61 lines
1.2 KiB
Go
61 lines
1.2 KiB
Go
// Copyright 2019 the u-root 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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//go:build aix || darwin || dragonfly || freebsd || nacl || netbsd || openbsd || solaris || linux
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// +build aix darwin dragonfly freebsd nacl netbsd openbsd solaris linux
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package rand
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import (
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"context"
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"fmt"
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"sync"
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"syscall"
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"golang.org/x/sys/unix"
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)
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// urandomReader is a contextReader.
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type urandomReader struct {
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once sync.Once
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// fd is expected to be non-blocking.
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fd int
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}
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func (r *urandomReader) init() error {
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var realErr error
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r.once.Do(func() {
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fd, err := unix.Open("/dev/urandom", unix.O_RDONLY, 0)
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if err != nil {
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realErr = fmt.Errorf("open(/dev/urandom): %v", err)
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return
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}
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r.fd = fd
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})
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return realErr
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}
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// ReadContext implements a cancelable read from /dev/urandom.
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func (r *urandomReader) ReadContext(ctx context.Context, b []byte) (int, error) {
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if err := r.init(); err != nil {
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return 0, err
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}
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for {
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n, err := unix.Read(r.fd, b)
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if err == nil {
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return n, nil
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}
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select {
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case <-ctx.Done():
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return 0, ctx.Err()
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default:
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if err != syscall.EAGAIN && err != syscall.EINTR {
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return n, err
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}
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}
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}
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}
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