echo/middleware/util.go

package middleware

import (
	"strings"
)

func matchScheme(domain, pattern string) bool {
	didx := strings.Index(domain, ":")
	pidx := strings.Index(pattern, ":")
	return didx != -1 && pidx != -1 && domain[:didx] == pattern[:pidx]
}

// matchSubdomain compares authority with wildcard
func matchSubdomain(domain, pattern string) bool {
	if !matchScheme(domain, pattern) {
		return false
	}
	didx := strings.Index(domain, "://")
	pidx := strings.Index(pattern, "://")
	if didx == -1 || pidx == -1 {
		return false
	}
	domAuth := domain[didx+3:]
	// to avoid long loop by invalid long domain
	if len(domAuth) > 253 {
		return false
	}
	patAuth := pattern[pidx+3:]

	domComp := strings.Split(domAuth, ".")
	patComp := strings.Split(patAuth, ".")
	for i := len(domComp)/2 - 1; i >= 0; i-- {
		opp := len(domComp) - 1 - i
		domComp[i], domComp[opp] = domComp[opp], domComp[i]
	}
	for i := len(patComp)/2 - 1; i >= 0; i-- {
		opp := len(patComp) - 1 - i
		patComp[i], patComp[opp] = patComp[opp], patComp[i]
	}

	for i, v := range domComp {
		if len(patComp) <= i {
			return false
		}
		p := patComp[i]
		if p == "*" {
			return true
		}
		if p != v {
			return false
		}
	}
	return false
}