github-events: Add GITHUB_ORGANIZATIONS_FILTER

Adds filter for only listening to events from specific orgs. In order to
install an App on multiple orgs (e.g. chainguard-dev, wolfi-os), we need to make it public.
This restricts the trampoline to only listen and forward to specific
orgs. If omitted, all events are forwarded.

modules/github-events/cmd/trampoline/main.go

@@ -38,6 +38,7 @@ var env = envconfig.MustProcess(context.Background(), &struct {
 	RequestedOnly []string `env:"REQUESTED_ONLY_WEBHOOK_ID"`
 	// If set, only events from the specified webhook IDs will be processed.
 	WebhookID []string `env:"WEBHOOK_ID"`
+	OrgFilter []string `env:"GITHUB_ORGANIZATIONS_FILTER"`
 }{})
 
 func main() {
@@ -58,7 +59,12 @@ func main() {
 	srv := &http.Server{
 		Addr:              fmt.Sprintf(":%d", env.Port),
 		ReadHeaderTimeout: 10 * time.Second,
-		Handler:           httpmetrics.Handler("trampoline", trampoline.NewServer(ceclient, secrets, env.WebhookID, env.RequestedOnly)),
+		Handler: httpmetrics.Handler("trampoline", trampoline.NewServer(ceclient, trampoline.ServerOptions{
+			Secrets:              secrets,
+			WebhookID:            env.WebhookID,
+			RequestedOnlyWebhook: env.RequestedOnly,
+			OrgFilter:            env.OrgFilter,
+		})),
 	}
 	clog.FatalContextf(ctx, "ListenAndServe: %v", srv.ListenAndServe())
 }

modules/github-events/internal/trampoline/server.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"mime"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/chainguard-dev/clog"
@@ -24,14 +25,23 @@ type Server struct {
 	// If webhookID is empty, the trampoline will listen to all events.
 	webhookID            []string
 	requestedOnlyWebhook []string
+	orgFilter            []string
 }
 
-func NewServer(client cloudevents.Client, secrets [][]byte, webhookID []string, requestedOnlyWebhook []string) *Server {
+type ServerOptions struct {
+	Secrets              [][]byte
+	WebhookID            []string
+	RequestedOnlyWebhook []string
+	OrgFilter            []string
+}
+
+func NewServer(client cloudevents.Client, opts ServerOptions) *Server {
 	return &Server{
 		client:               client,
-		secrets:              secrets,
-		requestedOnlyWebhook: requestedOnlyWebhook,
-		webhookID:            webhookID,
+		secrets:              opts.Secrets,
+		requestedOnlyWebhook: opts.RequestedOnlyWebhook,
+		webhookID:            opts.WebhookID,
+		orgFilter:            opts.OrgFilter,
 		clock:                clockwork.NewRealClock(),
 	}
 }
@@ -102,6 +112,22 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		log = log.With("action", msg.Action, "repo", msg.Repository.FullName)
 	}
 
+	// Filter webhook at org level.
+	if len(s.orgFilter) > 0 {
+		found := false
+		for _, org := range s.orgFilter {
+			if strings.HasPrefix(msg.Repository.FullName, org+"/") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			log.Warnf("ignoring event from repository %q due to non-matching org", msg.Repository.FullName)
+			w.WriteHeader(http.StatusAccepted)
+			return
+		}
+	}
+
 	log.Debugf("forwarding event: %s", t)
 
 	event := cloudevents.NewEvent()

modules/github-events/internal/trampoline/server_test.go

@@ -36,10 +36,13 @@ func TestTrampoline(t *testing.T) {
 
 	secret := []byte("hunter2")
 	clock := clockwork.NewFakeClock()
-	impl := NewServer(client, [][]byte{
-		[]byte("badsecret"), // This secret should be ignored
-		secret,
-	}, nil, nil)
+	opts := ServerOptions{
+		Secrets: [][]byte{
+			[]byte("badsecret"), // This secret should be ignored
+			secret,
+		},
+	}
+	impl := NewServer(client, opts)
 	impl.clock = clock
 
 	srv := httptest.NewServer(impl)
@@ -127,7 +130,7 @@ func sendevent(t *testing.T, client *http.Client, url string, eventType string,
 }
 
 func TestForbidden(t *testing.T) {
-	srv := httptest.NewServer(NewServer(&fakeClient{}, nil, nil, nil))
+	srv := httptest.NewServer(NewServer(&fakeClient{}, ServerOptions{}))
 	defer srv.Close()
 
 	// Doesn't really matter what we send, we just want to ensure we get a forbidden response
@@ -142,7 +145,11 @@ func TestForbidden(t *testing.T) {
 
 func TestWebhookIDFilter(t *testing.T) {
 	secret := []byte("hunter2")
-	srv := httptest.NewServer(NewServer(&fakeClient{}, [][]byte{secret}, []string{"doesnotmatch"}, nil))
+	opts := ServerOptions{
+		Secrets:   [][]byte{secret},
+		WebhookID: []string{"doesnotmatch"},
+	}
+	srv := httptest.NewServer(NewServer(&fakeClient{}, opts))
 	defer srv.Close()
 
 	// Send an event with the requested action
@@ -157,12 +164,19 @@ func TestWebhookIDFilter(t *testing.T) {
 
 func TestRequestedOnlyWebhook(t *testing.T) {
 	secret := []byte("hunter2")
-	srv := httptest.NewServer(NewServer(&fakeClient{}, [][]byte{secret}, nil, []string{"1234"}))
+	opts := ServerOptions{
+		Secrets:              [][]byte{secret},
+		RequestedOnlyWebhook: []string{"1234"},
+	}
+	srv := httptest.NewServer(NewServer(&fakeClient{}, opts))
 	defer srv.Close()
 
 	// Send an event with the requested action
 	resp, err := sendevent(t, srv.Client(), srv.URL, "check_run", map[string]interface{}{
 		"action": "requested",
+		"repository": map[string]interface{}{
+			"full_name": "org/repo",
+		},
 	}, secret)
 	if err != nil {
 		t.Fatalf("error sending event: %v", err)
@@ -180,3 +194,37 @@ func TestRequestedOnlyWebhook(t *testing.T) {
 		t.Fatalf("unexpected status: %v", resp.Status)
 	}
 }
+
+func TestOrgFilter(t *testing.T) {
+	secret := []byte("hunter2")
+	opts := ServerOptions{
+		Secrets:   [][]byte{secret},
+		OrgFilter: []string{"org"},
+	}
+	srv := httptest.NewServer(NewServer(&fakeClient{}, opts))
+	defer srv.Close()
+
+	// Send an event with the requested action
+	resp, err := sendevent(t, srv.Client(), srv.URL, "pull_request", map[string]interface{}{
+		"action": "opened",
+	}, secret)
+	if err != nil {
+		t.Fatalf("error sending event: %v", err)
+	}
+	if resp.StatusCode != http.StatusAccepted {
+		t.Fatalf("unexpected status: %v", resp.Status)
+	}
+
+	resp, err = sendevent(t, srv.Client(), srv.URL, "pull_request", map[string]interface{}{
+		"action": "opened",
+		"repository": map[string]interface{}{
+			"full_name": "org/repo",
+		},
+	}, secret)
+	if err != nil {
+		t.Fatalf("error sending event: %v", err)
+	}
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("unexpected status: %v", resp.Status)
+	}
+}

modules/github-events/main.tf

@@ -45,15 +45,21 @@ module "this" {
       }
       ports = [{ container_port = 8080 }]
       env = concat(
-        [{
-          name = "WEBHOOK_SECRET"
-          value_source = {
-            secret_key_ref = {
-              secret  = module.webhook-secret.secret_id
-              version = "latest"
+        [
+          {
+            name = "WEBHOOK_SECRET"
+            value_source = {
+              secret_key_ref = {
+                secret  = module.webhook-secret.secret_id
+                version = "latest"
+              }
             }
-          }
-        }],
+          },
+          {
+            name  = "GITHUB_ORGANIZATIONS_FILTER"
+            value = var.github_organizations
+          },
+        ],
         [for name, secret in var.additional_webhook_secrets : {
           name = "WEBHOOK_SECRET_${upper(name)}"
           value_source = {

modules/github-events/variables.tf

@@ -57,7 +57,7 @@ Additional secrets to be used by the service.
 
 See https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/cloud_run_v2_service#nested_env for related documentation.
 EOD
-  default = {}
+  default     = {}
 }
 
 variable "service-ingress" {
@@ -93,3 +93,9 @@ variable "squad" {
     error_message = "squad needs to specified or disable check by setting require_squad = false"
   }
 }
+
+variable "github_organizations" {
+  description = "csv string of GitHub organizations to allow."
+  type        = string
+  default     = ""
+}