Cntlm is a fast, lightweight NTLM/NTLMv2 authenticating HTTP proxy written in plain C. It serves as a middleman between local applications and a strict corporate proxy, converting unauthenticated or standard HTTP requests into fully authenticated NTLM corporate traffic. This is essential for local development tools (like Docker, npm, pip, or Git) that cannot natively negotiate Microsoft NTLM handshakes.
Configuring Cntlm for seamless internet access involves key stages: installation, credential hashing, configuration, and application integration. Core Configuration File Setup
The main configuration file is named cntlm.conf on Linux or cntlm.ini on Windows. When editing this file, do not wrap your parameter strings in quotes or escape spaces, as values are parsed literally. You must define these fundamental parameters:
Username: Your corporate network or proxy account user identity.
Domain: The corporate Active Directory or network domain name.
Proxy: The exact IP address (or pingable hostname) and port of your corporate parent proxy (e.g., 10.0.0.1:8080). You can add multiple Proxy lines for failover.
Listen: The local port where Cntlm will listen on your machine. The default is 3128. Generating Secure Hashes (No Plaintext Passwords)
To avoid saving your sensitive corporate password in plaintext inside the configuration file, utilize Cntlm’s built-in hashing flag. Cntlm: Fast NTLM Authentication Proxy in C
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