Create and attach an API Gateway resource policy to an API

To allow a user to access your API by calling the API execution service, you must create an API Gateway resource policy and attach the policy to the API. When you attach a policy to your API, it applies the permissions in the policy to the methods in the API. If you update the resource policy, you'll need to deploy the API.

Prerequisites

To update an API Gateway resource policy, you'll need the apigateway:UpdateRestApiPolicy permission and the apigateway:PATCH permission.

For an edge-optimized or Regional API, you can attach your resource policy to your API as you create it, or after it has been deployed. For a private API, you can't deploy your API without a resource policy. For more information, see Private REST APIs in API Gateway.

Attach a resource policy to an API Gateway API

The following procedure shows you how to attach a resource policy to an API Gateway API.

AWS Management Console

To attach a resource policy to an API Gateway API

1. Sign in to the API Gateway console at https://console.aws.amazon.com/apigateway.

2. Choose a REST API.

3. In the main navigation pane, choose Resource policy.

4. Choose Create policy.

5. (Optional) Choose Select a template to generate an example policy.

   In the example policies, placeholders are enclosed in double curly braces ("{{placeholder}}"). Replace each of the placeholders, including the curly braces, with the necessary information.

6. If you don't use one of the template examples, enter your resource policy.

7. Choose Save changes.

If the API has been deployed previously in the API Gateway console, you'll need to redeploy it for the resource policy to take effect.

AWS CLI

To use the AWS CLI to create a new API and attach a resource policy to it, call the create-rest-api command as follows:

aws apigateway create-rest-api \
    --name "api-name" \
    --policy "{\"jsonEscapedPolicyDocument\"}"

To use the AWS CLI to attach a resource policy to an existing API, call the update-rest-api command as follows:

aws apigateway update-rest-api \
    --rest-api-id api-id \
    --patch-operations op=replace,path=/policy,value='"{\"jsonEscapedPolicyDocument\"}"'

You can also attach your resource policy as a separate policy.json file and including it in your create-rest-api command. The following example create-rest-api creates a new API:

aws apigateway create-rest-api \
    --name "api-name" \
    --policy file://policy.json

policy.json is an API Gateway resource policy, such as Example: Deny API traffic based on source IP address or range.

AWS CloudFormation

You can use AWS CloudFormation to create an API with a resource policy. The following example creates a REST API with the example resource policy, Example: Deny API traffic based on source IP address or range.

AWSTemplateFormatVersion: 2010-09-09
Resources:
  Api:
    Type: 'AWS::ApiGateway::RestApi'
    Properties:
      Name: testapi
      Policy:
        Statement:
          - Action: 'execute-api:Invoke'
            Effect: Allow
            Principal: '*'
            Resource: 'execute-api/*'
          - Action: 'execute-api:Invoke'
            Effect: Deny
            Principal: '*'
            Resource: 'execute-api/*'
            Condition:
              IpAddress: 
                'aws:SourceIp': ["192.0.2.0/24", "198.51.100.0/24" ]
        Version: 2012-10-17
  Resource:
    Type: 'AWS::ApiGateway::Resource'
    Properties:
      RestApiId: !Ref Api
      ParentId: !GetAtt Api.RootResourceId
      PathPart: 'helloworld'
  MethodGet:
    Type: 'AWS::ApiGateway::Method'
    Properties:
      RestApiId: !Ref Api
      ResourceId: !Ref Resource
      HttpMethod: GET
      ApiKeyRequired: false
      AuthorizationType: NONE
      Integration:
        Type: MOCK 
  ApiDeployment:
    Type: 'AWS::ApiGateway::Deployment'
    DependsOn:
      - MethodGet
    Properties:
      RestApiId: !Ref Api
      StageName: test
              

Troubleshoot your resource policy

The following troubleshooting guidance might help resolve issues with your resource policy.

My API returns {"Message":"User: anonymous is not authorized to perform: execute-api:Invoke on resource: arn:aws:execute-api:us-east-1:********/****/****/"}

In your resource policy, if you set the Principal to an AWS principal, such as the following:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            ""Principal": {
                "AWS": [
                    "arn:aws:iam::account-id:role/developer",
                    "arn:aws:iam::account-id:role/Admin"
                ]
            },
            "Action": "execute-api:Invoke",
            "Resource": [
                "execute-api:/*"
            ]
        },
        ...
        }

You must use AWS_IAM authorization for every method in your API, or else your API returns the previous error message. For more instructions on how to turn on AWS_IAM authorization for a method, see Methods for REST APIs in API Gateway.

My resource policy is not updating

If you update the resource policy after the API is created, you'll need to deploy the API to propagate the changes after you've attached the updated policy. Updating or saving the policy alone won't change the runtime behavior of the API. For more information about deploying your API, see Deploy REST APIs in API Gateway.

My resource policy returns the following error: Invalid policy document. Please check the policy syntax and ensure that Principals are valid.

To troubleshoot this error, we first recommend that you check the policy syntax. For more information, see Access policy language overview for Amazon API Gateway. We also recommend that you check that all the principals specified are valid and haven’t been deleted.

In addition, if your API is in an opt-in Region, verify that all accounts in the resource policy have the Region enabled.