aws-lambda-cloudtrail-alert is an AWS Lambda script that will monitor your CloudTrail S3 bucket and send email alerts via SES when "interesting" events occur.
The script is designed to get you up and running quickly with minimal changes. You will need to customize the recipients, from, and subject variables at the top of the file. You will also probably want to tweak the interestingEvents() function to better match what events you find interesting.
Most of the work in getting this script running is setting up all the other AWS systems. I'll assume you already have CloudTrail configured to point to a bucket called cloudtrail.example.com. I'll also assume you already have a verified SES sender and you are using that for your "from" address.
You will need to create two IAM roles lambda-cloudtrail-exec and lambda-cloudtrail-invoke. The lambda-cloudtrail-exec needs a policy like this:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"logs:*"
],
"Resource": "arn:aws:logs:*:*:*"
},
{
"Effect":"Allow",
"Action":["ses:SendEmail", "ses:SendRawEmail"],
"Resource":"*"
},
{
"Effect": "Allow",
"Action": [
"s3:GetObject"
],
"Resource": [
"arn:aws:s3:::cloudtrail.example.com/*"
]
}
]
}
It will also need a trust relationship for lambda:
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "",
"Effect": "Allow",
"Principal": {
"Service": "lambda.amazonaws.com"
},
"Action": "sts:AssumeRole"
}
]
}
The lambda-cloudtrail-invoke role needs a policy like this:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Resource": [
"*"
],
"Action": [
"lambda:InvokeFunction"
]
}
]
}
It should have a trust relationship for the s3 bucket:
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "",
"Effect": "Allow",
"Principal": {
"Service": "s3.amazonaws.com"
},
"Action": "sts:AssumeRole",
"Condition": {
"StringEquals": {
"sts:ExternalId": "arn:aws:s3:::cloudtrail.example.com"
}
}
}
]
}
Configure the Lambda function as follows:
- Handler Name: handler
- Role: arn:aws:iam::{YOUR_AWS_ACCOUNT_NUMBER_HERE}:role/lambda-cloudtrail-exec
- Memory: 128 MB
- Timeout: 10s (adjust as necessary)
Configure the source for the function:
- Bucket: cloudtrail.example.com (use your actual bucket name)
- Invocation Role: arn:aws:iam::{YOUR_AWS_ACCOUNT_NUMBER_HERE}:role/lambda-cloudtrail-invoke
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