├── .gitignore
├── CHANGELOG.md
├── LICENSE.md
├── README.md
├── go.mod
├── go.sum
├── justfile
└── main.go


/.gitignore:
--------------------------------------------------------------------------------
 1 | # If you prefer the allow list template instead of the deny list, see community template:
 2 | # https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
 3 | #
 4 | # Binaries for programs and plugins
 5 | *.exe
 6 | *.exe~
 7 | *.dll
 8 | *.so
 9 | *.dylib
10 | 
11 | # Test binary, built with `go test -c`
12 | *.test
13 | 
14 | # Output of the go coverage tool, specifically when used with LiteIDE
15 | *.out
16 | 
17 | # Dependency directories (remove the comment below to include it)
18 | # vendor/
19 | 
20 | bin/
21 | 
22 | # Go workspace file
23 | go.work
24 | 
25 | extip
26 | 
27 | .DS_Store


--------------------------------------------------------------------------------
/CHANGELOG.md:
--------------------------------------------------------------------------------
 1 | <a name="v0.2.0"></a>
 2 | ## [v0.2.0] - 2023-03-03
 3 | ### Features
 4 | - now has the option to use a custom [extip server](https://github.com/hrbrmstr/extip-svr)
 5 | 
 6 | 
 7 | <a name="v0.1.0"></a>
 8 | ## [v0.1.0] - 2023-02-28
 9 | ### Features
10 | - initial release
11 | 


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/LICENSE.md:
--------------------------------------------------------------------------------
 1 | The MIT License (MIT)
 2 | 
 3 | Copyright (c) 2023 boB Rudis
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.


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/README.md:
--------------------------------------------------------------------------------
 1 | # extip - retrieve your external IP address via DNS
 2 | 
 3 | Small Golang package/cli that uses special DNS resolvers to return your external IP address.
 4 | 
 5 | By default it uses Google, OpenDNS, and Akamai. If there is a conflict between the resolver answers a message will be delivered on stderr with the conflicting values.
 6 | 
 7 | Alternatively, you can specify an [extip server](https://github.com/hrbrmstr/extip-svr) to use. See below for how to do that.
 8 | 
 9 | ## References
10 | 
11 | - [Bizarre and Unusual Uses of DNS](https://fosdem.org/2023/schedule/event/dns_bizarre_and_unusual_uses_of_dns/)
12 | - [Akamai blog](https://www.akamai.com/blog/developers/introducing-new-whoami-tool-dns-resolver-information)
13 | 
14 | ## Build
15 | 
16 | ```
17 | just build # requires https://github.com/casey/just
18 | ```
19 | 
20 | ## Install
21 | 
22 | ```
23 | go install -ldflags "-s -w" github.com/hrbrmstr/extip@latest
24 | ```
25 | 
26 | ## Options
27 | 
28 | ```
29 | Lookup external IP address via DNS.
30 | 
31 | Defaults to using Akamai, OpenDNS, and Google services.
32 | You can specify an extip server via the following command line options.
33 | NOTE: Both server and domain should be specified to override default behavior.
34 | More info about running an extip server can be found at <https://github.com/hrbrmstr/extip-svr>.
35 | 
36 | extip 0.2.0
37 | Usage: extip [--server EXTIP_SERVER] [--domain DOMAIN] [--record-type RECORD_TYPE] [--port PORT]
38 | 
39 | Options:
40 |   --server EXTIP_SERVER, -s EXTIP_SERVER
41 |                          extip-svr IP/FQDN. e.g., ip.rudis.net [env: EXTIP_SERVER]
42 |   --domain DOMAIN, -d DOMAIN
43 |                          Domain to use for IP Lookup. e.g., myip.is [env: EXTIP_DOMAIN]
44 |   --record-type RECORD_TYPE, -r RECORD_TYPE
45 |                          DNS record type to lookup. One of TXT or A. [default: TXT, env: EXTIP_RECORD_TYPE]
46 |   --port PORT, -p PORT   Port extip resolver is listening on. [default: 53, env: EXTIP_PORT]
47 |   --help, -h             display this help and exit
48 | ```
49 | 
50 | ## Usage
51 | 
52 | Default:
53 | 
54 | ```
55 | extip
56 | ```
57 | 
58 | Use an extip server:
59 | 
60 | ```
61 | extip -s ip.rudis.net -d ip.is
62 | ```


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/go.mod:
--------------------------------------------------------------------------------
1 | module github.com/hrbrmstr/extip
2 | 
3 | go 1.19
4 | 
5 | require (
6 | 	github.com/alexflint/go-arg v1.4.3 // indirect
7 | 	github.com/alexflint/go-scalar v1.1.0 // indirect
8 | )
9 | 


--------------------------------------------------------------------------------
/go.sum:
--------------------------------------------------------------------------------
 1 | github.com/alexflint/go-arg v1.4.3 h1:9rwwEBpMXfKQKceuZfYcwuc/7YY7tWJbFsgG5cAU/uo=
 2 | github.com/alexflint/go-arg v1.4.3/go.mod h1:3PZ/wp/8HuqRZMUUgu7I+e1qcpUbvmS258mRXkFH4IA=
 3 | github.com/alexflint/go-scalar v1.1.0 h1:aaAouLLzI9TChcPXotr6gUhq+Scr8rl0P9P4PnltbhM=
 4 | github.com/alexflint/go-scalar v1.1.0/go.mod h1:LoFvNMqS1CPrMVltza4LvnGKhaSpc3oyLEBUZVhhS2o=
 5 | github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 6 | github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 7 | github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 8 | github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 9 | github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
10 | github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
11 | gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
12 | gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
13 | 


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/justfile:
--------------------------------------------------------------------------------
 1 | #!/usr/bin/env just --justfile
 2 | 
 3 | set shell := ["zsh", "-cu"] 
 4 | 
 5 | # Lists the justfile commands
 6 | @default:
 7 |   @just --list
 8 | 
 9 | # Build the package
10 | @build:
11 |   go build -ldflags "-s -w" -o bin/extip
12 | 
13 | @run: build
14 | 	./bin/extip
15 | 
16 | # Be a good citizen
17 | @fmt:
18 |   go fmt
19 | 
20 | # Build for other platforms
21 | @release-build:
22 |   GOOS=windows GOARCH=386 go build -ldflags "-s -w" -o bin/extip.exe main.go && cd bin && zip extip.zip extip.exe && rm extip.exe
23 |   GOOS=linux GOARCH=amd64 go build -ldflags "-s -w" -o bin/extip-linux-amd64 main.go && cd bin && gzip extip-linux-amd64
24 |   GOOS=linux GOARCH=arm64 go build -ldflags "-s -w" -o bin/extip-linux-arm64 main.go && cd bin && gzip extip-linux-arm64
25 |   GOOS=darwin GOARCH=amd64 go build -ldflags "-s -w" -o bin/extip-darwin-amd64 main.go && cd bin && gzip extip-darwin-amd64
26 |   GOOS=darwin GOARCH=arm64 go build -ldflags "-s -w" -o bin/extip-darwin-arm64 main.go && cd bin && gzip extip-darwin-arm64
27 | 
28 | # Check results against dig. Requires dig.
29 | @test: build
30 |   [ "$(dig myip.opendns.com @resolver1.opendns.com +short)" = "$(./bin/extip)" ] && echo "Passed OpenDNS test"
31 |   [ "$(dig o-o.myaddr.1.google.com @ns1.google.com TXT +short | tr -d '"')" = "$(./bin/extip)" ] && echo "Passed Google test"
32 |   [ "$(dig +short TXT whoami.ds.akahelp.net @$(dig +short +answer NS akamai.com | head -1) | grep ns | sed -e 's/[^0-9\.\:]//g')" = "$(./bin/extip)" ] && echo "Passed Akamai test"
33 |   [ "$(dig +short TXT myip.is @ip.rudis.net | tr -d '"')" = "$(./bin/extip)" ] && echo "Passed custom extip server test"


--------------------------------------------------------------------------------
/main.go:
--------------------------------------------------------------------------------
  1 | package main
  2 | 
  3 | import (
  4 | 	"context"
  5 | 	"fmt"
  6 | 	"log"
  7 | 	"net"
  8 | 	"os"
  9 | 	"regexp"
 10 | 	"strconv"
 11 | 	"strings"
 12 | 	"time"
 13 | 
 14 | 	"github.com/alexflint/go-arg"
 15 | )
 16 | 
 17 | const (
 18 | 	version         = "0.2.0"
 19 | 	resolverTimeout = 10000
 20 | 	defaultPort     = 53
 21 | 
 22 | 	googleResolver  = "ns1.google.com"
 23 | 	openDNSResolver = "resolver1.opendns.com"
 24 | 
 25 | 	googleHost   = "o-o.myaddr.1.google.com"
 26 | 	openDNSHost  = "myip.opendns.com"
 27 | 	akamaiHost   = "whoami.ds.akahelp.net"
 28 | 	akamaiDomain = "akamai.com"
 29 | )
 30 | 
 31 | // Test if all strings in a list are equal
 32 | func AllEqual(a []string) bool {
 33 | 	for i := 1; i < len(a); i++ {
 34 | 		if a[i] != a[0] {
 35 | 			return false
 36 | 		}
 37 | 	}
 38 | 	return true
 39 | }
 40 | 
 41 | // Remove last char in a string if it is `suffix`
 42 | func TrimSuffix(s, suffix string) string {
 43 | 	hasSuf := strings.HasSuffix(s, suffix)
 44 | 	if hasSuf {
 45 | 		s = s[:len(s)-len(suffix)]
 46 | 	}
 47 | 	return s
 48 | }
 49 | 
 50 | // Setup a specific resovler to use for DNS lookups
 51 | func UseResolver(resolver string, port int) *net.Resolver {
 52 | 
 53 | 	return &net.Resolver{
 54 | 		PreferGo: true,
 55 | 		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
 56 | 			d := net.Dialer{Timeout: time.Millisecond * time.Duration(resolverTimeout)}
 57 | 			return d.DialContext(ctx, network, resolver+":"+strconv.Itoa(port))
 58 | 		},
 59 | 	}
 60 | 
 61 | }
 62 | 
 63 | // Get one of Akamai's authoritative nameservers
 64 | func AkamaiResolver() (string, error) {
 65 | 
 66 | 	ns, err := net.LookupNS(akamaiDomain)
 67 | 
 68 | 	nsHost := ""
 69 | 	if err == nil {
 70 | 		nsHost = TrimSuffix((*ns[0]).Host, ".")
 71 | 	}
 72 | 
 73 | 	return nsHost, err
 74 | 
 75 | }
 76 | 
 77 | // Get our local, external IP via Akamai's hack
 78 | //
 79 | // Akamai returns "ns" "ip.ad.dr.ess" so we have to get rid of cruft
 80 | func AkamaiExtIP() ([]string, error) {
 81 | 
 82 | 	regEx := regexp.MustCompile(`[^0-9\.\:]`)
 83 | 	akamaiResolver, err := AkamaiResolver()
 84 | 
 85 | 	if err != nil {
 86 | 		return []string{""}, err
 87 | 	}
 88 | 
 89 | 	r := UseResolver(akamaiResolver, defaultPort)
 90 | 	txts, err := r.LookupTXT(context.Background(), akamaiHost)
 91 | 
 92 | 	if err != nil {
 93 | 		return []string{""}, err
 94 | 	}
 95 | 
 96 | 	txts[0] = regEx.ReplaceAllString(txts[0], "")
 97 | 
 98 | 	return txts, err
 99 | 
100 | }
101 | 
102 | // Get our local, external IP via Google's hack
103 | func GoogleExtIP() ([]string, error) {
104 | 
105 | 	r := UseResolver(googleResolver, defaultPort)
106 | 	txts, err := r.LookupTXT(context.Background(), googleHost)
107 | 
108 | 	if err != nil {
109 | 		txts = []string{""}
110 | 	}
111 | 
112 | 	return txts, err
113 | 
114 | }
115 | 
116 | // Get our local, external IP via OpenDNS's hack
117 | func OpenDNSExtIP() ([]string, error) {
118 | 
119 | 	r := UseResolver(openDNSResolver, defaultPort)
120 | 	ips, err := r.LookupHost(context.Background(), openDNSHost)
121 | 
122 | 	if err != nil {
123 | 		ips = []string{""}
124 | 	}
125 | 
126 | 	return ips, err
127 | 
128 | }
129 | 
130 | // Get our local, external IP via custom extip resolver
131 | func CustomExtIP(resolver string, host string, rectype string, port int) ([]string, error) {
132 | 
133 | 	r := UseResolver(resolver, port)
134 | 
135 | 	var res [](string)
136 | 	var err error
137 | 
138 | 	if rectype == "A" {
139 | 		res, err = r.LookupHost(context.Background(), host)
140 | 	} else {
141 | 		res, err = r.LookupTXT(context.Background(), host)
142 | 	}
143 | 
144 | 	if err != nil {
145 | 		res = []string{""}
146 | 	}
147 | 
148 | 	return res, err
149 | 
150 | }
151 | 
152 | type args struct {
153 | 	Server     string `arg:"-s,--server,env:EXTIP_SERVER" help:"extip-svr IP/FQDN. e.g., ip.rudis.net" placeholder:"EXTIP_SERVER"`
154 | 	Domain     string `arg:"-d,--domain,env:EXTIP_DOMAIN" help:"Domain to use for IP Lookup. e.g., myip.is" placeholder:"DOMAIN"`
155 | 	RecordType string `arg:"-r,--record-type,env:EXTIP_RECORD_TYPE" help:"DNS record type to lookup. One of TXT or A." placeholder:"RECORD_TYPE" default:"TXT"`
156 | 	Port       int    `arg:"-p,--port,env:EXTIP_PORT" help:"Port extip resolver is listening on." placeholder:"PORT" default:"53"`
157 | }
158 | 
159 | func (args) Description() string {
160 | 	return "Lookup external IP address via DNS.\n\nDefaults to using Akamai, OpenDNS, and Google services.\nYou can specify an extip server via the following command line options.\nNOTE: Both server and domain should be specified to override default behavior.\nMore info about running an extip server can be found at <https://github.com/hrbrmstr/extip-svr>.\n"
161 | }
162 | 
163 | func (args) Version() string {
164 | 	return "extip " + version
165 | }
166 | 
167 | // TODO: Make this a proper CLI with cmdline options since we have 3 services
168 | func main() {
169 | 
170 | 	l := log.New(os.Stderr, "", 1)
171 | 
172 | 	var args args
173 | 
174 | 	arg.MustParse(&args)
175 | 
176 | 	if args.Server != "" && args.Domain != "" {
177 | 		custom, cerr := CustomExtIP(args.Server, args.Domain, args.RecordType, args.Port)
178 | 		if cerr != nil {
179 | 			l.Println("No DNS resolutions worked.")
180 | 			os.Exit(3)
181 | 		} else {
182 | 			fmt.Println(custom[0])
183 | 			os.Exit(0)
184 | 		}
185 | 
186 | 	}
187 | 
188 | 	opendns, oerr := OpenDNSExtIP()
189 | 	google, gerr := GoogleExtIP()
190 | 	akamai, aerr := AkamaiExtIP()
191 | 
192 | 	if (oerr != nil) && (gerr != nil) && (aerr != nil) {
193 | 		l.Println("No DNS resolutions worked.")
194 | 		os.Exit(2)
195 | 	}
196 | 
197 | 	if oerr != nil {
198 | 		l.Println("OpenDNS resolver query failed.")
199 | 		opendns[0] = "FAILED"
200 | 	}
201 | 
202 | 	if gerr != nil {
203 | 		l.Println("Google resolver query failed")
204 | 		google[0] = "FAILED"
205 | 	}
206 | 
207 | 	if aerr != nil {
208 | 		l.Println("Akamai resovler query failed")
209 | 		akamai[0] = "FAILED"
210 | 	}
211 | 
212 | 	// If at least one worked, compare the three; if not all equal then error out
213 | 	// otherwise return one of them.
214 | 
215 | 	if AllEqual([]string{akamai[0], google[0], opendns[0]}) {
216 | 
217 | 		fmt.Println(opendns[0])
218 | 
219 | 	} else {
220 | 
221 | 		l.Println("Resolvers have different ideas regarding your external IP address.")
222 | 		l.Printf("Akamai thinks it is: %s\n", akamai[0])
223 | 		l.Printf("Google thinks it is: %s\n", google[0])
224 | 		l.Printf("OpenDNS thinks it is: %s\n", opendns[0])
225 | 
226 | 		os.Exit(1)
227 | 
228 | 	}
229 | 
230 | }
231 | 


--------------------------------------------------------------------------------