Hatchet: SSRF via Unsigned UnsubscribeURL in SNS UnsubscribeConfirmation Handler

Summary

The SNS UnsubscribeConfirmation handler in internal/integrations/ingestors/sns/sns.go makes an unvalidated http.Get() call to payload.UnsubscribeURL without any URL restriction. Because UnsubscribeURL is intentionally excluded from the BuildSignature() signed field list, an attacker can replace this field in a legitimately AWS-signed message with an arbitrary internal URL, bypassing the VerifyPayload() signature check entirely and triggering a Server-Side Request Forgery (SSRF) against internal infrastructure — including the EC2 Instance Metadata Service (IMDS) at 169.254.169.254.

Impact

This is a Server-Side Request Forgery (SSRF) vulnerability. An attacker with a Hatchet account and an AWS Free Tier account can:

• Reach the EC2 IMDS endpoint and retrieve IAM temporary credentials if Hatchet is deployed on AWS
• Port-scan and probe internal services not exposed to the internet
• Access internal HTTP APIs (e.g., Kubernetes API server, internal dashboards) from the Hatchet server's network context