1 files changed, 77 insertions, 0 deletions
diff --git a/pkg/rand/rand_linux.go b/pkg/rand/rand_linux.go
new file mode 100644
index 000000000..fa6a21026
--- /dev/null
+++ b/pkg/rand/rand_linux.go
@@ -0,0 +1,77 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package rand implements a cryptographically secure pseudorandom number
+// generator.
+package rand
+
+import (
+	"bufio"
+	"crypto/rand"
+	"io"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// reader implements an io.Reader that returns pseudorandom bytes.
+type reader struct {
+	once         sync.Once
+	useGetrandom bool
+}
+
+// Read implements io.Reader.Read.
+func (r *reader) Read(p []byte) (int, error) {
+	r.once.Do(func() {
+		_, err := unix.Getrandom(p, 0)
+		if err != unix.ENOSYS {
+			r.useGetrandom = true
+		}
+	})
+
+	if r.useGetrandom {
+		return unix.Getrandom(p, 0)
+	}
+	return rand.Read(p)
+}
+
+// bufferedReader implements a threadsafe buffered io.Reader.
+type bufferedReader struct {
+	mu sync.Mutex
+	r  *bufio.Reader
+}
+
+// Read implements io.Reader.Read.
+func (b *bufferedReader) Read(p []byte) (int, error) {
+	b.mu.Lock()
+	n, err := b.r.Read(p)
+	b.mu.Unlock()
+	return n, err
+}
+
+// Reader is the default reader.
+var Reader io.Reader = &bufferedReader{r: bufio.NewReader(&reader{})}
+
+// Read reads from the default reader.
+func Read(b []byte) (int, error) {
+	return io.ReadFull(Reader, b)
+}
+
+// Init can be called to make sure /dev/urandom is pre-opened on kernels that
+// do not support getrandom(2).
+func Init() error {
+	p := make([]byte, 1)
+	_, err := Read(p)
+	return err
+}