lookup.go

// Copyright 2021 CertSync Contributors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0

package certsync

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"strings"
)

func validReverse(cfg *Config, ip net.IP, host string) bool {
	addrList, err := cfg.Resolver.LookupAddr(context.Background(), ip.String())
	if err != nil {
		return false
	}
	for _, a := range addrList {
		if strings.TrimSuffix(a, ".") == host {
			return true
		}
	}
	return false
}

// ValidateAddresses ...
func ValidateAddresses(cfg *Config, hostName string, hostAddr net.IP) error {
	addrList, err := cfg.Resolver.LookupIPAddr(context.Background(), hostName)
	if err != nil {
		return fmt.Errorf("validation failed due to lookup failure: %v", err)
	}
	for _, addr := range addrList {
		if addr.IP.Equal(hostAddr) && validReverse(cfg, addr.IP, hostName) {
			return nil
		}
	}
	return fmt.Errorf("address %q is not valid for host %q", hostAddr, hostName)
}

// IPFromRequest ...
func IPFromRequest(r *http.Request) (net.IP, error) {
	if r == nil {
		return nil, fmt.Errorf("requestor host:port is empty")
	}
	if r.Header.Get(headerXFF) != "" {
		ip := net.ParseIP(strings.Split(r.Header.Get(headerXFF), " ")[0])
		if ip != nil {
			return ip, nil
		}
	}
	h, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return nil, fmt.Errorf("invalid requestor host:port combination: %v", err)
	}
	ip := net.ParseIP(h)
	return ip, nil
}