58 lines
1.5 KiB
Go
58 lines
1.5 KiB
Go
// SPDX-License-Identifier: BSD-3-Clause
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package util
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import (
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"errors"
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"fmt"
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"strings"
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"time"
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"github.com/miekg/dns"
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)
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type Response struct {
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Answers Answers `json:"Response"` // These be DNS query answers
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}
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// The Answers struct is the basic structure of a DNS request
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// to be returned to the user upon making a request
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type Answers struct {
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Server string `json:"Server"` // The server to make the DNS request from
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Request uint16 `json:"Request"` // The type of request
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Name string `json:"Name"` // The domain name to make a DNS request for
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RTT time.Duration `json:"RTT"` // The time it took to make the DNS query
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}
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// Given an IP or phone number, return a canonical string to be queried
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func ReverseDNS(address string, query string) (string, error) {
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if query == "PTR" {
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return dns.ReverseAddr(address)
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} else if query == "NAPTR" {
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// get rid of characters not needed
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replacer := strings.NewReplacer("+", "", " ", "", "-", "")
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address = replacer.Replace(address)
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// reverse the order of the string
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address = reverse(address)
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var arpa strings.Builder
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// Make it canonical
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for _, c := range address {
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fmt.Fprintf(&arpa, "%c.", c)
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}
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arpa.WriteString("e164.arpa.")
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return arpa.String(), nil
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}
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return "", errors.New("ReverseDNS: -x flag given but no IP found")
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}
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// Reverse a string, return the string in reverse
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func reverse(s string) string {
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rns := []rune(s)
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for i, j := 0, len(rns)-1; i < j; i, j = i+1, j-1 {
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rns[i], rns[j] = rns[j], rns[i]
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}
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return string(rns)
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}
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