hostutil

Documentation

Overview

Package hostutil provides pure host-string normalization helpers shared across the proxy (policy matching, category lookups, scan/bypass keys). It is a self-contained seam (stdlib + golang.org/x/net/idna, no Culvert coupling) extracted from package main per ADR-0002 / ADR-0003 to unblock the catdb and scan clusters, which both depend on these helpers.

Index

• func NormalizeHost(host string) string
• func StripHostPort(host string) string

Functions

func NormalizeHost

func NormalizeHost(host string) string

NormalizeHost applies IDNA2008 normalization (RFC 5890) to a hostname, converting Unicode/Punycode domains to their canonical ASCII form. This prevents IDN homograph attacks where visually similar Unicode characters (e.g., Cyrillic 'а' vs Latin 'a') bypass blocklists and policy rules.

Returns the lowercased, IDNA-normalized host. If normalization fails (e.g., the host is an IP address or already ASCII), the input is returned lowercased — fail-open for usability since most hosts are pure ASCII.

func StripHostPort

func StripHostPort(host string) string

StripHostPort removes a trailing :port and IPv6 brackets from a host value, accepting all shapes that reach scan/bypass lookups: "host:port", "[v6]:port", "[v6]", bare "v6", and bare "host". A naive LastIndex(host, ":") cut corrupts bare IPv6 literals (already de-bracketed by net.SplitHostPort upstream) — "2001:db8::1" would become "2001:db8:".