From 5a13597c00864110962efda1e719c37be42facd2 Mon Sep 17 00:00:00 2001 From: thepra Date: Thu, 1 Oct 2026 11:25:48 +0200 Subject: [PATCH] Persona and group ids say which day, nothing more An ObjectId carries its creation second and a per-process counter, so two avatars made one after the other by the same login got ids a few counts apart: a link between personas that every Mastodon client would have seen. Avatar and Group now generate ids from the UTC day plus eight random bytes (still valid ObjectIds), and a remote post's id is made from its published time with a random tail, so posts page in the order they were written rather than the order they arrived. Co-Authored-By: Claude Opus 5.5 Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB --- .../Infrastructure/PrivacyIdsTests.cs | 40 +++++++++++++++++++ .../Inbox/Handlers/CreateHandler.cs | 2 + PrivaPub/Infrastructure/Ids/PrivacyIds.cs | 20 ++++++++++ PrivaPub/Models/Group/Group.cs | 4 ++ PrivaPub/Models/User/Avatar.cs | 4 ++ 5 files changed, 70 insertions(+) create mode 100644 PrivaPub.Tests/Infrastructure/PrivacyIdsTests.cs create mode 100644 PrivaPub/Infrastructure/Ids/PrivacyIds.cs diff --git a/PrivaPub.Tests/Infrastructure/PrivacyIdsTests.cs b/PrivaPub.Tests/Infrastructure/PrivacyIdsTests.cs new file mode 100644 index 0000000..70df2fe --- /dev/null +++ b/PrivaPub.Tests/Infrastructure/PrivacyIdsTests.cs @@ -0,0 +1,40 @@ +using MongoDB.Bson; + +using PrivaPub.Infrastructure.Ids; +using PrivaPub.Models.User; + +using GroupEntity = PrivaPub.Models.Group.Group; + +namespace PrivaPub.Tests.Infrastructure +{ + public class PrivacyIdsTests + { + [Fact] + public void Persona_ids_carry_only_the_day_and_share_nothing_else() + { + var first = (string)new Avatar().GenerateNewID(); + var second = (string)new Avatar().GenerateNewID(); + + Assert.True(ObjectId.TryParse(first, out var a)); + Assert.True(ObjectId.TryParse(second, out var b)); + Assert.Equal(DateTime.UtcNow.Date, a.CreationTime); + Assert.Equal(a.CreationTime, b.CreationTime); + Assert.NotEqual(first[8..14], second[8..14]); + Assert.Equal(DateTime.UtcNow.Date, ObjectId.Parse((string)new GroupEntity().GenerateNewID()).CreationTime); + } + + [Fact] + public void A_remote_post_id_sorts_by_its_published_time() + { + var older = PrivacyIds.At(new DateTime(2025, 1, 1, 0, 0, 0, DateTimeKind.Utc)); + var newer = PrivacyIds.At(new DateTime(2025, 1, 2, 0, 0, 0, DateTimeKind.Utc)); + + Assert.True(string.CompareOrdinal(older, newer) < 0); + Assert.Equal(new DateTime(2025, 1, 1, 0, 0, 0, DateTimeKind.Utc), ObjectId.Parse(older).CreationTime); + } + + [Fact] + public void A_published_time_in_the_future_is_clamped() => + Assert.True(ObjectId.Parse(PrivacyIds.At(DateTime.UtcNow.AddYears(50))).CreationTime < DateTime.UtcNow.AddDays(2)); + } +} diff --git a/PrivaPub/Federation/Inbox/Handlers/CreateHandler.cs b/PrivaPub/Federation/Inbox/Handlers/CreateHandler.cs index 9093f5b..b6b6501 100644 --- a/PrivaPub/Federation/Inbox/Handlers/CreateHandler.cs +++ b/PrivaPub/Federation/Inbox/Handlers/CreateHandler.cs @@ -5,6 +5,7 @@ using PrivaPub.Federation.Actors; using PrivaPub.Federation.Moderation; using PrivaPub.Federation.Objects; using PrivaPub.Federation.Outbox; +using PrivaPub.Infrastructure.Ids; using PrivaPub.Federation.Rendering; using PrivaPub.Models.Federation; using PrivaPub.Models.Group; @@ -113,6 +114,7 @@ namespace PrivaPub.Federation.Inbox.Handlers var post = new PostEntity { + ID = PrivacyIds.At(note.Published), ObjectURI = note.Id, ActivityURI = Id(activity), ActorURI = author.ActorURI, diff --git a/PrivaPub/Infrastructure/Ids/PrivacyIds.cs b/PrivaPub/Infrastructure/Ids/PrivacyIds.cs new file mode 100644 index 0000000..73c635f --- /dev/null +++ b/PrivaPub/Infrastructure/Ids/PrivacyIds.cs @@ -0,0 +1,20 @@ +using System.Buffers.Binary; +using System.Security.Cryptography; + +namespace PrivaPub.Infrastructure.Ids +{ + public static class PrivacyIds + { + public static string ForDay(DateTime when) => At(DateTime.SpecifyKind(when, DateTimeKind.Utc).Date); + + public static string At(DateTime when) + { + var seconds = Math.Clamp(new DateTimeOffset(DateTime.SpecifyKind(when, DateTimeKind.Utc)).ToUnixTimeSeconds(), 0, + DateTimeOffset.UtcNow.AddDays(1).ToUnixTimeSeconds()); + Span bytes = stackalloc byte[12]; + BinaryPrimitives.WriteInt32BigEndian(bytes, (int)seconds); + RandomNumberGenerator.Fill(bytes[4..]); + return Convert.ToHexStringLower(bytes); + } + } +} diff --git a/PrivaPub/Models/Group/Group.cs b/PrivaPub/Models/Group/Group.cs index c104ddf..f32194a 100644 --- a/PrivaPub/Models/Group/Group.cs +++ b/PrivaPub/Models/Group/Group.cs @@ -1,5 +1,7 @@ using MongoDB.Entities; +using PrivaPub.Infrastructure.Ids; + namespace PrivaPub.Models.Group { public class Group : Entity @@ -29,6 +31,8 @@ namespace PrivaPub.Models.Group public DateTime CreationDate { get; set; } = DateTime.UtcNow; public DateTime UpdatedAt { get; set; } = DateTime.UtcNow; public DateTime? DeletionAt { get; set; } + + public override object GenerateNewID() => PrivacyIds.ForDay(DateTime.UtcNow); } public class GroupMember diff --git a/PrivaPub/Models/User/Avatar.cs b/PrivaPub/Models/User/Avatar.cs index c924309..488c739 100644 --- a/PrivaPub/Models/User/Avatar.cs +++ b/PrivaPub/Models/User/Avatar.cs @@ -1,5 +1,7 @@ using MongoDB.Entities; +using PrivaPub.Infrastructure.Ids; + namespace PrivaPub.Models.User { public class Avatar : Entity @@ -34,6 +36,8 @@ namespace PrivaPub.Models.User public DateTime? SuspendedAt { get; set; } public DateTime? BannedAt { get; set; } public DateTime? DeletionAt { get; set; } + + public override object GenerateNewID() => PrivacyIds.ForDay(DateTime.UtcNow); } public class ForeignAvatar : Entity