windport/pkg/windscribe/csrf.go

package windscribe

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"time"
)

const (
	csrfExpire time.Duration = time.Second * 4
)

type CSRF struct {
	Token string `json:"csrf_token"`
	Time  int    `json:"csrf_time"`
}

func (c *client) CSRF(ctx context.Context) *CSRF {
	if c.csrf == nil || time.Now().Sub(time.Unix(int64(c.csrf.Time), 0)) > csrfExpire {
		var err error
		c.csrf, err = c.getCSRF(ctx)
		if err != nil {
			panic(err)
		}
	}

	return c.csrf
}

func (c *client) getCSRF(ctx context.Context) (*CSRF, error) {
	req, err := http.NewRequestWithContext(ctx, "POST", "https://res.windscribe.com/res/logintoken", strings.NewReader(""))
	if err != nil {
		return nil, err
	}

	fillReq(req)

	resp, err := c.hc.Do(req)
	if err != nil {
		return nil, err
	}

	var csrf CSRF

	decoder := json.NewDecoder(resp.Body)
	err = decoder.Decode(&csrf)
	if err != nil {
		return nil, err
	}
	cleanupBody(resp.Body)

	return &csrf, nil
}

var csrfRE = regexp.MustCompile(`^\s*csrf_(time|token) = '?([0-9a-f]+)'?;\s*$`)

func (c *client) getCSRFfromBody(ctx context.Context, body io.Reader) (*CSRF, error) {
	csrf := CSRF{}

	scan := bufio.NewScanner(body)
	for scan.Scan() {
		ln := scan.Text()
		m := csrfRE.FindStringSubmatch(ln)
		if len(m) == 3 {
			var err error
			switch m[1] {
			case "time":
				csrf.Time, err = strconv.Atoi(m[2])
				if err != nil {
					return nil, err
				}
			case "token":
				csrf.Token = m[2]
			}
		}
	}

	if err := scan.Err(); err != nil {
		return nil, err
	}

	if csrf.Token == "" || csrf.Time == 0 {
		return nil, fmt.Errorf("getCSRFfromBody: csrf is %+v", csrf)
	}

	return &csrf, nil
}