preSignUp.go

package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"net/url"
	"os"

	"github.com/aws/aws-lambda-go/lambda"
)

var(
	recaptchaSecret = os.Getenv("RECAPTCHA_SECRET")
)

func main() {
	lambda.Start(preSignUpHandler)
}

type Req map[string]interface{}

type RecaptchaResponse struct {
	Success     bool    `json:"success"`
	ChallengeTs string  `json:"challenge_ts"`
	Hostname    string  `json:"hostname"`
	Score       float64 `json:"score"`
	Action      string  `json:"action"`
}

func preSignUpHandler(ctx context.Context, req Req) (interface{}, error) {
	fmt.Println("called pre sign up")

	for k, v := range req {
		log.Println(fmt.Sprintf("%s => %v", k, v))
	}

	reqReq, isErr := req["request"].(map[string]interface{})
	if !isErr {
		return nil, errors.New("cannot convert response")
	}

	clientMetadata, isErr := reqReq["clientMetadata"].(map[string]interface{})
	if !isErr {
		return nil, errors.New("cannot convert clientMetadata")
	}

	recaptchaToken, isErr := clientMetadata["recaptchaToken"].(string)
	if !isErr {
		return nil, errors.New("cannot convert recaptchaToken")
	}

	recaptchaResponse, err := postRecaptchaSiteVerify(recaptchaToken)
	if err != nil {
		return nil, errors.New("failed post recaptcha site verify")
	}
	log.Println(fmt.Sprintf("%v", recaptchaResponse))

	return req, localVerify(recaptchaResponse)
}

func postRecaptchaSiteVerify(recaptchaToken string)(*RecaptchaResponse, error) {
	values := url.Values{}
	values.Add("secret", recaptchaSecret)
	values.Add("response", recaptchaToken)

	postResponse, err := http.PostForm(
		"https://www.google.com/recaptcha/api/siteverify",
		values,
	)
	if err != nil {
		return nil, errors.New(fmt.Sprintf("error reCAPTCHA post: %v", err))
	}

	defer postResponse.Body.Close()
	var recaptchaResponse RecaptchaResponse
	return &recaptchaResponse, json.NewDecoder(postResponse.Body).Decode(&recaptchaResponse)
}

func localVerify(recaptchaResponse *RecaptchaResponse) error {
	// TODO: write verify logic.
	errMsg := "recaptcha failed"
	if !recaptchaResponse.Success {
		return errors.New(errMsg)
	}
	if recaptchaResponse.Score < 0.5 {
		return errors.New(errMsg)
	}
	return nil
}