Integration / FileTransfer
FileTransferExternalIntegration Pattern

Int-FileTransfer-External

Problem

An internal backend workload or microservice requires secure, asynchronous, and reliable exchange of files or bulk data with an external user, partner, or system.

Solution

To facilitate secure file transfers, leverage a Managed Secure File Transfer Gateway deployed within a Public Subnet (Perimeter). This gateway authenticates external parties and securely manages the transfer of files to and from private subnets, utilizing robust object storage for interim data staging and ensuring isolation from internal backend workloads.

Cloud Paradigm

  • Asynchronous Data Exchange
  • Event-Driven Architecture (for notifications)
  • Edge Security (Ingress/Egress control)
  • Zero Trust Architecture
  • Managed Service Consumption
  • Object Storage as a Data Lake Ingestion Point

Implementation Guidelines

Solution Flow

Inbound Data Transfer Flow (External to Internal):

  1. External Party: An external system or user initiates a secure file transfer (e.g., SFTP, FTPS, HTTPS) over the Public Internet to the Managed Secure File Transfer Gateway.
  2. Edge Protection (WAF): Traffic first traverses a public-facing cloud edge, where Edge Protection (WAF) filters malicious requests and common attack patterns.
  3. Managed Secure File Transfer Gateway: The gateway authenticates the external party (e.g., SSH key, API key, OAuth/OIDC), terminates TLS, and enforces access policies. It then stages the incoming file into a designated, encrypted Object Storage bucket located in a Private Subnet (Workloads).
  4. Event Notification (Optional): Upon successful file upload, the Object Storage can trigger an event (e.g., message queue, serverless function) to notify downstream backend workloads or microservices.
  5. Backend Workload: An internal backend workload or microservice (e.g., data processing pipeline, ETL component) retrieves the file from the Object Storage bucket for processing, validation, and integration.

Outbound Data Transfer Flow (Internal to External):

  1. Backend Workload: An internal backend workload or microservice places the file intended for external consumption into a designated, encrypted Object Storage bucket in a Private Subnet (Workloads).
  2. Managed Secure File Transfer Gateway: The Managed Secure File Transfer Gateway (or a dedicated egress module) is configured to retrieve the file from the Object Storage bucket based on predefined schedules or event triggers.
  3. Managed NAT / Egress Gateway: If the gateway initiates the outbound connection from a private subnet, traffic is routed through a Managed NAT/Egress Gateway. This gateway enforces outbound FQDN whitelisting, performs network address translation, and provides a static, whitelisted egress IP.
  4. External Target: The Managed Secure File Transfer Gateway securely transfers the file (e.g., SFTP, FTPS, HTTPS) to the external partner's system over the Public Internet, originating from a controlled egress point.

Additional Details

  • Supported Protocols: Utilize modern secure protocols such as SFTP (SSH File Transfer Protocol), FTPS (FTP over TLS/SSL), or HTTPS-based file uploads/downloads. Legacy protocols like plain FTP or SCP must be strictly avoided.
  • Data Staging and Persistence: Files should be staged in highly available, durable, and encrypted Object Storage buckets. Implement lifecycle policies to manage file retention and archival based on business and compliance requirements.
  • File Naming and Metadata: Establish clear conventions for file naming, directory structures, and metadata to facilitate automated processing and auditing by both internal and external systems.
  • Monitoring and Auditing: Enable comprehensive logging and auditing for all file transfer activities (e.g., successful transfers, failures, authentication attempts, file access) on the Managed Secure File Transfer Gateway and Object Storage. Integrate these logs with a centralized observability platform.
  • Error Handling and Retries: Implement robust error handling, automated retries with backoff strategies, and alerting mechanisms for failed file transfers to ensure data integrity and operational resilience.
  • Transformation and Orchestration: For complex data transformations, protocol conversions, or multi-step processing workflows, delegate these responsibilities to dedicated Middleware Services or Data Integration Platforms rather than embedding them directly within the file transfer gateway.
  • Security Hardening: Regularly audit and harden the configuration of the Managed Secure File Transfer Gateway, including disabling unused protocols, enforcing strong cipher suites, and rotating credentials.

Security Controls

  • Perimeter Security: The Managed Secure File Transfer Gateway must reside in a Public Subnet (Perimeter) and be protected by Edge Protection (WAF) to defend against common web vulnerabilities and brute-force attacks.
  • Transport Security: Enforce strict Transport Layer Security (TLS 1.2 or higher) for all data in transit, including SFTP and HTTPS. Legacy or unencrypted protocols like FTP must be prohibited.
  • Authentication & Authorization:
    • For system-to-system integrations, use SSH Key Pairs (with strong passphrases) or API Key authentication for SFTP/HTTPS based transfers.
    • For external user access, integrate with an identity provider for OAuth 2.0/OpenID Connect (OIDC) authentication, followed by granular access control lists (ACLs) on file directories or object storage buckets.
  • Data at Rest Security: All files staged within the Secure File Transfer Gateway or Object Storage must be encrypted at rest using platform-managed or customer-managed encryption keys.
  • Malware and Vulnerability Scanning: Implement automated scanning of all incoming files for malware, viruses, and other malicious content immediately upon arrival and prior to processing by internal workloads.
  • Data Loss Prevention (DLP): Configure the Secure File Transfer Gateway and egress protection to inspect outbound file transfers for sensitive data leakage if required by compliance, preventing unauthorized data exfiltration.
  • Data Segregation: Never store sensitive or processed files directly within the Public Subnet (Perimeter). Use robust object storage in private subnets for durable and secure storage.