add s3 webhook-server-example

mcs-s3-webhook-server-example/.gitignore

@@ -0,0 +1 @@
+/mcs-s3-webhook-server-example

mcs-s3-webhook-server-example/README.md

@@ -0,0 +1,23 @@
+# Example S3 webhook server for MCS
+
+## Building
+```
+go build
+```
+
+You'll get the binary named `mcs-s3-webhook-server-example`.
+
+## Running
+
+```
+./mcs-s3-webhook-server-example
+```
+
+It will listen for HTTP requests on TCP port 33345. It assumes https forwarding from nginx.
+
+## Testing
+
+To test signature correctness:
+```
+go test
+```

mcs-s3-webhook-server-example/helpers.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+)
+
+func httpError(w http.ResponseWriter, code int, format string, args ...interface{}) {
+	text := fmt.Sprintf(format, args...)
+	log.Println(text)
+	http.Error(w, text, code)
+}

mcs-s3-webhook-server-example/hookserver.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/httputil"
+	"strings"
+)
+
+func main() {
+	http.HandleFunc("/", ServeHTTP)
+	log.Fatal(http.ListenAndServe(":33345", nil))
+}
+
+// general handler for all http requests
+func ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// dump all requests to stdout
+	dump, err := httputil.DumpRequest(r, true)
+	if err != nil {
+		httpError(w, http.StatusInternalServerError, "Failed to dump request")
+		return
+	}
+	fmt.Printf("%s\n", dump)
+
+	// X-Amz-Sns-Message-Type: SubscriptionConfirmation
+	snsType := strings.ToLower(r.Header.Get("X-Amz-Sns-Message-Type"))
+	switch snsType {
+	case "subscriptionconfirmation":
+		handleSubscriptionConfirmation(w, r)
+	case "notification":
+		handleNotification(w, r)
+	default:
+		httpError(w, http.StatusBadRequest, "Invalid SNS message type")
+	}
+}
+
+// handle all subscription confirmations
+func handleSubscriptionConfirmation(w http.ResponseWriter, r *http.Request) {
+	decoded := SubscriptionConfirmation{}
+	err := json.NewDecoder(r.Body).Decode(&decoded)
+	if err != nil {
+		httpError(w, http.StatusBadRequest, "Failed to decode JSON in the body: %s", err)
+		return
+	}
+
+	// assume https
+	fullURL := fmt.Sprintf("https://%s%s", r.Host, r.URL.String()) // r.URL doesn't contain protocol or host
+
+	response := struct {
+		Signature string `json:"signature"` // base64-encoded signature
+	}{
+		Signature: signSubscriptionHex(decoded, fullURL),
+	}
+	w.Header().Set("Content-Type", "application/json")
+	jsonBody, err := json.Marshal(&response)
+	if err != nil {
+		httpError(w, http.StatusInternalServerError, "Failed to marshal json: %s", err)
+		return
+	}
+
+	log.Printf("Responding with body: %s", jsonBody)
+	w.Write(jsonBody)
+}
+
+func handleNotification(w http.ResponseWriter, r *http.Request) {
+	// do nothing, just 200, we dump the request body in main handler already
+}

mcs-s3-webhook-server-example/signatures.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+)
+
+type SubscriptionConfirmation struct {
+	Timestamp        string // we need to give it to hmac byte-for-byte, "2019-12-26T19:29:12+03:00",
+	Type             string // always "SubscriptionConfirmation",
+	Message          string // always "You have chosen to subscribe to the topic $topic. To confirm the subscription you need to response with calculated signature",
+	TopicArn         string // for feeding into signature, "mcs2883541269|bucketA|s3:ObjectCreated:Put",
+	SignatureVersion int64  // always 1,
+	Token            string // for feeding into signature, "RPE5UuG94rGgBH6kHXN9FUPugFxj1hs2aUQc99btJp3E49tA"
+}
+
+// signSubscriptionHex returns hex-encoded signature for SNS webhook subscription confirmation
+func signSubscriptionHex(decoded SubscriptionConfirmation, fullURL string) string {
+	return hex.EncodeToString(signSubscription(decoded, fullURL))
+}
+
+// signSubscription returns array with a signature for SNS webhook subscription confirmation
+func signSubscription(decoded SubscriptionConfirmation, fullURL string) []byte {
+	// get timestamp+token hash first
+	firstMAC := hmac.New(sha256.New, []byte(decoded.Token))
+	firstMAC.Write([]byte(decoded.Timestamp))
+	firstHash := firstMAC.Sum(nil)
+	// then combine that with TopicArn
+	secondMAC := hmac.New(sha256.New, firstHash)
+	secondMAC.Write([]byte(decoded.TopicArn))
+	secondHash := secondMAC.Sum(nil)
+	// then combine that with full URL
+	thirdMAC := hmac.New(sha256.New, secondHash)
+	thirdMAC.Write([]byte(fullURL))
+	thirdHash := thirdMAC.Sum(nil)
+	return thirdHash
+}

mcs-s3-webhook-server-example/signatures_test.go

@@ -0,0 +1,46 @@
+package main
+
+import "testing"
+
+// signature = hmac_sha256_hex(“http://test.com”,
+//                 hmac_sha256(“mcs2883541269|bucketA|s3:ObjectCreated:Put”,
+//                 hmac_sha256(“2019-12-26T19:29:12+03:00”, “RPE5UuG94rGgBH6kHXN9FUPugFxj1hs2aUQc99btJp3E49tA”)))
+// results in ea3fce4bb15c6de4fec365d36bcebbc34ccddf54616d5ca12e1972f82b6d37af
+func TestSubscriptionConfirmationSignature(t *testing.T) {
+	fullURL := "http://test.com"
+	confirmation := SubscriptionConfirmation{
+		Timestamp:        "2019-12-26T19:29:12+03:00",
+		Type:             "",
+		Message:          "",
+		TopicArn:         "mcs2883541269|bucketA|s3:ObjectCreated:Put",
+		SignatureVersion: 1,
+		Token:            "RPE5UuG94rGgBH6kHXN9FUPugFxj1hs2aUQc99btJp3E49tA",
+	}
+	signature := signSubscriptionHex(confirmation, fullURL)
+	expected := "ea3fce4bb15c6de4fec365d36bcebbc34ccddf54616d5ca12e1972f82b6d37af"
+	if signature != expected {
+		t.Errorf("Wrong signature, expected %s, got %s", expected, signature)
+	}
+}
+
+func BenchmarkSubscriptionConfirmationSignature(b *testing.B) {
+	fullURL := "http://test.com"
+	confirmation := SubscriptionConfirmation{
+		Timestamp:        "2019-12-26T19:29:12+03:00",
+		Type:             "",
+		Message:          "",
+		TopicArn:         "mcs2883541269|bucketA|s3:ObjectCreated:Put",
+		SignatureVersion: 1,
+		Token:            "RPE5UuG94rGgBH6kHXN9FUPugFxj1hs2aUQc99btJp3E49tA",
+	}
+	expected := "ea3fce4bb15c6de4fec365d36bcebbc34ccddf54616d5ca12e1972f82b6d37af"
+	bytes := len(confirmation.Timestamp) + len(confirmation.TopicArn) + len(confirmation.Token) + len(fullURL) + len(expected)
+	b.SetBytes(int64(bytes))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		signature := signSubscriptionHex(confirmation, fullURL)
+		if signature != expected {
+			b.Errorf("Wrong signature, expected %s, got %s", expected, signature)
+		}
+	}
+}