Empty S3 bucket | Access point ARN region is empty - amazon-web-services

I am trying to list the contents of my S3 bucket. I went through all the configuration steps and created & authenticated a user (I'm using Amplify). For record
Auth.currentCredentials(); gives
Object {
"accessKeyId": "ASIA6NIS4CMFGX3FWTNF",
"authenticated": true,
"expiration": 2020-10-14T13:30:49.000Z,
"identityId": "eu-west-2:6890ebd2-e3f3-4e1d-9725-9f9218241f60",
"secretAccessKey": "CGZsahSl53ulG9BJqGueM78xlMGhKcOs33UP2GUC",
"sessionToken": "IQoJb3JpZ2luX2VjEIX//////////wEaCWV1LXdlc3QtM ...
}
My code:
async function listObjects() {
Storage.list('s3://amplify-mythirdapp-dev-170201-deployment/',
{
level:'public',
region:'eu-west-2',
bucket:'arn:aws:s3:::amplify-mythirdapp-dev-170201-deployment'
})
.then(result => console.log(result))
.catch(err => console.log(err));
}
Which throws an error: Access point ARN region is empty
If I instead do bucket:amplify-mythirdapp-dev-170201-deployment it just returns Array []
But aws s3api list-objects --bucket amplify-mythirdapp-dev-170201-deployment correctly lists objects
What am I missing?
FYI I've also asked this question at aws-amplify/amplify-js/issues/2828.

Related

I wan't to create presigned url post, but always failed

thanks for greate packages!
I have problem when i create development with localstack using S3 service to create presignedurl post.
I have run localstack with SERVICES=s3 DEBUG=1 S3_SKIP_SIGNATURE_VALIDATION=1 localstack start
I have settings AWS_ACCESS_KEY_ID=test AWS_SECRET_ACCESS_KEY=test AWS_DEFAULT_REGION=us-east-1 AWS_ENDPOINT_URL=http://localhost:4566 S3_Bucket=my-bucket
I make sure have the bucket
> awslocal s3api list-buckets
{
"Buckets": [
{
"Name": "my-bucket",
"CreationDate": "2021-11-16T08:43:23+00:00"
}
],
"Owner": {
"DisplayName": "webfile",
"ID": "bcaf1ffd86f41161ca5fb16fd081034f"
}
}
I try create presigned url, and running in console with this
s3_client_sync.create_presigned_post(bucket_name=settings.S3_Bucket, object_name="application/test.png", fields={"Content-Type": "image/png"}, conditions=[["Expires", 3600]])
and have return like this
{'url': 'http://localhost:4566/kredivo-thailand',
'fields': {'Content-Type': 'image/png',
'key': 'application/test.png',
'AWSAccessKeyId': 'test',
'policy': 'eyJleHBpcmF0aW9uIjogIjIwMjEtMTEtMTZUMTE6Mzk6MjNaIiwgImNvbmRpdGlvbnMiOiBbWyJFeHBpcmVzIiwgMzYwMF0sIHsiYnVja2V0IjogImtyZWRpdm8tdGhhaWxhbmQifSwgeyJrZXkiOiAiYXBwbGljYXRpb24vdGVzdC5wbmcifV19',
'signature': 'LfFelidjG+aaTOMxHL3fRPCw/xM='}}
And i test using insomnia
and i have read log in localstack
2021-11-16T10:54:04:DEBUG:localstack.services.s3.s3_utils: Received presign S3 URL: http://localhost:4566/my-bucket/application/test.png?AWSAccessKeyId=test&Policy=eyJleHBpcmF0aW9uIjogIjIwMjEtMTEtMTZUMTE6Mzk6MjNaIiwgImNvbmRpdGlvbnMiOiBbWyJFeHBpcmVzIiwgMzYwMF0sIHsiYnVja2V0IjogImtyZWRpdm8tdGhhaWxhbmQifSwgeyJrZXkiOiAiYXBwbGljYXRpb24vdGVzdC5wbmcifV19&Signature=LfFelidjG%2BaaTOMxHL3fRPCw%2FxM%3D&Expires=3600
2021-11-16T10:54:04:WARNING:localstack.services.s3.s3_utils: Signatures do not match, but not raising an error, as S3_SKIP_SIGNATURE_VALIDATION=1
2021-11-16T10:54:04:INFO:localstack.services.s3.s3_utils: Presign signature calculation failed: <Response [403]>
what i missing, so i cannot create the presignedurl post ?
The problem is with your AWS configuration -
AWS_ACCESS_KEY_ID=test // Should be an Actual access Key for the IAM user
AWS_SECRET_ACCESS_KEY=test // Should be an Actual Secret Key for the IAM user
AWS_DEFAULT_REGION=us-east-1
AWS_ENDPOINT_URL=http://localhost:4566 // Endpoint seems wrong
S3_Bucket=my-bucket // Actual Bucket Name in AWS S3 console
For more information, try to read here and setup your environment with correct AWS credentials - Setup AWS Credentials

AWS SDK v3 Assume role for a client

I'm writing a Node JS app using AWS JS SDK v3. I am correctly using STS to assume role and retrieve credentials. The assume call response is such:
{
"$metadata": {
"httpStatusCode": 200,
"requestId": "xxx",
"attempts": 1,
"totalRetryDelay": 0
},
"Credentials": {
"AccessKeyId": "xxx",
"SecretAccessKey": "xxx",
"SessionToken": "xxx",
"Expiration": "2021-02-26T15:40:17.000Z"
},
"AssumedRoleUser": {
"AssumedRoleId": "xxx",
"Arn": "arn:aws:sts::xxx"
}
}
I am taking the credentials and passing them to a DynamoDBClient constructor (along with region).
import { DynamoDBClient, ListTablesCommand } from '#aws-sdk/client-dynamodb';
public getTablesList(region: string) {
const credentials = await getCredentialsFromSTS(region);
const clientParams = Object.assign(credentials, region); // This just merges two JSONs into one
const dbClient = new DynamoDBClient(clientParams);
const command = new ListTablesCommand({});
const response = await dbClient.send(command);
console.log(response);
}
What I get in the response is a list of only the tables of the account, that runs my code. The tables in the account where I am assuming the role are not present. Maybe I am assuming the role wrongly? I tried to package the credentials in a "Credentials" key, but that didn't help either.
const clientParams = Object.assign({ Credentials: credentials }, region);
Any idea what I am doing wrong here? Maybe the DDBClient is not assuming it as it should, but is there a way to check the assumed role for the DBClient? I found a namespace called RoleInfo in the documentation, but I don't know how to invoke it.
Please read the documentation of the DynamoDBClient parameter object: https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#constructor-property
The credentials fields are lower-case whereas in the STS result they are upper-case.
There are also more errors in your code, such as the Object.assign(credentials, region); call. region here is a string, so by assigning it into credentials you will not get a property named "region" with the value of that region variable, but you will get numeric properties, each with one character of the region string.
The correct initialization should be:
const credentials = await getCredentialsFromSTS(region);
const dbClient = new DynamoDBClient({
region: region,
credentials: {
accessKeyId: credentials.AccessKeyId,
secretAccessKey: credentials.SecretAccessKey,
sessionToken: credentials.SessionToken,
}
});

Read and Copy S3 inventory data from SNS topic trigger with AWS lambda function

I am a data analyst and new to AWS lambda functions. I have an s3 bucket where I store the Inventory data from our data-lake which is generated using Inventory feature under S3 Management tab.
So lets say the inventory data (reports) looks like this:
s3://my-bucket/allobjects/data/report-1.csv.gz
s3://my-bucket/allobjects/data/report-2.csv.gz
s3://my-bucket/allobjects/data/report-3.csv.gz
Regardless of the file contents, I have an Event setup for s3://my-bucket/allobjects/data/ which notifies an SNS topic during any event like GET or PUT. (I cant change this workflow due to strict governance)
Now, I am trying to create a Lambda Function with this SNS topic as a trigger and simply move the inventory-report files generated by the S3 Inventory feature under
s3://my-bucket/allobjects/data/
and repartition it as follows:
s3://my-object/allobjects/partitiondata/year=2019/month=01/day=29/report-1.csv.gz
s3://my-object/allobjects/partitiondata/year=2019/month=01/day=29/report-2.csv.gz
s3://my-object/allobjects/partitiondata/year=2019/month=01/day=29/report-3.csv.gz
How can I achieve this using the lambda function (node.js or python is fine) reading an SNS topic? Any help is appreciated.
I tried something like this based on some smaple code i found online but it didnt help.
console.log('Loading function');
var AWS = require('aws-sdk');
AWS.config.region = 'us-east-1';
exports.handler = function(event, context) {
console.log("\n\nLoading handler\n\n");
var sns = new AWS.SNS();
sns.publish({
Message: 'File(s) uploaded successfully',
TopicArn: 'arn:aws:sns:_my_ARN'
}, function(err, data) {
if (err) {
console.log(err.stack);
return;
}
console.log('push sent');
console.log(data);
context.done(null, 'Function Finished!');
});
};
The preferred method would be for the Amazon S3 Event to trigger the AWS Lambda function directly. But since you cannot alter this port, the flow would be:
The Amazon S3 Event will send a message to an Amazon SNS topic.
The AWS Lambda function is subscribed to the SNS topic, so it is triggered and receives the message from S3.
The Lambda function extracts the Bucket and Key, then calls S3 to copy_object() to another location. (There is no move command. You will need to copy the object to a new bucket/key.)
The content of the event field is something like:
{
"Records": [
{
"EventSource": "aws:sns",
"EventVersion": "1.0",
"EventSubscriptionArn": "...",
"Sns": {
"Type": "Notification",
"MessageId": "1c3189f0-ffd3-53fb-b60b-dd3beeecf151",
"TopicArn": "...",
"Subject": "Amazon S3 Notification",
"Message": "{\"Records\":[{\"eventVersion\":\"2.1\",\"eventSource\":\"aws:s3\",\"awsRegion\":\"ap-southeast-2\",\"eventTime\":\"2019-01-30T02:42:07.129Z\",\"eventName\":\"ObjectCreated:Put\",\"userIdentity\":{\"principalId\":\"AWS:AIDAIZCFQCOMZZZDASS6Q\"},\"requestParameters\":{\"sourceIPAddress\":\"54.1.1.1\"},\"responseElements\":{\"x-amz-request-id\":\"...",\"x-amz-id-2\":\"..."},\"s3\":{\"s3SchemaVersion\":\"1.0\",\"configurationId\":\"...\",\"bucket\":{\"name\":\"stack-lake\",\"ownerIdentity\":{\"principalId\":\"...\"},\"arn\":\"arn:aws:s3:::stack-lake\"},\"object\":{\"key\":\"index.html\",\"size\":4378,\"eTag\":\"...\",\"sequencer\":\"...\"}}}]}",
"Timestamp": "2019-01-30T02:42:07.212Z",
"SignatureVersion": "1",
"Signature": "...",
"SigningCertUrl": "...",
"UnsubscribeUrl": "...",
"MessageAttributes": {}
}
}
]
}
Thus, the name of the uploaded Object needs to be extracted from the Message.
You could use code like this:
import json
def lambda_handler(event, context):
for record1 in event['Records']:
message = json.loads(record1['Sns']['Message'])
for record2 in message['Records']:
bucket = record2['s3']['bucket']['name'])
key = record2['s3']['object']['key'])
# Do something here with bucket and key
return {
'statusCode': 200,
'body': json.dumps(event)
}

AWS S3 Can't do anything with one file

I'm having issues trying to remove a file from my s3 bucket with the following name: Patrick bla bla 1 PV#05-06-2018-19:42:01.jpg
If I try to rename it through the s3 console, it just says that the operation failed. If I try to delete it, the operation will "succeed" but the file will still be there.
I've tried removing it through the aws cli, when listing the object I get this back
{
"LastModified": "2018-06-05T18:42:05.000Z",
"ETag": "\"b67gcb5f8166cab8145157aa565602ab\"",
"StorageClass": "STANDARD",
"Key": "test/\bPatrick bla bla 1 PV#05-06-2018-19:42:01.jpg",
"Owner": {
"DisplayName": "dev",
"ID": "bd65671179435c59d01dcdeag231786bbf6088cb1ca4881adf3f5e17ea7e0d68"
},
"Size": 1247277
},
But if I try to delete or head it, the cli won't find it.
s3api head-object --bucket mybucket --key "test/\bPatrick bla bla 1 PV#05-06-2018-20:09:37.jpg"
An error occurred (404) when calling the HeadObject operation: Not Found
Is there any way to remove, rename or just move this image from the folder?
Regards
It looks like your object's key begins with a backspace (\b) character. I'm sure there is a way to manage this using the awscli but I haven't worked out what it is yet.
Here's a Python script that works for me:
import boto3
s3 = boto3.client('s3')
Bucket ='avondhupress'
Key='test/\bPatrick bla bla 1 PV#05-06-2018-19:42:01.jpg'
s3.delete_object(Bucket=bucket, Key=key)
Or the equivalent in node.js:
const aws = require('aws-sdk');
const s3 = new aws.S3({ region: 'us-east-1', signatureVersion: 'v4' });
const params = {
Bucket: 'avondhupress',
Key: '\bPatrick bla bla 1 PV#05-06-2018-19:42:01.jpg',
};
s3.deleteObject(params, (err, data) => {
if (err) console.error(err, err.stack);
});

aws lambda function getting access denied when getObject from s3

I am getting an acccess denied error from S3 AWS service on my Lambda function.
This is the code:
// dependencies
var async = require('async');
var AWS = require('aws-sdk');
var gm = require('gm').subClass({ imageMagick: true }); // Enable ImageMagick integration.
exports.handler = function(event, context) {
var srcBucket = event.Records[0].s3.bucket.name;
// Object key may have spaces or unicode non-ASCII characters.
var key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, " "));
/*
{
originalFilename: <string>,
versions: [
{
size: <number>,
crop: [x,y],
max: [x, y],
rotate: <number>
}
]
}*/
var fileInfo;
var dstBucket = "xmovo.transformedimages.develop";
try {
//TODO: Decompress and decode the returned value
fileInfo = JSON.parse(key);
//download s3File
// get reference to S3 client
var s3 = new AWS.S3();
// Download the image from S3 into a buffer.
s3.getObject({
Bucket: srcBucket,
Key: key
},
function (err, response) {
if (err) {
console.log("Error getting from s3: >>> " + err + "::: Bucket-Key >>>" + srcBucket + "-" + key + ":::Principal>>>" + event.Records[0].userIdentity.principalId, err.stack);
return;
}
// Infer the image type.
var img = gm(response.Body);
var imageType = null;
img.identify(function (err, data) {
if (err) {
console.log("Error image type: >>> " + err);
deleteFromS3(srcBucket, key);
return;
}
imageType = data.format;
//foreach of the versions requested
async.each(fileInfo.versions, function (currentVersion, callback) {
//apply transform
async.waterfall([async.apply(transform, response, currentVersion), uploadToS3, callback]);
}, function (err) {
if (err) console.log("Error on excecution of watefall: >>> " + err);
else {
//when all done then delete the original image from srcBucket
deleteFromS3(srcBucket, key);
}
});
});
});
}
catch (ex){
context.fail("exception through: " + ex);
deleteFromS3(srcBucket, key);
return;
}
function transform(response, version, callback){
var imageProcess = gm(response.Body);
if (version.rotate!=0) imageProcess = imageProcess.rotate("black",version.rotate);
if(version.size!=null) {
if (version.crop != null) {
//crop the image from the coordinates
imageProcess=imageProcess.crop(version.size[0], version.size[1], version.crop[0], version.crop[1]);
}
else {
//find the bigger and resize proportioned the other dimension
var widthIsMax = version.size[0]>version.size[1];
var maxValue = Math.max(version.size[0],version.size[1]);
imageProcess=(widthIsMax)?imageProcess.resize(maxValue):imageProcess.resize(null, maxValue);
}
}
//finally convert the image to jpg 90%
imageProcess.toBuffer("jpg",{quality:90}, function(err, buffer){
if (err) callback(err);
callback(null, version, "image/jpeg", buffer);
});
}
function deleteFromS3(bucket, filename){
s3.deleteObject({
Bucket: bucket,
Key: filename
});
}
function uploadToS3(version, contentType, data, callback) {
// Stream the transformed image to a different S3 bucket.
var dstKey = fileInfo.originalFilename + "_" + version.size + ".jpg";
s3.putObject({
Bucket: dstBucket,
Key: dstKey,
Body: data,
ContentType: contentType
}, callback);
}
};
This is the error on Cloudwatch:
AccessDenied: Access Denied
This is the stack error:
at Request.extractError (/var/runtime/node_modules/aws-sdk/lib/services/s3.js:329:35)
at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:105:20)
at Request.emit (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:77:10)
at Request.emit (/var/runtime/node_modules/aws-sdk/lib/request.js:596:14)
at Request.transition (/var/runtime/node_modules/aws-sdk/lib/request.js:21:10)
at AcceptorStateMachine.runTo (/var/runtime/node_modules/aws-sdk/lib/state_machine.js:14:12)
at /var/runtime/node_modules/aws-sdk/lib/state_machine.js:26:10
at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:37:9)
at Request.<anonymous> (/var/runtime/node_modules/aws-sdk/lib/request.js:598:12)
at Request.callListeners (/var/runtime/node_modules/aws-sdk/lib/sequential_executor.js:115:18)
Without any other description or info
on S3 bucket permissions allow to everyone put list and delete.
What can I do to access the S3 bucket?
PS: on Lambda event properties the principal is correct and has administrative privileges.
Interestingly enough, AWS returns 403 (access denied) when the file does not exist. Be sure the target file is in the S3 bucket.
If you are specifying the Resource don't forget to add the sub folder specification as well. Like this:
"Resource": [
"arn:aws:s3:::BUCKET-NAME",
"arn:aws:s3:::BUCKET-NAME/*"
]
Your Lambda does not have privileges (S3:GetObject).
Go to IAM dashboard, check the role associated with your Lambda execution. If you use AWS wizard, it automatically creates a role called oneClick_lambda_s3_exec_role. Click on Show Policy. It should show something similar to the attached image. Make sure S3:GetObject is listed.
I ran into this issue and after hours of IAM policy madness, the solution was to:
Go to S3 console
Click bucket you are interested in.
Click 'Properties'
Unfold 'Permissions'
Click 'Add more permissions'
Choose 'Any Authenticated AWS User' from dropdown. Select 'Upload/Delete' and 'List' (or whatever you need for your lambda).
Click 'Save'
Done.
Your carefully written IAM role policies don't matter, neither do specific bucket policies (I've written those too to make it work). Or they just don't work on my account, who knows.
[EDIT]
After a lot of tinkering the above approach is not the best. Try this:
Keep your role policy as in the helloV post.
Go to S3. Select your bucket. Click Permissions. Click Bucket Policy.
Try something like this:
{
"Version": "2012-10-17",
"Id": "Lambda access bucket policy",
"Statement": [
{
"Sid": "All on objects in bucket lambda",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::AWSACCOUNTID:root"
},
"Action": "s3:*",
"Resource": "arn:aws:s3:::BUCKET-NAME/*"
},
{
"Sid": "All on bucket by lambda",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::AWSACCOUNTID:root"
},
"Action": "s3:*",
"Resource": "arn:aws:s3:::BUCKET-NAME"
}
]
}
Worked for me and does not require for you to share with all authenticated AWS users (which most of the time is not ideal).
If you have encryption set on your S3 bucket (such as AWS KMS), you may need to make sure the IAM role applied to your Lambda function is added to the list of IAM > Encryption keys > region > key > Key Users for the corresponding key that you used to encrypt your S3 bucket at rest.
In my screenshot, for example, I added the CyclopsApplicationLambdaRole role that I have applied to my Lambda function as a Key User in IAM for the same AWS KMS key that I used to encrypt my S3 bucket. Don't forget to select the correct region for your key when you open up the Encryption keys UI.
Find the execution role you've applied to your Lambda function:
Find the key you used to add encryption to your S3 bucket:
In IAM > Encryption keys, choose your region and click on the key name:
Add the role as a Key User in IAM Encryption keys for the key specified in S3:
If all the other policy ducks are in a row, S3 will still return an Access Denied message if the object doesn't exist AND the requester doesn't have ListBucket permission on the bucket.
From https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectGET.html:
...If the object you request does not exist, the error Amazon S3
returns depends on whether you also have the s3:ListBucket permission.
If you have the s3:ListBucket permission on the bucket, Amazon S3 will
return an HTTP status code 404 ("no such key") error. if you don’t
have the s3:ListBucket permission, Amazon S3 will return an HTTP
status code 403 ("access denied") error.
I too ran into this issue, I fixed this by providing s3:GetObject* in the ACL as it is attempting to obtain a version of that object.
I tried to execute a basic blueprint Python lambda function [example code] and I had the same issue. My execition role was lambda_basic_execution
I went to S3 > (my bucket name here) > permissions .
Because I'm beginner, I used the Policy Generator provided by Amazon rather than writing JSON myself: http://awspolicygen.s3.amazonaws.com/policygen.html
my JSON looks like this:
{
"Id": "Policy153536723xxxx",
"Version": "2012-10-17",
"Statement": [
{
"Sid": "Stmt153536722xxxx",
"Action": [
"s3:GetObject"
],
"Effect": "Allow",
"Resource": "arn:aws:s3:::tokabucket/*",
"Principal": {
"AWS": [
"arn:aws:iam::82557712xxxx:role/lambda_basic_execution"
]
}
}
]
And then the code executed nicely:
I solved my problem following all the instruction from the AWS - How do I allow my Lambda execution role to access my Amazon S3 bucket?:
Create an AWS Identity and Access Management (IAM) role for the Lambda function that grants access to the S3 bucket.
Modify the IAM role's trust policy.
Set the IAM role as the Lambda function's execution role.
Verify that the bucket policy grants access to the Lambda function's execution role.
I was trying to read a file from s3 and create a new file by changing content of file read (Lambda + Node). Reading file from S3 did not had any problem. As soon I tried writing to S3 bucket I get 'Access Denied' error.
I tried every thing listed above but couldn't get rid of 'Access Denied'. Finally I was able to get it working by giving 'List Object' permission to everyone on my bucket.
Obviously this not the best approach but nothing else worked.
After searching for a long time i saw that my bucket policy was only allowed read access and not put access:
"Version": "2012-10-17",
"Statement": [
{
"Sid": "PublicListGet",
"Effect": "Allow",
"Principal": "*",
"Action": [
"s3:List*",
"s3:Get*",
"s3:Put*"
],
"Resource": [
"arn:aws:s3:::bucketName",
"arn:aws:s3:::bucketName/*"
]
}
]
}
Also another issue might be that in order to fetch objects from cross region you need to initialize new s3 client with other region name like:
const getS3Client = (region) => new S3({ region })
I used this function to get s3 client based on region.
I was struggling with this issue for hours. I was using AmazonS3EncryptionClient and nothing I did helped. Then I noticed that the client is actually deprecated, so I thought I'd try switching to the builder model they have:
var builder = AmazonS3EncryptionClientBuilder.standard()
.withEncryptionMaterials(new StaticEncryptionMaterialsProvider(encryptionMaterials))
if (accessKey.nonEmpty && secretKey.nonEmpty) builder = builder.withCredentials(new AWSStaticCredentialsProvider(new BasicAWSCredentials(accessKey.get, secretKey.get)))
builder.build()
And... that solved it. Looks like Lambda has trouble injecting the credentials in the old model, but works well in the new one.
I was getting the same error "AccessDenied: Access Denied" while cropping s3 images using lambda function. I updated the s3 bucket policy and IAM role inline policy as per the document link given below.
But still, I was getting the same error. Then I realised, I was trying to give "public-read" access in a private bucket. After removed ACL: 'public-read' from S3.putObject problem get resolved.
https://aws.amazon.com/premiumsupport/knowledge-center/access-denied-lambda-s3-bucket/
I had this error message in aws lambda environment when using boto3 with python:
botocore.exceptions.ClientError: An error occurred (AccessDenied) when calling the GetObject operation: Access Denied
It turns out I needed an extra permission because I was using object tags. If your objects have tags you will need
s3:GetObject AND s3:GetObjectTagging for getting the object.
I have faced the same problem when creating Lambda function that should have read S3 bucket content. I created the Lambda function and S3 bucket using AWS CDK. To solve this within AWS CDK, I used magic from the docs.
Resources that use execution roles, such as lambda.Function, also
implement IGrantable, so you can grant them access directly instead of
granting access to their role. For example, if bucket is an Amazon S3
bucket, and function is a Lambda function, the code below grants the
function read access to the bucket.
bucket.grantRead(function);