Identity Pool Role Can't Access S3 Bucket Access Point

Summary: I am using AWS Amplify Auth class with a pre-configured Cognito User Pool for authentication. After authentication, I am using the Cognito ID token to fetch identity pool credentials (using AWS CredentialProviders SDK) whose assumed role is given access to an S3 access point. I then attempt to fetch a known object from the bucket's access point using the AWS S3 SDK. The problem is that the request returns a response of 403 Forbidden instead of successfully getting the object, despite my role policy and bucket (access point) policy allowing the s3:GetObject action on the resource.

I am assuming something is wrong with the way my policies are set up. Code snippets below.

I am also concerned I'm not getting the right role back from the credentials provider, but I don't allow unauthenticated roles on the identity pool so I am not sure, and I don't know how to verify the role being sent back in the credentials' session token to check.

I also may not be configuring the sdk client objects properly, but I followed the documentation provided to the best of my understanding from the documentation (I am using AWS SDK v3, not v2, so slightly different syntax and uses modular imports)

Backend Configurations - IAM

Identity Pool: Authenticated Role Trust Policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Federated": "cognito-identity.amazonaws.com"
            },
            "Action": [
                "sts:AssumeRoleWithWebIdentity",
                "sts:TagSession"
            ],
            "Condition": {
                "StringEquals": {
                    "cognito-identity.amazonaws.com:aud": "<MY_IDENTITY_POOL_ID>"
                },
                "ForAnyValue:StringLike": {
                    "cognito-identity.amazonaws.com:amr": "authenticated"
                }
            }
        }
    ]
}

Identity Pool: Authenticated Role S3 Access Policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "s3:GetObject",
                "s3:GetObjectVersion"
            ],
            "Resource": "arn:aws:s3:::<MY_ACCESS_POINT_NAME>/object/*"
        }
    ]
}

Backend Configurations - S3

S3 Bucket and Access Points: Block All Public Access

S3 Bucket CORS Policy:

[
    {
        "AllowedHeaders": [
            "*"
        ],
        "AllowedMethods": [
            "GET",
            "PUT",
            "HEAD"
        ],
        "AllowedOrigins": [
            "*"
        ],
        "ExposeHeaders": [],
        "MaxAgeSeconds": 300
    }
]

S3 Bucket Policy (Delegates Access Control to Access Points):

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "DelegateAccessControlToAccessPoints",
            "Effect": "Allow",
            "Principal": {
                "AWS": "*"
            },
            "Action": "*",
            "Resource": [
                "arn:aws:s3:::<MY_BUCKET_NAME>",
                "arn:aws:s3:::<MY_BUCKET_NAME>/*"
            ],
            "Condition": {
                "StringEquals": {
                    "s3:DataAccessPointAccount": "<MY_ACCT_ID>"
                }
            }
        }
    ]
}

Access Point Policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowAccessPointToGetObjects",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::<ACCT_ID>:role/<MY_IDENTITY_POOL_AUTH_ROLE_NAME>"
            },
            "Action": [
                "s3:GetObject",
                "s3:GetObjectVersion"
            ],
            "Resource": "arn:aws:s3:<REGION>:<ACCT_ID>:accesspoint/<MY_ACCESS_POINT_NAME>/object/*"
        }
    ]
}

Front End AuthN & AuthZ

Amplify Configuration of User Pool Auth

Amplify.configure({
  Auth: {
    region: '<REGION>',
    userPoolId: '<MY_USER_POOL_ID>',
    userPoolWebClientId: '<MY_USER_POOL_APP_CLIENT_ID>'
  }
})

User AuthZ process: On user login event, call Amplify's Auth.signIn() which returns type CognitoUser:

// Log in user (error checking ommitted here for post)
const CognitoUser = await Auth.signIn(email, secret);

// Get ID Token JWT
const CognitoIdToken = CognitoUser.signInUserSession.getIdToken().getJwtToken();

// Use @aws-sdk/credentials-provider to get Identity Pool Credentials
const credentials = fromCognitoIdentityPool({
    clientConfig: { region: '<REGION>' },
    identityPoolId: '<MY_IDENTITY_POOL_ID>',
    logins: {
        'cognito-idp.<REGION>.amazonaws.com/<MY_USER_POOL_ID>': CognitoIdToken
    }
})

// Create S3 SDK Client
client = new S3Client({
    region: '<REGION>',
    credentials
})

// Format S3 GetObjectCommand parameters for object to get from access point
const s3params = {
    Bucket: '<MY_ACCESS_POINT_ARN>',
    Key: '<MY_OBJECT_KEY>'
}

// Create S3 client command object
const getObjectCommand = new GetObjectCommand(s3params);

// Get object from access point (execute command)
const response = await client.send(getObjectCommand); // -> 403 FORBIDDEN