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217 lines
4.4 KiB
217 lines
4.4 KiB
package common
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import (
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crand "crypto/rand"
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mrand "math/rand"
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"sync"
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"time"
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)
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const (
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strChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" // 62 characters
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)
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// pseudo random number generator.
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// seeded with OS randomness (crand)
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var prng struct {
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sync.Mutex
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*mrand.Rand
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}
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func reset() {
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b := cRandBytes(8)
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var seed uint64
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for i := 0; i < 8; i++ {
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seed |= uint64(b[i])
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seed <<= 8
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}
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prng.Lock()
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prng.Rand = mrand.New(mrand.NewSource(int64(seed)))
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prng.Unlock()
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}
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func init() {
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reset()
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}
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// Constructs an alphanumeric string of given length.
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// It is not safe for cryptographic usage.
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func RandStr(length int) string {
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chars := []byte{}
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MAIN_LOOP:
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for {
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val := prng.Int63()
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for i := 0; i < 10; i++ {
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v := int(val & 0x3f) // rightmost 6 bits
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if v >= 62 { // only 62 characters in strChars
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val >>= 6
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continue
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} else {
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chars = append(chars, strChars[v])
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if len(chars) == length {
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break MAIN_LOOP
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}
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val >>= 6
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}
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}
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}
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return string(chars)
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}
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// It is not safe for cryptographic usage.
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func RandUint16() uint16 {
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return uint16(RandUint32() & (1<<16 - 1))
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}
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// It is not safe for cryptographic usage.
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func RandUint32() uint32 {
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prng.Lock()
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u32 := prng.Uint32()
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prng.Unlock()
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return u32
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}
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// It is not safe for cryptographic usage.
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func RandUint64() uint64 {
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return uint64(RandUint32())<<32 + uint64(RandUint32())
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}
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// It is not safe for cryptographic usage.
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func RandUint() uint {
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prng.Lock()
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i := prng.Int()
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prng.Unlock()
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return uint(i)
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}
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// It is not safe for cryptographic usage.
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func RandInt16() int16 {
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return int16(RandUint32() & (1<<16 - 1))
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}
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// It is not safe for cryptographic usage.
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func RandInt32() int32 {
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return int32(RandUint32())
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}
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// It is not safe for cryptographic usage.
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func RandInt64() int64 {
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return int64(RandUint64())
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}
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// It is not safe for cryptographic usage.
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func RandInt() int {
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prng.Lock()
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i := prng.Int()
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prng.Unlock()
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return i
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}
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// It is not safe for cryptographic usage.
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func RandInt31() int32 {
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prng.Lock()
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i31 := prng.Int31()
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prng.Unlock()
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return i31
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}
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// It is not safe for cryptographic usage.
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func RandInt63() int64 {
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prng.Lock()
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i63 := prng.Int63()
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prng.Unlock()
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return i63
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}
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// Distributed pseudo-exponentially to test for various cases
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// It is not safe for cryptographic usage.
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func RandUint16Exp() uint16 {
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bits := RandUint32() % 16
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if bits == 0 {
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return 0
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}
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n := uint16(1 << (bits - 1))
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n += uint16(RandInt31()) & ((1 << (bits - 1)) - 1)
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return n
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}
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// Distributed pseudo-exponentially to test for various cases
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// It is not safe for cryptographic usage.
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func RandUint32Exp() uint32 {
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bits := RandUint32() % 32
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if bits == 0 {
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return 0
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}
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n := uint32(1 << (bits - 1))
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n += uint32(RandInt31()) & ((1 << (bits - 1)) - 1)
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return n
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}
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// Distributed pseudo-exponentially to test for various cases
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// It is not safe for cryptographic usage.
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func RandUint64Exp() uint64 {
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bits := RandUint32() % 64
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if bits == 0 {
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return 0
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}
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n := uint64(1 << (bits - 1))
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n += uint64(RandInt63()) & ((1 << (bits - 1)) - 1)
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return n
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}
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// It is not safe for cryptographic usage.
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func RandFloat32() float32 {
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prng.Lock()
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f32 := prng.Float32()
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prng.Unlock()
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return f32
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}
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// It is not safe for cryptographic usage.
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func RandTime() time.Time {
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return time.Unix(int64(RandUint64Exp()), 0)
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}
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// RandBytes returns n random bytes from the OS's source of entropy ie. via crypto/rand.
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// It is not safe for cryptographic usage.
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func RandBytes(n int) []byte {
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// cRandBytes isn't guaranteed to be fast so instead
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// use random bytes generated from the internal PRNG
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bs := make([]byte, n)
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for i := 0; i < len(bs); i++ {
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bs[i] = byte(RandInt() & 0xFF)
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}
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return bs
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}
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// RandIntn returns, as an int, a non-negative pseudo-random number in [0, n).
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// It panics if n <= 0.
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// It is not safe for cryptographic usage.
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func RandIntn(n int) int {
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prng.Lock()
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i := prng.Intn(n)
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prng.Unlock()
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return i
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}
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// RandPerm returns a pseudo-random permutation of n integers in [0, n).
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// It is not safe for cryptographic usage.
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func RandPerm(n int) []int {
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prng.Lock()
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perm := prng.Perm(n)
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prng.Unlock()
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return perm
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}
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// NOTE: This relies on the os's random number generator.
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// For real security, we should salt that with some seed.
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// See github.com/tendermint/go-crypto for a more secure reader.
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func cRandBytes(numBytes int) []byte {
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b := make([]byte, numBytes)
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_, err := crand.Read(b)
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if err != nil {
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PanicCrisis(err)
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}
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return b
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}
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