Getwd()
 	if err != nil {
@@ -421,17 +423,25 @@ func copyFile(src, dst string) error {
 
 func Update() error {
 	// Download the binary
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	cmd := exec.Command("bash", "-c", `
-	curl -L -o /tmp/hishtory-client.intoto.jsonl https://api.hishtory.dev/download/hishtory-linux-amd64.intoto.jsonl; 
-	curl -L -o /tmp/hishtory-client https://api.hishtory.dev/download/hishtory-linux-amd64; 
-	chmod +x /tmp/hishtory-client`)
-	cmd.Stdout = &stdout
-	cmd.Stderr = &stderr
-	err := cmd.Run()
+	respBody, err := ApiGet("/api/v1/download")
 	if err != nil {
-		return fmt.Errorf("failed to download update: %v, stdout=%#v, stderr=%#v", err, stdout.String(), stderr.String())
+		return fmt.Errorf("failed to download update info: %v", err)
+	}
+	var downloadData shared.UpdateInfo
+	err = json.Unmarshal(respBody, &downloadData)
+	if err != nil {
+		return fmt.Errorf("failed to parse update info: %v", err)
+	}
+	if downloadData.Version == Version {
+		fmt.Printf("Latest version (v0.%s) is already installed\n", Version)
+	}
+	err = downloadFile("/tmp/hishtory-client", downloadData.LinuxAmd64Url)
+	if err != nil {
+		return err
+	}
+	err = downloadFile("/tmp/hishtory-client.intoto.jsonl", downloadData.LinuxAmd64AttestationUrl)
+	if err != nil {
+		return err
 	}
 
 	// Verify the SLSA attestation
@@ -440,7 +450,7 @@ func Update() error {
 		return fmt.Errorf("failed to verify SLSA provenance of the updated binary, aborting update: %v", err)
 	}
 
-	// Unlink the existing binary
+	// Unlink the existing binary so we can overwrite it even though it is still running
 	homedir, err := os.UserHomeDir()
 	if err != nil {
 		return fmt.Errorf("failed to get user's home directory: %v", err)
@@ -449,16 +459,39 @@ func Update() error {
 	if err != nil {
 		return fmt.Errorf("failed to unlink %s for update: %v", path.Join(homedir, shared.HISHTORY_PATH, "hishtory"), err)
 	}
+
 	// Install the new one
+	cmd := exec.Command("chmod", "+x", "/tmp/hishtory-client")
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("failed to chmod +x the update: %v", err)
+	}
 	cmd = exec.Command("/tmp/hishtory-client", "install")
 	err = cmd.Run()
 	if err != nil {
 		return fmt.Errorf("failed to update: %v", err)
 	}
-	fmt.Println("Successfully updated hishtory!")
+	fmt.Printf("Successfully updated hishtory from v0.%s to %s\n", Version, downloadData.Version)
 	return nil
 }
 
+func downloadFile(filename, url string) error {
+	resp, err := http.Get(url)
+	if err != nil {
+		return fmt.Errorf("failed to download file at %s to %s: %v", url, filename, err)
+	}
+	defer resp.Body.Close()
+
+	out, err := os.Create(filename)
+	if err != nil {
+		return fmt.Errorf("failed to save file to %s: %v", filename, err)
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, resp.Body)
+	return err
+}
+
 func getServerHostname() string {
 	if server := os.Getenv("HISHTORY_SERVER"); server != "" {
 		return server