85 lines
1.6 KiB
Go
85 lines
1.6 KiB
Go
// Copyright (C) 2022 Marius Schellenberger
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// crypto parts taken from https://github.com/filosottile/age
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package crypto
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import (
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"cachefs/pkg/provider"
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"crypto/rand"
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"encoding/binary"
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"io"
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"math"
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)
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func isZero(nonce []byte) bool {
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for i := 0; i < len(nonce); i++ {
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if nonce[i] != 0 {
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return false
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}
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}
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return true
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}
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func initNonce(f provider.File) (nonce []byte, err error) {
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nonce = make([]byte, KDFNonceSize)
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n, err := io.ReadFull(f, nonce)
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if err != nil || n != len(nonce) || isZero(nonce) {
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_, err = io.ReadFull(rand.Reader, nonce)
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if err != nil {
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return
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}
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_, err = f.Seek(0, io.SeekStart)
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if err != nil {
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return
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}
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_, err = f.Write(nonce)
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}
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return
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}
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func incNonce(nonce *[NonceSize]byte) {
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for i := len(nonce) - 2; i >= 0; i-- {
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nonce[i]++
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if nonce[i] != 0 {
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break
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} else if i == 0 {
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// The counter is 88 bits, this is unreachable.
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panic("stream: chunk counter wrapped around")
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}
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}
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}
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func Size(s int64) int64 {
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return KDFNonceSize + s + (int64(math.Ceil(float64(s)/ChunkSize)) * Overhead)
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}
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func RealSize(s int64) int64 {
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s -= KDFNonceSize
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return s - (((s / FullSize) + 1) * Overhead)
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}
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func chunkNum(o int64) int64 {
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return int64(math.Ceil(float64(o) / ChunkSize))
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}
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func align(o int64) (cn, off, roff int64) {
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cn = chunkNum(o)
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off = cn * FullSize
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roff = o - (cn * ChunkSize)
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if roff < 0 {
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cn--
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off = cn * FullSize
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roff = o - (cn * ChunkSize)
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}
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return
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}
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func inc(nonce *[NonceSize]byte, n int64) {
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for i := int64(0); i < n; i++ {
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incNonce(nonce)
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}
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}
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func put(nonce *[NonceSize]byte, n int64) {
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binary.BigEndian.PutUint64((*nonce)[3:11], uint64(n))
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}
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