-
-
Notifications
You must be signed in to change notification settings - Fork 0
/
random.go
60 lines (55 loc) · 1.72 KB
/
random.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
// Package random provides facilities to generate random values.
// It leverages the default Source of standard 'math/rand' package
// that is thread-safe.
package random
import (
crand "crypto/rand"
"encoding/binary"
"math/big"
mrand "math/rand"
"time"
)
const charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
// init initializes the default Source of 'math/rand' package.
// It tries to do so by using a random number generated by 'crypto/rand'
// package as seed.
// If the call to 'crypto/rand' fails, the startup timestamp in nanoseconds
// is used as seed.
//
// Why? because 'math/rand' is simpler to use, however we need to provide
// a random number as a seed to make this package more reliable.
// 'crypto/rand' is good for retrieving the initial seed but it
// can return an error, in such case we resort to a unix timestamp
// that should not be too bad for our use case.
func init() {
var b [8]byte
_, err := crand.Read(b[:])
if err != nil {
mrand.Seed(time.Now().UnixNano())
return
}
mrand.Seed(int64(binary.LittleEndian.Uint64(b[:])))
}
// String returns a randomly generated string that can contain
// numbers, uppercase and lowercase letters.
func String(length int) string {
b := make([]byte, length)
for i := range b {
b[i] = charset[mrand.Intn(len(charset))]
}
return string(b)
}
// StringSecure returns a cryptographically secure randomly generated
// string that can contain numbers, uppercase and lowercase letters.
func StringSecure(length int) (string, error) {
b := make([]byte, length)
for i := range b {
l := big.NewInt(int64(len(charset)))
num, err := crand.Int(crand.Reader, l)
if err != nil {
return "", err
}
b[i] = charset[num.Int64()]
}
return string(b), nil
}