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webhook.go
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webhook.go
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package webhooksource
import (
"context"
"errors"
"fmt"
"io"
"net/http"
"strings"
"time"
"go.uber.org/zap"
cloudevents "github.com/cloudevents/sdk-go/v2"
pkgadapter "knative.dev/eventing/pkg/adapter/v2"
"knative.dev/pkg/logging"
)
const (
serverPort uint16 = 8080
serverShutdownGracePeriod = time.Second * 10
queryPrefix = "q"
headerPrefix = "h"
)
type webhookHandler struct {
eventType string
eventSource string
extensionAttributesFrom *ExtensionAttributesFrom
username string
password string
corsAllowOrigin string
ceClient cloudevents.Client
logger *zap.SugaredLogger
mt *pkgadapter.MetricTag
}
// Start implements pkgadapter.Adapter
// Runs the server for receiving HTTP events until ctx gets cancelled.
func (h *webhookHandler) Start(ctx context.Context) error {
ctx = pkgadapter.ContextWithMetricTag(ctx, h.mt)
m := http.NewServeMux()
m.HandleFunc("/", h.handleAll(ctx))
m.HandleFunc("/health", healthCheckHandler)
s := &http.Server{
Addr: fmt.Sprintf(":%d", serverPort),
Handler: m,
ReadTimeout: 5 * time.Second,
}
return runHandler(ctx, s)
}
// runHandler runs the HTTP event handler until ctx gets cancelled.
func runHandler(ctx context.Context, s *http.Server) error {
logging.FromContext(ctx).Info("Starting webhook event handler")
errCh := make(chan error)
go func() {
errCh <- s.ListenAndServe()
}()
handleServerError := func(err error) error {
if err != http.ErrServerClosed {
return fmt.Errorf("during server runtime: %w", err)
}
return nil
}
select {
case <-ctx.Done():
logging.FromContext(ctx).Info("HTTP event handler is shutting down")
ctx, cancel := context.WithTimeout(context.Background(), serverShutdownGracePeriod)
defer cancel()
if err := s.Shutdown(ctx); err != nil {
return fmt.Errorf("during server shutdown: %w", err)
}
return handleServerError(<-errCh)
case err := <-errCh:
return handleServerError(err)
}
}
// handleAll receives all webhook events at a single resource, it
// is up to this function to parse event wrapper and dispatch.
// nolint:gocyclo
func (h *webhookHandler) handleAll(ctx context.Context) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
if h.corsAllowOrigin != "" {
w.Header().Set("Access-Control-Allow-Origin", h.corsAllowOrigin)
}
if r.Body == nil {
h.handleError(errors.New("request without body not supported"), http.StatusBadRequest, w)
return
}
if h.username != "" && h.password != "" {
us, ps, ok := r.BasicAuth()
if !ok {
h.handleError(errors.New("wrong authentication header"), http.StatusBadRequest, w)
return
}
if us != h.username || ps != h.password {
h.handleError(errors.New("credentials are not valid"), http.StatusUnauthorized, w)
return
}
}
defer r.Body.Close()
body, err := io.ReadAll(r.Body)
if err != nil {
h.handleError(err, http.StatusInternalServerError, w)
return
}
event := cloudevents.NewEvent(cloudevents.VersionV1)
event.SetType(h.eventType)
event.SetSource(h.eventSource)
// Add extension attributes if configured
if h.extensionAttributesFrom != nil {
if h.extensionAttributesFrom.path {
event.SetExtension("path", r.URL.Path)
}
if h.extensionAttributesFrom.method {
event.SetExtension("method", r.Method)
}
if h.extensionAttributesFrom.host {
event.SetExtension("host", r.Host)
}
if h.extensionAttributesFrom.queries {
for k, v := range r.URL.Query() {
if len(v) == 1 {
event.SetExtension(sanitizeCloudEventAttributeName(queryPrefix+k), v[0])
} else {
for i := range v {
event.SetExtension(sanitizeCloudEventAttributeName(
fmt.Sprintf("%s%s%d", queryPrefix, k, i)), v[i])
}
}
}
}
if h.extensionAttributesFrom.headers {
for k, v := range r.Header {
// Prevent Authorization header from being added
// as a CloudEvent attribute
if k == "Authorization" {
continue
}
if k == "Ce-Id" {
if len(v) != 0 {
event.SetID(v[0])
}
continue
}
if k == "Ce-Subject" {
if len(v) != 0 {
event.SetSubject(v[0])
}
continue
}
if len(v) == 1 {
event.SetExtension(sanitizeCloudEventAttributeName(headerPrefix+k), v[0])
} else {
for i := range v {
event.SetExtension(sanitizeCloudEventAttributeName(
fmt.Sprintf("%s%s%d", headerPrefix, k, i)), v[i])
}
}
}
}
}
if err := event.SetData(r.Header.Get("Content-Type"), body); err != nil {
h.handleError(fmt.Errorf("failed to set event data: %w", err), http.StatusInternalServerError, w)
return
}
rEvent, result := h.ceClient.Request(ctx, event)
if !cloudevents.IsACK(result) {
h.handleError(fmt.Errorf("could not send Cloud Event: %w", result), http.StatusInternalServerError, w)
return
}
if rEvent == nil || rEvent.Data() == nil {
w.WriteHeader(http.StatusNoContent)
return
}
w.WriteHeader(http.StatusOK)
}
}
func (h *webhookHandler) handleError(err error, code int, w http.ResponseWriter) {
h.logger.Errorw("An error occurred", zap.Error(err))
http.Error(w, err.Error(), code)
}
func healthCheckHandler(w http.ResponseWriter, _ *http.Request) {
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
w.WriteHeader(http.StatusOK)
}
// nolint:gocyclo
func sanitizeCloudEventAttributeName(name string) string {
// only lowercase accepted
name = strings.ToLower(name)
// strip non valid characters
needsStripping := false
for i := range name {
if !((name[i] >= 'a' && name[i] <= 'z') || (name[i] >= '0' && name[i] <= '9')) {
needsStripping = true
break
}
}
if needsStripping {
stripped := []byte{}
for i := range name {
if (name[i] >= 'a' && name[i] <= 'z') || (name[i] >= '0' && name[i] <= '9') {
stripped = append(stripped, name[i])
}
}
name = string(stripped)
}
// truncate if longer than 20 characters
if len(name) > 20 {
name = name[:20]
}
// data is a reserved element at CloudEvents
if name == "data" || name == "path" || name == "method" || name == "host" {
return "data0"
}
return name
}