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77 lines
2.1 KiB
77 lines
2.1 KiB
3 years ago
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// Copyright 2021 by David A. Golden. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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// Package pbkdf2 implements password-based key derivation using the PBKDF2
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// algorithm described in RFC 2898 and RFC 8018.
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//
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// It provides a drop-in replacement for `golang.org/x/crypto/pbkdf2`, with
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// the following benefits:
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//
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// - Released as a module with semantic versioning
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//
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// - Does not pull in dependencies for unrelated `x/crypto/*` packages
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//
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// - Supports Go 1.9+
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//
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// See https://tools.ietf.org/html/rfc8018#section-4 for security considerations
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// in the selection of a salt and iteration count.
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package pbkdf2
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import (
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"crypto/hmac"
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"encoding/binary"
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"hash"
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)
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// Key generates a derived key from a password using the PBKDF2 algorithm. The
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// inputs include salt bytes, the iteration count, desired key length, and a
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// constructor for a hashing function. For example, for a 32-byte key using
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// SHA-256:
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//
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// key := Key([]byte("trustNo1"), salt, 10000, 32, sha256.New)
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func Key(password, salt []byte, iterCount, keyLen int, h func() hash.Hash) []byte {
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prf := hmac.New(h, password)
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hLen := prf.Size()
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numBlocks := keyLen / hLen
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// Get an extra block if keyLen is not an even number of hLen blocks.
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if keyLen%hLen > 0 {
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numBlocks++
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}
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Ti := make([]byte, hLen)
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Uj := make([]byte, hLen)
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dk := make([]byte, 0, hLen*numBlocks)
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buf := make([]byte, 4)
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for i := uint32(1); i <= uint32(numBlocks); i++ {
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// Initialize Uj for j == 1 from salt and block index.
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// Initialize Ti = U1.
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binary.BigEndian.PutUint32(buf, i)
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prf.Reset()
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prf.Write(salt)
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prf.Write(buf)
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Uj = Uj[:0]
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Uj = prf.Sum(Uj)
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// Ti = U1 ^ U2 ^ ... ^ Ux
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copy(Ti, Uj)
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for j := 2; j <= iterCount; j++ {
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prf.Reset()
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prf.Write(Uj)
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Uj = Uj[:0]
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Uj = prf.Sum(Uj)
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for k := range Uj {
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Ti[k] ^= Uj[k]
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}
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}
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// DK = concat(T1, T2, ... Tn)
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dk = append(dk, Ti...)
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}
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return dk[0:keyLen]
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}
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