feat: rate limit emails to two per address per hour

Foxnouns.Backend/Database/DatabaseContext.cs

@@ -66,6 +66,7 @@ public class DatabaseContext(DbContextOptions options) : DbContext(options)
     public DbSet<Application> Applications { get; init; } = null!;
     public DbSet<TemporaryKey> TemporaryKeys { get; init; } = null!;
     public DbSet<DataExport> DataExports { get; init; } = null!;
+    public DbSet<SentEmail> SentEmails { get; init; } = null!;
 
     public DbSet<PrideFlag> PrideFlags { get; init; } = null!;
     public DbSet<UserFlag> UserFlags { get; init; } = null!;
@@ -84,6 +85,10 @@ public class DatabaseContext(DbContextOptions options) : DbContext(options)
         modelBuilder.Entity<Member>().HasIndex(m => new { m.UserId, m.Name }).IsUnique();
         modelBuilder.Entity<Member>().HasIndex(m => m.Sid).IsUnique();
         modelBuilder.Entity<TemporaryKey>().HasIndex(k => k.Key).IsUnique();
+        modelBuilder.Entity<DataExport>().HasIndex(d => d.Filename).IsUnique();
+        modelBuilder.Entity<SentEmail>().HasIndex(e => new { e.Email, e.SentAt });
+
+        // Two indexes on auth_methods, one for fediverse auth and one for all other types.
         modelBuilder
             .Entity<AuthMethod>()
             .HasIndex(m => new
@@ -94,7 +99,6 @@ public class DatabaseContext(DbContextOptions options) : DbContext(options)
             })
             .HasFilter("fediverse_application_id IS NOT NULL")
             .IsUnique();
-        modelBuilder.Entity<DataExport>().HasIndex(d => d.Filename).IsUnique();
 
         modelBuilder
             .Entity<AuthMethod>()

Foxnouns.Backend/Database/Migrations/20241211193653_AddSentEmailCache.cs

@@ -0,0 +1,53 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using NodaTime;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Foxnouns.Backend.Database.Migrations
+{
+    /// <inheritdoc />
+    [DbContext(typeof(DatabaseContext))]
+    [Migration("20241211193653_AddSentEmailCache")]
+    public partial class AddSentEmailCache : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "sent_emails",
+                columns: table => new
+                {
+                    id = table
+                        .Column<int>(type: "integer", nullable: false)
+                        .Annotation(
+                            "Npgsql:ValueGenerationStrategy",
+                            NpgsqlValueGenerationStrategy.IdentityByDefaultColumn
+                        ),
+                    email = table.Column<string>(type: "text", nullable: false),
+                    sent_at = table.Column<Instant>(
+                        type: "timestamp with time zone",
+                        nullable: false
+                    ),
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("pk_sent_emails", x => x.id);
+                }
+            );
+
+            migrationBuilder.CreateIndex(
+                name: "ix_sent_emails_email_sent_at",
+                table: "sent_emails",
+                columns: new[] { "email", "sent_at" }
+            );
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(name: "sent_emails");
+        }
+    }
+}

Foxnouns.Backend/Database/Migrations/DatabaseContextModelSnapshot.cs

@@ -1,5 +1,4 @@
 // <auto-generated />
-using System;
 using System.Collections.Generic;
 using Foxnouns.Backend.Database;
 using Foxnouns.Backend.Database.Models;
@@ -20,7 +19,7 @@ namespace Foxnouns.Backend.Database.Migrations
         {
 #pragma warning disable 612, 618
             modelBuilder
-                .HasAnnotation("ProductVersion", "8.0.7")
+                .HasAnnotation("ProductVersion", "9.0.0")
                 .HasAnnotation("Relational:MaxIdentifierLength", 63);
 
             NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
@@ -46,12 +45,12 @@ namespace Foxnouns.Backend.Database.Migrations
                         .HasColumnType("text")
                         .HasColumnName("name");
 
-                    b.Property<string[]>("RedirectUris")
+                    b.PrimitiveCollection<string[]>("RedirectUris")
                         .IsRequired()
                         .HasColumnType("text[]")
                         .HasColumnName("redirect_uris");
 
-                    b.Property<string[]>("Scopes")
+                    b.PrimitiveCollection<string[]>("Scopes")
                         .IsRequired()
                         .HasColumnType("text[]")
                         .HasColumnName("scopes");
@@ -193,7 +192,7 @@ namespace Foxnouns.Backend.Database.Migrations
                         .HasColumnType("jsonb")
                         .HasColumnName("fields");
 
-                    b.Property<string[]>("Links")
+                    b.PrimitiveCollection<string[]>("Links")
                         .IsRequired()
                         .HasColumnType("text[]")
                         .HasColumnName("links");
@@ -303,6 +302,33 @@ namespace Foxnouns.Backend.Database.Migrations
                     b.ToTable("pride_flags", (string)null);
                 });
 
+            modelBuilder.Entity("Foxnouns.Backend.Database.Models.SentEmail", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("email");
+
+                    b.Property<Instant>("SentAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("sent_at");
+
+                    b.HasKey("Id")
+                        .HasName("pk_sent_emails");
+
+                    b.HasIndex("Email", "SentAt")
+                        .HasDatabaseName("ix_sent_emails_email_sent_at");
+
+                    b.ToTable("sent_emails", (string)null);
+                });
+
             modelBuilder.Entity("Foxnouns.Backend.Database.Models.TemporaryKey", b =>
                 {
                     b.Property<long>("Id")
@@ -359,7 +385,7 @@ namespace Foxnouns.Backend.Database.Migrations
                         .HasColumnType("boolean")
                         .HasColumnName("manually_expired");
 
-                    b.Property<string[]>("Scopes")
+                    b.PrimitiveCollection<string[]>("Scopes")
                         .IsRequired()
                         .HasColumnType("text[]")
                         .HasColumnName("scopes");
@@ -428,7 +454,7 @@ namespace Foxnouns.Backend.Database.Migrations
                         .HasColumnType("timestamp with time zone")
                         .HasColumnName("last_sid_reroll");
 
-                    b.Property<string[]>("Links")
+                    b.PrimitiveCollection<string[]>("Links")
                         .IsRequired()
                         .HasColumnType("text[]")
                         .HasColumnName("links");

Foxnouns.Backend/Database/Models/SentEmail.cs

@@ -0,0 +1,13 @@
+using System.ComponentModel.DataAnnotations.Schema;
+using NodaTime;
+
+namespace Foxnouns.Backend.Database.Models;
+
+public class SentEmail
+{
+    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+    public int Id { get; init; }
+
+    public required string Email { get; init; }
+    public required Instant SentAt { get; init; }
+}

Foxnouns.Backend/Services/DataCleanupService.cs

@@ -33,13 +33,24 @@ public class DataCleanupService(
 
     public async Task InvokeAsync(CancellationToken ct = default)
     {
-        _logger.Information("Cleaning up expired users");
+        _logger.Debug("Cleaning up sent email cache");
+        await CleanEmailsAsync(ct);
+
+        _logger.Debug("Cleaning up expired users");
         await CleanUsersAsync(ct);
 
-        _logger.Information("Cleaning up expired data exports");
+        _logger.Debug("Cleaning up expired data exports");
         await CleanExportsAsync(ct);
     }
 
+    private async Task CleanEmailsAsync(CancellationToken ct = default)
+    {
+        Instant expiry = clock.GetCurrentInstant() - Duration.FromHours(2);
+        int count = await db.SentEmails.Where(e => e.SentAt < expiry).ExecuteDeleteAsync(ct);
+        if (count != 0)
+            _logger.Information("Deleted {Count} entries from the sent email cache", expiry);
+    }
+
     private async Task CleanUsersAsync(CancellationToken ct = default)
     {
         Instant selfDeleteExpires = clock.GetCurrentInstant() - User.DeleteAfter;

Foxnouns.Backend/Services/MailService.cs

@@ -12,13 +12,25 @@
 //
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
+using Coravel.Mailer.Mail;
 using Coravel.Mailer.Mail.Interfaces;
 using Coravel.Queuing.Interfaces;
+using Foxnouns.Backend.Database;
+using Foxnouns.Backend.Database.Models;
 using Foxnouns.Backend.Mailables;
+using Microsoft.EntityFrameworkCore;
+using NodaTime;
 
 namespace Foxnouns.Backend.Services;
 
-public class MailService(ILogger logger, IMailer mailer, IQueue queue, Config config)
+public class MailService(
+    ILogger logger,
+    IMailer mailer,
+    IQueue queue,
+    IClock clock,
+    Config config,
+    IServiceProvider serviceProvider
+)
 {
     private readonly ILogger _logger = logger.ForContext<MailService>();
 
@@ -26,10 +38,8 @@ public class MailService(ILogger logger, IMailer mailer, IQueue queue, Config co
     {
         queue.QueueAsyncTask(async () =>
         {
-            _logger.Debug("Sending account creation email to {ToEmail}", to);
+            await SendEmailAsync(
-            try
+                to,
-            {
-                await mailer.SendAsync(
                 new AccountCreationMailable(
                     config,
                     new AccountCreationMailableView
@@ -40,11 +50,6 @@ public class MailService(ILogger logger, IMailer mailer, IQueue queue, Config co
                     }
                 )
             );
-            }
-            catch (Exception exc)
-            {
-                _logger.Error(exc, "Sending account creation email");
-            }
         });
     }
 
@@ -53,9 +58,8 @@ public class MailService(ILogger logger, IMailer mailer, IQueue queue, Config co
         _logger.Debug("Sending add email address email to {ToEmail}", to);
         queue.QueueAsyncTask(async () =>
         {
-            try
+            await SendEmailAsync(
-            {
+                to,
-                await mailer.SendAsync(
                 new AddEmailMailable(
                     config,
                     new AddEmailMailableView
@@ -67,11 +71,40 @@ public class MailService(ILogger logger, IMailer mailer, IQueue queue, Config co
                     }
                 )
             );
+        });
+    }
+
+    private async Task SendEmailAsync<T>(string to, Mailable<T> mailable)
+    {
+        try
+        {
+            // ReSharper disable SuggestVarOrType_SimpleTypes
+            await using var scope = serviceProvider.CreateAsyncScope();
+            await using var db = scope.ServiceProvider.GetRequiredService<DatabaseContext>();
+            // ReSharper restore SuggestVarOrType_SimpleTypes
+
+            Instant now = clock.GetCurrentInstant();
+
+            int count = await db.SentEmails.CountAsync(e =>
+                e.Email == to && e.SentAt > (now - Duration.FromHours(1))
+            );
+            if (count >= 2)
+            {
+                _logger.Information(
+                    "Have already sent 2 or more emails to {ToAddress} in the past hour, not sending new email",
+                    to
+                );
+                return;
+            }
+
+            await mailer.SendAsync(mailable);
+
+            db.SentEmails.Add(new SentEmail { Email = to, SentAt = now });
+            await db.SaveChangesAsync();
         }
         catch (Exception exc)
         {
-                _logger.Error(exc, "Sending add email address email");
+            _logger.Error(exc, "Sending email");
         }
-        });
     }
 }