Creating a Backend Custom Authorizer

Constraints

FunctionGraph is required for custom authorizers. If FunctionGraph is unavailable in the selected region, custom authorizers are not supported.

Creating a Function for Backend Custom Authentication

1. Log in to the FunctionGraph console.
2. In the navigation pane on the left, choose Functions > Function List.
3. Click Create Function and create a function based on the following table.

   Table 1 Configuring the function

   Parameter	Description
   Create With	Select Create from scratch.
   Function Type	Type of the function. Default: Event function.
   Region	Select the same region as that of APIG.
   Project	Projects group and isolate resources (including compute, storage, and network resources) across physical regions. A default project is provided for each Huawei Cloud region, and subprojects can be created under each default project. Users can be granted permissions to access all resources in a specific project. The selected region is used by default.
   Function Name	Set this name as planned. Using naming rules facilitates future search.
   Enterprise Project	Enterprise projects group and manage resources across regions. Resources in enterprise projects are logically isolated. default is selected by default.
   Agency	An agency that delegates FunctionGraph to access other cloud services. For this example, select Use no agency.
   Runtime	Python 2.7 is used as an example.

4. Click Create Function.
5. After the function is created, go to the function details page.

   The function code must meet the following requirements:

   • The custom user data contained in the function code must be in the following format: event["user_data"].
   • The custom user data corresponds to the user data defined for the custom authorizer. You can define the user data in any format.
   • The response of the function cannot be greater than 1 MB and must be displayed in the following format:

     {
         "statusCode":200,
         "body": "{\"status\": \"allow\", \"context\": {\"user\": \"abc\"}}"
     }

     The body field is a character string, which is JSON-decoded as follows:

     {
     	"status": "allow/deny",
     	"context": {
     		"user": "abc"
     	}
     }

     • The statusCode field is mandatory. If FunctionGraph is running properly and the code of the function complies with specifications, the value of statusCode is the response code of the function.
       • If response code is not 200, APIG considers that the function is abnormal and returns error code 500 and error information Internal server error.
       • When the relaxed mode of the custom authorizer is turned on and the function fails to connect or returns a 500 or 503 code, the authorizer does not check the status field in the body field. Instead, it will immediately return a message indicating that the API was successfully invoked. And the context field obtained from the function code will be empty.
     • The status field is mandatory and is used to identify the authentication result. The authentication result can only be allow or deny. allow indicates that the authentication is successful, and deny indicates that the authentication fails.
     • The context field is optional. It can be key-value pairs, but the key value cannot be a JSON object or an array. If the gateway supports the authorizer_context_support_num_bool feature, the key value can be a number or a Boolean value.

       The context field contains custom user data. After successful authentication, the user data is mapped to the backend parameters. The parameter name in context is case-sensitive and must be the same as the system parameter name. The parameter name in context must start with a letter and contain 1 to 32 characters, including uppercase letters, lowercase letters, digits, underscores (_), and hyphens (-).

       After successful backend authentication, the value abc of user in context is mapped to the test parameter in the Header location of backend requests and passed to the backend service.

   Example user data:

   # -*- coding:utf-8 -*-
   import json
   import base64
   def handler(event, context):
       exampleuserdata=base64.b64encode(event["user_data"])
       resp = {
           'statusCode': 200,
           'body': json.dumps({
               "status":"allow",
               "context":{
                   "user":exampleuserdata
               }
           })   
       }
       return json.dumps(resp)

6. Test the function. In the Configure Test Event dialog box, select blank-template, and set the following test event:

   {"user_data": "123"}

   Click Save. Then click Test.

   If the execution result is Success, the test is successful.

   Next, go to the APIG console to create a backend custom authorizer.

Creating a Backend Custom Authorizer

Before creating a backend custom authorizer, ensure that the function backend used for backend custom authentication has been created. Otherwise, create a function API first. For details, see Creating a Function for Backend Custom Authentication.

1. Go to the APIG console.
2. Select a dedicated gateway at the top of the navigation pane.

3. In the navigation pane, choose API Management > API Policies.
4. On the Custom Authorizers page, click Create Custom Authorizer. Configure the custom authorizer parameters based on the following table.

   Table 2 Parameters for creating a custom authorizer

   Parameter	Description
   Name	Authorizer name. It can contain 3 to 64 characters and must start with a letter. Only letters, digits, and underscores (_) are allowed.
   Type	Select Backend.
   Function URN	Select a function backend for custom authentication. Only function backends in the Deployed state can be selected.
   Version/Alias	Select a function version or alias. For details, see FunctionGraph User Guide.
   Max. Cache Age (s)	The time for caching authentication results. The value ranges from 0s to 3,600s. 0 indicates that authentication results will not be cached.
   Relaxed Mode	When this option is enabled, APIG accepts client requests even when FunctionGraph cannot connect or returns an error code starting with "5". If there is a retry request, the last returned result is used. When this option is enabled, if a custom authorizer is used for backend authentication of an API, the value of the backend authentication parameter is empty. The relaxed mode has security risks. Therefore, exercise caution when selecting this mode.
   Identity Sources	Request parameters used for authentication. This parameter is mandatory only if you set Type to Frontend, and Max. Cache Age (s) is greater than 0. When the cache is used, this parameter is used as a search criterion to query authentication results.
   Send Request Body	Determine whether to send the body of each API request to the authentication function. If you enable this option, the request body will be sent to the authentication function in the same way as the headers and query strings.
   User Data	Customized request parameters to be used together with Identity Sources when APIG invokes a function. The value contains 1 to 2,048 characters.

5. Click OK.