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40 lines
886 B
Go
40 lines
886 B
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package rand
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import (
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"internal/syscall/unix"
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"sync"
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)
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func init() {
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altGetRandom = getRandomLinux
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}
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var (
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once sync.Once
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useSyscall bool
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)
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func pickStrategy() {
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// Test whether we should use the system call or /dev/urandom.
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// We'll fall back to urandom if:
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// - the kernel is too old (before 3.17)
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// - the machine has no entropy available (early boot + no hardware
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// entropy source?) and we want to avoid blocking later.
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var buf [1]byte
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n, err := unix.GetRandom(buf[:], unix.GRND_NONBLOCK)
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useSyscall = n == 1 && err == nil
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}
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func getRandomLinux(p []byte) (ok bool) {
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once.Do(pickStrategy)
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if !useSyscall {
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return false
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}
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n, err := unix.GetRandom(p, 0)
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return n == len(p) && err == nil
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}
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