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29 lines
879 B
Go
29 lines
879 B
Go
// Copyright (c) 2021 Tulir Asokan
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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// Package hkdfutil contains a simple wrapper for golang.org/x/crypto/hkdf that reads a specified number of bytes.
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package hkdfutil
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import (
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"crypto/sha256"
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"fmt"
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"golang.org/x/crypto/hkdf"
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)
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func SHA256(key, salt, info []byte, length uint8) []byte {
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data := make([]byte, length)
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h := hkdf.New(sha256.New, key, salt, info)
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n, err := h.Read(data)
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if err != nil {
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// Length is limited to 255 by being uint8, so these errors can't actually happen
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panic(fmt.Errorf("failed to expand key: %w", err))
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} else if uint8(n) != length {
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panic(fmt.Errorf("didn't read enough bytes (got %d, wanted %d)", n, length))
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}
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return data
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}
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