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@ -1,12 +1,9 @@
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package repository
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import (
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"crypto/rand"
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"encoding/binary"
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"hash/maphash"
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"github.com/restic/restic/internal/restic"
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"github.com/dchest/siphash"
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)
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// An indexMap is a chained hash table that maps blob IDs to indexEntries.
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@ -23,7 +20,7 @@ type indexMap struct {
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buckets []*indexEntry
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numentries uint
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key0, key1 uint64 // Key for hash randomization.
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mh maphash.Hash
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free *indexEntry // Free list.
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}
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@ -113,25 +110,20 @@ func (m *indexMap) grow() {
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}
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func (m *indexMap) hash(id restic.ID) uint {
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// We use siphash with a randomly generated 128-bit key, to prevent
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// backups of specially crafted inputs from degrading performance.
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// We use maphash to prevent backups of specially crafted inputs
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// from degrading performance.
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// While SHA-256 should be collision-resistant, for hash table indices
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// we use only a few bits of it and finding collisions for those is
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// much easier than breaking the whole algorithm.
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h := uint(siphash.Hash(m.key0, m.key1, id[:]))
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m.mh.Reset()
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_, _ = m.mh.Write(id[:])
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h := uint(m.mh.Sum64())
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return h & uint(len(m.buckets)-1)
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}
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func (m *indexMap) init() {
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const initialBuckets = 64
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m.buckets = make([]*indexEntry, initialBuckets)
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var buf [16]byte
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if _, err := rand.Read(buf[:]); err != nil {
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panic(err) // Very little we can do here.
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}
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m.key0 = binary.LittleEndian.Uint64(buf[:8])
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m.key1 = binary.LittleEndian.Uint64(buf[8:])
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}
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func (m *indexMap) len() uint { return m.numentries }
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MichaelEischer
1 year ago
committed by
GitHub