Fix Insecure Webhooks in Revel
Insecure webhooks in Revel frameworks typically stem from a lack of origin verification. If your endpoint blindly trusts POST data without validating a cryptographic signature (HMAC), any script-kiddie can spoof events to trigger internal logic, leading to unauthorized state changes or data corruption. Real-world security requires a shared secret and timing-safe comparison.
The Vulnerable Pattern
func (c Webhook) Receive() revel.Result {
var data map[string]interface{}
c.Params.BindJSON(&data)
// VULNERABILITY: No signature check.
// Anyone can POST to this endpoint.
log.Printf("Processing event: %v", data["event"])
return c.RenderJSON(map[string]string{"status": "ok"})
}The Secure Implementation
The fix implements HMAC-SHA256 signature verification. Key steps: 1. Retrieve the raw request body before it's parsed. 2. Calculate the HMAC using a server-side secret. 3. Use 'hmac.Equal' for comparison—this is critical to prevent timing attacks that could leak the signature byte-by-byte. If the signatures don't match, the request is discarded with a 403 Forbidden before any business logic executes.
func (c Webhook) Receive() revel.Result { secret := []byte(revel.Config.StringDefault("webhook.secret", "")) signature := c.Request.Header.Get("X-Hub-Signature-256")body, _ := io.ReadAll(c.Request.GetBody()) // Always use a fresh reader for subsequent binding if needed c.Request.SetBody(io.NopCloser(bytes.NewBuffer(body))) h := hmac.New(sha256.New, secret) h.Write(body) expectedSignature := "sha256=" + hex.EncodeToString(h.Sum(nil)) if !hmac.Equal([]byte(signature), []byte(expectedSignature)) { revel.AppLog.Warn("Invalid webhook signature detected") return c.Forbidden() } var data map[string]interface{} c.Params.BindJSON(&data) return c.RenderJSON(map[string]string{"status": "verified"})
}
Your Revel API
might be exposed to Insecure Webhooks
74% of Revel apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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