When using the perfect forward secrecy (PFS) key exchange, how does a firewall behave when SSL Inbound Inspection is enabled?
- It acts as meddler-in-the-middle between the client and the internal server.
- It acts transparently between the client and the internal server.
- It decrypts inbound and outbound SSH connections.
- It decrypts traffic between the client and the external server.
Answer(s): A
Explanation:
Perfect Forward Secrecy (PFS) is a cryptographic feature in SSL/TLS key exchange that ensures each session uses a unique key that is not derived from previous sessions. This prevents attackers from decrypting historical encrypted traffic even if they obtain the server's private key.
When SSL Inbound Inspection is enabled on a Palo Alto Networks Next-Generation Firewall (NGFW), the firewall decrypts inbound encrypted traffic destined for an internal server to inspect it for threats, malware, or policy violations.
Firewall Behavior with PFS and SSL Inbound Inspection
Meddler-in-the-Middle (MITM) Role Since PFS prevents session key reuse, the firewall cannot use static keys for decryption. Instead, it must act as a man-in-the-middle (MITM) between the client and the internal server.
Decryption Process
The firewall terminates the SSL session from the external client.
It then establishes a new encrypted session between itself and the internal server.
This allows the firewall to decrypt, inspect, and then re-encrypt traffic before forwarding it to the server.
Security Implications
This approach ensures threat detection and policy enforcement before encrypted traffic reaches critical internal servers.
However, it breaks end-to-end encryption since the firewall acts as an intermediary.
Why Other Options Are Incorrect?
B) It acts transparently between the client and the internal server.
Incorrect, because SSL Inbound Inspection requires the firewall to actively terminate and re-establish SSL connections, making it a non-transparent MITM.
C) It decrypts inbound and outbound SSH connections.
Incorrect, because SSL Inbound Inspection applies only to SSL/TLS traffic, not SSH connections. SSH decryption requires a different feature (e.g., SSH Proxy).
D) It decrypts traffic between the client and the external server.
Incorrect, because SSL Inbound Inspection is designed to inspect traffic destined for an internal server, not external connections. SSL Forward Proxy would be used for outbound traffic decryption.
Reference to Firewall Deployment and Security Features:
Firewall Deployment SSL Inbound Inspection is used in enterprise environments to monitor encrypted traffic heading to internal servers.
Security Policies Decryption policies control which inbound SSL sessions are decrypted.
VPN Configurations PFS is commonly used in IPsec VPNs, ensuring that keys change per session.
Threat Prevention Enables deep inspection of SSL/TLS traffic to detect malware, exploits, and data leaks.
WildFire Integration Extracts potentially malicious files from encrypted traffic for advanced sandboxing and malware detection.
Panorama Provides centralized management of SSL decryption logs and security policies.
Zero Trust Architectures Ensures encrypted traffic is continuously inspected, aligning with Zero Trust security principles.
Thus, the correct answer is:
A) It acts as meddler-in-the-middle between the client and the internal server.
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