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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