ASP.NET OWIN OAuth:遇到的2个refresh token问题

之前写过2篇关于refresh token的生成与持久化的博文:1)Web API与OAuth:既生access token,何生refresh token;2)ASP.NET OWIN OAuth:refresh token的持久化

之后我们在CNBlogsRefreshTokenProvider中这样实现了refresh token的生成与持久化:

public class CNBlogsRefreshTokenProvider : AuthenticationTokenProvider
{
    private IRefreshTokenService _refreshTokenService;

    public CNBlogsRefreshTokenProvider(IRefreshTokenService refreshTokenService)
    {
        _refreshTokenService = refreshTokenService;
    }

    public override async Task CreateAsync(AuthenticationTokenCreateContext context)
    {
        if (string.IsNullOrEmpty(context.Ticket.Identity.Name)) return;

        var clientId = context.OwinContext.Get<string>("as:client_id");
        if (string.IsNullOrEmpty(clientId)) return;

        var refreshTokenLifeTime = context.OwinContext.Get<string>("as:clientRefreshTokenLifeTime");
        if (string.IsNullOrEmpty(refreshTokenLifeTime)) return;

        //generate access token
        RandomNumberGenerator cryptoRandomDataGenerator = new RNGCryptoServiceProvider();
        byte[] buffer = new byte[60];
        cryptoRandomDataGenerator.GetBytes(buffer);
        var refreshTokenId = Convert.ToBase64String(buffer).TrimEnd('=').Replace('+', '-').Replace('/', '_');

        var refreshToken = new RefreshToken()
        {
            Id = refreshTokenId,
            ClientId = new Guid(clientId),
            UserName = context.Ticket.Identity.Name,
            IssuedUtc = DateTime.UtcNow,
            ExpiresUtc = DateTime.UtcNow.AddSeconds(Convert.ToDouble(refreshTokenLifeTime)),
            ProtectedTicket = context.SerializeTicket(),
            IP = context.Request.GetUserIp()
        };

        context.Ticket.Properties.IssuedUtc = refreshToken.IssuedUtc;
        context.Ticket.Properties.ExpiresUtc = refreshToken.ExpiresUtc;

        if (await _refreshTokenService.Save(refreshToken))
        {
            context.SetToken(refreshTokenId);
        }
    }

    public override async Task ReceiveAsync(AuthenticationTokenReceiveContext context)
    {
        var refreshToken = await _refreshTokenService.Get(context.Token);

        if (refreshToken != null)
        {
            context.DeserializeTicket(refreshToken.ProtectedTicket);
            var result = await _refreshTokenService.Remove(context.Token);
        }
    }
}
CNBlogsRefreshTokenProvider

后来发现一个问题(这是遇到的第1个问题),在用户不登录的情况下,以client credentials grant方式获取access token时,也会生成refresh token并且保存至数据库。而refresh token是为了解决以resource owner password credentials grant方式获取access token时多次输入用户名与密码的麻烦。所以,对于client credentials grant的场景,生成refresh token完全没有必要。

于是,就得想办法避免这种refresh token生不逢时的情况。后来,找到了解决方法,很简单,只需在CreateAsync的重载方法的开头加上如下的代码:

public class CNBlogsRefreshTokenProvider : AuthenticationTokenProvider
{
    public override async Task CreateAsync(AuthenticationTokenCreateContext context)
    {
        if (string.IsNullOrEmpty(context.Ticket.Identity.Name)) return;
        //...
    }
}

遇到的第2个问题是,Client多次以resource owner password credentials grant的方式获取refresh token,会生成多个refresh token,并且会在数据库中保存多条记录。

通常情况的操作是,Client以resource owner password credentials grant的方式获取refresh token,并之将保存。需要更新access token时就用这个refresh token去更新,更新的同时会生成新的refresh token,并且将原先的refresh token删除。对应的实现代码如下:

public override async Task ReceiveAsync(AuthenticationTokenReceiveContext context)
{
    var refreshToken = await _refreshTokenService.Get(context.Token);

    if (refreshToken != null)
    {
        context.DeserializeTicket(refreshToken.ProtectedTicket);
        var result = await _refreshTokenService.Remove(context.Token);
    }
}

但是当Client多次获取多个refresh token时,只有那个用于刷新access token的refresh token会被删除,其他的refresh token会成为无人问津的垃圾留在数据库中。为了爱护环境,不乱扔垃圾,我们得解决这个问题。

解决的思路是在生成新的refresh token并将之保存至数据库之前,将对应于这个用户(resource owner)及这个client的所有refresh token删除。删除所依据的条件是ClientId与UserId,由于之前持久化refresh token时只保存了UserName,没有保存UserId,所以要给RefreshToken增加UserId属性。然后给Application层的IRefreshTokenService接口增加删除方法:

public interface IRefreshTokenService
{
    //...
    Task<bool> Remove(Guid clientId, Guid userId);
}

(该方法的实现省略)

接着在CNBlogsRefreshTokenProvider中保存refresh token之前,调用这个方法:

public class CNBlogsRefreshTokenProvider : AuthenticationTokenProvider
{
    private IRefreshTokenService _refreshTokenService;

    public override async Task CreateAsync(AuthenticationTokenCreateContext context)
    {
            var refreshToken = new RefreshToken()
        {
            //...
            UserId = (await UCenterService.GetUser(context.Ticket.Identity.Name)).UserID,
            //...
        };            

        await _refreshTokenService.Remove(refreshToken.ClientId, refreshToken.UserId);

        if (await _refreshTokenService.Save(refreshToken))
        {
            context.SetToken(refreshTokenId);
        }
    }
}

这样就解决了第2个问题。 

posted @ 2015-07-27 16:16 dudu 阅读(...) 评论(...) 编辑 收藏