1 files changed, 149 insertions, 0 deletions
diff --git a/src/crypto/rand/util_test.go b/src/crypto/rand/util_test.go
new file mode 100644
index 0000000..9caf8e9
--- /dev/null
+++ b/src/crypto/rand/util_test.go
@@ -0,0 +1,149 @@
+// Copyright 2013 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_test
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"math/big"
+	mathrand "math/rand"
+	"testing"
+	"time"
+)
+
+// https://golang.org/issue/6849.
+func TestPrimeSmall(t *testing.T) {
+	for n := 2; n < 10; n++ {
+		p, err := rand.Prime(rand.Reader, n)
+		if err != nil {
+			t.Fatalf("Can't generate %d-bit prime: %v", n, err)
+		}
+		if p.BitLen() != n {
+			t.Fatalf("%v is not %d-bit", p, n)
+		}
+		if !p.ProbablyPrime(32) {
+			t.Fatalf("%v is not prime", p)
+		}
+	}
+}
+
+// Test that passing bits < 2 causes Prime to return nil, error
+func TestPrimeBitsLt2(t *testing.T) {
+	if p, err := rand.Prime(rand.Reader, 1); p != nil || err == nil {
+		t.Errorf("Prime should return nil, error when called with bits < 2")
+	}
+}
+
+func TestPrimeNondeterministic(t *testing.T) {
+	r := mathrand.New(mathrand.NewSource(42))
+	p0, err := rand.Prime(r, 32)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 128; i++ {
+		r.Seed(42)
+		p, err := rand.Prime(r, 32)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if p.Cmp(p0) != 0 {
+			return
+		}
+	}
+	t.Error("Prime always generated the same prime given the same input")
+}
+
+func TestInt(t *testing.T) {
+	// start at 128 so the case of (max.BitLen() % 8) == 0 is covered
+	for n := 128; n < 140; n++ {
+		b := new(big.Int).SetInt64(int64(n))
+		if i, err := rand.Int(rand.Reader, b); err != nil {
+			t.Fatalf("Can't generate random value: %v, %v", i, err)
+		}
+	}
+}
+
+type countingReader struct {
+	r io.Reader
+	n int
+}
+
+func (r *countingReader) Read(p []byte) (n int, err error) {
+	n, err = r.r.Read(p)
+	r.n += n
+	return n, err
+}
+
+// Test that Int reads only the necessary number of bytes from the reader for
+// max at each bit length
+func TestIntReads(t *testing.T) {
+	for i := 0; i < 32; i++ {
+		max := int64(1 << uint64(i))
+		t.Run(fmt.Sprintf("max=%d", max), func(t *testing.T) {
+			reader := &countingReader{r: rand.Reader}
+
+			_, err := rand.Int(reader, big.NewInt(max))
+			if err != nil {
+				t.Fatalf("Can't generate random value: %d, %v", max, err)
+			}
+			expected := (i + 7) / 8
+			if reader.n != expected {
+				t.Errorf("Int(reader, %d) should read %d bytes, but it read: %d", max, expected, reader.n)
+			}
+		})
+	}
+}
+
+// Test that Int does not mask out valid return values
+func TestIntMask(t *testing.T) {
+	for max := 1; max <= 256; max++ {
+		t.Run(fmt.Sprintf("max=%d", max), func(t *testing.T) {
+			for i := 0; i < max; i++ {
+				if testing.Short() && i == 0 {
+					i = max - 1
+				}
+				var b bytes.Buffer
+				b.WriteByte(byte(i))
+				n, err := rand.Int(&b, big.NewInt(int64(max)))
+				if err != nil {
+					t.Fatalf("Can't generate random value: %d, %v", max, err)
+				}
+				if n.Int64() != int64(i) {
+					t.Errorf("Int(reader, %d) should have returned value of %d, but it returned: %v", max, i, n)
+				}
+			}
+		})
+	}
+}
+
+func testIntPanics(t *testing.T, b *big.Int) {
+	defer func() {
+		if err := recover(); err == nil {
+			t.Errorf("Int should panic when called with max <= 0: %v", b)
+		}
+	}()
+	rand.Int(rand.Reader, b)
+}
+
+// Test that passing a new big.Int as max causes Int to panic
+func TestIntEmptyMaxPanics(t *testing.T) {
+	b := new(big.Int)
+	testIntPanics(t, b)
+}
+
+// Test that passing a negative value as max causes Int to panic
+func TestIntNegativeMaxPanics(t *testing.T) {
+	b := new(big.Int).SetInt64(int64(-1))
+	testIntPanics(t, b)
+}
+
+func BenchmarkPrime(b *testing.B) {
+	r := mathrand.New(mathrand.NewSource(time.Now().UnixNano()))
+	for i := 0; i < b.N; i++ {
+		rand.Prime(r, 1024)
+	}
+}