Performing SSL/TLS Inspection Configuration

Overview

SSL/TLS inspection (also called SSL decryption, HTTPS inspection, or TLS break-and-inspect) intercepts encrypted traffic between clients and servers to inspect the cleartext content for malware, data exfiltration, policy violations, and command-and-control communications. The inspection device acts as a trusted man-in-the-middle, terminating the TLS session from the client, inspecting the plaintext content, and establishing a new TLS session to the destination server. With over 95% of web traffic now encrypted, organizations without TLS inspection have a massive blind spot. This skill covers configuring TLS inspection on next-generation firewalls, deploying trusted CA certificates, managing exemptions for certificate-pinned applications, and ensuring compliance with privacy regulations.

When to Use

• When conducting security assessments that involve performing ssl tls inspection configuration
• When following incident response procedures for related security events
• When performing scheduled security testing or auditing activities
• When validating security controls through hands-on testing

Prerequisites

• Next-generation firewall or secure web gateway with TLS inspection capability
• Internal Certificate Authority (CA) for signing inspection certificates
• Endpoint certificate management (GPO, MDM, or manual deployment)
• Privacy and legal review for TLS inspection scope
• Understanding of PKI, X.509 certificates, and TLS handshake

Core Concepts

SSL/TLS Inspection Modes

Forward Proxy Process

Client                  Firewall/Proxy              Web Server
  │                         │                          │
  │──TLS ClientHello──────→│                          │
  │                         │──TLS ClientHello───────→│
  │                         │←─TLS ServerHello────────│
  │                         │  (real server cert)      │
  │                         │                          │
  │                         │  [Validates server cert]  │
  │                         │  [Generates proxy cert   │
  │                         │   signed by internal CA]  │
  │                         │                          │
  │←─TLS ServerHello───────│                          │
  │  (proxy-signed cert)    │                          │
  │                         │                          │
  │──Encrypted data────────→│  [Decrypt, Inspect]      │
  │                         │──Encrypted data────────→│
  │←─Encrypted data─────────│  [Decrypt, Inspect]      │
  │                         │←─Encrypted data─────────│

Certificate Trust Chain

Enterprise Root CA
  └── Subordinate CA (SSL Inspection)
        └── Dynamically Generated Server Certificates
             (CN matches requested server)

Workflow

Step 1: Generate Internal CA for SSL Inspection

# Create private key for SSL Inspection CA
openssl genrsa -aes256 -out ssl-inspect-ca.key 4096

# Create CA certificate (5 year validity)
openssl req -new -x509 -key ssl-inspect-ca.key \
  -sha256 -days 1825 \
  -out ssl-inspect-ca.crt \
  -subj "/C=US/ST=California/O=Corp Inc/OU=Network Security/CN=Corp SSL Inspection CA" \
  -extensions v3_ca \
  -config <(cat <<EOF
[req]
distinguished_name = req_dn
x509_extensions = v3_ca

[req_dn]

[v3_ca]
basicConstraints = critical,CA:TRUE,pathlen:0
keyUsage = critical,digitalSignature,keyCertSign,cRLSign
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always
EOF
)

# Verify certificate
openssl x509 -in ssl-inspect-ca.crt -text -noout

Step 2: Deploy CA Certificate to Endpoints

Windows (Group Policy):

# Import CA cert to trusted root store via GPO
# Computer Configuration > Policies > Windows Settings >
# Security Settings > Public Key Policies > Trusted Root CAs

# Or deploy via PowerShell
Import-Certificate -FilePath "\\server\share\ssl-inspect-ca.crt" `
  -CertStoreLocation "Cert:\LocalMachine\Root"

# Verify deployment
Get-ChildItem Cert:\LocalMachine\Root | Where-Object {
    $_.Subject -like "*SSL Inspection CA*"
}

macOS (MDM profile or manual):

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