From 0370e58aec017cdd748f7a1d08bd7154fe79a20f Mon Sep 17 00:00:00 2001
From: Alvie Rahman <alvierahman90@gmail.com>
Date: Wed, 28 Jul 2021 16:20:06 +0100
Subject: [PATCH] Initial commit

---
 config.json |   9 +++++
 example.sh  |   2 +
 go.mod      |   5 +++
 go.sum      |   2 +
 main.go     | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 readme.md   |   7 ++++
 6 files changed, 137 insertions(+)
 create mode 100644 config.json
 create mode 100755 example.sh
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 main.go
 create mode 100644 readme.md

diff --git a/config.json b/config.json
new file mode 100644
index 0000000..d7d9f38
--- /dev/null
+++ b/config.json
@@ -0,0 +1,9 @@
+{
+  "Services": {
+    "test": {
+      "Script": "./example.sh",
+      "Secret": "THISISVERYSECRET",
+      "SignatureHeader": "X-Gitea-Signature"
+    }
+  }
+}
diff --git a/example.sh b/example.sh
new file mode 100755
index 0000000..517a5c2
--- /dev/null
+++ b/example.sh
@@ -0,0 +1,2 @@
+#!/usr/bin/bash
+date >> test_output
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..ae6a7b3
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module git.alra.uk/alvierahman90/ghookr
+
+go 1.16
+
+require github.com/gorilla/mux v1.8.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..5350288
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
+github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..d82a193
--- /dev/null
+++ b/main.go
@@ -0,0 +1,112 @@
+package main
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+
+	"github.com/gorilla/mux"
+)
+
+var config_filename = "/etc/ghookr.json"
+
+func main() {
+	// Used for testing purposes... generates hmac string
+	if os.Getenv("HMACGEN") == "true" {
+		input, err := ioutil.ReadAll(os.Stdin)
+		secret := os.Getenv("SECRET")
+		if err != nil {
+			panic(err.Error())
+		}
+		fmt.Println(getSha256HMACSignature([]byte(secret), string(input)))
+		return
+	}
+	r := mux.NewRouter()
+	r.HandleFunc("/webhook/{service}", webhook)
+
+	port := ":80"
+	if p, ok := os.LookupEnv("PORT"); ok {
+		port = fmt.Sprintf(":%v", p)
+	}
+
+	if p, ok := os.LookupEnv("CONFIG"); ok {
+		config_filename = p
+	}
+
+	log.Fatal(http.ListenAndServe(port, r))
+}
+
+func webhook(w http.ResponseWriter, r *http.Request) {
+	// TODO run any specified tests before running script
+
+	service_name := mux.Vars(r)["service"]
+
+	payload := ""
+	if p, err := ioutil.ReadAll(r.Body); err != nil {
+		writeResponse(w, 500, "Internal Server Error: Could not read payload")
+		return
+	} else {
+		payload = string(p)
+	}
+
+	raw_config, err := ioutil.ReadFile(config_filename)
+	if err != nil {
+		writeResponse(w, 500, "Internal Server Error: Could not open config file")
+		return
+	}
+	config := Config{}
+	json.Unmarshal(raw_config, &config)
+
+	var service = Service{}
+	if val, ok := config.Services[string(service_name)]; !ok {
+		writeResponse(w, 404, "Service Not Found")
+		return
+	} else {
+		service = val
+	}
+
+	signature := r.Header.Get(service.SignatureHeader)
+	if signature == getSha256HMACSignature([]byte(service.Secret), payload) {
+		writeResponse(w, 400, "Bad Request: Signatures do not match")
+		return
+	}
+
+	if stdout, err := exec.Command(service.Script, payload).Output(); err != nil {
+		writeResponse(w, 500, err.Error())
+		return
+	} else {
+		writeResponse(w, 200, string(stdout))
+		return
+	}
+}
+
+func writeResponse(w http.ResponseWriter, responseCode int, responseString string) {
+	w.WriteHeader(responseCode)
+	w.Write([]byte(fmt.Sprintf("%v %v", responseCode, responseString)))
+}
+
+func getSha256HMACSignature(secret []byte, data string) string {
+	h := hmac.New(sha256.New, secret)
+	io.WriteString(h, data)
+	return hex.EncodeToString(h.Sum(nil))
+}
+
+type Service struct {
+	Gitea           bool
+	Script          string
+	Secret          string
+	SignatureHeader string
+	Tests           []string
+}
+
+type Config struct {
+	Services map[string]Service
+}
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..53f39e6
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,7 @@
+# gohookr
+
+A _really_ simple webhook receiver.
+
+Check config.json for an example configuration.
+
+Default config path is `/etc/ghookr.conf`, can be overriden with `CONFIG` environment variable.