crypto/rand: handle EAGAIN reads from /dev/urandom

Fixes #9205

Change-Id: Iacd608ba43332008984aa8ece17dcb5757f27b3f
Reviewed-on: https://go-review.googlesource.com/1611
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/crypto/rand/eagain.go b/src/crypto/rand/eagain.go
new file mode 100644 (file)
index 0000000..2c853d0
--- /dev/null
+++ b/src/crypto/rand/eagain.go
@@ -0,0 +1,27 @@
+// 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.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package rand
+
+import (
+       "os"
+       "syscall"
+)
+
+func init() {
+       isEAGAIN = unixIsEAGAIN
+}
+
+// unixIsEAGAIN reports whether err is a syscall.EAGAIN wrapped in a PathError.
+// See golang.org/issue/9205
+func unixIsEAGAIN(err error) bool {
+       if pe, ok := err.(*os.PathError); ok {
+               if errno, ok := pe.Err.(syscall.Errno); ok && errno == syscall.EAGAIN {
+                       return true
+               }
+       }
+       return false
+}

diff --git a/src/crypto/rand/rand_unix.go b/src/crypto/rand/rand_unix.go
index 62d0fbdb350c4d7013186893b3d065e1ce5b8a02..75c36e05b34020f92e057fd2966f073cf0e40c74 100644 (file)
--- a/src/crypto/rand/rand_unix.go
+++ b/src/crypto/rand/rand_unix.go
@@ -58,12 +58,28 @@ func (r *devReader) Read(b []byte) (n int, err error) {
                if runtime.GOOS == "plan9" {
                        r.f = f
                } else {
-                       r.f = bufio.NewReader(f)
+                       r.f = bufio.NewReader(hideAgainReader{f})
                }
        }
        return r.f.Read(b)
 }
 
+var isEAGAIN func(error) bool // set by eagain.go on unix systems
+
+// hideAgainReader masks EAGAIN reads from /dev/urandom.
+// See golang.org/issue/9205
+type hideAgainReader struct {
+       r io.Reader
+}
+
+func (hr hideAgainReader) Read(p []byte) (n int, err error) {
+       n, err = hr.r.Read(p)
+       if err != nil && isEAGAIN != nil && isEAGAIN(err) {
+               err = nil
+       }
+       return
+}
+
 // Alternate pseudo-random implementation for use on
 // systems without a reliable /dev/urandom.