[dev.boringcrypto] crypto/rand: use BoringCrypto

Change-Id: Ie630eff90f7fee9b359683930aec2daf96c1bdfe
Reviewed-on: https://go-review.googlesource.com/55473
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

src/crypto/internal/boring/boring.go

@@ -37,3 +37,7 @@ func UnreachableExceptTests() {
 		panic("boringcrypto: invalid code execution")
 	}
 }
+
+type fail string
+
+func (e fail) Error() string { return "boringcrypto: " + string(e) + " failed" }

src/crypto/internal/boring/notboring.go

@@ -15,3 +15,11 @@ func Unreachable() {}
 // UnreachableExceptTests marks code that should be unreachable
 // when BoringCrypto is in use. It is a no-op without BoringCrypto.
 func UnreachableExceptTests() {}
+
+type randReader int
+
+func (randReader) Read(b []byte) (int, error) {
+	panic("boringcrypto: not available")
+}
+
+const RandReader = randReader(0)

src/crypto/internal/boring/rand.go

@@ -0,0 +1,25 @@
+// Copyright 2017 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.
+
+// +build linux,amd64
+// +build !cmd_go_bootstrap
+
+package boring
+
+// #include "goboringcrypto.h"
+import "C"
+import "unsafe"
+
+type randReader int
+
+func (randReader) Read(b []byte) (int, error) {
+	// Note: RAND_bytes should never fail; the return value exists only for historical reasons.
+	// We check it even so.
+	if len(b) > 0 && C._goboringcrypto_RAND_bytes((*C.uint8_t)(unsafe.Pointer(&b[0])), C.size_t(len(b))) == 0 {
+		return 0, fail("RAND_bytes")
+	}
+	return len(b), nil
+}
+
+const RandReader = randReader(0)

src/crypto/rand/rand_unix.go

@@ -13,6 +13,7 @@ import (
 	"bufio"
 	"crypto/aes"
 	"crypto/cipher"
+	"crypto/internal/boring"
 	"io"
 	"os"
 	"runtime"
@@ -26,6 +27,10 @@ const urandomDevice = "/dev/urandom"
 // This is sufficient on Linux, OS X, and FreeBSD.
 
 func init() {
+	if boring.Enabled {
+		Reader = boring.RandReader
+		return
+	}
 	if runtime.GOOS == "plan9" {
 		Reader = newReader(nil)
 	} else {
@@ -45,6 +50,7 @@ type devReader struct {
 var altGetRandom func([]byte) (ok bool)
 
 func (r *devReader) Read(b []byte) (n int, err error) {
+	boring.Unreachable()
 	if altGetRandom != nil && r.name == urandomDevice && altGetRandom(b) {
 		return len(b), nil
 	}
@@ -108,6 +114,7 @@ type reader struct {
 }
 
 func (r *reader) Read(b []byte) (n int, err error) {
+	boring.Unreachable()
 	r.mu.Lock()
 	defer r.mu.Unlock()
 	n = len(b)