fix(custom-resources): ArrayBufferView decodes underlying buffer instead of the view

[s12v]

Issue

Related to #19065

Reason for this change

Sample app to reproduce:

import {Stack, StackProps} from 'aws-cdk-lib';
import {Construct} from 'constructs';
import {KeySpec, KeyUsage} from "aws-cdk-lib/aws-kms";
import cr = require('aws-cdk-lib/custom-resources');
import kms = require('aws-cdk-lib/aws-kms');

export class SampleStack extends Stack {
    constructor(scope: Construct, id: string, props?: StackProps) {
        super(scope, id, props);

        // Create key
        const kmsKey = new kms.Key(this, 'SampleKey', {
            keySpec: KeySpec.ECC_NIST_P256,
            keyUsage: KeyUsage.SIGN_VERIFY,
        });

        // Export public key
        const publicKeyApiCall = new cr.AwsCustomResource(this, 'PublicKey', {
            onCreate: {
                service: 'KMS',
                action: 'GetPublicKey',
                physicalResourceId: cr.PhysicalResourceId.of('PublicKey'),
                parameters: {
                    KeyId: kmsKey.keyArn,
                },
            },
            policy: cr.AwsCustomResourcePolicy.fromSdkCalls({
                resources: cr.AwsCustomResourcePolicy.ANY_RESOURCE,
            }),
        });

        const publicKey = publicKeyApiCall.getResponseField('PublicKey');
        this.exportValue(publicKey, {name: 'PublicKey'})
    }
}

Expected result: value of the PublicKey property of the KMS GetPublicKey API response.

Actual result: the entire underlying buffer of the response:

 2024-05-27T22:03:20.837Z	d9886a79-a519-4e21-99a5-5dffc09a2fec	INFO	API response {
    CustomerMasterKeySpec: 'ECC_NIST_P256',
    KeyId: 'arn:aws:kms:us-west-2:...:key/21e7d06f-b638-400b-82f3-613cca94abe1',
    KeySpec: 'ECC_NIST_P256',
    KeyUsage: 'SIGN_VERIFY',
    PublicKey: "0Y0\x13\x06\x07*�H�=\x02\x01\x06\b*�H�=\x03\x01\x07\x03B\x00\x04\b�I�Do�BgnM>l�hl�UF��'��hj�v�l��ɖ���b�\tf�=TC���\x10\n" +
      '[\rCC_�(\x15X1b~8\x00Z\x00\x00\x00a\x00\x00\x00z\x00\x00\x00/\x00\x00\x00/\x00\x00\x00\x10|\bv�U\x00\x00سjw�U\x00\x00\x00\x00\x02~\x01t_s\x00\x00\x00\x00Erro`~\bv�U\x00\x00 �jw�U\x00\x00\x00\x00\x00\x00���\x7F\x00\x00\x00\x00���\x7F\x00\x00\x00\x00\x01ninx�jw�U\x00\x00\x04\x00\x00\x00\x01\x00\x00\x00=\x00on bas8}\bv�U\x00\x00x�jw�U\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00`~\bv�U\x00\x00��jw�U\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00�z\bv�U\x00\x00\x03\x00\x00\x00�U\x00\x00�jw�U\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00ȳjw�U\x00\x00@�jw�U\x00\x00��jw�U\x00\x00��jw�U\x00\x00�y\bv�U\x00\x00дjw�U\x00\x00\x00\x00\x00\x00���\x7F�\x03\x04v�U\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00K���\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00�ϘV�\x7F\x00\x00\x00\x00\x00\x00�U\x00\x00X\x04\x04v�U\x00\x00X�jw�U\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00�\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00�ϘV�\x7F\x00\x00\x18�jw�U\x00\x00\x01\x00\x00\x00\x01e\x00\x00fromStri\x02\x00\x00\x00�U\x00\x00�\x05\x04v�U\x00\x00��jw�U\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00�\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00�ϘV�\x7F\x00\x00X�jw�U\x00\x00\x00\x00\x00\
...

Which causes CloudFormation to fail with error ❌ SampleStack failed: Error: The stack named SampleStack failed to deploy: UPDATE_ROLLBACK_COMPLETE: Response object is too long.

Root cause: Uint8Array references an ArrayBuffer with offset and length. When using value.buffer, the entire buffer (entire response body) is used, while Uint8Array only references a part of it.

Description of changes

Decode the value instead of the underlying buffer.

Description of how you validated changes

Updated a unit test.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

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[TheRealAmazonKendra]

We will definitely need to see the output of updated integ tests to properly assess this one. If you're hesitant to update them all prior to getting feedback (I wouldn't blame you, it's tedious) please get at least one updated and then tag me and I'll do a review.

[TheRealAmazonKendra]

Also, the PR title of a fix should describe the bug, not the solution as it goes in our changelog. It should also contain the link of the issue it is resolving, please link this issue in this PR for tracking: #19065

[aws-cdk-automation]

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