Update dependencies

vendor/github.com/u-root/uio/rand/random_urandom.go

@@ -0,0 +1,60 @@
+// Copyright 2019 the u-root Authors. All rights reserved
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build aix || darwin || dragonfly || freebsd || nacl || netbsd || openbsd || solaris || linux
+// +build aix darwin dragonfly freebsd nacl netbsd openbsd solaris linux
+
+package rand
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// urandomReader is a contextReader.
+type urandomReader struct {
+	once sync.Once
+
+	// fd is expected to be non-blocking.
+	fd int
+}
+
+func (r *urandomReader) init() error {
+	var realErr error
+	r.once.Do(func() {
+		fd, err := unix.Open("/dev/urandom", unix.O_RDONLY, 0)
+		if err != nil {
+			realErr = fmt.Errorf("open(/dev/urandom): %v", err)
+			return
+		}
+		r.fd = fd
+	})
+	return realErr
+}
+
+// ReadContext implements a cancelable read from /dev/urandom.
+func (r *urandomReader) ReadContext(ctx context.Context, b []byte) (int, error) {
+	if err := r.init(); err != nil {
+		return 0, err
+	}
+	for {
+		n, err := unix.Read(r.fd, b)
+		if err == nil {
+			return n, nil
+		}
+		select {
+		case <-ctx.Done():
+			return 0, ctx.Err()
+
+		default:
+			if err != syscall.EAGAIN && err != syscall.EINTR {
+				return n, err
+			}
+		}
+	}
+}