AWS API Gateway IAM Authentication - amazon-web-services

I have a group of aws api gateways which I am trying to restrict access to them through only one internal lambda function. I created a role, added the AmazonAPIGatewayInvokeFullAccess policy to it and assigned this role to the lambda function. However, I am still not able to access the APIs from the lambda and getting 403s. Thanks for your help.

Under IAM you need to add trust relationship with apigateway.amazonaws.com

Related

AWS Lambda doesn't have DynamoDB permissions when invoked by URL/API Gateway

We have a pair of existing AWS Lambda functions that read/write from a DynamoDB table. I created a new function and table; the function is very basic, just does a putItem on the DynamoDB table. I can successfully invoke it with the test functionality in Lambda.
However, if I invoke the Lambda function using the FunctionURL or via API Gateway, I get the following error.
Yet in Configuration > Permissions in the Lambda interface I clearly see the permission:
Suggestions where to check next? Comparison to our existing, working functions hasn't revealed anything; everything I have checked in configured the same.
Thanks!
When you invoke the lambda function in the lambda console, lambda is using an Execution role.
When you invoke the lambda function via API gateway or via the function URL, it is likely that you are using IAM authorization. As a result, lambda is using the role of the principal who invoked the function (in this case, PatientWellnessDeregistration-role-3ospc0u3).
The execution role is configured correctly, but the IAM role of the principal is lacking the required permissions.
Further reading:
https://docs.aws.amazon.com/lambda/latest/dg/lambda-intro-execution-role.html
https://docs.aws.amazon.com/lambda/latest/dg/urls-auth.html
What you could optionally check is that API Gateway is authorized to call your new Lambda. If so, then the Resource-based policy of the Lambda (still in the Permissions tab) should have something similar to:
Resource-based policy example:

CDK AWS Is it possible to grant a role access to a specific method or is it only possible to grant for the whole API?

I have the following
let lambdaFunction = <some lambda construct here>
lambdaFunction.grantInvoke(props.invocationRole);
And that grants hydra the ability to invoke that lambda, but what if I had an api endpoint method?
let endpoint = resource.addMethod(method['method'], lambdaIntegration, {
authorizationType: AuthorizationType.IAM,
requestValidator: props.requestValidator,
requestModels: {'application/json': props.validationModel}
})
Is it possible to grant the role that I have access to just this endpoint access or do I have to do it on the api gateway resource level?
I have no experience with API Gateway, however it looks like it does support access control using the specificity of a particular endpoint.
Reference Docs:
https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-control-access-using-iam-policies-to-invoke-api.html
Using the CDK, you can apply a policy with the same structure as the examples in the docs.

API Gateway IAM role to access DynamoDB

So I am following this Tutorial
I have created a role and attached the AmazonDynamoDBFullAccess policy to it ...
When I assign this role to Gateway API .... like this
I keep getting this error ...
Execution failed due to configuration error: API Gateway does not have
permission to assume the provided role
Isn't the "AmazonDynamoDBFullAccess" policy that I have applied to my role "MyDynamoRole" enough to give Gateway API necessary permissions ?
Found a solution ....
Under "Role --> Trust Relationship", I have added another service i.e. API Gateway ...
"apigateway.amazonaws.com"
and all good now ...
For people that might be struggling to create a role via the console, the hack is to use EC2 or Lambda based IAM roles to create a generic role and then edit the Trust Relationships to have the service.
"apigateway.amazonaws.com"

Cannot set S3 as api gateway AWS service

I'm trying to setup a Amazon API Gateway proxy which would be connected to s3 bucket to just proxy each file/object from the bucket to the API Gateway endpoint. (I need this because i need some files to be passed through other HTTP verbs, and s3 does not allow POST method).
The thing is that I cannot select 'S3' as aws service
Can someone provide me some guidance?
To allow the API to invoke required Amazon S3 actions, you must have appropriate IAM policies attached to an IAM role. The next section describes how to verify and to create, if necessary, the required IAM role and policies.
For your API to view or list Amazon S3 buckets and objects, you can use the IAM-provided AmazonS3ReadOnlyAccess policy in the IAM role.
Please read documentation here to know full setup
It should be under a name Simple Storege Service (S3)

Use AWS Lambda to access S3 using only Roles

I have a Lambda function written in Java I and I want it to access S3 (putObject).
I do not want to use or store credentials in my Lambda function in order to access S3. Instead, I would like to use IAM roles.
How can I code an AWS S3 client inside my java code (that would be ran by Lambda) that won't need any credentials and assume that the Lambda has the appropriate Role?
You don't need to store credentials in your lambda functions. All funtions run with a role - the role you set when you created the function. Since the lambda function has a role, you can add or remove permissions from this role as needed, without changing the function itself
Manage Permissions: Using an IAM Role (Execution Role)
Each Lambda function has an IAM role (execution role) associated with
it. You specify the IAM role when you create your Lambda function.
Permissions you grant to this role determine what AWS Lambda can do
when it assumes the role. There are two types of permissions that you
grant to the IAM role:
If your Lambda function code accesses other AWS resources, such as to
read an object from an S3 bucket or write logs to CloudWatch Logs, you
need to grant permissions for relevant Amazon S3 and CloudWatch
actions to the role. If the event source is stream-based (Amazon
Kinesis Streams and DynamoDB streams), AWS Lambda polls these streams
on your behalf. AWS Lambda needs permissions to poll the stream and
read new records on the stream so you need to grant the relevant
permissions to this role.
http://docs.aws.amazon.com/lambda/latest/dg/intro-permission-model.html