SocialPub/PrivaPub.Tests/Support/RemoteActor.cs

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;

using PrivaPub.Federation.Signing;

using System.Globalization;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json.Nodes;

namespace PrivaPub.Tests.Support
{
	public sealed class RemoteActor
	{
		readonly RSA _key = RSA.Create(2048);
		readonly bool _namesSharedInbox;
		readonly bool _hasWall;
		readonly string _ed25519;

		// sharedInbox: whether its document names its server's shared inbox (endpoints.sharedInbox), as Mastodon's do; wall:
		// whether it has a wall (sm:wall, Smithereen's); ed25519: whether it has an Ed25519 key (FEP-521a) to prove what it
		// sends (FEP-8b32)
		public RemoteActor(Peer peer, string name, string origin = default, string type = "Person", bool sharedInbox = false, bool wall = false,
			bool ed25519 = false)
		{
			_ed25519 = ed25519 ? PrivaPub.Federation.Signing.IntegrityProofs.NewSeed() : default;
			Name = $"{name}{Guid.NewGuid():N}"[..20];
			Id = $"{origin ?? peer.A}/users/{Name}";
			Type = type;
			_namesSharedInbox = sharedInbox;
			_hasWall = wall;
			peer.Serve($"/users/{Name}", Document().ToJsonString());
		}

		public string Type { get; }

		public string Name { get; }
		public string Id { get; }
		public string KeyId => Id + "#main-key";
		public string SharedInbox => Id.Split("/users/")[0] + "/inbox";
		public string Wall => Id + "/wall";

		// the activity with its proof by this actor's Ed25519 key
		public JsonObject Prove(JsonObject activity)
		{
			activity["proof"] = PrivaPub.Federation.Signing.IntegrityProofs.Create(activity, Id + "#ed25519-key", _ed25519, DateTime.UtcNow);
			return activity;
		}

		public JsonObject Document()
		{
			var document = new JsonObject
			{
				["id"] = Id,
				["type"] = Type,
				["preferredUsername"] = Name,
				["inbox"] = Id + "/inbox",
				["followers"] = Id + "/followers",
				["outbox"] = Id + "/outbox",
				["featured"] = Id + "/featured",
				["publicKey"] = new JsonObject
				{
					["id"] = KeyId,
					["owner"] = Id,
					["publicKeyPem"] = _key.ExportSubjectPublicKeyInfoPem()
				}
			};
			if (_namesSharedInbox)
				document["endpoints"] = new JsonObject { ["sharedInbox"] = SharedInbox };
			if (_hasWall)
				document["wall"] = Wall;
			if (_ed25519 != default)
				document["assertionMethod"] = new JsonArray(new JsonObject
				{
					["id"] = Id + "#ed25519-key", ["type"] = "Multikey", ["controller"] = Id,
					["publicKeyMultibase"] = PrivaPub.Federation.Signing.IntegrityProofs.Multikey(PrivaPub.Federation.Signing.IntegrityProofs.PublicKey(_ed25519))
				});
			return document;
		}

		public HttpRequestMessage SignedGet(string path, string host = "privapub.test")
		{
			var date = DateTimeOffset.UtcNow.ToString("r", CultureInfo.InvariantCulture);
			var request = new HttpRequestMessage(HttpMethod.Get, path);
			request.Headers.TryAddWithoutValidation("Date", date);
			request.Headers.TryAddWithoutValidation("Accept", "application/activity+json");
			request.Headers.TryAddWithoutValidation("Signature", Signature($"(request-target): get {path}\nhost: {host}\ndate: {date}", "(request-target) host date"));
			return request;
		}

		public HttpRequestMessage SignedPost(string path, JsonNode activity, string host = "privapub.test", string date = default)
		{
			var body = Encoding.UTF8.GetBytes(activity.ToJsonString());
			date ??= DateTimeOffset.UtcNow.ToString("r", CultureInfo.InvariantCulture);
			var digest = HttpSignatures.Digest(body);
			var request = new HttpRequestMessage(HttpMethod.Post, path) { Content = new ByteArrayContent(body) };
			request.Content.Headers.TryAddWithoutValidation("Content-Type", "application/activity+json");
			request.Headers.TryAddWithoutValidation("Date", date);
			request.Headers.TryAddWithoutValidation("Digest", digest);
			request.Headers.TryAddWithoutValidation("Signature",
				Signature($"(request-target): post {path}\nhost: {host}\ndate: {date}\ndigest: {digest}", "(request-target) host date digest"));
			return request;
		}

		// the same delivery signed as RFC 9421 does it (WordPress, Ghost, Fedify), for `signedFor` when it is not where the
		// request goes
		public HttpRequestMessage MessageSignedPost(string path, JsonNode activity, string signedFor = default, string origin = "https://privapub.test")
		{
			var body = Encoding.UTF8.GetBytes(activity.ToJsonString());
			var request = new HttpRequestMessage(HttpMethod.Post, new Uri(origin + (signedFor ?? path))) { Content = new ByteArrayContent(body) };
			request.Content.Headers.TryAddWithoutValidation("Content-Type", "application/activity+json");
			MessageSignatures.Sign(request, KeyId, _key.ExportPkcs8PrivateKeyPem(), body);
			request.RequestUri = new Uri(origin + path);
			return request;
		}

		public string PrivateKeyPem => _key.ExportPkcs8PrivateKeyPem();

		public string PublicKeyPem => _key.ExportSubjectPublicKeyInfoPem();

		string Signature(string signingString, string headers)
		{
			var signature = Convert.ToBase64String(_key.SignData(Encoding.UTF8.GetBytes(signingString), HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1));
			return $"keyId=\"{KeyId}\",algorithm=\"rsa-sha256\",headers=\"{headers}\",signature=\"{signature}\"";
		}

		public HttpRequest Get(string host, string path)
		{
			var date = DateTimeOffset.UtcNow.ToString("r", CultureInfo.InvariantCulture);
			var context = new DefaultHttpContext();
			context.Request.Method = "GET";
			context.Request.Host = new HostString(host);
			context.Request.Path = path;
			context.Features.Get<IHttpRequestFeature>().RawTarget = path;
			context.Request.Headers["Date"] = date;
			context.Request.Headers["Signature"] = Signature($"(request-target): get {path}\nhost: {host}\ndate: {date}", "(request-target) host date");
			return context.Request;
		}

		public HttpRequest Post(string host, string path, JsonNode activity)
		{
			var body = Encoding.UTF8.GetBytes(activity.ToJsonString());
			var date = DateTimeOffset.UtcNow.ToString("r", CultureInfo.InvariantCulture);
			var digest = HttpSignatures.Digest(body);
			var context = new DefaultHttpContext();
			context.Request.Method = "POST";
			context.Request.Host = new HostString(host);
			context.Request.Path = path;
			context.Features.Get<IHttpRequestFeature>().RawTarget = path;
			context.Request.Headers["Date"] = date;
			context.Request.Headers["Digest"] = digest;
			context.Request.Headers["Content-Type"] = "application/activity+json";
			context.Request.Headers["Signature"] = Signature($"(request-target): post {path}\nhost: {host}\ndate: {date}\ndigest: {digest}", "(request-target) host date digest");
			context.Request.Body = new MemoryStream(body);
			context.Request.ContentLength = body.Length;
			return context.Request;
		}
	}
}