` with your value:import json
import gzip
import base64
import boto3
sns_client = boto3.client('sns')
def lambda_handler(event, context):
decoded_event = json.loads(gzip.decompress(base64.b64decode(event['awslogs']['data'])))
body = '''
{filtermatch}
'''.format(
loggroup=decoded_event['logGroup'],
logstream=decoded_event['logStream'],
filtermatch=decoded_event['logEvents'][0]['message'],
)
print(body)
filterMatch = json.loads(body)
data = []
if 'http' in filterMatch['event']:
data.append(filterMatch['event']['http']['hostname'])
elif 'tls' in filterMatch['event']:
data.append(filterMatch['event']['tls']['sni'])
result = 'Domain accessed ' + 1*' ' + (data[0]) + 1*' ' 'via AWS Network Firewall ' + 1*' ' + (filterMatch['firewall_name'])
print(result)
message = {'ServerName': result}
send_to_sns = sns_client.publish(
TargetArn=, #Replace with the SNS topic ARN
Message=json.dumps({'default': json.dumps(message),
'sms': json.dumps(message),
'email': json.dumps(message)}),
Subject='Server Name passed through the Network Firewall',
MessageStructure='json'
)
This code sample parses the CloudWatch Logs content and captures the server name provided by the SNI in the HTTPS header. | App developer |
| Create the Lambda function. | To create the Lambda function, follow the instructions in the [Lambda documentation](https://docs.aws.amazon.com/lambda/latest/dg/getting-started.html#getting-started-create-function) and choose **Python 3.9** for **Runtime**. | Cloud administrator |
| Add the code to the Lambda function. | To add your Python code to the Lambda function that you created earlier, follow the instructions in the [Lambda documentation](https://docs.aws.amazon.com/lambda/latest/dg/configuration-function-zip.html#configuration-function-update). | Cloud administrator |
| Add CloudWatch Logs as a trigger to the Lambda function. | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/prescriptive-guidance/latest/patterns/use-network-firewall-to-capture-the-dns-domain-names-from-the-server-name-indication-sni-for-outbound-traffic.html)For more information, see [Using Lambda with CloudWatch Logs](https://docs.aws.amazon.com/lambda/latest/dg/services-cloudwatchlogs.html) in the Lambda documentation. | Cloud administrator |
| Add SNS publish permissions. | Add the **sns:Publish** permission to the Lambda execution role, so that Lambda can make API calls to publish messages to SNS. [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/prescriptive-guidance/latest/patterns/use-network-firewall-to-capture-the-dns-domain-names-from-the-server-name-indication-sni-for-outbound-traffic.html){
"Version": "2012-10-17",
"Statement": [
{
"Sid": "AllowSNSPublish",
"Effect": "Allow",
"Action": [
"sns:GetTopicAttributes",
"sns:Subscribe",
"sns:Unsubscribe",
"sns:Publish"
],
"Resource": "*"
}
]
} | Cloud administrator |
### Test the functionality of your SNS notification
| Task | Description | Skills required |
| --- | --- | --- |
| Send traffic through Network Firewall. | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/prescriptive-guidance/latest/patterns/use-network-firewall-to-capture-the-dns-domain-names-from-the-server-name-indication-sni-for-outbound-traffic.html){
"Type": "Notification",
"MessageId": "",
"TopicArn": "arn:aws:sns:us-west-2:123456789:testSNSTopic",
"Subject": "Server Name passed through the Network Firewall",
"Message": "{\"ServerName\": \"Domain 'aws.amazon.com' accessed via AWS Network Firewall 'AWS-Network-Firewall-Multi-AZ-firewall\"}",
"Timestamp": "2022-03-22T04:10:04.217Z",
"SignatureVersion": "1",
"Signature": "",
"SigningCertURL": "",
"UnsubscribeURL": ""
}Then, check the Network Firewall alert log in Amazon CloudWatch by following the instructions in the [Amazon CloudWatch documentation](https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/SearchDataFilterPattern.html). The alert log shows the following output:{
"firewall_name": "AWS-Network-Firewall-Multi-AZ-firewall",
"availability_zone": "us-east-2b",
"event_timestamp": "",
"event": {
"timestamp": "2021-03-22T04:10:04.214222+0000",
"flow_id": ,
"event_type": "alert",
"src_ip": "10.1.3.76",
"src_port": 22761,
"dest_ip": "99.86.59.73",
"dest_port": 443,
"proto": "TCP",
"alert": {
"action": "allowed",
"signature_id": 2,
"rev": 0,
"signature": "",
"category": "",
"severity": 3
},
"tls": {
"subject": "CN=aws.amazon.com",
"issuerdn": "C=US, O=Amazon, OU=Server CA 1B, CN=Amazon",
"serial": "",
"fingerprint": "",
"sni": "aws.amazon.com",
"version": "TLS 1.2",
"notbefore": "2020-09-30T00:00:00",
"notafter": "2021-09-23T12:00:00",
"ja3": {},
"ja3s": {}
},
"app_proto": "tls"
}
} | Test engineer |