aws lambda function getting access denied when getObject from s3

Question

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.

Answer 1

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.