feat: bind each node to the binary it runs at its first handshake; refuse changes that are not in a CI-signed manifest [CI]

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

@@ -96,5 +96,34 @@ public sealed class UpdateBridge
         }
     }
 
+    /// <summary>
+    /// 握手时自述的二进制：正在运行的可执行文件的哈希，加上宿主机更新器验过的、安装这个版本时用的 CI 签名清单（更新器写在只读的 <c>update-status/</c>）。
+    /// 容器节点以外（没有更新器）没有清单，只有哈希；读不到可执行文件时返回 null（不做绑定）。
+    /// </summary>
+    public BinaryAttestation? Attest()
+    {
+        if (NodeBinary.Sha256Hex is not { } hash)
+        {
+            return null;
+        }
+
+        string? manifest = ReadSmall("installed.manifest", MaxManifestBytes);
+        string? signature = ReadSmall("installed.sig", MaxSignatureBytes);
+        return manifest is not null && signature is not null ? new BinaryAttestation(hash, manifest, signature) : new BinaryAttestation(hash, null, null);
+    }
+
+    private string? ReadSmall(string name, int maxBytes)
+    {
+        try
+        {
+            string path = Path.Combine(Path.GetDirectoryName(_statusFile)!, name);
+            return File.Exists(path) && new FileInfo(path).Length <= maxBytes ? File.ReadAllText(path, Encoding.UTF8) : null;
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            return null;
+        }
+    }
+
     private static bool Same(string path, byte[] content) => File.Exists(path) && File.ReadAllBytes(path).AsSpan().SequenceEqual(content);
 }