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lib/rand: Various fixes (#6474)
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@ -9,10 +9,7 @@
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package rand
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import (
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"crypto/md5"
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cryptoRand "crypto/rand"
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"encoding/binary"
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"io"
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mathRand "math/rand"
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"reflect"
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)
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@ -20,16 +17,16 @@ import (
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// Reader is the standard crypto/rand.Reader, re-exported for convenience
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var Reader = cryptoRand.Reader
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// randomCharset contains the characters that can make up a randomString().
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// randomCharset contains the characters that can make up a rand.String().
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const randomCharset = "2345679abcdefghijkmnopqrstuvwxyzACDEFGHJKLMNPQRSTUVWXYZ"
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var (
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// defaultSecureSource is a concurrency safe math/rand.Source with a
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// cryptographically sound base.
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defaltSecureSource = newSecureSource()
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defaultSecureSource = newSecureSource()
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// defaultSecureRand is a math/rand.Rand based on the secure source.
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defaultSecureRand = mathRand.New(defaltSecureSource)
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defaultSecureRand = mathRand.New(defaultSecureSource)
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)
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// String returns a strongly random string of characters (taken from
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@ -43,19 +40,14 @@ func String(l int) string {
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return string(bs)
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}
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// Int63 returns a strongly random int63
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// Int63 returns a strongly random int63.
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func Int63() int64 {
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return defaltSecureSource.Int63()
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return defaultSecureSource.Int63()
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}
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// Int64 returns a strongly random int64
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// Int64 returns a strongly random int64.
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func Int64() int64 {
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var bs [8]byte
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_, err := io.ReadFull(cryptoRand.Reader, bs[:])
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if err != nil {
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panic("randomness failure: " + err.Error())
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}
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return int64(binary.BigEndian.Uint64(bs[:]))
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return int64(defaultSecureSource.Uint64())
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}
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// Intn returns, as an int, a non-negative strongly random number in [0,n).
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@ -64,18 +56,7 @@ func Intn(n int) int {
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return defaultSecureRand.Intn(n)
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}
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// SeedFromBytes calculates a weak 64 bit hash from the given byte slice,
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// suitable for use a predictable random seed.
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func SeedFromBytes(bs []byte) int64 {
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h := md5.New()
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h.Write(bs)
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s := h.Sum(nil)
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// The MD5 hash of the byte slice is 16 bytes long. We interpret it as two
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// uint64s and XOR them together.
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return int64(binary.BigEndian.Uint64(s[0:]) ^ binary.BigEndian.Uint64(s[8:]))
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}
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// Shuffle the order of elements
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// Shuffle the order of elements in slice.
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func Shuffle(slice interface{}) {
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rv := reflect.ValueOf(slice)
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swap := reflect.Swapper(slice)
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@ -8,23 +8,6 @@ package rand
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import "testing"
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func TestSeedFromBytes(t *testing.T) {
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// should always return the same seed for the same bytes
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tcs := []struct {
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bs []byte
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v int64
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}{
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{[]byte("hello world"), -3639725434188061933},
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{[]byte("hello worlx"), -2539100776074091088},
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}
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for _, tc := range tcs {
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if v := SeedFromBytes(tc.bs); v != tc.v {
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t.Errorf("Unexpected seed value %d != %d", v, tc.v)
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}
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}
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}
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func TestRandomString(t *testing.T) {
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for _, l := range []int{0, 1, 2, 3, 4, 8, 42} {
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s := String(l)
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@ -37,6 +37,10 @@ func (s *secureSource) Seed(int64) {
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}
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func (s *secureSource) Int63() int64 {
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return int64(s.Uint64() & (1<<63 - 1))
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}
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func (s *secureSource) Uint64() uint64 {
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var buf [8]byte
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// Read eight bytes of entropy from the buffered, secure random number
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@ -50,8 +54,5 @@ func (s *secureSource) Int63() int64 {
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}
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// Grab those bytes as an uint64
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v := binary.BigEndian.Uint64(buf[:])
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// Mask of the high bit and return the resulting int63
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return int64(v & (1<<63 - 1))
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return binary.BigEndian.Uint64(buf[:])
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}
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