Develop Reference

Consume WebAPI2 site from Android client with Google Authentication

I've been wracking my brain these past two days to try and understand how to use the authentication built into ASP.NET's WebAPI 2 using Google as an external authentication, and not being familiar with OAuth 2, I'm quite lost. I have followed this tutorial to set up the sign-in button on my Android client and send the "idToken" to the Web API. I've also followed this (now out of date) tutorial on setting up Google as an external login.
The problem happens when I try to send it I get {"error":"unsupported_grant_type"} as a response. Some other tutorials lead me to believe that the POST to mysite.com/token does not contain the correct data. This means I'm either building the request incorrectlyon the client, I'm somehow handling it incorrectly on the backend, I'm sending it to the wrong url, or I'm doing something entirely else wrong.
I found this SO answer which says to get a URL from /api/Accounts/ExternalLogins, but the sign-in button already gives me the access token that would supply to me (if I understand that correctly).
If someone could help me out here on what the exact process should be from start to finish, that would be amazing.
UPDATE: Okay, so here are some things that I've learned since I asked this question.
website.com/token URI is the redirect for the built in OAuth server in the WebAPI2 template. This is not useful for this particular problem.
The id_token is an encoded JWT token.
The website.com/signin-google URI is the redirect for normal Google login, but does not accept these tokens.
I may have to write my own AuthenticationFilter that uses the Google Client library to authorize through the Google API.
UPDATE 2: I'm still working on getting this AuthenticationFilter Implementation. Things seem to be going well at this point, but I'm getting stuck on some things. I've been using this example to get the token verification code, and this tutorial to get the AuthenticationFilter code. The result is a mix of both of them. I'll post it here as an answer once it's complete.
Here are my current problems:
Producing an IPrincipal as output. The verification example makes a ClaimPrincipal, but the AuthenticationFilter example code uses a UserManager to match the username to an existing user and returns that principal. The ClaimsPrincipal as created in the verification example directly does not auto-associate with the existing user, so I need to attempt to match some element of the claims to an existing user. So how do I do that?
I still have an incomplete idea of what a proper flow for this is. I'm currently using the Authentication header to pass my id_token string using a custom scheme: "goog_id_token". The client must send their id_token for every method called on the API with this custom AuthenticationFilter. I have no idea how this would usually be done in a professional environment. It seems like a common enough use case that there would be tons of information about it, but I haven't seen it. I have seen the normal OAuth2 flow, and since I'm only using an ID Token, and not an Access Token I'm a bit lost on what an ID Token is supposed to be used for, where it falls in a flow, and where it's supposed to live in an HTTP packet. And because I didn't know these things, I've kind of been making it up as I go along.

Wow, I did it. I figured it out. I... I can't believe it.
As metioned in my question Update 2, this code is assembled from Google's official API C# example and Microsoft's Custom AuthenticationFilter tutorial and code example. I'm going to paste the AuthorizeAsync() here and go over what each block of code does. If you think you see an issue, please feel free to mention it.
public async Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
{
bool token_valid = false;
HttpRequestMessage request = context.Request;
// 1. Look for credentials in the request
//Trace.TraceInformation(request.ToString());
string idToken = request.Headers.Authorization.Parameter.ToString();
The client adds the Authorization header field with the scheme followed by a single space, followed by the id token. It looks something like Authorization: id-token-goog IaMS0m3.Tok3nteXt.... Putting the ID token in the body as given in the google documentation made no sense in this filter so I decided to put it in the header. For some reason it was difficult to pull custom headers from the HTTP packets so I just decided to use the Authorization header with a custom scheme followed by the ID token.
// 2. If there are no credentials, do nothing.
if (idToken == null)
{
Trace.TraceInformation("No credentials.");
return;
}
// 3. If there are credentials, but the filter does not recognize
// the authentication scheme, do nothing.
if (request.Headers.Authorization.Scheme != "id-token-goog")
// Replace this with a more succinct Scheme title.
{
Trace.TraceInformation("Bad scheme.");
return;
}
This whole point of a filter is to ignore requests that the filter doesn't govern (unfamiliar auth schemes, etc), and make judgement on requests that it's supposed to govern. Allow valid authentication to pass to the downstream AuthorizeFilter or directly to the Controller.
I made up the scheme "id-token-goog" because I had no idea if there was an existing scheme for this use case. If there is, somebody please let me know and I'll fix it. I guess it doesn't particularly matter at the moment as long as my clients all know the scheme.
// 4. If there are credentials that the filter understands, try to validate them.
if (idToken != null)
{
JwtSecurityToken token = new JwtSecurityToken(idToken);
JwtSecurityTokenHandler jsth = new JwtSecurityTokenHandler();
// Configure validation
Byte[][] certBytes = getCertBytes();
Dictionary<String, X509Certificate2> certificates =
new Dictionary<String, X509Certificate2>();
for (int i = 0; i < certBytes.Length; i++)
{
X509Certificate2 certificate =
new X509Certificate2(certBytes[i]);
certificates.Add(certificate.Thumbprint, certificate);
}
{
// Set up token validation
TokenValidationParameters tvp = new TokenValidationParameters()
{
ValidateActor = false, // check the profile ID
ValidateAudience =
(CLIENT_ID != ConfigurationManager
.AppSettings["GoogClientID"]), // check the client ID
ValidAudience = CLIENT_ID,
ValidateIssuer = true, // check token came from Google
ValidIssuer = "accounts.google.com",
ValidateIssuerSigningKey = true,
RequireSignedTokens = true,
CertificateValidator = X509CertificateValidator.None,
IssuerSigningKeyResolver = (s, securityToken, identifier, parameters) =>
{
return identifier.Select(x =>
{
// TODO: Consider returning null here if you have case sensitive JWTs.
/*if (!certificates.ContainsKey(x.Id))
{
return new X509SecurityKey(certificates[x.Id]);
}*/
if (certificates.ContainsKey(x.Id.ToUpper()))
{
return new X509SecurityKey(certificates[x.Id.ToUpper()]);
}
return null;
}).First(x => x != null);
},
ValidateLifetime = true,
RequireExpirationTime = true,
ClockSkew = TimeSpan.FromHours(13)
};
This is all unchanged from the Google example. I have almost no idea what it does. This basically does some magic in creating a JWTSecurityToken, a parsed, decoded version of the token string, and sets up the validation parameters. I'm not sure why the bottom portion of this section is in it's own statement block, but it has something to do with the CLIENT_ID and that comparison. I'm not sure when or why the value of CLIENT_ID would ever change, but apparently it's necessary...
try
{
// Validate using the provider
SecurityToken validatedToken;
ClaimsPrincipal cp = jsth.ValidateToken(idToken, tvp, out validatedToken);
if (cp != null)
{
cancellationToken.ThrowIfCancellationRequested();
ApplicationUserManager um =
context
.Request
.GetOwinContext()
.GetUserManager<ApplicationUserManager>();
Get the user manager from the OWIN context. I had to dig around in context intellisense until I found GetOwinCOntext(), and then found that I had to add using Microsoft.Aspnet.Identity.Owin; in order to add the partial class that included the method GetUserManager<>().
ApplicationUser au =
await um
.FindAsync(
new UserLoginInfo(
"Google",
token.Subject)
);
This was the very last thing I had to fix. Again, I had to dig through um Intellisense to find all of the Find functions and their overrides. I had noticed from the Identity Framework-created tables in my database that there is one called UserLogin, whose rows contain a provider, a provider key, and a user FK. The FindAsync() takes a UserLoginInfo object, which contains only a provider string and a provider key. I had a hunch that these two things were now related. I had also recalled that there was a field in the token format that included a key-looking field that was a long number that started with a 1.
validatedToken seems to be basically empty, not null, but an empty SecurityToken. This is why I use token instead of validatedToken. I'm thinking there must be something wrong with this, but since the cp is not null, which is a valid check for a failed validation, it makes enough sense that the original token is valid.
// If there is no user with those credentials, return
if (au == null)
{
return;
}
ClaimsIdentity identity =
await um
.ClaimsIdentityFactory
.CreateAsync(um, au, "Google");
context.Principal = new ClaimsPrincipal(identity);
token_valid = true;
Here I have to create a new ClaimsPrincipal since the one created above in validation is empty (apparently that's correct). Took a guess on what the third parameter of CreateAsync() should be. It seems to work that way.
}
}
catch (Exception e)
{
// Multiple certificates are tested.
if (token_valid != true)
{
Trace.TraceInformation("Invalid ID Token.");
context.ErrorResult =
new AuthenticationFailureResult(
"Invalid ID Token.", request);
}
if (e.Message.IndexOf("The token is expired") > 0)
{
// TODO: Check current time in the exception for clock skew.
Trace.TraceInformation("The token is expired.");
context.ErrorResult =
new AuthenticationFailureResult(
"Token is expired.", request);
}
Trace.TraceError("Error occurred: " + e.ToString());
}
}
}
}
The rest is just exception catching.
Thanks for checking this out. Hopefully you can look at my sources and see which components came from which codebase.

HTTP request wrapper (method, headers, parameters) for HttpURLConnection?

Spoiled by Python (e.g. requests.post(url, data={'p1':'v1','p2':'v2'}, headers={'H1': 'V1'})), I am looking for an equivalent to use on Android.
My code is already run on separate Threads, so I don't need AsyncWhatever.
HttpURLConnection is recommended for Android because it is all kinds of lightweight, but the equivalent of the Python request is... large.
I see multiple partial (e.g. pre-encoded params string) solutions, and several problems to work around. Rather than risk mistakes or overlooking something writing it myself, I ask:
Is such a wrapper available already, a request(Method, String, Map<String,String>, Map<String,String>), or similar?
I expect such a solution to need little code per call, and manage all weirdness (e.g. pre-Froyo keepAlive hack) itself.

I suppose I have the right solution for you. Had the same problem (spoiled by Node.js request) and didn't like the "interface" of HttpURLConnection.
You can find a tiny library without dependencies which wrappes HttpURLConnection in a way that not so common use cases can be implemented by using the wrapped HUC. It's called DavidWebb. There is also a link to alternative libraries in case you miss something.
A typical POST request with JSON payload and JSON response with some headers would look like this:
JSONObject postObj = new JSONObject();
postObj.put("p1", "v1");
postObj.put("p2", "v2");
Webb webb = Webb.create();
Response<JSONObject> response = webb
.post("http://www.example.com/app/myresource")
.header("x-date-header", new Date())
.header("x-other-header", "some-text")
.body(postObj)
.connectTimeout(3000)
.asJsonObject();
if (response.isSuccess()) {
JSONObject outcome = response.getBody();
// ...
} else {
System.out.println(response.getStatusCode());
System.out.println(response.getResponseMessage());
System.out.println(response.getErrorBody());
}
There are many ways to set default values for the Webb instance and use or overwrite them in the Request object.
The library is well tested, especially on Android, but it has no specific code or dependencies on Android API, so you have to manage keepAlive for Froyo by yourself.

Android: Using server-side when working with Parse

Me and my friend are working on an app., and we wish to use Parse.com as our data base from which we can retrieve info.
We can't decide what is the best way to access the data on Parse. For the sake of the example, our app. (i.e. client side) needs something stored on the Parse data base (say some number) - should it directly run the query using the Parse API, or should it make a request to a server side, let it retrieve that number from Parse, and send it back to the client?
We know there's no definite answer, but we couldn't find answer regarding this specific situation. We read this post: When to use client-side or server-side?,
but this not exactly the same case.
I claim that we should try to seperate as much as possible from client side and data bases, and leave these queries run by someone who's in charge (server), where my friend claims this adds unnecessary complication, since it's very natural to use the tools supplied by Parse to access the data base from the client side, without the need for a protocol etc.
We'd appriciate any advice,
Thank you.

In general, go right ahead and make a normal call.
I'd encourage you to do that first in any case, to get everything working on both ends.
Then if necessary go to Cloud Code.
If you are going to do more than one platform (ie iOS and Android), cloud code can be a huge timesaver.
BUT don't forget that for simple calls, cloud code is a waste of time. "Normal" Parse calls are amazingly, incredibly, amazingly, fast and quick to work with.
There is absolutely nothing "wrong" with using normal Parse calls - so do that.
Regarding the question, when do you literally have to use a cloud code call -- you'll know, because you won't be able to do it with a normal call :)
Don't forget very often you can simply use "afterSave" or "beforeSave" in cloud code, to do a huge amount of work. You often don't literally need to go to a "custom call" in cloud code.
Here's a fantastic
Rule of thumb for Parse cloud code --------->
If you have to do "more than one thing" ... in that case you will likely have to make it a cloud code function. If you have to do "three or more things" then DEFINITELY make it a cloud code function.
That's a good rule of thumb.
(Again, as I say, often just an "afterSave" or similar works brilliantly...rather than literally writing a full custom call.)
Here's a typical example of a cloud call that saves 18 billion lines of code in all the platforms covered by the dotcom. First the cloud code...
Parse.Cloud.define("clientRequestHandleInvite", function(request, response)
{
// called from the client, to accept an invite from invitorPerson
var thisUserObj = request.user;
var invitorPersonId = request.params.invitorPersonId;
var theMode = request.params.theMode;
// theMode is likely "accept" or "ignore"
console.log( "clientRequestAcceptInvite called.... invitorPersonId " + invitorPersonId + " By user: " + thisUserObj.id );
console.log( "clientRequestAcceptInvite called.... theMode is " + theMode );
if ( invitorPersonId == undefined || invitorPersonId == "" )
{
response.error("Problem in clientRequestAcceptInvite, 'invitorPersonId' missing or blank?");
return;
}
var query = new Parse.Query(Parse.User);
query.get(
invitorPersonId,
{
success: function(theInvitorPersonObject)
{
console.log("clientRequestFriendRemove ... internal I got the userObj ...('no response' mode)");
if ( theMode == "accept" )
{
createOneNewHaf( thisUserObj, theInvitorPersonObject );
createOneNewHaf( theInvitorPersonObject, thisUserObj );
}
// in both cases "accept" or "ignore", delete the invite in question:
// and on top of that you have to do it both ways
deleteFromInvites( theInvitorPersonObject, thisUserObj );
deleteFromInvites( thisUserObj, theInvitorPersonObject );
// (those further functions exist in the cloud code)
// for now we'll just go with the trick of LETTING THOSE RUN
// so DO NOT this ........... response.success( "removal attempt underway" );
// it's a huge problem with Parse that (so far, 2014) is poorly handled:
// READ THIS:
// parse.com/questions/can-i-use-a-cloud-code-function-within-another-cloud-code-function
},
error: function(object,error)
{
console.log("clientRequestAcceptInvite ... internal unusual failure: " + error.code + " " + error.message);
response.error("Problem, internal problem?");
return;
}
}
);
}
);
If you are new to Parse it's incredibly hard to figure out how to call these from Android or iOS! Here's that one being called from Android ...
this will save you a day of messing about with HashMaps :)
private static void handleInvite( ParseUser invitor, final boolean accepted )
{
String invitorId = invitor.getObjectId();
// you must SEND IDs, NOT PARSEUSER OBJECTS to cloud code. Sucks!
String cloudKode;
cloudKode = (accepted? "accept" : "ignore");
HashMap<String, Object> dict = new HashMap<String, Object>();
dict.put( "invitorPersonId", invitorId );
dict.put( "theMode", cloudKode );
Toast.makeText(State.mainContext, "contacting...", Toast.LENGTH_SHORT).show();
ParseCloud.callFunctionInBackground(
"clientRequestHandleInvite",
dict,
new FunctionCallback<Object>()
{
#Override
public void done(Object s, ParseException e)
{
Toast.makeText(State.mainContext, "blah", Toast.LENGTH_SHORT).show();
// be careful with handling the exception on return...
}
});
}
And here's the same cloud call from iOS ... well for now, until you have to do it in SWIFT
-(void)tableView:(UITableView *)tableView
commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath
{
int thisRow = indexPath.row;
PFUser *delFriend = [self.theFriends objectAtIndex:thisRow];
NSLog(#"you wish to delete .. %#", [delFriend fullName] );
// note, this cloud call is happily is set and forget
// there's no return either way. life's like that sometimes
[PFCloud callFunctionInBackground:#"clientRequestFriendRemove"
withParameters:#{
#"removeThisFriendId":delFriend.objectId
}
block:^(NSString *serverResult, NSError *error)
{
if (!error)
{
NSLog(#"ok, Return (string) %#", serverResult);
}
}];
[self back]; // that simple
}
Note For the iOS/Swift experience, click to: How to make this Parse.com cloud code call? which includes comments from the Parse.com team. Hope it saves someone some typing, cheers

Facebook Graph API unlike a liked post

I have a method in my app that allows the user to "like" a post in his/her news feed. It's done with a simple graph request using HttpMethod.POST. But when I try to do an "unlike" action using HttpMethod.DELETE, I get an error callback:
02-08 00:35:57.298: I/Detail(2628): {Response: responseCode: 403, graphObject: null, error:
{HttpStatus: 403, errorCode: 200, errorType: OAuthException, errorMessage: (#200)
Feed story publishing to other users is disabled for this application}, isFromCache:false}
Now I assume this has something to do with the latest attempt to make all apps that integrate with Facebook use all Facebook looking dialogs and styles, but I could be wrong. Here's the roadmap post that has me suspicious:
Removing ability to post to friends walls via Graph API We will
remove the ability to post to a user's friends' walls via the Graph
API. Specifically, posts against [user_id]/feed where [user_id] is
different from the session user, or stream.publish calls where the
target_id user is different from the session user, will fail. If you
want to allow people to post to their friends' timelines, invoke the
feed dialog. Stories that include friends via user mentions tagging or
action tagging will show up on the friend’s timeline (assuming the
friend approves the tag). For more info, see this blog post.
Any ideas on what I could be doing wrong, or is Facebook just ruining me? Thanks!
EDIT: Here's the code I'm using to run the request.
Request likeRequest = new Request(Utility.fbSession, null, null, null, new Request.Callback() {
#Override
public void onCompleted(Response response) {
String responseString = response.toString();
Log.i("Detail", responseString);
updateDetail();
}
});
HttpMethod nextLikeCall = HttpMethod.DELETE;
likeRequest.setHttpMethod(nextLikeCall);
likeRequest.setGraphPath(itemId+"/likes");
likeRequest.executeAsync();

When you grab the post id from the graph data, it should be in a format like: XXXXX_YYYYY. The XXXXX is simply the users id and YYYYY is the actual post id. What you need to do is extract and use just the YYYYY portion of the post id that graph gives you. so instead of graph.facebook.com/XXXXX_YYYYY/likes.... you want to send graph.facebook.com/YYYYY/likes. This will work with both liking and unliking, you can test in graph explorer first before hacking together a substring extraction method.
Not sure how to extract a section of a string on Android, but I know in Objective-C/iOS, it can be done like this (code not tested, for reference/idea) :
SString *actualPostIdStr; //The String we will put the actual postId in
NSString *oldIdStr = //<the string in format XXXXX_YYYYY>
NSInteger charCount = [oldIdStr length]; //get the length of the original XXXXX_YYYYY string
NSRange fRangeCount = [oldIdStr rangeOfString:#"_"]; //get count of characters to remove (XXXXXX)
if (fRangeCount.location != NSNotFound){
NSInteger startingPos = fRangeCount.location + 1; //get the starting character position of the actual postId
actualPostIdStr = [[oldIdStr substringWithRange:NSMakeRange(startingPos, charCount - startingPos)] copy];
}
Hope this helps.
EDIT:
Ok, so I have been playing around with likes all day... It seems that this method sometimes doesn't work, but it all depends on the type of graph object which you are attempting to like/unlike. For example... plain status posts, this method works perfectly. However, I ran into a problem when trying to like a photo with a message/story post object. It turns out, in the graph data for this type of post object with photo, there is an additional paramter called "object_id", in addition to the plain "id" that is in status post graph data. in this case, with the photo and story post, you need to pass the "object_id", unaltered for successful unliking.
This mess seems like either a bug on FB's end, or they are making changes and disallowing likes/unlikes from graph api & just forgot/haven't to told us yet :) hopefully the former. In the mean time, you're just going to have to use my above answer, but just make sure you test with as many different types of post objects you can find, and use if conditions when a different id (portion of "id"... "object_id"... etc) is required.

Sometimes Daniel McCarthy's method don't work. In this case we need get Graph API request XXX_YYYY, find field object_id and unlike this object_id fid.

Propper way to handle dumping and reloading of JSON data containing special characters on android?

Not sure if this has been answered already but a quick search didn't turn up a satisfying result..
I'm stuck with the following scenario:
web service with REST API and JSON formatted data blobs
android client app talking to this service and locally caching / processing the data
The we service is run by a German company so some of the strings in the result data contain special characters like German umlauts:
// example resonse
[
{
"title" : "reward 1",
"description" : "Ein gro\u00dfer Kaffee f\u00fcr dich!"
},
{
"title" : "reward 2",
"description" : "Eine Pizza f\u00fcr dich!"
},
...
]
Locally the app is parsing the data using a set of classes which mirror the response objects (e.g. Reward and RewardResponse classes for the upper example). Each of these classes can read and dump itself from / to JSON - however this is where things get ugly.
Taking the example above org.json will correctly parse the data and the resulting strings will contain proper Unicode versions of the special characters 'ß' (\u00df) and 'ü' (\u00fc).
final RewardResponse response = new RewardResponse(jsonData);
final Reward reward = response.get(0);
// this will print "Ein großer Kaffee für dich!"
Log.d("dump server data", reward.getDescription());
final Reward reward2 = new Reward(reward.toJSON());
// this will print "Ein gro�er Kaffee f�r dich!"
Log.d("dump reloaded data", reward2.getDescription());
As you can see there is a problem with loading the data generated by JSONObject.toString().
Mainly whats happening is that JSONObject will parse escapes in the form of "\uXXXX" but it will dump them as plain UTF-8 text.
In turn, when parsing it won't properly read the unicode and instead insert a replacement character in the result string (� above \uffff as code point).
My current workaround consists of a look-up table containing the Unicode Latin1 supplement characters and their respective escaped versions (\u00a0 up to \u00ff). But this also means I have to go over each and every dumped JSON text and replace the characters with their escaped versions each time I dump something.
Please tell me there is a better way for this!
(Note: there is this question however he had problems with local file encoding on disk.
My problem above, as you can see, is reproducible without ever writing to disk)
EDIT: As requested in the comments here's the toJSON() method:
public final String toJSON() {
JSONObject obj = new JSONObject();
// mTitle and mDescription contain the unmodified
// strings received from parsing.
obj.put("title", mTitle);
obj.put("description", mDescription);
return obj.toString();
}
As a side note it makes no difference if I use JSONObject.toString() or a JSONStringer.
(The documentation advises to use .toString())
EDIT: just to remove Reward from the equation, this reproduces the problem:
final JSONObject inputData = new JSONObject("{\"description\":\"Ein gro\\u00dfer Kaffee\"}");
final JSONObject parsedData = new JSONObject(inputData.toString());
Log.d("inputData", inputData.getString("description"));
Log.d("parsedData", parsedData.getString("description"));

[Note: posted as an answer for better formatting]
I just tried the example
final JSONObject inputData = new JSONObject("{\"description\":\"Ein gro\\u00dfer Kaffee\"}");
final JSONObject parsedData = new JSONObject(inputData.toString());
Log.d("inputData", inputData.getString("description"));
Log.d("parsedData", parsedData.getString("description"));
on my Nexus 7 running Android 4.2.1, and on Nexus S running 4.1.2, and it works as intended:
D/inputData(17281): Ein großer Kaffee
D/parsedData(17281): Ein großer Kaffee
In which Android version did you see the problem?