libgocryptfs/internal/nametransform/diriv_cache.go
Jakob Unterwurzacher 944eaf2fb5 fusefronted: expire dir IV cache after one second
The Back In Time backup tool (https://github.com/bit-team/backintime)
wants to write directly into the ciphertext dir.
This may cause the cached directory IV to become out-of-date.
Having an expiry time limits the inconstency to one second, like
attr_timeout does for the kernel getattr cache.
2016-11-01 10:57:39 +01:00

64 lines
1.4 KiB
Go

package nametransform
import (
"sync"
"time"
)
// Single-entry DirIV cache. Stores the directory IV and the encrypted
// path.
type dirIVCache struct {
// Directory the DirIV belongs to
dir string
// Time the entry expires.
// The cached entry my become out-of-date if the ciphertext directory is
// modifed behind the back of gocryptfs. Having an expiry time limits the
// inconstency to one second, like attr_timeout does for the kernel
// getattr cache.
expiry time.Time
// The DirIV
iv []byte
// Ecrypted version of "dir"
cDir string
// Invalidated?
cleared bool
sync.RWMutex
}
// lookup - fetch entry for "dir" from the cache
func (c *dirIVCache) lookup(dir string) ([]byte, string) {
c.RLock()
defer c.RUnlock()
if c.cleared || c.dir != dir {
return nil, ""
}
if time.Since(c.expiry) > 0 {
c.cleared = true
return nil, ""
}
return c.iv, c.cDir
}
// store - write entry for "dir" into the cache
func (c *dirIVCache) store(dir string, iv []byte, cDir string) {
c.Lock()
defer c.Unlock()
c.cleared = false
c.iv = iv
c.dir = dir
c.cDir = cDir
// Set expiry time one second into the future
c.expiry = time.Now().Add(1 * time.Second)
}
// Clear ... clear the cache.
// Exported because it is called from fusefrontend when directories are
// renamed or deleted.
func (c *dirIVCache) Clear() {
c.Lock()
defer c.Unlock()
c.cleared = true
}