feat: add cloudflare turnstile captcha (#1327)

* feat: add cloudflare turnstile captcha

* fix: rename turnstile to cloudflare turnstile

captcha/turnstile.go

@@ -0,0 +1,66 @@
+// Copyright 2022 The Casdoor Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package captcha
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+const CloudflareTurnstileVerifyUrl = "https://challenges.cloudflare.com/turnstile/v0/siteverify"
+
+type CloudflareTurnstileProvider struct{}
+
+func NewCloudflareTurnstileProvider() *CloudflareTurnstileProvider {
+	captcha := &CloudflareTurnstileProvider{}
+	return captcha
+}
+
+func (captcha *CloudflareTurnstileProvider) VerifyCaptcha(token, clientSecret string) (bool, error) {
+	reqData := url.Values{
+		"secret":   {clientSecret},
+		"response": {token},
+	}
+	resp, err := http.PostForm(CloudflareTurnstileVerifyUrl, reqData)
+	if err != nil {
+		return false, err
+	}
+
+	defer resp.Body.Close()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return false, err
+	}
+
+	type captchaResponse struct {
+		Success    bool     `json:"success"`
+		ErrorCodes []string `json:"error-codes"`
+	}
+	captchaResp := &captchaResponse{}
+	err = json.Unmarshal(body, captchaResp)
+	if err != nil {
+		return false, err
+	}
+
+	if len(captchaResp.ErrorCodes) > 0 {
+		return false, errors.New(strings.Join(captchaResp.ErrorCodes, ","))
+	}
+
+	return captchaResp.Success, nil
+}