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/fleet/src/Fleet.Core/BinaryAttestation.cs

@@ -0,0 +1,43 @@
+using System.Security.Cryptography;
+
+namespace Fleet.Core;
+
+/// <summary>
+/// 节点握手时自述的「我跑的是哪个二进制」：正在运行的可执行文件的 SHA-256，以及（容器节点）宿主机更新器验过的 CI 签名清单和签名。
+/// 服务端在节点第一次握手成功的那一刻把哈希绑定到这个节点，之后哈希对不上就不让它继续运行。
+/// </summary>
+public sealed record BinaryAttestation(string Sha256, string? Manifest, string? Signature);
+
+/// <summary>
+/// 正在运行的二进制的哈希。Linux 上读 <c>/proc/self/exe</c>：它指向进程启动时映射的那个映像，磁盘上的文件之后被换掉也不影响，
+/// 所以「运行期间被替换、重启后换了别的」的情况下一次握手就会对不上。算一次，之后缓存。
+/// </summary>
+public static class NodeBinary
+{
+    private static readonly Lazy<string?> s_hash = new(Compute);
+
+    /// <summary>小写十六进制；读不到可执行文件时为 null（这样的节点不做绑定）。</summary>
+    public static string? Sha256Hex => s_hash.Value;
+
+    /// <summary>在后台先算好，免得第一次握手等它。</summary>
+    public static void Prime() => _ = Task.Run(() => s_hash.Value);
+
+    private static string? Compute()
+    {
+        try
+        {
+            string? path = OperatingSystem.IsLinux() && File.Exists("/proc/self/exe") ? "/proc/self/exe" : Environment.ProcessPath;
+            if (path is null)
+            {
+                return null;
+            }
+
+            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete, 1 << 16);
+            return Convert.ToHexStringLower(SHA256.HashData(stream));
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            return null;
+        }
+    }
+}

backend/fleet/src/Fleet.Core/ErrorCode.cs

@@ -27,4 +27,6 @@ public static class FleetErrors
     public static readonly ErrorCode JoinTokenExpired = new("fleet_join_token_expired");
     public static readonly ErrorCode ProofInvalid = new("fleet_proof_invalid");
     public static readonly ErrorCode FrameTooLarge = new("fleet_frame_too_large");
+    /// <summary>节点现在跑的二进制和它第一次握手时绑定的不一致，也不在 CI 签名的更新清单里。</summary>
+    public static readonly ErrorCode BinaryMismatch = new("fleet_binary_mismatch");
 }