mirror of https://github.com/hashicorp/consul
84 lines
2.3 KiB
Go
84 lines
2.3 KiB
Go
// Copyright (c) HashiCorp, Inc.
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// SPDX-License-Identifier: BUSL-1.1
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package dnsutil
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import (
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"errors"
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"net"
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"regexp"
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"slices"
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"strings"
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"github.com/miekg/dns"
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)
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// MaxLabelLength is the maximum length for a name that can be used in DNS.
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const (
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MaxLabelLength = 63
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arpaLabel = "arpa"
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arpaIPV4Label = "in-addr"
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arpaIPV6Label = "ip6"
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)
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// InvalidNameRe is a regex that matches characters which can not be included in
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// a DNS name.
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var InvalidNameRe = regexp.MustCompile(`[^A-Za-z0-9\\-]+`)
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// matches valid DNS labels according to RFC 1123, should be at most 63
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// characters according to the RFC
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var validLabel = regexp.MustCompile(`^[a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?$`)
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// IsValidLabel returns true if the string given is a valid DNS label (RFC 1123).
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// Note: the only difference between RFC 1035 and RFC 1123 labels is that in
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// RFC 1123 labels can begin with a number.
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func IsValidLabel(name string) bool {
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return validLabel.MatchString(name)
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}
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// ValidateLabel is similar to IsValidLabel except it returns an error
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// instead of false when name is not a valid DNS label. The error will contain
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// reference to what constitutes a valid DNS label.
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func ValidateLabel(name string) error {
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if !IsValidLabel(name) {
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return errors.New("a valid DNS label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character")
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}
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return nil
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}
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// IPFromARPA returns the net.IP address from a fully-qualified ARPA PTR domain name.
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// If the address is an invalid format, it returns nil.
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func IPFromARPA(arpa string) net.IP {
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labels := dns.SplitDomainName(arpa)
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if len(labels) != 6 && len(labels) != 34 {
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return nil
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}
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// The last two labels should be "in-addr" or "ip6" and "arpa"
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if labels[len(labels)-1] != arpaLabel {
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return nil
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}
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var ip net.IP
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switch labels[len(labels)-2] {
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case arpaIPV4Label:
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parts := labels[:len(labels)-2]
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slices.Reverse(parts)
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ip = net.ParseIP(strings.Join(parts, "."))
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case arpaIPV6Label:
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parts := labels[:len(labels)-2]
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slices.Reverse(parts)
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// Condense the different words of the address
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address := strings.Join(parts[0:4], "")
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for i := 4; i <= len(parts)-4; i = i + 4 {
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word := parts[i : i+4]
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address = address + ":" + strings.Join(word, "")
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}
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ip = net.ParseIP(address)
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// default: fallthrough
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}
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return ip
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}
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