1.0

.gitignore

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+src/mbdns
+src/mbdns.conf
+bin/*
+dist/*

CHANGELOG

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+# 08-09-2018
+
+Functioning implementation tested on `darwin-amd64`, `freebsd-amd64` and `linux-mipsle`
+
++ [x] `darwin-amd64` (macOS 10.13)
++ [x] `freebsd-amd64` (FreeNAS 11)
++ [x] `linux-mipsle` (EdgeOS 1.10, ER-X)
++ [x] Runs from secured JSON-based config
++ [x] Supports `A` and `AAAA` record types against the correct API endpoint
++ [x] Error diagnosis on non-200 returns
++ [x] 1s delay between record update attempts (compile time)
++ [x] 300s delay between full loop update attempts (compile time)
++ [x] Scripts for building a release with embedded `BuildVersion`, `BuildDate` and `GitRev` (printed to console at start)
+
+# 09-09-2018
+
++ [x] Support relocating and renaming `./mbdns.conf` with `--config`

CONTRIBUTING.md

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+# Contributing to mbdns
+
+We welcome contributions to `mbdns` of any kind, including documentation, functional patches, bug reports, issues, feature requests, feature implementations, pull requests, etc.
+
+## Building mbdns
+
+Run [src/build-test](/src/build-test) to build a single binary from your git checkout. `go build` will place it into `../bin/mbdns`.
+
+Run [src/build-rel RELEASE_NAME](/src/build-rel) if you'd like to build all supports binaries for a release. The release script will put the current git revision for `HEAD` into `BuildVersion` if you don't supply `RELEASE_NAME`. `go build` will place binaries into `../bin/RELEASE_NAME`.
+
+## Current supported platform configs
+
+While there's no golang code in `mbdns` that isn't portable to any platform that golang supports, the release build script only builds for platforms we've tested and are known to work.
+
+Those configs are:
+
+| GOOS    | GOARCH | Hardware and OS platform(s)         |
+| :-----: | :----: | :---------------------------------- |
+| linux   | arm    | QNAP                                |
+| linux   | mipsle | Ubiquiti EdgeRouter X, EdgeOS v1.10 |
+| darwin  | amd64  | macOS 10.13, iMac 5K                |
+| freebsd | amd64  | freenas/11.1-stable, HP gen8 G1610T |
+| linux   | amd64  | Ubuntu 18.04 LTS                    |
+
+## Golang requirements
+
+`mbdns` has no special golang requirements. Releases are currently generated by `go version go1.11 darwin/amd64`.
+
+## Licensing
+
+`mbdns` is [MIT licensed](/LICENSE).

README.md

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+# mbdns
+
+`mbdns` is a dynamic DNS update client for the [Mythic Beasts](https://www.mythic-beasts.com/support/api/primary) Primary DNS system, supporting their IPv4 and IPv6 endpoints. Written in [golang](https://golang.org), it supports common home network infrastructure operating systems (FreeBSD, EdgeOS, Linux) and common platform architectures (amd64 and MIPS).
+
+## Configuring mbdns
+
+Take [doc/mbdns.conf.sample](/doc/mbdns.conf.sample) and configure it to your needs, saving as `mbdns.conf`. `mbdns.conf` must be valid JSON or `mbdns` will fail to start.
+
+## Deploying mbdns
+
+* Copy the `mbdns` binary (usually named `mbdns-VERSION-OS-ARCH`) and `mbdns.conf` to your target platform
+* chmod 0400 mbdns.conf so the Mythic Beasts API tokens can only be read by the user you deploy as (ideally use a specific user). `mbdns` will check for you and fail to start if the config is insecurely readable.
+* Run the `mbdns` binary. It will run until you kill it.
+* By default the `mbdns` binary will look for `./mbdns.conf`. You can relocate it (and rename it) and tell `mbdns` with `--config`.
+  * `mbdns --config /etc/mbdns/mbdns.conf`
+
+`mbdns` is written in golang and builds as a statically linked library with no dependencies.
+
+## Practical running
+
+`mbdns` logs to `stdout`. If your target OS supports it, redirect stdout to a file, logrotate that file, and run the binary in the background via the daemonising system of your choice. `mbdns` makes no attempt to daemonise itself.
+
+`mbdns --version` prints the version information and exits immediately.
+
+Running on a Unix-like might go something like this (assuming `mbdns` is in `$PATH`):
+
+`nohup mbdns --config /etc/mbdns/mbdns.conf > /var/log/mbdns 2>&1 &`
+
+## Logging
+
+`mbdns` logs the following:
+
+* version, build date and git commit SHA1 on startup
+* the path to the config file
+* the update command it is attempting to run for the host and domain
+* success or failure including record type and TTL in both cases
+* a small handful of at-startup failure messages if it can't run (no conf, invalid JSON, insecure conf)
+* a message saying it is processing records if it can cleanly start
+
+## License
+
+`mbdns` is MIT licensed

doc/ARCHITECTURE.md

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+# Basic architecture of mbdns
+
+- [x] Read JSON-encoded `[domain token host ttl]` record tuples from a (checked) `0400` file called `mbdns.conf` that lives next to the binary
+- [x] Iterate over each tuple and:
+    - [x] https `POST` `"domain=t.domain;password=t.token;command=REPLACE t.host t.ttl A DYNAMIC_IP"` to `dnsapi.mythic-beasts.com`
+    - [x] Record success and failure but don't handle failure. Just try again later next time around the loop.
+- [x] Do that in loop with a compile-time loop sleep in a background thread/goroutine, running daemonised
+- [x] Some basic logging to stdout
+
+# JSON file format
+
+Because of the way golang does magic unmarshalling into structs, our golang code self-documents the JSON format.
+
+```go
+type record struct {
+	Domain string
+	Token  string
+	Host   string
+    TTL    string
+    Record string
+}
+```
+
+Is unmarshalled from:
+
+```json
+[
+    {
+        "domain" : "some_domain",
+        "token"  : "mythic_beasts_api_token",
+        "host"   : "hostname",
+        "ttl"    : "3600",
+        "record" : "A"
+    }
+]
+```
+
+# Communicating with the Mythic Beasts Primary DNS API
+
+Documentation: [here](https://www.mythic-beasts.com/support/api/primary)
+
+API URL: `https://dnsapi.mythic-beasts.com/`
+
+`GET` is supported but we'll use `POST`. `POST` needs an `application/x-www-form-urlencoded`, which we get from [`net/http`](https://golang.org/pkg/net/http/#pkg-overview)'s `PostForm()` API.
+
+Building the payload is easy:
+
+`http.PostForm(mythicbeastsUrl, url.Values{"key": {"value"}, "key2": {"value2"}} ...)`
+
+So we'll do:
+
+`http.PostForm(mbUrl, url.Values{"domain": {record.Domain}, "password": {record.Token}, "command": {builtCommand}})`
+
+We use the `REPLACE` command and build the rest of the `builtCommand` payload with a `Sprintf()` formatted const string.
+
+`REPLACE` takes the form `REPLACE host TTL record DYNAMIC_IP`
+
+We get HTTP response code 200 (OK) back on success, 4xx in the event of a failure.

doc/mbdns.conf.sample

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+[
+    {
+        "domain" : "yourdomain.com",
+        "token" : "domain_api_password",
+        "host" : "hostname",
+        "ttl" : "3600",
+        "record": "A"
+    },
+    {
+        "domain" : "yourdomain.com",
+        "token" : "domain_api_password",
+        "host" : "hostname",
+        "ttl" : "3600",
+        "record": "AAAA"     
+    }
+]

src/build-rel

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+#!/usr/local/bin/zsh
+
+GIT_SHA=$(git rev-parse --short HEAD)
+B=../bin
+D=../dist
+
+R=${1}
+[[ -z ${R} ]] && R=${GIT_SHA}
+
+[[ -d ${B}/${R} ]] && rm -rf ${B}/${R}
+mkdir -p ${B}/${R}
+[[ -d ${D}/${R} ]] && rm -rf ${D}/${R}
+mkdir -p ${D}/${R}
+
+LDFLAGS="-X main.BuildVersion=${R} -X main.BuildDate=`date -u '+%Y%m%d'` -X main.GitRev=${GIT_SHA}"
+
+GOOS=linux   GOARCH=arm    go build -ldflags ${LDFLAGS} -o ${B}/${R}/mbdns-${R}-linux-arm     mbdns.go 
+GOOS=linux   GOARCH=mipsle go build -ldflags ${LDFLAGS} -o ${B}/${R}/mbdns-${R}-linux-mipsle  mbdns.go
+GOOS=darwin  GOARCH=amd64  go build -ldflags ${LDFLAGS} -o ${B}/${R}/mbdns-${R}-darwin-amd64  mbdns.go
+GOOS=freebsd GOARCH=amd64  go build -ldflags ${LDFLAGS} -o ${B}/${R}/mbdns-${R}-freebsd-amd64 mbdns.go
+GOOS=linux   GOARCH=amd64  go build -ldflags ${LDFLAGS} -o ${B}/${R}/mbdns-${R}-linux-amd64   mbdns.go
+
+for i (linux-arm linux-mipsle darwin-amd64 freebsd-amd64 linux-amd64) do
+    P=mbdns-${R}-${i}
+    mkdir -p ${D}/${R}/${P}
+    cp ../doc/mbdns.conf.sample ${D}/${R}/${P}
+    cp ../README.md             ${D}/${R}/${P}
+    cp ../LICENSE               ${D}/${R}/${P}
+    cp ${B}/${R}/${P}           ${D}/${R}/${P}
+    tar czf ${D}/${R}/${P}.tar.gz -C ${D}/${R} ${P}
+    rm -rf ${D}/${R}/${P}
+done

src/build-test

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+#!/usr/local/bin/zsh
+
+GIT_SHA=$(git rev-parse --short HEAD)
+R=${GIT_SHA}
+
+LDFLAGS="-X main.BuildVersion=${R} -X main.BuildDate=`date -u '+%Y%m%d'` -X main.GitRev=${GIT_SHA}"
+
+go build -ldflags ${LDFLAGS} -o ../bin/mbdns mbdns.go 

src/mbdns.go

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+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"time"
+)
+
+type record struct {
+	Domain string
+	Token  string
+	Host   string
+	TTL    string
+	Record string
+}
+
+const mbConfigFile string = "mbdns.conf"
+const mbURLv4 string = "https://dnsapi4.mythic-beasts.com/"
+const mbURLv6 string = "https://dnsapi6.mythic-beasts.com/"
+const mbCommand string = "REPLACE %s %s %s DYNAMIC_IP"
+const mbLoopWaitSeconds string = "300s"
+const mbRecordUpdateWaitSeconds string = "1s"
+const mbResponseError string = "updating %s.%s (%s, %s) failed with %s"
+const mbResponseSuccess string = "updating %s.%s (%s, %s) succeeded"
+const mbLogActivity string = "running %s for %s.%s"
+const mbStartupBanner string = "mbdns %s %s (git %s)"
+const mbConfigPathBanner string = "config path: %s"
+const mbRecordA = "A"
+const mbRecordAAAA = "AAAA"
+
+var records []record
+
+// BuildVersion passed in via ldflags
+var BuildVersion string
+
+// BuildDate passed in via ldflags
+var BuildDate string
+
+// GitRev passed in via ldflags
+var GitRev string
+
+func process() {
+	loopSleepDuration, _ := time.ParseDuration(mbLoopWaitSeconds)
+	recordSleepDuration, _ := time.ParseDuration(mbRecordUpdateWaitSeconds)
+
+	for {
+		for i := range records {
+			command := fmt.Sprintf(mbCommand, records[i].Host, records[i].TTL, records[i].Record)
+			logActivityMsg := fmt.Sprintf(mbLogActivity, command, records[i].Host, records[i].Domain)
+
+			log.Println(logActivityMsg)
+
+			mbURL := mbURLv4
+
+			if records[i].Record != mbRecordA && records[i].Record != mbRecordAAAA {
+				continue
+			}
+
+			if records[i].Record == mbRecordAAAA {
+				mbURL = mbURLv6
+			}
+
+			response, err := http.PostForm(mbURL, url.Values{"domain": {records[i].Domain}, "password": {records[i].Token}, "command": {command}})
+
+			if err != nil {
+				log.Println(fmt.Sprintf(mbResponseError, records[i].Host, records[i].Domain, records[i].Record, records[i].TTL, err.Error()))
+				continue
+			}
+
+			defer response.Body.Close()
+
+			if response.StatusCode != 200 {
+				log.Println(fmt.Sprintf(mbResponseError, records[i].Host, records[i].Domain, records[i].Record, records[i].TTL, response.Status))
+
+				body, _ := ioutil.ReadAll(response.Body)
+				log.Printf("%s", body)
+
+				continue
+			}
+
+			log.Println(fmt.Sprintf(mbResponseSuccess, records[i].Host, records[i].Domain, records[i].Record, records[i].TTL))
+
+			time.Sleep(recordSleepDuration)
+		}
+
+		time.Sleep(loopSleepDuration)
+	}
+}
+
+func main() {
+	log.SetOutput(os.Stdout)
+
+	var configFile string
+	var printVer bool
+	flag.StringVar(&configFile, "config", mbConfigFile, "Config file path")
+	flag.BoolVar(&printVer, "version", false, "Print version banner and exit")
+	flag.Parse()
+
+	if printVer {
+		fmt.Println(fmt.Sprintf(mbStartupBanner, BuildVersion, BuildDate, GitRev))
+		os.Exit(0)
+	}
+
+	log.Println(fmt.Sprintf(mbStartupBanner, BuildVersion, BuildDate, GitRev))
+
+	log.Println(fmt.Sprintf(mbConfigPathBanner, configFile))
+
+	if _, err := os.Stat(configFile); os.IsNotExist(err) {
+		log.Fatal("config does not exist. Exiting...")
+	}
+
+	f, err := os.Lstat(configFile)
+
+	if err != nil {
+		log.Fatal("could not stat config. Exiting...")
+	}
+
+	if f.Mode() != 0400 {
+		log.Fatal("config is potentially insecure. Exiting...")
+	}
+
+	log.Println("mbdns reading config")
+
+	tuples, err := ioutil.ReadFile(configFile)
+
+	if err != nil {
+		log.Fatal("could not read config records. Exiting...")
+	}
+
+	err = json.Unmarshal(tuples, &records)
+
+	if err != nil {
+		log.Fatal("could not process config. Invalid JSON? Exiting...")
+	}
+
+	log.Println("mbdns is processing records")
+
+	go process()
+	select {}
+}