Fix sign bit

ammario · ammario · commit 6ad317ebda3d · 2023-06-15T01:54:24.000Z
diff --git a/cryptorand/numbers.go b/cryptorand/numbers.go
@@ -10,26 +10,28 @@ type cryptoSource struct {
 	err error
 }
 
-func (*cryptoSource) Seed(seed int64) {
+func (*cryptoSource) Seed(_ int64) {
 	// Intentionally disregard seed
 }
 
 func (c *cryptoSource) Int63() int64 {
-	var seed int64
-	err := binary.Read(rand.Reader, binary.BigEndian, &seed)
+	var n int64
+	err := binary.Read(rand.Reader, binary.BigEndian, &n)
 	if err != nil {
 		c.err = err
 	}
-	return 0
+	// The sign bit must be cleared to ensure the final value is non-negative.
+	n &= 0x7fffffffffffffff
+	return n
 }
 
 func (c *cryptoSource) Uint64() uint64 {
-	var seed uint64
-	err := binary.Read(rand.Reader, binary.BigEndian, &seed)
+	var n uint64
+	err := binary.Read(rand.Reader, binary.BigEndian, &n)
 	if err != nil {
 		c.err = err
 	}
-	return 0
+	return n
 }
 
 // secureRand returns a cryptographically secure random number generator.
diff --git a/cryptorand/numbers_test.go b/cryptorand/numbers_test.go
@@ -26,7 +26,7 @@ func TestIntn(t *testing.T) {
 		v, err := cryptorand.Intn(100)
 		require.NoError(t, err, "unexpected error from Intn")
 		t.Logf("value: %v <- random?", v)
-		require.True(t, v >= 0, "values must be positive")
+		require.GreaterOrEqual(t, v, 0, "values must be positive")
 		require.True(t, v < 100, "values must be less than 100")
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -10,26 +10,28 @@ type cryptoSource struct {`
`10`	`10`	`err error`
`11`	`11`	`}`
`12`	`12`
`13`		`-func (*cryptoSource) Seed(seed int64) {`
	`13`	`+func (*cryptoSource) Seed(_ int64) {`
`14`	`14`	`// Intentionally disregard seed`
`15`	`15`	`}`
`16`	`16`
`17`	`17`	`func (c *cryptoSource) Int63() int64 {`
`18`		`- var seed int64`
`19`		`- err := binary.Read(rand.Reader, binary.BigEndian, &seed)`
	`18`	`+ var n int64`
	`19`	`+ err := binary.Read(rand.Reader, binary.BigEndian, &n)`
`20`	`20`	`if err != nil {`
`21`	`21`	`c.err = err`
`22`	`22`	`}`
`23`		`- return 0`
	`23`	`+ // The sign bit must be cleared to ensure the final value is non-negative.`
	`24`	`+ n &= 0x7fffffffffffffff`
	`25`	`+ return n`
`24`	`26`	`}`
`25`	`27`
`26`	`28`	`func (c *cryptoSource) Uint64() uint64 {`
`27`		`- var seed uint64`
`28`		`- err := binary.Read(rand.Reader, binary.BigEndian, &seed)`
	`29`	`+ var n uint64`
	`30`	`+ err := binary.Read(rand.Reader, binary.BigEndian, &n)`
`29`	`31`	`if err != nil {`
`30`	`32`	`c.err = err`
`31`	`33`	`}`
`32`		`- return 0`
	`34`	`+ return n`
`33`	`35`	`}`
`34`	`36`
`35`	`37`	`// secureRand returns a cryptographically secure random number generator.`
Original file line number	Diff line number	Diff line change
`@@ -26,7 +26,7 @@ func TestIntn(t *testing.T) {`
`26`	`26`	`v, err := cryptorand.Intn(100)`
`27`	`27`	`require.NoError(t, err, "unexpected error from Intn")`
`28`	`28`	`t.Logf("value: %v <- random?", v)`
`29`		`- require.True(t, v >= 0, "values must be positive")`
	`29`	`+ require.GreaterOrEqual(t, v, 0, "values must be positive")`
`30`	`30`	`require.True(t, v < 100, "values must be less than 100")`
`31`	`31`	`}`
`32`	`32`