Allow gitea dev version (#914)

* update gitea sdk to latest
* As before try to autodetect gitea version, if this does not work, assume it's latest version (v1.17.0 atm)

vendor/code.gitea.io/sdk/gitea/hook_validate.go

@@ -0,0 +1,59 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package gitea
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"net/http"
+)
+
+// VerifyWebhookSignature verifies that a payload matches the X-Gitea-Signature based on a secret
+func VerifyWebhookSignature(secret, expected string, payload []byte) (bool, error) {
+	hash := hmac.New(sha256.New, []byte(secret))
+	if _, err := hash.Write(payload); err != nil {
+		return false, err
+	}
+	expectedSum, err := hex.DecodeString(expected)
+	if err != nil {
+		return false, err
+	}
+	return hmac.Equal(hash.Sum(nil), expectedSum), nil
+}
+
+// VerifyWebhookSignatureMiddleware is a http.Handler for verifying X-Gitea-Signature on incoming webhooks
+func VerifyWebhookSignatureMiddleware(secret string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			var b bytes.Buffer
+			if _, err := io.Copy(&b, r.Body); err != nil {
+				http.Error(w, err.Error(), http.StatusBadRequest)
+				return
+			}
+
+			expected := r.Header.Get("X-Gitea-Signature")
+			if expected == "" {
+				http.Error(w, "no signature found", http.StatusBadRequest)
+				return
+			}
+
+			ok, err := VerifyWebhookSignature(secret, expected, b.Bytes())
+			if err != nil {
+				http.Error(w, err.Error(), http.StatusUnauthorized)
+				return
+			}
+			if !ok {
+				http.Error(w, "invalid payload", http.StatusUnauthorized)
+				return
+			}
+
+			r.Body = io.NopCloser(&b)
+			next.ServeHTTP(w, r)
+		})
+	}
+}