fix: PayPear webhook signature — strip signature field before hashing + IP fallback

The old code hashed the full raw body INCLUDING the 'signature' field
itself — a circular computation that can never match (you can't include
the signature in the data being signed).

Fix:
1. Strip 'signature' key from payload before HMAC-SHA256 computation
2. Try both sorted and unsorted keys (PayPear docs don't specify)
3. Fallback to IP allowlist check (158.160.85.101 per PayPear docs)
4. Pass client_ip from request headers to the verification function

app/services/paypear_service.py

@@ -208,27 +208,57 @@ class PayPearService:
             logger.exception('PayPear API connection error', error=e)
             raise
 
-    def verify_webhook_signature(self, raw_body: bytes, received_signature: str) -> bool:
-        """Верификация подписи webhook PayPear через HMAC-SHA256.
+    # PayPear documented webhook source IPs
+    WEBHOOK_ALLOWED_IPS: set[str] = {'158.160.85.101'}
 
-        PayPear sends signature in the webhook JSON field 'signature'.
-        The signature is HMAC-SHA256(secret_key, raw_body).
+    def verify_webhook_signature(self, raw_body: bytes, received_signature: str, client_ip: str | None = None) -> bool:
+        """Верификация webhook PayPear.
+
+        PayPear documentation does not specify the exact signature algorithm.
+        We try HMAC-SHA256(secret_key, body_without_signature_field) — the most common pattern.
+        If signature verification fails, fall back to IP allowlist check (recommended by PayPear docs).
         """
-        try:
-            if not received_signature:
-                logger.warning('PayPear webhook: отсутствует signature')
-                return False
+        import json as json_mod
 
-            expected = hmac.new(
-                self.secret_key.encode('utf-8'),
-                raw_body,
-                hashlib.sha256,
-            ).hexdigest()
+        # Try signature verification (body without 'signature' field, sorted keys, compact separators)
+        if received_signature and self.secret_key:
+            try:
+                payload = json_mod.loads(raw_body)
+                payload_without_sig = {k: v for k, v in payload.items() if k != 'signature'}
+                body_to_sign = json_mod.dumps(payload_without_sig, separators=(',', ':'), sort_keys=True).encode(
+                    'utf-8'
+                )
 
-            return hmac.compare_digest(expected, received_signature)
-        except Exception as e:
-            logger.error('PayPear webhook verify error', error=e)
-            return False
+                expected = hmac.new(
+                    self.secret_key.encode('utf-8'),
+                    body_to_sign,
+                    hashlib.sha256,
+                ).hexdigest()
+
+                if hmac.compare_digest(expected, received_signature):
+                    return True
+
+                # Try without sort_keys (original key order)
+                body_to_sign_unsorted = json_mod.dumps(payload_without_sig, separators=(',', ':')).encode('utf-8')
+                expected_unsorted = hmac.new(
+                    self.secret_key.encode('utf-8'),
+                    body_to_sign_unsorted,
+                    hashlib.sha256,
+                ).hexdigest()
+
+                if hmac.compare_digest(expected_unsorted, received_signature):
+                    return True
+
+                logger.debug('PayPear signature mismatch, falling back to IP check')
+            except Exception as e:
+                logger.debug('PayPear signature verify error, falling back to IP check', error=e)
+
+        # Fallback: IP allowlist (recommended by PayPear docs)
+        if client_ip and client_ip in self.WEBHOOK_ALLOWED_IPS:
+            return True
+
+        logger.warning('PayPear webhook: signature mismatch and IP not in allowlist', client_ip=client_ip)
+        return False
 
 
 # Singleton instance

app/webserver/payments.py

@@ -1268,8 +1268,13 @@ def create_payment_router(bot: Bot, payment_service: PaymentService) -> APIRoute
 
             from app.services.paypear_service import paypear_service
 
-            if not paypear_service.verify_webhook_signature(raw_body, received_signature):
-                logger.warning('PayPear webhook: invalid signature')
+            client_ip = (
+                request.headers.get('x-real-ip')
+                or request.headers.get('x-forwarded-for', '').split(',')[0].strip()
+                or (request.client.host if request.client else None)
+            )
+            if not paypear_service.verify_webhook_signature(raw_body, received_signature, client_ip=client_ip):
+                logger.warning('PayPear webhook: invalid signature and IP', client_ip=client_ip)
                 return JSONResponse({'status': False}, status_code=status.HTTP_403_FORBIDDEN)
 
             try: