From fb4926df1e6d4f99fbe22ab77e7af8be2db10464 Mon Sep 17 00:00:00 2001
From: Matt Burchett <matt@mattburchett.com>
Date: Mon, 26 Nov 2018 22:56:21 -0600
Subject: [PATCH] Initial commit

---
 cmd/main.go              | 30 ++++++++++++++++
 config.json              |  5 +++
 pkg/config/config.go     | 43 +++++++++++++++++++++++
 pkg/model/model.go       | 13 +++++++
 pkg/resolver/resolver.go | 74 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 165 insertions(+)
 create mode 100644 cmd/main.go
 create mode 100644 config.json
 create mode 100644 pkg/config/config.go
 create mode 100644 pkg/model/model.go
 create mode 100644 pkg/resolver/resolver.go

diff --git a/cmd/main.go b/cmd/main.go
new file mode 100644
index 0000000..1320e3b
--- /dev/null
+++ b/cmd/main.go
@@ -0,0 +1,30 @@
+package main
+
+import (
+	"flag"
+	"log"
+
+	"git.linuxrocker.com/mattburchett/go_tab-magic/pkg/config"
+	"git.linuxrocker.com/mattburchett/go_tab-magic/pkg/resolver"
+)
+
+func main() {
+	var c string
+	var debug bool
+
+	flag.StringVar(&c, "config", "", "Configuration to load")
+	flag.BoolVar(&debug, "debug", false, "Enables Debugging Mode")
+	flag.Parse()
+
+	// Stop the app if they're missing required flags.
+	if c == "" {
+		log.Fatal("You need to specify a configuration file.")
+	}
+
+	cfg, err := config.GetConfig(c, debug)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	resolver.PerformZoneTransfer(cfg)
+}
diff --git a/config.json b/config.json
new file mode 100644
index 0000000..98a04ce
--- /dev/null
+++ b/config.json
@@ -0,0 +1,5 @@
+{
+    "resolver": "172.19.0.5",
+    "resolverPort": 53,
+    "domains": [ "kc.linuxrocker.com"]
+}
\ No newline at end of file
diff --git a/pkg/config/config.go b/pkg/config/config.go
new file mode 100644
index 0000000..2b35286
--- /dev/null
+++ b/pkg/config/config.go
@@ -0,0 +1,43 @@
+package config
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+)
+
+// Config - This struct will hold configuration components.
+type Config struct {
+	Resolver     string   `json:"resolver"`
+	ResolverPort int      `json:"resolverPort"`
+	Domains      []string `json:"domains"`
+}
+
+//GetConfig gets the configuration values for the api using the file in the supplied configPath.
+func GetConfig(configPath string, debug bool) (Config, error) {
+	if _, err := os.Stat(configPath); os.IsNotExist(err) {
+		return Config{}, fmt.Errorf("could not find the config file at path %s", configPath)
+	}
+	if debug {
+		log.Println("Loading Configuration File: " + configPath)
+	}
+	return loadConfigFromFile(configPath)
+}
+
+//if the config loaded from the file errors, no defaults will be loaded and the app will exit.
+func loadConfigFromFile(configPath string) (conf Config, err error) {
+	file, err := os.Open(configPath)
+	if err != nil {
+		log.Printf("Error opening config file: %v", err)
+	} else {
+		defer file.Close()
+
+		err = json.NewDecoder(file).Decode(&conf)
+		if err != nil {
+			log.Printf("Error decoding config file: %v", err)
+		}
+	}
+
+	return conf, err
+}
diff --git a/pkg/model/model.go b/pkg/model/model.go
new file mode 100644
index 0000000..2a886fa
--- /dev/null
+++ b/pkg/model/model.go
@@ -0,0 +1,13 @@
+package model
+
+type Results struct {
+	IP       string `json:"ip"`
+	Hostname string `json:"hostname"`
+	TXT      string `json:"TXT,omitempty"`
+}
+
+type UniqResults struct {
+	IP       string `json:"ip"`
+	Hostname string `json:"hostname"`
+	TXT      string `json:"TXT,omitempty"`
+}
diff --git a/pkg/resolver/resolver.go b/pkg/resolver/resolver.go
new file mode 100644
index 0000000..c3cf426
--- /dev/null
+++ b/pkg/resolver/resolver.go
@@ -0,0 +1,74 @@
+package resolver
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"strings"
+
+	"git.linuxrocker.com/mattburchett/go_tab-magic/pkg/config"
+	"github.com/miekg/dns"
+)
+
+// LookupName returns IPv4 address from A record or error.
+func lookupName(fqdn, serverAddr string) (string, error) {
+	m := &dns.Msg{}
+	m.SetQuestion(dns.Fqdn(fqdn), dns.TypeA)
+	in, err := dns.Exchange(m, serverAddr)
+	if err != nil {
+		return "", err
+	}
+	if len(in.Answer) < 1 {
+		return "", errors.New("no Answer")
+	}
+	if a, ok := in.Answer[0].(*dns.A); ok {
+		ip := a.A.String()
+		return ip, nil
+	}
+	return "", errors.New("no A record returned")
+}
+
+func PerformZoneTransfer(config config.Config) {
+	data := make([]string, 0)
+
+	// Do the transfer
+	for _, i := range config.Domains {
+		server := fmt.Sprintf("%s:%d", config.Resolver, config.ResolverPort)
+		tr := dns.Transfer{}
+		m := &dns.Msg{}
+		m.SetAxfr(dns.Fqdn(i))
+		in, err := tr.In(m, server)
+		if err != nil {
+			log.Fatal(err)
+		}
+		for ex := range in {
+			for _, a := range ex.RR {
+				var ip, hostname, txt string
+				switch v := a.(type) {
+				case *dns.TXT:
+					txt = string(v.Txt[0])
+					hostname = v.Hdr.Name
+					cip, err := lookupName(strings.TrimRight(v.Hdr.Name, "."), server)
+					if err != nil || cip == "" {
+						continue
+					}
+					ip = cip
+				case *dns.A:
+					ip = v.A.String()
+					hostname = v.Hdr.Name
+				case *dns.CNAME:
+					cip, err := lookupName(v.Target, server)
+					if err != nil || cip == "" {
+						continue
+					}
+					ip = cip
+					hostname = v.Hdr.Name
+				default:
+					continue
+				}
+				data = append(data, fmt.Sprintf("%v %v %v", hostname, ip, txt))
+			}
+		}
+	}
+	fmt.Println(data)
+}