1 files changed, 90 insertions, 0 deletions
diff --git a/modules/recaptcha/recaptcha.go b/modules/recaptcha/recaptcha.go
new file mode 100644
index 00000000..1777d169
--- /dev/null
+++ b/modules/recaptcha/recaptcha.go
@@ -0,0 +1,90 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package recaptcha
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+)
+
+// Response is the structure of JSON returned from API
+type Response struct {
+	Success     bool        `json:"success"`
+	ChallengeTS string      `json:"challenge_ts"`
+	Hostname    string      `json:"hostname"`
+	ErrorCodes  []ErrorCode `json:"error-codes"`
+}
+
+const apiURL = "api/siteverify"
+
+// Verify calls Google Recaptcha API to verify token
+func Verify(ctx context.Context, response string) (bool, error) {
+	post := url.Values{
+		"secret":   {setting.Service.RecaptchaSecret},
+		"response": {response},
+	}
+	// Basically a copy of http.PostForm, but with a context
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
+		util.URLJoin(setting.Service.RecaptchaURL, apiURL), strings.NewReader(post.Encode()))
+	if err != nil {
+		return false, fmt.Errorf("Failed to create CAPTCHA request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return false, fmt.Errorf("Failed to send CAPTCHA response: %s", err)
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return false, fmt.Errorf("Failed to read CAPTCHA response: %s", err)
+	}
+
+	var jsonResponse Response
+	err = json.Unmarshal(body, &jsonResponse)
+	if err != nil {
+		return false, fmt.Errorf("Failed to parse CAPTCHA response: %s", err)
+	}
+	var respErr error
+	if len(jsonResponse.ErrorCodes) > 0 {
+		respErr = jsonResponse.ErrorCodes[0]
+	}
+	return jsonResponse.Success, respErr
+}
+
+// ErrorCode is a reCaptcha error
+type ErrorCode string
+
+// String fulfills the Stringer interface
+func (e ErrorCode) String() string {
+	switch e {
+	case "missing-input-secret":
+		return "The secret parameter is missing."
+	case "invalid-input-secret":
+		return "The secret parameter is invalid or malformed."
+	case "missing-input-response":
+		return "The response parameter is missing."
+	case "invalid-input-response":
+		return "The response parameter is invalid or malformed."
+	case "bad-request":
+		return "The request is invalid or malformed."
+	case "timeout-or-duplicate":
+		return "The response is no longer valid: either is too old or has been used previously."
+	}
+	return string(e)
+}
+
+// Error fulfills the error interface
+func (e ErrorCode) Error() string {
+	return e.String()
+}