Optimizing Etlin HTTP Proxy for Enterprise Deployments

How to Configure Etlin HTTP Proxy for Secure Web TrafficEnsuring secure web traffic is essential for modern networks. Etlin HTTP Proxy can act as a central control point to enforce security policies, cache content, filter malicious requests, and provide visibility into HTTP/HTTPS traffic. This guide walks you through planning, installation, configuration, TLS interception considerations, access control, logging, performance tuning, and maintenance to deploy Etlin as a secure, reliable HTTP proxy.

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Overview and planning

Before deploying Etlin HTTP Proxy, define your goals and constraints:

• Traffic coverage: Will Etlin handle HTTP only, or also HTTPS (TLS interception/termination)?
• Network placement: Transparent (inline) or explicit (clients configure proxy)?
• Authentication: Will you use user-based auth (Kerberos, NTLM, LDAP) or IP-based policies?
• Privacy and legal: TLS interception has privacy and legal implications — ensure consent and compliance.
• High availability and scaling: Single proxy, active/passive, or cluster/load-balancer?
• Logging and retention: Define which logs you need (access, error, TLS details) and retention policies.

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System requirements and prerequisites

• A supported OS (Linux distributions are typical — Debian/Ubuntu, CentOS/RHEL).
• Sufficient CPU, memory, and disk (TLS termination is CPU-intensive; allocate more CPU and RAM for large volumes).
• Network interfaces for management and traffic handling.
• Valid TLS certificates (for interception/termination or for the proxy’s management UI/API).
• Access to directory/auth services if you plan to integrate authentication (LDAP/AD).
• Administrative access to client configuration mechanisms (GPOs, mobile device management, PAC files, or DHCP WPAD).

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Installation

1. Obtain the Etlin HTTP Proxy package for your OS (official repository, package, or binary).
2. Install dependencies (SSL/TLS libraries like OpenSSL, logging tools, systemd service files).
3. Install the package (example for Debian/Ubuntu):

   
   sudo dpkg -i etlin-proxy_latest_amd64.deb sudo apt-get -f install 

4. Enable and start the service:

   
   sudo systemctl enable etlin-proxy sudo systemctl start etlin-proxy 

5. Verify the service is running and listening on the configured ports:

   
   sudo ss -lntp | grep etlin 

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Basic configuration structure

Etlin configuration commonly uses a main config file and modular includes for policies, ACLs, and certificates. Typical sections:

• Global settings: listening ports, worker threads, logging level, admin interface.
• Network listeners: HTTP port (usually ⁄₈₀₈₀) and HTTPS intercept/forward ports.
• Access control lists (ACLs): allow/deny rules by IP, user, destination, or URL regex.
• Authentication backends: LDAP, Kerberos, local file.
• Caching policy: cache size, object size limits, cache refresh rules.
• TLS settings: CA certificate for interception, certificate rotation, allowed TLS versions, cipher suites.
• Logging: access formats, rotation, remote logging (SIEM), and retention.

Example (simplified) snippet format:

global {   listen 0.0.0.0:3128   workers 8   log_level info } listener https_intercept {   port 3129   tls_intercept true   ca_cert /etc/etlin/ca.pem } acl {   allow 10.0.0.0/8   deny all } 

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Enabling HTTPS/TLS interception (mitm)

Intercepting HTTPS enables content scanning, URL filtering, and DLP, but has strong privacy and legal implications. Only enable when you have legal authority and user consent.

Steps:

1. Generate a private CA for Etlin (or use an internal PKI). Protect the CA private key.

   
   openssl genrsa -out etlin-ca.key 4096 openssl req -x509 -new -nodes -key etlin-ca.key -sha256 -days 3650 -out etlin-ca.crt -subj "/CN=Etlin Internal CA" 

2. Install the CA certificate into client trust stores (domain-joined Windows via Group Policy, MDM for mobile devices, or manual install for BYOD).
3. Configure Etlin to use the CA for on-the-fly certificate generation and to intercept TLS: set CA path, enable SNI-based filtering, and define allowed/disallowed hosts for interception.
4. Configure cipher suites and minimum TLS versions. Prefer disabling TLS 1.0/1.1 and weak ciphers.
5. Implement exclusions for sensitive services (banking, medical, legal) to avoid intercepting those domains.
6. Test interception with a controlled client and verify the client sees Etlin’s CA as the issuer for intercepted connections.

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Authentication and authorization

• For domain environments, integrate with Kerberos or NTLM for single sign-on. Configure SPNs and ensure time sync.
• LDAP/AD: configure bind DN, search base, and group-based rules for granular policies.
• Fallback: basic auth or client certificate authentication for non-domain devices.
• Map authenticated identities to policies (e.g., students vs. staff, contractors vs. employees).

Example policy rules:

• Allow staff HTTPS access to internal SaaS; block P2P sites for contractors.
• Rate-limit guest network users and apply stricter content filtering.

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Access control, URL filtering, and malware scanning

• Use ACLs to permit/deny networks, users, or destinations.
• Integrate URL categorization feeds (commercial or open-source) to filter malicious/phishing content.
• Connect Etlin to an antivirus/malware scanning engine for file scanning in transit (e.g., ClamAV or commercial engines via ICAP).
• Block or sanitize downloads by file type and size.
• Enforce Safe Search and other search engine parameters via header and URL rewrites.

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Logging, monitoring, and alerting

• Configure detailed access logs: timestamp, client IP, username, request URL, method, status, bytes, and TLS details when intercepted.
• Forward logs to a central SIEM (syslog, RFC5424) and set up dashboards for top domains, blocked requests, and user activity.
• Monitor resource usage (CPU, memory, disk I/O) and TLS session counts.
• Create alerts for unusual traffic spikes, high error rates, or certificate expiration.

Log rotation example:

/var/log/etlin/access.log {   daily   rotate 14   compress   missingok   notifempty } 

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Performance tuning and caching

• Allocate worker threads/processes based on CPU cores; TLS offload requires more CPU.
• Use HTTP caching for static assets; set appropriate cache-control rules and size limits.
• Consider dedicated SSD for cache storage to reduce latency.
• Tune OS network parameters (file descriptors, TCP backlog, ephemeral port ranges) for high concurrency.
• Offload TLS using hardware accelerators or an upstream TLS terminator if needed.

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High availability and scaling

• For redundancy, deploy multiple Etlin instances behind a load balancer (L4/L7) or use DNS-based failover.
• Synchronize configuration and CA across nodes (securely distribute CA private key or use a separate signing service).
• Use shared caching layer or consistent hashing to improve cache hit rates across cluster.
• Implement health checks for automatic removal of unhealthy nodes.

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Backup, certificate rotation, and maintenance

• Rotate the Etlin CA and server certificates before expiration; maintain a clear rotation schedule.
• Backup configuration files, ACLs, and keys securely (encrypted backups, limited access).
• Regularly update Etlin and dependencies for security patches.
• Periodically audit ACLs, exceptions, and logs for policy drift.

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Testing and verification

• Functional tests: browse common sites, test blocked categories, and confirm caching behavior.
• TLS tests: verify certificate chains on intercepted sessions, confirm TLS versions and ciphers.
• Load testing: simulate peak user load and measure latency, CPU, and memory.
• Security tests: run vulnerability scans and verify sensitive-site exceptions are honored.

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Common troubleshooting

• Clients see certificate warnings: confirm CA installed and trust chain valid.
• Slow performance: check CPU (TLS), disk I/O (cache), and network latency.
• Authentication failures: confirm time sync, SPNs, and correct bind credentials.
• Blocked legitimate sites: review URL categories and whitelist exceptions carefully.

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Example minimal configuration checklist

• [ ] Define scope and legal policy for TLS interception
• [ ] Generate and securely store Etlin CA and server certificates
• [ ] Install CA to client trust stores
• [ ] Install Etlin and enable HTTP listener (3128)
• [ ] Configure HTTPS interception and exclusion list
• [ ] Integrate authentication backend (LDAP/Kerberos)
• [ ] Enable URL filtering and malware scanning (ICAP)
• [ ] Configure logging and SIEM forwarding
• [ ] Load test and enable HA if required
• [ ] Schedule backups and certificate rotation

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Implementing Etlin HTTP Proxy for secure web traffic requires thoughtful planning, especially around HTTPS interception and privacy. Following the steps above gives you a practical roadmap from installation to scaling and maintenance.