refactor!: rename the project from Monitor to MoShiro [CI]

Namespaces, assemblies, solution, binaries, images, systemd units, config paths, environment variables, protocol methods and the Linux user are all renamed. Breaking: existing databases, node identities and installed units must be recreated.

backend/shared/MoShiro.Measurement/Update/UpdateBridge.cs

@@ -0,0 +1,100 @@
+using System.Text;
+using System.Text.Json;
+using Fleet.Core;
+using MoShiro.Protocol;
+
+namespace MoShiro.Measurement;
+
+/// <summary>
+/// 节点进程和宿主机更新器之间的文件交换（容器里 <c>/etc/moshiro</c>，也就是数据目录）：
+/// 节点把面板发来的清单和签名写进 <c>update/</c>，把「更新」请求写成 <c>update/apply.request</c>；更新器验签并更新，状态由宿主更新器写在只读挂载的 <c>update-status/status.json</c>。
+/// 节点进程不执行任何命令，也不信任清单的内容（验签在宿主机上）。没有安装更新器时目录写不了或没人读，调用只是返回 false。
+/// </summary>
+public sealed class UpdateBridge
+{
+    private const int MaxManifestBytes = 4096;
+    private const int MaxSignatureBytes = 512;
+    private const int MaxStatusBytes = 4096;
+
+    private readonly string _updateDirectory;
+    private readonly string _statusFile;
+    private readonly Action<string, byte[]> _write;
+    private readonly INodeLog _log;
+
+    /// <param name="write">写数据目录里的文件（相对路径，原子替换）：由节点传入 <c>ConfigStore.Write</c>——常驻进程里只有它可以写文件。</param>
+    public UpdateBridge(string dataDirectory, Action<string, byte[]> write, INodeLog log)
+    {
+        _updateDirectory = Path.Combine(dataDirectory, "update");
+        _statusFile = Path.Combine(dataDirectory, "update-status", "status.json");
+        _write = write;
+        _log = log;
+    }
+
+    /// <summary>放下面板发来的清单和签名（和已有的一样就不动，免得每次重连都惊动更新器）。先写清单、后写签名：更新器监视的是签名文件。</summary>
+    public bool WriteOffer(UpdateOfferParams offer)
+    {
+        byte[] manifest = Encoding.UTF8.GetBytes(offer.Manifest);
+        byte[] signature = Encoding.UTF8.GetBytes(offer.Signature);
+        if (manifest.Length is 0 or > MaxManifestBytes || signature.Length is 0 or > MaxSignatureBytes)
+        {
+            _log.Warn("ignoring an update offer of an unexpected size");
+            return false;
+        }
+
+        try
+        {
+            string manifestPath = Path.Combine(_updateDirectory, "offer.manifest");
+            string signaturePath = Path.Combine(_updateDirectory, "offer.sig");
+            if (Same(manifestPath, manifest) && Same(signaturePath, signature))
+            {
+                return true;
+            }
+
+            _write("update/offer.manifest", manifest);
+            _write("update/offer.sig", signature);
+            _log.Info("update offer received");
+            return true;
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            _log.Warn("could not store the update offer (is the updater installed?)", ("err", ex.Message));
+            return false;
+        }
+    }
+
+    /// <summary>请求更新：写一个空的 <c>apply.request</c>（更新器验签通过、清单更新才会真的动手）。</summary>
+    public bool RequestApply()
+    {
+        try
+        {
+            _write("update/apply.request", []);
+            _log.Info("update requested");
+            return true;
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            _log.Warn("could not request the update (is the updater installed?)", ("err", ex.Message));
+            return false;
+        }
+    }
+
+    /// <summary>更新器的状态；没有安装更新器、文件不存在或内容不对时返回 null。</summary>
+    public UpdateStatus? ReadStatus()
+    {
+        try
+        {
+            if (!File.Exists(_statusFile) || new FileInfo(_statusFile).Length > MaxStatusBytes)
+            {
+                return null;
+            }
+
+            return JsonSerializer.Deserialize(File.ReadAllBytes(_statusFile), MoShiroJsonContext.Default.UpdateStatus);
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException or JsonException)
+        {
+            return null;
+        }
+    }
+
+    private static bool Same(string path, byte[] content) => File.Exists(path) && File.ReadAllBytes(path).AsSpan().SequenceEqual(content);
+}