Child Item

Token refreshing C#

I'm building an app in .net and accessing the app's folder for resources. So far everything is going smoothly, but i have no idea how to refresh the token in my app. I tried using the example code from OauthBasic from github, but i have a vague understanding of it and doesn't work for me. Would appreciate some help and guidance with it as i have no idea how to set it up. Thanks in advance.

Find more posts tagged with

API

Abuse

Comments

@Melisek wrote:
... So far everything is going smoothly, but i have no idea how to refresh the token in my app. ...

As far as you have set/constructed your Dropbox client object properly (as shown in all examples - including basic), you wont need to refresh any token explicitly. The client object does take care and refresh whenever need without your explicit action/instruction. 😉 That's it. Do you provide the refresh token every time new client object brings up or... not exactly? 🧐

Hope this gives direction.

As Здравко said, as long as you provide the required credentials, the Dropbox .NET SDK will handle the refresh process for you automatically. I see you've already mentioned the example of getting and using a refresh token in the OauthBasic example (non-PKCE, meant for server-side apps); there's also the OAuthPKCE example (PKCE, meant for client-side apps).

Can you elaborate on what you mean when you say it "doesn't work" for you? What have you done so far, and what specifically isn't working and how?

When i run my app, the Run task is probably stopping at some point as when i try to acces dropbox files it throws out a NullReferenceException of the DropboxClient and i have no clue on how to get the refresh token. Also the ApiKey and ApiSecret are replaced in my code.

Here is what i have inside my app so far:

public partial class RWindow : Form
    {
        //Dropbox stuff
        private const string ApiKey = "";

        private const string ApiSecret = "";

        private const string LoopbackHost = "http://127.0.0.1:52475/";

        // URL to receive OAuth 2 redirect from Dropbox server.
        // You also need to register this redirect URL on https://www.dropbox.com/developers/apps.
        private static readonly Uri RedirectUri = new Uri(LoopbackHost + "authorize");

        // URL to receive access token from JS.
        private static readonly Uri JSRedirectUri = new Uri(LoopbackHost + "token");

        static DropboxClient dbx;
        private List<string> fileNames = new List<string>();
        private string folder;


        public RWindow()
        {
            InitializeComponent();
            var task = Task.Run((Func<Task>)Run);
            task.Wait();
        }

        static async Task Run()
        {
            DropboxCertHelper.InitializeCertPinning();

            string[] scopeList = new string[3] { "files.metadata.read", "files.content.read", "account_info.read" };
            var uid = await AcquireAccessToken(scopeList, IncludeGrantedScopes.None);
            if (string.IsNullOrEmpty(uid))
            {
                return;
            }

            var httpClient = new HttpClient(new WebRequestHandler { ReadWriteTimeout = 10 * 1000 })
            {
                Timeout = TimeSpan.FromMinutes(20)
            };

            try
            {
                var config = new DropboxClientConfig("SimplePKCEOAuthApp")
                {
                    HttpClient = httpClient
                };

                dbx = new DropboxClient(Settings.Default.RefreshToken, ApiKey, config);

                await dbx.RefreshAccessToken(scopeList);
                await AcquireAccessToken(scopeList, IncludeGrantedScopes.User);

                dbx = new DropboxClient(Settings.Default.AccessToken, Settings.Default.RefreshToken, ApiKey, ApiSecret, config);
            }
            catch (HttpException e)
            {
                Debug.WriteLine("Exception reported from RPC layer");
                Debug.WriteLine("    Status code: {0}", e.StatusCode);
                Debug.WriteLine("    Message    : {0}", e.Message);
                if (e.RequestUri != null)
                {
                    Debug.WriteLine("    Request uri: {0}", e.RequestUri);
                }
            }
        }

        private static async Task HandleOAuth2Redirect(HttpListener http)
        {
            var context = await http.GetContextAsync();

            // We only care about request to RedirectUri endpoint.
            while (context.Request.Url.AbsolutePath != RedirectUri.AbsolutePath)
            {
                context = await http.GetContextAsync();
            }

            context.Response.ContentType = "text/html";

            // Respond with a page which runs JS and sends URL fragment as query string
            // to TokenRedirectUri.
            using (var file = File.OpenRead("index.html"))
            {
                file.CopyTo(context.Response.OutputStream);
            }

            context.Response.OutputStream.Close();
        }

        private static async Task<Uri> HandleJSRedirect(HttpListener http)
        {
            var context = await http.GetContextAsync();

            // We only care about request to TokenRedirectUri endpoint.
            while (context.Request.Url.AbsolutePath != JSRedirectUri.AbsolutePath)
            {
                context = await http.GetContextAsync();
            }

            var redirectUri = new Uri(context.Request.QueryString["url_with_fragment"]);

            return redirectUri;
        }

        private static async Task<string> AcquireAccessToken(string[] scopeList, IncludeGrantedScopes includeGrantedScopes)
        {
            Settings.Default.Reset();

            var accessToken = Settings.Default.AccessToken;
            var refreshToken = Settings.Default.RefreshToken;

            if (string.IsNullOrEmpty(accessToken))
            {
                try
                {
                    Debug.WriteLine("Waiting for credentials.");
                    var state = Guid.NewGuid().ToString("N");
                    var authorizeUri = DropboxOAuth2Helper.GetAuthorizeUri(OAuthResponseType.Code, ApiKey, RedirectUri, state: state, tokenAccessType: TokenAccessType.Offline, scopeList: scopeList, includeGrantedScopes: includeGrantedScopes);
                    var http = new HttpListener();
                    http.Prefixes.Add(LoopbackHost);

                    http.Start();

                    System.Diagnostics.Process.Start(authorizeUri.ToString());

                    // Handle OAuth redirect and send URL fragment to local server using JS.
                    await HandleOAuth2Redirect(http);

                    // Handle redirect from JS and process OAuth response.
                    var redirectUri = await HandleJSRedirect(http);

                    var tokenResult = await DropboxOAuth2Helper.ProcessCodeFlowAsync(redirectUri, ApiKey, ApiSecret, RedirectUri.ToString(), state);
                    accessToken = tokenResult.AccessToken;
                    refreshToken = tokenResult.RefreshToken;
                    var uid = tokenResult.Uid;
                    Debug.WriteLine("Uid: {0}", uid);
                    Debug.WriteLine("AccessToken: {0}", accessToken);
                    if (tokenResult.RefreshToken != null)
                    {
                        Debug.WriteLine("RefreshToken: {0}", refreshToken);
                        Settings.Default.RefreshToken = refreshToken;
                    }
                    if (tokenResult.ExpiresAt != null)
                    {
                        Debug.WriteLine("ExpiresAt: {0}", tokenResult.ExpiresAt);
                    }
                    if (tokenResult.ScopeList != null)
                    {
                        Debug.WriteLine("Scopes: {0}", String.Join(" ", tokenResult.ScopeList));
                    }
                    Settings.Default.AccessToken = accessToken;
                    Settings.Default.Uid = uid;
                    Settings.Default.Save();
                    http.Stop();
                    return uid;
                }
                catch (Exception e)
                {
                    Debug.WriteLine("Error: {0}", e.Message);
                    return null;
                }
            }

            return null;
        }
//Rest of my code that handles requesting and downloading files stored in the application. Works properly when using the generated short-lived token in app console.
}

Also found this error

An error occurred trying to start process 'https://www.dropbox.com/oauth2/authorize?response_type=code&client_id=XXXXXXXXXXXXXXX&redirect_uri=http%3A%2F%2F127.0.0.1%3A52475%2Fauthorize&state=a6a4da2fe0f44dfe91c14f6a0917c8ac&token_access_type=offline&scope=files.metadata.read files.content.read account_info.read' with working directory 'C:\Programming\C#\MelisekGameManager\MelisekGameManager\bin\Debug\net6.0-windows'. Can't find specified file.: Error: {0}

To clarify, are you seeing the NullReferenceException in addition to the "Can't find specified file" error, or are you no longer getting a NullReferenceException?

Either way, is that the entirety of the error/output you're getting? Please be sure to share the whole error/output and whatever details you can if not, as it's not quite clear here. For example, if your IDE shows which line something is failing on, please show that.

Anyway, it sounds like that "Can't find specified file" error is occurring when attempting to launch the authorization URL in the system browser, on the System.Diagnostics.Process.Start line, but is the authorization page actually launching in the browser or not? It's unclear why that would fail but it may depend on your particular environment. For example, it sounds similar to this issue.

That's the entirety of the error output unless this is also paired with the error output:

Exception thrown: „System.ComponentModel.Win32Exception” in System.Diagnostics.Process.dll

The nullreference shows because the dropbox client isn't getting assigned in the Run tast as it doesn't reach this point of the task. The authorization page doesn't open.

Are you certain that Windows machine, used as a DUT, has properly set default web browser? 🧐 Try set it anew or change to some other. If no luck yet, test again with a bit changed 'authorizeUri'. Add to following line:

@Melisek wrote:

...

...
                    System.Diagnostics.Process.Start(authorizeUri.ToString());

...

...a real browser name to avoid relying on system settings (possibly broken). It can come up something like:

System.Diagnostics.Process.Start("firefox", authorizeUri.ToString());

Of course, other web browser can be used (on your opinion) too!

Let see the result...🤔

@Melisek Thanks for following up. As Здравко said, please make sure the environment has a default web browser set.

Otherwise, it looks like you may be using Windows Forms, so please refer to this post for options, as it appears you may need to use something other than System.Diagnostics.Process.Start in that environment.

Yes i'm using WPF.

After giving the full path to the browser executable, it opens in the browser with the authorization site and for some reason opens two tabs passing into the URLS: http://files.content.read and http://account_info.read. But after allowing the app in the authorization site it throws this exception:

Exception thrown: „System.IO.FileNotFoundException” in System.Private.CoreLib.dll
Exception thrown: „System.IO.FileNotFoundException” in System.Private.CoreLib.dll
Could not find file 'C:\Programming\C#\MelisekGameManager\MelisekGameManager\bin\Debug\net6.0-windows\index.html'.: Error: {0}

I think it's probably because i used the OauthBasic instead of OauthPKCE.

Seems improper argument quoting. Space chars are used as a scopes separator, but the same chars are arguments separators too. Try following version:

System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(authorizeUri.ToString()) {UseShellExecute = true});

I believe, now it's gonna work. 😉

Good luck.

Replaced it and it's still the same (i added the path to the browser). Checked it on another browser just in case, and it persists on there too.

If you mean the missing file, are you certain 'C:\Programming\C#\MelisekGameManager\MelisekGameManager\bin\Debug\net6.0-windows\index.html' exists? 🤔 Take a look.

it doesn't exist there.

Ok so i created the index.html in the project and included it into the build folder, and as of now opening still opens that 2 additional tabs for no reason, after completing oauth it opens the site, but the app window doesn't open.

I set up some breakpoints to test where the code stops, and it gets stuck on the AcquireAccessToken Task.

Realized there was and index.html in the github repo so copied the code from it and now i get this exception on task.Wait:

System.AggregateException: „One or more errors occurred. (Method not found: 'Void System.Net.Http.HttpClientHandler.CheckDisposedOrStarted()'.)”

InternalException

MissingMethodException: Method not found: 'Void System.Net.Http.HttpClientHandler.CheckDisposedOrStarted()'.

After some tinkering around i finally managed to get everything working! I removed the HttpClient and some lines that were not needed/unwanted and the app is running without any problems. I got the refresh token from the returned message and everything works fine without needing to authorize in the browser. Thank you for your time helping me.

Actually i have one (probably) last question. Why does it throw out a AuthException: missing_scope/.. exception when downloading a file using dbx.Files.DownloadAsync. I'm refreshing for a new token with file.content.read permission as shown below, yet i can't download it. The result of RefreshAccessToken returns true.

I can also read file info like its name.

static async Task Run()
        {
            DropboxCertHelper.InitializeCertPinning();

            Settings.Default.RefreshToken = refreshToken;

            string[] scopeList = new string[3] { "files.metadata.read", "files.content.read", "account_info.read" };

            var config = new DropboxClientConfig("SimplePKCEOAuthApp");

            dbx = new DropboxClient(Settings.Default.AccessToken, Settings.Default.RefreshToken, ApiKey, ApiSecret, config);
            Debug.WriteLine(await dbx.RefreshAccessToken(scopeList));
        }

A 'missing_scope' error indicates that while the app is permitted to use that scope, the particular access token you're using to make the API call does not have that scope granted. Also, be aware that just adding a scope to your app via the App Console does not retroactively grant that scope to existing access tokens.

That being the case, to make any API calls that require that scope, you'll need to get a new access token/refresh token with that scope. That is, you'll need to process the app authorization flow again, starting from GetAuthorizeUri, with the necessary scope specified. Just calling RefreshAccessToken with the added scope won't grant that scope, since you can't automatically get an access token with a scope not actually authorized by the user when creating that refresh token originally.

Refer to the OAuth Guide and authorization documentation for more information.

Now i found out why two additional tabs were opening.

https://www.dropbox.com/oauth2/authorize?response_type=code&client_id=XXXXXXXX&redirect_uri=http%3A%2F%2F127.0.0.1%3A52475%2Fauthorize&state=XXXXX&token_access_type=offline&scope=files.metadata.read files.content.read account_info.read&code_challenge_method=S256&code_challenge=XXXX

The OauthFlow.GetauthorizeUri returned the url with spaces instead of + in the scopes.

@Melisek Thanks for pointing that out! I'll ask the team to fix that up.

I'm trying to replace the spaces with + but it ignores it. Can't generate a refresh token with the scopes because of that.

RedirectUri.ToString().Replace(" ", "+")

Easiest workaround would be proper quoting. 😉 (As would be on command line)

You mean as a char? If yes then i tried that too.

I mean something like:

"\"" + RedirectUri.ToString() + "\""

It works for me. 😉 In such a way the space char comes scopes separator only, but not arguments separator.

Nvm i did it in the wrong line.

I replaced the chars in the redirectUri for the token result, not where i open the browser and pass in the url.

but now i get this:

Exception thrown: „Dropbox.Api.OAuth2Exception” in Dropbox.Api.dll
Exception thrown: „Dropbox.Api.OAuth2Exception” in System.Private.CoreLib.dll
invalid_grant: Error: {0}

@Melisek An 'invalid_grant' error typically indicates an misconfiguration of the parameters for the OAuth flow, such as an incorrect authorization code, mismatched redirect URI, etc. You should be able to get a more specific error message like this:

try
{
    // ... your ProcessCodeFlowAsync call ...

}
catch (OAuth2Exception ex)
{
// ...
	Console.WriteLine(ex.ErrorDescription);
// ...
}

It prints out a redirect_uri mismatch

@Melisek That indicates that the redirect URI you're supplying when exchanging the authorization code doesn't match the one used to retrieve it originally. Make sure you're supplying the same redirectUri value to both GetAuthorizeUri and ProcessCodeFlowAsync.

I had a mismatch of variables because of letter capitalization. Now i get the refresh token, acces token, uid, expiration date and the scopes returned, yet i still get the 400 Bad request error when calling client functions.

Name all your vars properly to avoid confusion! For instance, is 'RedirectUri' really means redirect URI or ... something else? 😉

Featured Links

Tags

Child Item