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.
Solution 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.
Solution 2:
Interestingly enough, AWS returns 403 (access denied) when the file does not exist. Be sure the target file is in the S3 bucket.
Solution 3:
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/*"
]
Solution 4:
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).
Solution 5:
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:
