happyDomain/utils/dns.go

// Copyright or © or Copr. happyDNS (2020)
//
// contact@happydomain.org
//
// This software is a computer program whose purpose is to provide a modern
// interface to interact with DNS systems.
//
// This software is governed by the CeCILL license under French law and abiding
// by the rules of distribution of free software.  You can use, modify and/or
// redistribute the software under the terms of the CeCILL license as
// circulated by CEA, CNRS and INRIA at the following URL
// "http://www.cecill.info".
//
// As a counterpart to the access to the source code and rights to copy, modify
// and redistribute granted by the license, users are provided only with a
// limited warranty and the software's author, the holder of the economic
// rights, and the successive licensors have only limited liability.
//
// In this respect, the user's attention is drawn to the risks associated with
// loading, using, modifying and/or developing or reproducing the software by
// the user in light of its specific status of free software, that may mean
// that it is complicated to manipulate, and that also therefore means that it
// is reserved for developers and experienced professionals having in-depth
// computer knowledge. Users are therefore encouraged to load and test the
// software's suitability as regards their requirements in conditions enabling
// the security of their systems and/or data to be ensured and, more generally,
// to use and operate it in the same conditions as regards security.
//
// The fact that you are presently reading this means that you have had
// knowledge of the CeCILL license and that you accept its terms.

package utils

import (
	"github.com/miekg/dns"
)

// SplitN splits a string into N sized string chunks.
// This function is a copy of https://github.com/miekg/dns/blob/master/types.go#L1509
// awaiting its exportation
func SplitN(s string, n int) []string {
	if len(s) < n {
		return []string{s}
	}
	sx := []string{}
	p, i := 0, n
	for {
		if i <= len(s) {
			sx = append(sx, s[p:i])
		} else {
			sx = append(sx, s[p:])
			break

		}
		p, i = p+n, i+n
	}

	return sx
}

// IsDNSSECType returns true if the given rrtype is generally autogenerated by
// NS server.
func IsDNSSECType(rrtype uint16) bool {
	return rrtype == dns.TypeNSEC ||
		rrtype == dns.TypeNSEC3 ||
		rrtype == dns.TypeNSEC3PARAM ||
		rrtype == dns.TypeDNSKEY ||
		rrtype == dns.TypeRRSIG
}

// DomainFQDN normalizes the domain by adding the origin if it is relative (not
// ended by .).
func DomainFQDN(subdomain string, origin string) string {
	if subdomain == "" || subdomain[len(subdomain)-1] == '.' {
		return subdomain
	} else if subdomain == "@" {
		return origin
	} else {
		return subdomain + "." + origin
	}
}

// DomainJoin appends each relative domains passed as argument.
func DomainJoin(domains ...string) (ret string) {
	for _, d := range domains {
		if d == "@" {
			break
		} else if d != "" {
			ret += "." + d
		}

		if len(ret) > 0 && ret[len(ret)-1] == '.' {
			break
		}
	}

	if len(ret) >= 1 {
		ret = ret[1:]
	}

	return
}