110 lines
2.5 KiB
Go
110 lines
2.5 KiB
Go
package captcha
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import (
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"crypto/sha256"
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"encoding/base64"
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"image"
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"strconv"
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"sync"
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"time"
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)
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var expiredScanInterval = 60 * time.Second
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type ICaptchaDB interface {
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New(data string) (ICaptcha, ID)
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SetExpiration(expire time.Duration)
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Image(id ID) (*image.Image, error)
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Solve(id ID, answer Answer) (bool, error)
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IsSolved(id ID) bool
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GetExpireInterval() time.Duration
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}
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type CaptchaDB struct {
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DB map[ID]ICaptcha
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ExpireInterval time.Duration
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mut sync.Mutex
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}
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// SetExpiration stores expire value and starts a goroutine
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// that checks for expired CAPTCHAs every minute.
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func (cdb *CaptchaDB) SetExpiration(expire time.Duration) {
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cdb.ExpireInterval = expire
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if expire < expiredScanInterval {
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expiredScanInterval = expire
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}
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go func() {
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for {
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n := time.Now().Second()
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sleepFor := expiredScanInterval - (time.Duration(n) * time.Second % expiredScanInterval)
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time.Sleep(sleepFor)
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for id, captcha := range cdb.DB {
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if time.Now().Sub(captcha.Expire()) <= 0 {
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delete(cdb.DB, id)
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}
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}
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}
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}()
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}
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// New accepts an ICaptcha instance, generates an ID and store it in a database.
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// `data` string is an additional random data used to generate an ID,
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// e.g. IP-address.
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func (cdb *CaptchaDB) New(data string, captcha ICaptcha) (ICaptcha, ID) {
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idHash := sha256.New()
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idHash.Write([]byte(data))
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idHash.Write([]byte(strconv.FormatInt(time.Now().UnixMicro(), 16)))
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idHash.Write([]byte(captcha.GetAnswer()))
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id := ID(base64.RawURLEncoding.EncodeToString(idHash.Sum(nil)))
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cdb.mut.Lock()
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defer cdb.mut.Unlock()
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cdb.DB[id] = captcha
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return captcha, id
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}
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// Image returns image for a captcha.
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func (cdb *CaptchaDB) Image(id ID) (*image.Image, error) {
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if c, ok := cdb.DB[id]; ok {
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return c.GetImage(), nil
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}
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return nil, errorNotFound
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}
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// Solve compares given answer with a stored one and if failed
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// deletes a captcha from database.
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func (cdb *CaptchaDB) Solve(id ID, answer Answer) (bool, error) {
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cdb.mut.Lock()
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defer cdb.mut.Unlock()
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if c, ok := cdb.DB[id]; ok {
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ok = c.Solve(answer)
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if !ok {
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delete(cdb.DB, id)
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}
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return ok, nil
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}
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return false, errorNotFound
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}
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// IsSolved checks if captcha was solved and removes it
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// from a database.
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func (cdb *CaptchaDB) IsSolved(id ID) (bool, error) {
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cdb.mut.Lock()
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defer cdb.mut.Unlock()
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if c, ok := cdb.DB[id]; ok {
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ok = c.IsSolved()
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delete(cdb.DB, id)
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return ok, nil
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}
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return false, errorNotFound
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}
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func (cdb *CaptchaDB) GetExpireInterval() time.Duration {
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return cdb.ExpireInterval
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}
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