63 lines
1.5 KiB
Go
63 lines
1.5 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package rand implements a cryptographically secure pseudorandom number
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// generator.
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package rand
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import (
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"crypto/rand"
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"io"
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"sync"
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"golang.org/x/sys/unix"
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)
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// reader implements an io.Reader that returns pseudorandom bytes.
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type reader struct {
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once sync.Once
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useGetrandom bool
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}
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// Read implements io.Reader.Read.
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func (r *reader) Read(p []byte) (int, error) {
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r.once.Do(func() {
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_, err := unix.Getrandom(p, 0)
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if err != unix.ENOSYS {
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r.useGetrandom = true
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}
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})
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if r.useGetrandom {
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return unix.Getrandom(p, 0)
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}
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return rand.Read(p)
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}
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// Reader is the default reader.
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var Reader io.Reader = &reader{}
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// Read reads from the default reader.
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func Read(b []byte) (int, error) {
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return io.ReadFull(Reader, b)
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}
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// Init can be called to make sure /dev/urandom is pre-opened on kernels that
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// do not support getrandom(2).
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func Init() error {
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p := make([]byte, 1)
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_, err := Read(p)
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return err
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}
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