在Unity中使用IAP插件接入iOS支付时，需要解析从插件中取得的收据信息，苹果官方文档解释该收据是按ans.1编码的。

既然是特殊格式，那就需要相应的解析方法，先找找有没有前人栽的树。

https://github.com/shoshins/apple-receipt

已经有人把*造好了，那我们就可以开工了。

以下使用dotnet3.1。

在工程中引入包。

<ItemGroup>
    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
    <PackageReference Include="Apple.Receipt.Parser" Version="2.1.0" />
    <PackageReference Include="Apple.Receipt.Models" Version="2.1.0" />
    <PackageReference Include="Apple.Receipt.Verificator" Version="2.1.0" />
</ItemGroup>

相关命名空间。

using System;
using System.Threading.Tasks;
using Apple.Receipt.Parser.Modules;
using Apple.Receipt.Parser.Services;
using Apple.Receipt.Models;
using Apple.Receipt.Verificator.Models;
using Apple.Receipt.Verificator.Models.IAPVerification;
using Apple.Receipt.Verificator.Modules;
using Apple.Receipt.Verificator.Services;
using Microsoft.Extensions.DependencyInjection;

实现两个类，一个负责解析收据，一个校验收据。

public class AppleReceiptParser : IDisposable
{
    private readonly IServiceProvider _container;

    public AppleReceiptParser()
    {
        var services = new ServiceCollection();
        services.RegisterAppleReceiptParser();
        _container = services.BuildServiceProvider();
    }

    public void Dispose()
    {
        if (_container is IDisposable disposable)
        {
            disposable.Dispose();
        }
    }

    public AppleAppReceipt TryParse(string base64Payload)
    {
        var data = Convert.FromBase64String(base64Payload);
        var parserService = _container.GetRequiredService<IAppleReceiptParserService>();
        return parserService.GetAppleReceiptFromBytes(data);
    }
}

public class AppleReceiptVerificator : IDisposable
{
    private readonly IServiceProvider _container;

    public AppleReceiptVerificator(bool sandbox)
    {
        var services = new ServiceCollection();
        services.RegisterAppleReceiptVerificator(data =>
        {
            // 订阅用参数
            // data.VerifyReceiptSharedSecret = "Your Shared Key";
            data.VerificationType = sandbox ? AppleReceiptVerificationType.Sandbox : AppleReceiptVerificationType.Production;
            data.AllowedBundleIds = new[] { "Your.App.Id", "com.mbaasy.ios.demo" };
        });

        _container = services.BuildServiceProvider();
    }

    public void Dispose()
    {
        if (_container is IDisposable disposable)
        {
            disposable.Dispose();
        }
    }

    public async Task<bool> CheckVerificator(string base64Payload)
    {
        var verificator = _container.GetRequiredService<IAppleReceiptVerificatorService>();
        var result = await verificator.VerifyAppleReceiptAsync(base64Payload).ConfigureAwait(false);

        Console.WriteLine(result.Message);

        var response = result.AppleVerificationResponse;
        if (response == null)
            return false;

        // 检查状态码
        if (response.StatusCode != IAPVerificationResponseStatus.Ok)
            return false;

        // 检查返回收据
        // result.AppleVerificationResponse.Receipt

        return true;
    }
}

最后测试。

class Program
{
    static void Main(string[] args)
    {
        const string appleAppReceipt =
            "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";

        using (var parser = new AppleReceiptParser())
        {
            var receipt = parser.TryParse(appleAppReceipt);
            Console.WriteLine($"bundle Id {receipt.BundleId}");
        }

        var task = Verify(appleAppReceipt);
        task.Wait();
    }

    static async Task Verify(string payload)
    {
        using (var verificator = new AppleReceiptVerificator(true))
        {
            await verificator.CheckVerificator(payload);
        }
    }
}

appleAppReceipt数据可以在Unity中接入IAP插件后，在真机上尝试购买获得自己App的购买收据。