Custom Authentication

By default, all applications allow anonymous users to connect and do not have any authentication mechanism.
Photon provides the option to implement custom authentication for Photon applications.

Custom Authentication with Photon is flexible.
It supports well known third-party authentication providers as well as fully personalized solutions for that matter.

We provide sample implementations of authentication providers via a Git repository.
Feel free to fork the repository and send us your pull requests.
You find the sources on GitHub.

Authentication Flow

The following steps describe the general flow of the authentication process.

1. Your client passes info about which authentication provider to use and the necessary authentication data to the Photon server with Connect().
2. The Photon server gets the desired authentication provider for your application and takes one of these steps
   • The authentication provider configuration is found -> the authentication proceeds with step 3.
   • The authentication provider configuration is not found -> the client will be either allowed to connect or rejected, depending on a setting of your application
3. The Photon server calls the authentication provider with the authentication info passed with Connect().
   • The authentication provider is online -> the authentication proceeds with step 4.
   • The authentication provider is offline -> the client will be either allowed to connect or rejected, depending on the corresponding provider setting.
4. The authentication provider processes the authentication information and returns the result to the Photon Server
5. Depending on the authentication result, the client will be either successfully authenticated or rejected

Implementation

Client Side

On the client side, the API will handle custom authentication - you only set the relevant parameters and the target custom authentication service once.
Once setup, connect and handle eventual errors.

Example:

Server Side

Once the web server receives the authentication request, the query parameters should be checked and validated.
As an example, credentials could be compared to existing ones stored in a database.

If the received parameters are missing or are invalid the returned results should be { "ResultCode": 3, "Message": "Invalid parameters." }

After finishing the validation the outcome should be returned as follow:

• Success: { "ResultCode": 1, "UserId": <userId> }
• Failure: { "ResultCode": 2, "Message": "Authentication failed. Wrong credentials." }

Advanced Features

Other than authenticating users, extra information can be returned from the authentication provider.
In order to do so, the user should establish some kind of protocol between client and the web service who plays the role of the "authenticator".

Sending Data to Server

The easiest and simplest thing to do is an "all or nothing" strategy:
choose whether or not to return a static number of variables to the client.
But some use cases require a more complex approach where the web service returns data "on-demand" based on what the client has requested.
This subsection explains how the client can send data to the web service.
The data can be the credentials necessary for authentication plus any extra parameters.
The extra parameters are what could be used, among other things, to request piece of data available from server side to be returned within the authentication response.
This is pretty useful as it saves extra API calls and simplifies the login workflow.

In some rare cases, authentication may require a lot of data.
On the other hand, most web servers have a limit for the number of characters used in the query string or a threshold for the length of the URL.
That is why Photon offers the possibility of changing the HTTP method to POST from the client, in C# SDKs, this is done by explicitly setting the AuthenticationValues.AuthPostData field to a value.
The latter can be of type string or byte[] or Dictionary<string, object>.
In case of Dictionary<string, object>, the payload will be converted to a JSON string and the HTTP request's Content-Type will be set to "applicaton/json".
In C# SDKs, the AuthenticationValues class offers setters methods for each supported type.

Since this could be a requirement or a constraint, the POST method option is also available for anyone who opts for receiving authentication requests as POST method from web service.

In other words, to send authentication parameters you are free to use query string or POST data or both.
The following table gives the possible combinations.

AuthPostData	AuthGetParameters	HTTP method
null	*	GET
empty string	*	GET
string (not null, not empty)	*	POST
byte[] (not null, can be empty)	*	POST
Dictionary<string, object> (not null, can be empty)	*	POST (Content-Type="application/json")

Returning Data to Client

Since Photon server is a proxy between the client and the web service, you should take note of the variables that could be handled by Photon servers.

Like all HTTP incoming responses received by Photon server, the web server should return a JSON object that includes a ResultCode and an optional Message.
Additionally, here is a list of what Photon servers can expect from the web service during authentication.

• UserId:
  this could be used as a parameter of the authentication itself or it could be requested from client side.
  This is always forwarded to the client when received by Photon servers.
  Otherwise, if AuthenticationValues.UserId was not initially set a randomly generated UserId will be sent back to client.
  This will override the value of UserId in client and cannot be changed after that.
  This should be returned only in case of ResultCode value 1.
  Example: { "ResultCode": 1, "UserId": "SomeUniqueStringId" }
• Data: JSON object that contains any extra values that should be returned to the client.
  Keep in mind that nested arrays or objects are not supported.
  This should be returned only in case of ResultCode values 0 or 1.
  Example: { "ResultCode": 0, "Data": { "S": "Vpqmazljnbr=", "A": [ 1, -5, 9 ] } }

The ResultCode is the only required return variable, anything else is optional.
The following table summarizes what could be returned by the web server.

*: This may be useful for implementing OAuth 2.0 for instance or two-step verification.

Reading Data from Client

Here is a code snippet of how to get the returned values from the response:

Data Types Conversion

In this section, only the type of data exchanged between Photon server and the web service is explained.
For more information about data types between clients and Photon servers please refer to serialization in Photon page.

Photon Server -> Web Service

C# / .NET (Photon supported types)	JavaScript / JSON
byte	number
short
int
long
double
bool	bool
string	string
byte[] (byte array length < short.MaxValue)	string (Base64 encoded)
T[] (array of supported type T, length < short.MaxValue)	array
Hashtable (of supported types, count < short.MaxValue, preferably Photon implementation)	object
Dictionary (keys and values of supported types, count < short.MaxValue)	object
null	null

Sample request data (types are concatenated)

As sent from Photon Server:

JSON

{
    "(Dictionary<String,Object>)Dictionary":{
        "(Int32)dk_int":"1",
        "(String)dk_str":"dv2",
        "(Boolean)dk_bool":"True"
    },
    "(Hashtable)Hashtable":{
        "(Byte)hk_byte":"255",
        "(Object[])hk_array":[
            "(Int32)0",
            "(String)xy",
            "(Boolean)False"
        ],
        "hk_null":"null"
    },
    "null":"null",
    "(String[])string[]":[
        "PUN",
        "TB",
        "RT",
        "Bolt",
        "Chat"
    ],
    "(Byte[])byte[]":[
        "255",
        "0"
    ],
    "(Int16[])short[]":[
        "-32768",
        "32767"
    ],
    "(Int32[])int[]":[
        "-2147483648",
        "2147483647"
    ],
    "(Int64[])long[]":[
        "-9223372036854775808",
        "9223372036854775807"
    ],
    "(Single[])float[]":[
        "-3.402823E+38",
        "3.402823E+38"
    ],
    "(Double[])double[]":[
        "-1.79769313486232E+308",
        "1.79769313486232E+308"
    ],
    "(Boolean[])bool[]":[
        "True",
        "False"
    ]
}

As read by Web Service:

JSON

{
    "(object)Dictionary":{
        "dk_int":"(number)1",
        "dk_str":"(string)dv2",
        "dk_bool":"(boolean)true"
    },
    "(object)Hashtable":{
        "(number)hk_byte":"255",
        "(array)hk_array":[
            "(number)0",
            "(string)xy",
            "(boolean)false"
        ],
        "hk_null":null
    },
    "null":null,
    "(array)string[]":[
        "(string)PUN",
        "(string)TB",
        "(string)RT",
        "(string)Bolt",
        "(string)Chat"
    ],
    "byte[]":"(string)/wA=",
    "(array)short[]":[
        "(number)-32768",
        "(number)32767"
    ],
    "(array)int[]":[
        "(number)-2147483648",
        "(number)2147483647"
    ],
    "(array)long[]":[
        "(number)-9223372036854776000",
        "(number)9223372036854776000"
    ],
    "(array)float[]":[
        "(number)-3.40282347e+38",
        "(number)3.40282347e+38"
    ],
    "(array)double[]":[
        "(number)-1.7976931348623157e+308",
        "(number)1.7976931348623157e+308"
    ],
    "(array)bool[]":[
        "(boolean)true",
        "(boolean)false"
    ]
}

Web Service -> Photon Server

Here is a table that matches each JavaScript/JSON type to its equivalent one in C#/.Net :

JavaScript / JSON	C# / .Net
object	Dictionary
array	object[] (array of objects)
number (integral)	long
number (floating)	double
string	string
boolean	bool
null (not a type)	null
undefined (when sent)	null

Sample response data (types are concatenated)

As sent from Web Service:

JSON

{
    "(object)number": {
        "(number)MAX_VALUE": "1.7976931348623157e+308",
        "(number)MIN_VALUE": "5e-324"
    },
    "(object)object": {
        "(string)string": "xyz",
        "null": null,
        "(boolean)bool": "false",
        "(undefined)undefined": "undefined",
        "(number)float": "-3.14",
        "(number)integer": "123456"
    },
    "(array)array": [
        "(string)xyz",
        "(number)0",
        "(boolean)true",
        null,
        "(undefined)undefined"
    ]
}

As read from Photon Server:

JSON

{
    "(Dictionary<String,Object>)number":{
        "(Double)MAX_VALUE":"1.79769313486232E+308",
        "(Double)MIN_VALUE":"4.94065645841247E-324"
    },
    "(Dictionary<String,Object>)object":{
        "(String)string":"xyz",
        "null":"null",
        "(Boolean)bool":"False",
        "(Double)float":"-3.14",
        "(Int64)integer":"123456"
    },
    "(Object[])array":[ 
        "(String)xyz",
        "(Int64)0",
        "(Boolean)True",
        "null",
        "null"
    ]
}

Troubleshooting

In case the authentication URL you configured in your dashboard returns some HTTP error, the Photon server pauses the authentication calls for a short time to avoid some overhead.
Take this "backoff" time into consideration when configuring or testing your URLs.

Best Practices

• The returned result from the authentication provider should contain a readable Message especially in case of failure.
  This will save you a lot of debugging pain.
• From dashboard, set static key/value pairs that should not be set from client side.
  This will prevent duplicate keys in the resulting query string.
• For security reasons, do not send plain text passwords as authentication parameter.
• It is recommended to set query string parameters from Photon dashboard.
  That way you can check the origin of the request.
• Make use of the AuthenticationValues methods to set parameters and do not affect a value directly to AuthGetParameters.
  This will prevent malformed query string.

Use Case Example: Block Old Client Versions

You can use custom authentication to refuse connections incoming from clients using old versions (or unexpected versions) and return a specific error so you can ask the user to update.
To do this you need to send the version in the custom authentication request. It is up to you to decide if you want to do it as query string parameter or a POST data argument.
In the example below we will use query string parameter:

If your custom authentication URL is https://example.com then the request will be sent as https://example.com?version={version}.
From your authentication provider implementation you should get and compare the version received.
If the version is allowed return { "ResultCode": 1 }.
If not you should return a ResultCode with a custom value of your choice (different than 1), preferably with a message.
Example: { "ResultCode": 5, "Message": "Version not allowed." }.

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