Imported Upstream version 1.4upstream/1.4

1 files changed, 39 insertions, 0 deletions

diff --git a/src/crypto/rand/rand_linux.go b/src/crypto/rand/rand_linux.go
new file mode 100644
index 000000000..8cb59c75d
--- /dev/null
+++ b/src/crypto/rand/rand_linux.go
@@ -0,0 +1,39 @@
+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rand
+
+import (
+	"internal/syscall"
+	"sync"
+)
+
+func init() {
+	altGetRandom = getRandomLinux
+}
+
+var (
+	once       sync.Once
+	useSyscall bool
+)
+
+func pickStrategy() {
+	// Test whether we should use the system call or /dev/urandom.
+	// We'll fall back to urandom if:
+	// - the kernel is too old (before 3.17)
+	// - the machine has no entropy available (early boot + no hardware
+	//   entropy source?) and we want to avoid blocking later.
+	var buf [1]byte
+	n, err := syscall.GetRandom(buf[:], syscall.GRND_NONBLOCK)
+	useSyscall = n == 1 && err == nil
+}
+
+func getRandomLinux(p []byte) (ok bool) {
+	once.Do(pickStrategy)
+	if !useSyscall {
+		return false
+	}
+	n, err := syscall.GetRandom(p, 0)
+	return n == len(p) && err == nil
+}