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[backend/core] Stricter validation of activity identifiers (ISH-233)

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Laura Hausmann 2024-03-24 19:36:47 +01:00
parent 25a50ef9eb
commit b4152b7c3d
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1 changed files with 49 additions and 16 deletions
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65
Iceshrimp.Backend/Core/Federation/ActivityPub/ActivityFetcherService.cs
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@ -1,5 +1,6 @@
using System.Net;
using System.Net.Http.Headers;
using Iceshrimp.Backend.Core.Configuration;
using Iceshrimp.Backend.Core.Database;
using Iceshrimp.Backend.Core.Database.Tables;
using Iceshrimp.Backend.Core.Extensions;
@ -8,12 +9,14 @@ using Iceshrimp.Backend.Core.Federation.ActivityStreams.Types;
using Iceshrimp.Backend.Core.Middleware;
using Iceshrimp.Backend.Core.Services;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
namespace Iceshrimp.Backend.Core.Federation.ActivityPub;
public class ActivityFetcherService(
IOptions<Config.InstanceSection> config,
HttpClient client,
HttpRequestService httpRqSvc,
SystemUserService systemUserSvc,
@ -38,52 +41,82 @@ public class ActivityFetcherService(
return await FetchRawActivityAsync(url, actor, keypair);
}
public async Task<IEnumerable<ASObject>> FetchActivityAsync(
public async Task<IEnumerable<ASObject>> FetchActivityAsync(string url, User actor, UserKeypair keypair)
{
var (activity, finalUri) = await FetchActivityInternal(url, actor, keypair);
if (activity == null) return [];
var activityUri = new Uri(activity.Id);
if (activityUri.ToString() == finalUri.ToString())
return [activity];
if (new Uri(activity.Id).Host != finalUri.Host)
throw GracefulException.UnprocessableEntity("Activity identifier doesn't match final host");
(activity, finalUri) = await FetchActivityInternal(url, actor, keypair);
if (activity == null) return [];
activityUri = new Uri(activity.Id);
if (activityUri.ToString() == finalUri.ToString())
return [activity];
throw GracefulException
.UnprocessableEntity("Activity identifier still doesn't match final URL after second fetch attempt");
}
private async Task<(ASObject? obj, Uri finalUri)> FetchActivityInternal(
string url, User actor, UserKeypair keypair, int recurse = 3
)
{
var request = httpRqSvc.GetSigned(url, AcceptableActivityTypes, actor, keypair).DisableAutoRedirects();
var response = await client.SendAsync(request);
var requestHost = new Uri(url).Host;
if (requestHost == config.Value.WebDomain || requestHost == config.Value.AccountDomain)
throw GracefulException.UnprocessableEntity("Refusing to fetch activity from local domain");
var request = httpRqSvc.GetSigned(url, AcceptableActivityTypes, actor, keypair);
var response = await client.SendAsync(request);
if (IsRedirect(response))
{
var location = response.Headers.Location;
if (location == null) throw new Exception("Redirection requested but no location header found");
if (recurse <= 0) throw new Exception("Redirection requested but recurse counter is at zero");
return await FetchActivityAsync(location.ToString(), actor, keypair, --recurse);
return await FetchActivityInternal(location.ToString(), actor, keypair, --recurse);
}
var finalUri = response.RequestMessage?.RequestUri ??
throw new Exception("RequestMessage must not be null at this stage");
if (!response.IsSuccessStatusCode)
{
if (response.StatusCode == HttpStatusCode.Gone)
throw AuthFetchException.NotFound("The remote user no longer exists.");
logger.LogDebug("Failed to fetch activity: response status was {code}", response.StatusCode);
return [];
return (null, finalUri);
}
if (!IsValidActivityContentType(response.Content.Headers.ContentType))
{
logger.LogDebug("Failed to fetch activity: content type {type} is invalid",
response.Content.Headers.ContentType);
return [];
return (null, finalUri);
}
var finalUri = response.RequestMessage?.RequestUri ??
throw new Exception("RequestMessage must not be null at this stage");
var input = await response.Content.ReadAsStringAsync();
var json = JsonConvert.DeserializeObject<JObject?>(input);
var res = LdHelpers.Expand(json) ?? throw new GracefulException("Failed to expand JSON-LD object");
var activities =
res.Select(p => p.ToObject<ASObject>(new JsonSerializer { Converters = { new ASObjectConverter() } }) ??
throw new GracefulException("Failed to deserialize activity"))
.ToList();
if (res is not [{ } token])
throw new GracefulException("Received zero or more than one activity");
if (activities.Any(p => new Uri(p.Id).Host != finalUri.Host))
throw new GracefulException("Activity identifier doesn't match final host");
var activity = token.ToObject<ASObject>(new JsonSerializer { Converters = { new ASObjectConverter() } }) ??
throw new GracefulException("Failed to deserialize activity");
return activities;
if (finalUri.Host == config.Value.WebDomain || finalUri.Host == config.Value.WebDomain)
throw GracefulException.UnprocessableEntity("Refusing to process activity from local domain");
return (activity, finalUri);
}
private static bool IsRedirect(HttpResponseMessage response)