1 files changed, 147 insertions, 0 deletions
diff --git a/src/crypto/rand/rand_unix.go b/src/crypto/rand/rand_unix.go
new file mode 100644
index 000000000..62d0fbdb3
--- /dev/null
+++ b/src/crypto/rand/rand_unix.go
@@ -0,0 +1,147 @@
+// Copyright 2010 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 plan9 solaris
+
+// Unix cryptographically secure pseudorandom number
+// generator.
+
+package rand
+
+import (
+	"bufio"
+	"crypto/aes"
+	"crypto/cipher"
+	"io"
+	"os"
+	"runtime"
+	"sync"
+	"time"
+)
+
+const urandomDevice = "/dev/urandom"
+
+// Easy implementation: read from /dev/urandom.
+// This is sufficient on Linux, OS X, and FreeBSD.
+
+func init() {
+	if runtime.GOOS == "plan9" {
+		Reader = newReader(nil)
+	} else {
+		Reader = &devReader{name: urandomDevice}
+	}
+}
+
+// A devReader satisfies reads by reading the file named name.
+type devReader struct {
+	name string
+	f    io.Reader
+	mu   sync.Mutex
+}
+
+// altGetRandom if non-nil specifies an OS-specific function to get
+// urandom-style randomness.
+var altGetRandom func([]byte) (ok bool)
+
+func (r *devReader) Read(b []byte) (n int, err error) {
+	if altGetRandom != nil && r.name == urandomDevice && altGetRandom(b) {
+		return len(b), nil
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.f == nil {
+		f, err := os.Open(r.name)
+		if f == nil {
+			return 0, err
+		}
+		if runtime.GOOS == "plan9" {
+			r.f = f
+		} else {
+			r.f = bufio.NewReader(f)
+		}
+	}
+	return r.f.Read(b)
+}
+
+// Alternate pseudo-random implementation for use on
+// systems without a reliable /dev/urandom.
+
+// newReader returns a new pseudorandom generator that
+// seeds itself by reading from entropy.  If entropy == nil,
+// the generator seeds itself by reading from the system's
+// random number generator, typically /dev/random.
+// The Read method on the returned reader always returns
+// the full amount asked for, or else it returns an error.
+//
+// The generator uses the X9.31 algorithm with AES-128,
+// reseeding after every 1 MB of generated data.
+func newReader(entropy io.Reader) io.Reader {
+	if entropy == nil {
+		entropy = &devReader{name: "/dev/random"}
+	}
+	return &reader{entropy: entropy}
+}
+
+type reader struct {
+	mu                   sync.Mutex
+	budget               int // number of bytes that can be generated
+	cipher               cipher.Block
+	entropy              io.Reader
+	time, seed, dst, key [aes.BlockSize]byte
+}
+
+func (r *reader) Read(b []byte) (n int, err error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	n = len(b)
+
+	for len(b) > 0 {
+		if r.budget == 0 {
+			_, err := io.ReadFull(r.entropy, r.seed[0:])
+			if err != nil {
+				return n - len(b), err
+			}
+			_, err = io.ReadFull(r.entropy, r.key[0:])
+			if err != nil {
+				return n - len(b), err
+			}
+			r.cipher, err = aes.NewCipher(r.key[0:])
+			if err != nil {
+				return n - len(b), err
+			}
+			r.budget = 1 << 20 // reseed after generating 1MB
+		}
+		r.budget -= aes.BlockSize
+
+		// ANSI X9.31 (== X9.17) algorithm, but using AES in place of 3DES.
+		//
+		// single block:
+		// t = encrypt(time)
+		// dst = encrypt(t^seed)
+		// seed = encrypt(t^dst)
+		ns := time.Now().UnixNano()
+		r.time[0] = byte(ns >> 56)
+		r.time[1] = byte(ns >> 48)
+		r.time[2] = byte(ns >> 40)
+		r.time[3] = byte(ns >> 32)
+		r.time[4] = byte(ns >> 24)
+		r.time[5] = byte(ns >> 16)
+		r.time[6] = byte(ns >> 8)
+		r.time[7] = byte(ns)
+		r.cipher.Encrypt(r.time[0:], r.time[0:])
+		for i := 0; i < aes.BlockSize; i++ {
+			r.dst[i] = r.time[i] ^ r.seed[i]
+		}
+		r.cipher.Encrypt(r.dst[0:], r.dst[0:])
+		for i := 0; i < aes.BlockSize; i++ {
+			r.seed[i] = r.time[i] ^ r.dst[i]
+		}
+		r.cipher.Encrypt(r.seed[0:], r.seed[0:])
+
+		m := copy(b, r.dst[0:])
+		b = b[m:]
+	}
+
+	return n, nil
+}