👀 Views: 72 💬 Answers: 1 📅 Created: 2025-07-17

aws lambda s3 permissions JavaScript

I'm relatively new to this, so bear with me. I have a Lambda function written in Node.js (v14.x) that needs to read and write files to an S3 bucket, but I'm consistently working with an 'Access Denied' behavior when trying to access the bucket. The Lambda function is triggered by an S3 event, and I have set up a bucket policy that should allow it to perform `s3:GetObject` and `s3:PutObject` actions. However, the behavior continues. Here’s the relevant part of my S3 bucket policy: ```json { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::123456789012:role/myLambdaExecutionRole" }, "Action": ["s3:GetObject", "s3:PutObject"], "Resource": "arn:aws:s3:::my-bucket-name/*" } ] } ``` I’ve confirmed that my Lambda execution role has the necessary permissions as well: ```json { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": ["logs:*"], "Resource": "*" }, { "Effect": "Allow", "Action": ["s3:GetObject", "s3:PutObject"], "Resource": "arn:aws:s3:::my-bucket-name/*" } ] } ``` I even tried adding the S3 bucket policy that grants access to `*` for testing purposes, but still get the same behavior. Here’s the behavior I receive when the Lambda function attempts to access the S3 bucket: ``` An behavior occurred: AccessDenied - Access Denied ``` I’ve checked for typos in the bucket name, and the Lambda function is in the same region as the S3 bucket. Additionally, I’m using the AWS SDK for JavaScript (v2) to access the bucket like this: ```javascript const AWS = require('aws-sdk'); const s3 = new AWS.S3(); const params = { Bucket: 'my-bucket-name', Key: 'path/to/myfile.txt', }; s3.getObject(params, (err, data) => { if (err) console.log(err, err.stack); else console.log(data); }); ``` Any advice on why I'm still getting this 'Access Denied' behavior and how I can resolve it? I’ve exhausted all the common troubleshooting steps I could think of, and I’d appreciate any insights or strategies for debugging this scenario. What's the best practice here? For context: I'm using Javascript on Ubuntu. Am I missing something obvious?