119 lines
2.6 KiB
Go
119 lines
2.6 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 ID string
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// NewID generates an ID as a sha256 hash of additionalData, current time
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// and answer encoded with base64 in raw URL variant.
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func NewID(additionalData string, answer Answer) ID {
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idHash := sha256.New()
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idHash.Write([]byte(additionalData))
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idHash.Write([]byte(strconv.FormatInt(time.Now().UnixMicro(), 16)))
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idHash.Write([]byte(answer))
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return ID(base64.RawURLEncoding.EncodeToString(idHash.Sum(nil)))
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}
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type ICaptchaDB interface {
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New(data string) (ICaptcha, ID)
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SetExpiry(expiry time.Duration)
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GetExpiry() 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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}
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type CaptchaDB struct {
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DB map[ID]ICaptcha
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ExpireIn time.Duration
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sync.Mutex
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}
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// SetExpiry 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) SetExpiry(expire time.Duration) {
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cdb.ExpireIn = 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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sleepFor := expiredScanInterval - (time.Duration(time.Now().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.Expiry()) <= 0 {
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cdb.Lock()
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defer cdb.Unlock()
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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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id := NewID(data, captcha.GetAnswer())
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cdb.Lock()
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defer cdb.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.Lock()
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defer cdb.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.Lock()
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defer cdb.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) GetExpiry() time.Duration {
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return cdb.ExpireIn
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}
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