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hcaptcha.go
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hcaptcha.go
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package hcaptcha
import (
"context"
"encoding/json"
"errors"
"fmt"
"io"
"net/http"
"net/url"
)
var (
// ResponseContextKey is the default request's context key that response of a hcaptcha request is kept.
ResponseContextKey interface{} = "hcaptcha"
// DefaultFailureHandler is the default HTTP handler that is fired on hcaptcha failures. See `Client.FailureHandler`.
DefaultFailureHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
http.Error(w, http.StatusText(http.StatusTooManyRequests), http.StatusTooManyRequests)
})
// PostMaxMemory is the max memory for a form, defaults to 32MB
PostMaxMemory int64 = 32 << 20
)
// Client represents the hcaptcha client.
// It contains the underline HTTPClient which can be modified before API calls.
type Client struct {
HTTPClient *http.Client
// FailureHandler if specified, fired when user does not complete hcaptcha successfully.
// Failure and error codes information are kept as `Response` type
// at the Request's Context key of "hcaptcha".
//
// Defaults to a handler that writes a status code of 429 (Too Many Requests)
// and without additional information.
FailureHandler http.Handler
// Optional checks for siteverify
// The user's IP address.
RemoteIP string
// The sitekey you expect to see.
SiteKey string
secret string
}
// Response is the hcaptcha JSON response.
type Response struct {
ChallengeTS string `json:"challenge_ts"`
Hostname string `json:"hostname"`
ErrorCodes []string `json:"error-codes,omitempty"`
Success bool `json:"success"`
Credit bool `json:"credit,omitempty"`
}
// New accepts a hpcatcha secret key and returns a new hcaptcha HTTP Client.
//
// Instructions at: https://docs.hcaptcha.com/.
//
// See its `Handler` and `SiteVerify` for details.
func New(secret string) *Client {
return &Client{
HTTPClient: http.DefaultClient,
FailureHandler: DefaultFailureHandler,
secret: secret,
}
}
// Handler is the HTTP route middleware featured hcaptcha validation.
// It calls the `SiteVerify` method and fires the "next" when user completed the hcaptcha successfully,
//
// otherwise it calls the Client's `FailureHandler`.
//
// The hcaptcha's `Response` (which contains any `ErrorCodes`)
// is saved on the Request's Context (see `GetResponseFromContext`).
func (c *Client) Handler(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
v := c.SiteVerify(r)
r = r.WithContext(context.WithValue(r.Context(), ResponseContextKey, v))
if v.Success {
next.ServeHTTP(w, r)
return
}
if c.FailureHandler != nil {
c.FailureHandler.ServeHTTP(w, r)
}
})
}
// HandlerFunc same as `Handler` but it accepts and returns a type of `http.HandlerFunc` instead.
func (c *Client) HandlerFunc(next func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
return c.Handler(http.HandlerFunc(next)).ServeHTTP
}
// responseFormValue = "h-captcha-response"
const apiURL = "https://hcaptcha.com/siteverify"
// SiteVerify accepts a "r" Request and a secret key (https://dashboard.hcaptcha.com/settings).
// It returns the hcaptcha's `Response`.
// The `response.Success` reports whether the validation passed.
// Any errors are passed through the `response.ErrorCodes` field.
func (c *Client) SiteVerify(r *http.Request) (response Response) {
generatedResponseID, err := getFormValue(r, "h-captcha-response")
if err != nil {
response.ErrorCodes = append(response.ErrorCodes, err.Error())
return
}
if generatedResponseID == "" {
response.ErrorCodes = append(response.ErrorCodes,
"form[h-captcha-response] is empty")
return
}
// Call VerifyToken for verification after extracting token
// Check token before call to maintain backwards compatibility
return c.VerifyToken(generatedResponseID)
}
// VerifyToken accepts a token and a secret key (https://dashboard.hcaptcha.com/settings).
// It returns the hcaptcha's `Response`.
// The `response.Success` reports whether the validation passed.
// Any errors are passed through the `response.ErrorCodes` field.
// Same as SiteVerify except token is provided by caller instead of being extracted from HTTP request
func (c *Client) VerifyToken(tkn string) (response Response) {
if tkn == "" {
response.ErrorCodes = append(response.ErrorCodes, errors.New("tkn is empty").Error())
return
}
values := url.Values{
"secret": {c.secret},
"response": {tkn},
}
// Add remoteIP if set
if c.RemoteIP != "" {
values.Add("remoteip", c.RemoteIP)
}
// Add sitekey if set
if c.SiteKey != "" {
values.Add("sitekey", c.SiteKey)
}
resp, err := c.HTTPClient.PostForm(apiURL, values)
if err != nil {
response.ErrorCodes = append(response.ErrorCodes, err.Error())
return
}
body, err := io.ReadAll(resp.Body)
resp.Body.Close()
if err != nil {
response.ErrorCodes = append(response.ErrorCodes, err.Error())
return
}
err = json.Unmarshal(body, &response)
if err != nil {
response.ErrorCodes = append(response.ErrorCodes, err.Error())
return
}
return
}
func getFormValue(r *http.Request, key string) (string, error) {
err := r.ParseMultipartForm(PostMaxMemory)
if err != nil && err != http.ErrNotMultipart {
return "", err
}
if form := r.Form; len(form) > 0 {
return form.Get(key), nil
}
if form := r.PostForm; len(form) > 0 {
return form.Get(key), nil
}
if m := r.MultipartForm; m != nil {
if len(m.Value) > 0 {
if values := m.Value[key]; len(values) > 0 {
return values[0], nil
}
}
}
return "", nil
}
// Get returns the hcaptcha `Response` of the current "r" request and reports whether was found or not.
func Get(r *http.Request) (Response, bool) {
v := r.Context().Value(ResponseContextKey)
if v != nil {
if response, ok := v.(Response); ok {
return response, true
}
}
return Response{}, false
}
// HTMLForm is the default HTML form for clients.
// It's totally optional, use your own code for the best possible result depending on your web application.
// See `ParseForm` and `RenderForm` for more.
var HTMLForm = `<form action="%s" method="POST">
<script src="https://hcaptcha.com/1/api.js"></script>
<div class="h-captcha" data-sitekey="%s"></div>
<input type="submit" name="button" value="OK">
</form>`
// ParseForm parses the `HTMLForm` with the necessary parameters and returns
// its result for render.
func ParseForm(dataSiteKey, postActionRelativePath string) string {
return fmt.Sprintf(HTMLForm, postActionRelativePath, dataSiteKey)
}
// RenderForm writes the `HTMLForm` to "w" response writer.
// See `_examples/basic/register_form.html` example for a custom form instead.
func RenderForm(w http.ResponseWriter, dataSiteKey, postActionRelativePath string) (int, error) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
return fmt.Fprint(w, ParseForm(dataSiteKey, postActionRelativePath))
}