Refactored endpoint to use new payment verification process

MidrandBooksApi/MidrandBooksApi.csproj

@@ -53,13 +53,13 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="LiteCharms.Features" Version="1.64.0" />
+    <PackageReference Include="LiteCharms.Features" Version="1.65.0" />
   </ItemGroup>
 
   <!-- UI -->
   <ItemGroup>
     <PackageReference Include="ANM.Blazored.Toast" Version="0.1.1" />
-    <PackageReference Include="LiteCharms.Features.MidrandBooks" Version="1.64.0" />
+    <PackageReference Include="LiteCharms.Features.MidrandBooks" Version="1.65.0" />
 
     <!-- Global Usings -->
     <Using Include="Blazored.Toast.Services" />
@@ -85,6 +85,7 @@
 
   <!-- Shared Global Usings -->
   <ItemGroup>
+    <Using Include="System.Web" />
     <Using Include="System.Diagnostics" />
     <Using Include="System.Reflection" />
     <Using Include="Microsoft.Extensions.DependencyInjection.Extensions" />

MidrandBooksApi/Payments/Endpoints/ConfirmationEndpoint.cs

@@ -1,6 +1,6 @@
-using LiteCharms.Features.Hasher;
+using LiteCharms.Features.MidrandBooks.Payments;
 using LiteCharms.Features.MidrandBooks.Payments.Events;
-using LiteCharms.Features.Models;
+using LiteCharms.Features.MidrandBooks.Payments.Models;
 using LiteCharms.Features.Quartz.Abstractions;
 
 namespace MidrandBooksApi.Payments.Endpoints;
@@ -12,32 +12,51 @@ public sealed class ConfirmationEndpoint : IEndpoint
 
     public void Map(IEndpointRouteBuilder builder)
     {
-        builder.MapPost("payments/payfast/confirm", async (HttpRequest request, HashService hashService,
+        builder.MapPost("payments/payfast/confirm", async (HttpRequest request, PayfastService payfastService,
-            IJobOrchestrator jobOrchestrator, CancellationToken cancellationToken) =>
+            IJobOrchestrator jobOrchestrator, IConfiguration configuration, IHostEnvironment hostEnvironment, CancellationToken cancellationToken) =>
         {
             using Activity? activity = PaymentActivitySource.StartActivity("ReceivePayfastWebhook", ActivityKind.Server);
+
             activity?.SetTag("messaging.system", "payfast");
             activity?.SetTag("messaging.destination.name", "payments/confirm");
 
+            string? remoteIp = request.HttpContext.Connection.RemoteIpAddress?.ToString();
+
+            var ipValidation = await payfastService.ValidateReferrerIpAsync(remoteIp!, cancellationToken);
+
+            if (ipValidation.IsFailed || !ipValidation.Value) return Results.Unauthorized();
+
             var formCollection = await request.ReadFormAsync(cancellationToken);
 
-            if (!formCollection.TryGetValue("signature", out var signatureValues) || string.IsNullOrWhiteSpace(signatureValues.ToString())) 
+            if (!formCollection.TryGetValue("signature", out var signatureValues) || string.IsNullOrWhiteSpace(signatureValues.ToString()))
                 return Results.BadRequest("Missing Payfast validation signature.");
 
-            string incomingSignature = signatureValues.ToString();
+            string incomingSignature = signatureValues.ToString().Trim();
+            var payload = ParseForm(formCollection, incomingSignature);
 
-            var payload = new PayfastWebhookPayload
+            var paramDictionary = payload.ToParamDictionary();
-            {
+            string? passphrase = configuration["HasherSettings:PayfastPassphrase"];
-                Amount = formCollection.TryGetValue("amount", out var amountValues) ? amountValues.ToString() : null,
-                ItemName = formCollection.TryGetValue("item_name", out var itemValues) ? itemValues.ToString() : null,
-                MPaymentId = formCollection.TryGetValue("m_payment_id", out var paymentIdValues) ? paymentIdValues.ToString() : null
-            };
 
-            var validationResult = hashService.VerifyPayfastWebhookSignature(payload, incomingSignature);
+            var signatureCheck = PayfastService.GenerateSignature(paramDictionary, passphrase);
 
-            if (validationResult.IsFailed || !validationResult.Value) return Results.Unauthorized();
+            if (signatureCheck.IsFailed || !string.Equals(signatureCheck.Value, incomingSignature, StringComparison.OrdinalIgnoreCase))
+                return Results.Unauthorized();
 
-            await jobOrchestrator.SendAsync(PayfastPaymentConfirmationReceivedEvent.Create(payload, payload.MPaymentId!), cancellationToken);
+            var formPairs = formCollection.Select(kvp => $"{kvp.Key}={HttpUtility.UrlEncode(kvp.Value.ToString())}");
+
+            string rawQueryParamString = string.Join("&", formPairs);
+
+            bool isSandbox = !hostEnvironment.IsProduction();
+
+            var serverConfirmation = await payfastService.ValidateServerConfirmationAsync(rawQueryParamString, isSandbox, cancellationToken);
+
+            if (serverConfirmation.IsFailed || !serverConfirmation.Value)
+                return Results.Unauthorized();
+
+            var notification = PayfastPaymentConfirmationReceivedEvent.Create(payload, payload.MerchantPaymentId!,
+                performBackgroundChecks: false); // Set to false because comprehensive checks are completed inline above
+
+            await jobOrchestrator.SendAsync(notification, cancellationToken);
 
             activity?.SetStatus(ActivityStatusCode.Ok);
 
@@ -51,4 +70,25 @@ public sealed class ConfirmationEndpoint : IEndpoint
         .Produces(StatusCodes.Status401Unauthorized)
         .WithTags(EndpointTags.Payments);
     }
-}
+
+    private static PayfastWebhookPayload ParseForm(IFormCollection formCollection, string incomingSignature) => new()
+    {
+        MerchantId = formCollection.TryGetValue("merchant_id", out var mId) ? mId.ToString() : null,
+        MerchantKey = formCollection.TryGetValue("merchant_key", out var mKey) ? mKey.ToString() : null,
+        Signature = incomingSignature,
+        MerchantPaymentId = formCollection.TryGetValue("m_payment_id", out var mPayId) ? mPayId.ToString() : null,
+        PaymentId = formCollection.TryGetValue("pf_payment_id", out var pfPayId) ? pfPayId.ToString() : null,
+        PaymentStatus = formCollection.TryGetValue("payment_status", out var status) ? status.ToString() : null,
+        ItemName = formCollection.TryGetValue("item_name", out var item) ? item.ToString() : null,
+        ItemDescription = formCollection.TryGetValue("item_description", out var desc) ? desc.ToString() : null,
+        AmountGross = formCollection.TryGetValue("amount_gross", out var gross) ? gross.ToString() : null,
+        AmountFee = formCollection.TryGetValue("amount_fee", out var fee) ? fee.ToString() : null,
+        AmountNet = formCollection.TryGetValue("amount_net", out var net) ? net.ToString() : null,
+        NameFirst = formCollection.TryGetValue("name_first", out var first) ? first.ToString() : null,
+        NameLast = formCollection.TryGetValue("name_last", out var last) ? last.ToString() : null,
+        EmailAddress = formCollection.TryGetValue("email_address", out var email) ? email.ToString() : null,
+        CustomStr1 = formCollection.TryGetValue("custom_str1", out var cStr1) ? cStr1.ToString() : null,
+        CustomInt1 = formCollection.TryGetValue("custom_int1", out var cInt1) ? cInt1.ToString() : null,
+        Token = formCollection.TryGetValue("token", out var tok) ? tok.ToString() : null
+    };
+}

MidrandBooksApi/Setup.cs

@@ -40,6 +40,8 @@ public static class Setup
 
     public static IServiceCollection AddApiServices(this IServiceCollection services, IConfiguration configuration)
     {
+        services.AddHttpClient();
+
         services.AddApiVersioning(options =>
         {
             options.DefaultApiVersion = new ApiVersion(1);

MidrandBooksApi/appsettings.json

@@ -1,4 +1,13 @@
 {
+  "ValidPayfastHosts": [
+    "www.payfast.co.za",
+    "sandbox.payfast.co.za",
+    "w1w.payfast.co.za",
+    "w2w.payfast.co.za",
+    "ips.payfast.co.za",
+    "api.payfast.co.za",
+    "payment.payfast.io"
+  ],
   "HasherSettings": {
     "MinHashLength": 11
   },

midrandbooksapi-uat.yml

@@ -19,6 +19,13 @@ data:
   BookshopS3Settings__Region: "garage"
   BookshopS3Settings__BucketName: "bookshop"
   BookshopS3Settings__CdnBaseUrl: "https://bookshop.cdn.khongisa.co.za"
+  ValidPayfastHosts__0: "www.payfast.co.za"
+  ValidPayfastHosts__1: "sandbox.payfast.co.za"
+  ValidPayfastHosts__2: "w1w.payfast.co.za"
+  ValidPayfastHosts__3: "w2w.payfast.co.za"
+  ValidPayfastHosts__4: "ips.payfast.co.za"
+  ValidPayfastHosts__5: "api.payfast.co.za"
+  ValidPayfastHosts__6: "payment.payfast.io"
 ---
 apiVersion: v1
 kind: Secret