backend: require confirmation for signed channel updates [CI]

backend/src/MoShiro.Backend.Application/Updates/BackendUpdates.cs

@@ -0,0 +1,118 @@
+using Fleet.Core;
+using Microsoft.Extensions.Hosting;
+using MoShiro.Protocol;
+
+namespace MoShiro.Backend.Application;
+
+/// <summary>宿主机更新器的文件信箱端口。面板只写签名清单和确认的 seq，不执行命令。</summary>
+public interface IBackendUpdateFiles
+{
+    ValueTask WriteOfferAsync(string manifest, string signature, CancellationToken ct);
+
+    ValueTask<UpdateStatus?> ReadStatusAsync(CancellationToken ct);
+
+    ValueTask<long?> ReadRequestAsync(CancellationToken ct);
+
+    ValueTask RequestAsync(long seq, CancellationToken ct);
+}
+
+public sealed record BackendUpdateView(string Channel, bool Enabled, string State, string? CurrentTag, string? CurrentDigest, ReleaseOffer? Available, string? Error);
+
+/// <summary>Backend 的发布通知和确认。新清单只显示为可用更新，宿主机必须收到对应 seq 的确认才会重启。</summary>
+public sealed class BackendUpdates : IHostedService
+{
+    private readonly ReleaseService _releases;
+    private readonly IBackendUpdateFiles _files;
+    private readonly BackendOptions _options;
+
+    public BackendUpdates(ReleaseService releases, IBackendUpdateFiles files, BackendOptions options)
+    {
+        _releases = releases;
+        _files = files;
+        _options = options;
+    }
+
+    public static string ChannelOf(BackendOptions options)
+    {
+        if (options.UpdateChannel is "dev" or "release")
+        {
+            return options.UpdateChannel;
+        }
+
+        if (options.UpdateChannel != "auto")
+        {
+            throw new InvalidOperationException("UpdateChannel must be auto, dev or release");
+        }
+
+        string imageNamespace = options.ImageNamespace.Trim('/');
+        if (imageNamespace == "moshiro-dev" || imageNamespace.EndsWith("/moshiro-dev", StringComparison.Ordinal))
+        {
+            return "dev";
+        }
+
+        if (imageNamespace == "moshiro" || imageNamespace.EndsWith("/moshiro", StringComparison.Ordinal))
+        {
+            return "release";
+        }
+
+        return BuildInfo.Tag is { } tag && (tag.StartsWith("dev-", StringComparison.Ordinal) || tag.StartsWith("main-", StringComparison.Ordinal)) ? "dev" : "release";
+    }
+
+    public async ValueTask<BackendUpdateView> GetAsync(CancellationToken ct)
+    {
+        string channel = ChannelOf(_options);
+        ReleaseOffer? offer = await _releases.GetBackendAsync(channel, ct);
+        UpdateStatus? status = await _files.ReadStatusAsync(ct);
+        bool installed = offer is not null && (status?.Current == offer.Digest || BuildInfo.Tag == offer.Tag);
+        // 只有更新器确认过同一份清单才允许按钮执行；旧状态不能被套到新的清单上。
+        bool verified = offer is not null && status?.Available?.Seq == offer.Seq && status.Available.Digest == offer.Digest;
+        string state = status?.State ?? "unavailable";
+        if (installed)
+        {
+            state = "up_to_date";
+        }
+        else if (offer is not null && !verified && state is not ("invalid" or "failed" or "rolled_back"))
+        {
+            state = status is null ? "unavailable" : "checking";
+        }
+
+        if (verified && state == "available" && await _files.ReadRequestAsync(ct) == offer!.Seq)
+        {
+            state = "requested";
+        }
+
+        return new BackendUpdateView(channel, status is not null, state, BuildInfo.Tag, status?.Current, installed ? null : offer, status?.Error);
+    }
+
+    public async ValueTask<Result<bool>> ConfirmAsync(long seq, CancellationToken ct)
+    {
+        // 与 webhook 共用发布锁：确认之后即使又来了一个 tag，信箱中的请求仍只认本次确认的 seq。
+        await _releases.BackendGate.WaitAsync(ct);
+        try
+        {
+            BackendUpdateView view = await GetAsync(ct);
+            if (!view.Enabled || view.State != "available" || view.Available?.Seq != seq)
+            {
+                return Result<bool>.Fail(MoShiroErrors.PreconditionFailed, "the offered release changed or has not been verified by the host updater; refresh before confirming");
+            }
+
+            await _files.RequestAsync(seq, ct);
+            return Result<bool>.Ok(true);
+        }
+        finally
+        {
+            _releases.BackendGate.Release();
+        }
+    }
+
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        string channel = ChannelOf(_options);
+        if (await _releases.GetBackendAsync(channel, cancellationToken) is { } offer)
+        {
+            await _files.WriteOfferAsync(offer.Manifest, offer.Signature, cancellationToken);
+        }
+    }
+
+    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}