72 lines
2.3 KiB
Go
72 lines
2.3 KiB
Go
package store
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import (
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"crypto/subtle"
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"database/sql"
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"encoding/base64"
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"time"
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)
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// genDeletionToken returns a 32-char url-safe random token
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func genDeletionToken() string {
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b := make([]byte, 24)
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cryptoRead(b)
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return base64.RawURLEncoding.EncodeToString(b)
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}
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// TimeNow is overridable in tests to inject the clock.
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var TimeNow = time.Now
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// registerRead applies the burn-after-read budget for one view (#49).
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// For pastes with reads_limit set: the viewer's paste_views row is checked;
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// a view within the burn viewer window of the viewer's last view is deduped
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// (count=false). Otherwise reads_used is incremented, and the paste is
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// soft-deleted (burned) once reads_used reaches reads_limit. Viewers without
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// a cookie (plain API clients) count as their own viewer id "".
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// For legacy plain burn_after_read pastes (no reads_limit), any read burns.
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// Returns the number of reads remaining (0 when burned), or nil when no
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// budget is set. view_count is tracked separately and unaffected.
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func (s *Store) RegisterRead(row *PasteRow, viewerID string, burnWindowMinutes int) (remaining *int, count bool) {
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if !row.ReadsLimit.Valid {
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if row.BurnAfterRead {
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s.SoftDelete(row.ID)
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r := 0
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return &r, true
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}
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return nil, false
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}
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now := TimeNow().Unix()
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var last sql.NullInt64
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s.db.QueryRow(`SELECT last_viewed FROM paste_views WHERE paste_id=? AND viewer_id=?`,
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row.ID, viewerID).Scan(&last)
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if last.Valid && now-last.Int64 < int64(burnWindowMinutes)*60 {
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r := int(row.ReadsLimit.Int64) - row.ReadsUsed
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if r < 0 {
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r = 0
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}
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return &r, false
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}
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s.db.Exec(`INSERT INTO paste_views (paste_id, viewer_id, last_viewed) VALUES (?,?,?)
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ON CONFLICT(paste_id, viewer_id) DO UPDATE SET last_viewed = excluded.last_viewed`,
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row.ID, viewerID, now)
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used := row.ReadsUsed + 1
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s.db.Exec(`UPDATE pastes SET reads_used=? WHERE id=?`, used, row.ID)
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if int64(used) >= row.ReadsLimit.Int64 {
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s.SoftDelete(row.ID)
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}
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r := int(row.ReadsLimit.Int64) - int(used)
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if r < 0 {
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r = 0
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}
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return &r, true
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}
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// Burned reports whether a read-limited paste has exhausted its budget.
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func (row *PasteRow) Burned() bool {
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return row.ReadsLimit.Valid && int64(row.ReadsUsed) >= row.ReadsLimit.Int64
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}
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func DeletionTokenEqual(stored, given string) bool {
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return subtle.ConstantTimeCompare([]byte(stored), []byte(given)) == 1
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}
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