137 lines
3.1 KiB
Go
137 lines
3.1 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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"errors"
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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 errorNotFound = errors.New("captcha not found")
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var defaultExpiredScanInterval = 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 CaptchaDB interface {
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New(data string, captcha Captcha) (Captcha, ID)
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GetExpiry() time.Duration
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Image(id ID, style string) (*image.Image, error)
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Solve(id ID, answer Answer) (bool, error)
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IsSolved(id ID) (bool, error)
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cleanExpired()
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}
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type InMemoryCaptchaDB struct {
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sync.Mutex
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db map[ID]Captcha
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expireIn time.Duration
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expireScanInterval time.Duration
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}
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func NewInMemoryCaptchaDB(expire time.Duration) *InMemoryCaptchaDB {
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db := &InMemoryCaptchaDB{
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db: make(map[ID]Captcha),
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expireIn: expire}
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if expire < defaultExpiredScanInterval {
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db.expireScanInterval = expire
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} else {
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db.expireScanInterval = defaultExpiredScanInterval
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}
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db.cleanExpired()
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return db
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}
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// New accepts an Captcha 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 *InMemoryCaptchaDB) New(data string, captcha Captcha) (Captcha, ID) {
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id := NewID(data, captcha.Answer())
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cdb.Lock()
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cdb.db[id] = captcha
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cdb.Unlock()
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return captcha, id
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}
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// cleanExpired starts a goroutine that deletes expired CAPTCHAs.
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func (cdb *InMemoryCaptchaDB) cleanExpired() {
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go func() {
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for {
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sleepFor := cdb.expireScanInterval - (time.Duration(time.Now().Second()) % cdb.expireScanInterval)
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time.Sleep(sleepFor)
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cdb.Lock()
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for id, captcha := range cdb.db {
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if time.Since(captcha.Expiry()) >= cdb.expireIn {
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delete(cdb.db, id)
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}
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}
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cdb.Unlock()
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}
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}()
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}
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// GetExpiry returns time for how long captcha will last.
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func (cdb *InMemoryCaptchaDB) GetExpiry() time.Duration {
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return cdb.expireIn
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}
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// Image returns image for a captcha.
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func (cdb *InMemoryCaptchaDB) Image(id ID, style string) (*image.Image, 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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return c.Image(style), 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 *InMemoryCaptchaDB) 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 *InMemoryCaptchaDB) 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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