Replace math/rand with crypto/rand

Since the Windows tests were still failing, we are replacing the random number generation with math/rand with random string generation via crypto/rand
This commit is contained in:
Winni Neessen 2022-10-26 14:05:25 +02:00
parent 5bf0c10525
commit 8484e557d0
Signed by: wneessen
GPG key ID: 5F3AF39B820C119D
2 changed files with 80 additions and 7 deletions

12
msg.go
View file

@ -12,7 +12,6 @@ import (
"fmt"
ht "html/template"
"io"
"math/rand"
"mime"
"net/mail"
"os"
@ -357,12 +356,11 @@ func (m *Msg) SetMessageID() {
if err != nil {
hn = "localhost.localdomain"
}
ct := time.Now().UnixNano()
r := rand.New(rand.NewSource(ct))
rn := r.Int63()
pid := os.Getpid() * (r.Intn(10000) + 1)
cts := fmt.Sprintf("%d", ct)
mid := fmt.Sprintf("%d.%d.%s@%s", pid, rn, cts[:16], hn)
rn, _ := randNum(100000000)
rm, _ := randNum(10000)
rs, _ := randomStringSecure(25)
pid := os.Getpid() * rm
mid := fmt.Sprintf("%d.%d%d.%s@%s", pid, rn, rm, rs, hn)
m.SetMessageIDWithValue(mid)
}

75
random.go Normal file
View file

@ -0,0 +1,75 @@
// SPDX-FileCopyrightText: 2022 Winni Neessen <winni@neessen.dev>
//
// SPDX-License-Identifier: MIT
package mail
import (
"crypto/rand"
"encoding/binary"
"fmt"
"math/big"
"strings"
)
// Range of characters for the secure string generation
const cr = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
// Bitmask sizes for the string generators (based on 93 chars total)
const (
letterIdxBits = 7 // 7 bits to represent a letter index
letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits
)
// randomStringSecure returns a random, n long string of characters. The character set is based
// on the s (special chars) and h (human readable) boolean arguments. This method uses the
// crypto/random package and therfore is cryptographically secure
func randomStringSecure(n int) (string, error) {
rs := strings.Builder{}
rs.Grow(n)
crl := len(cr)
rp := make([]byte, 8)
_, err := rand.Read(rp)
if err != nil {
return rs.String(), err
}
for i, c, r := n-1, binary.BigEndian.Uint64(rp), letterIdxMax; i >= 0; {
if r == 0 {
_, err := rand.Read(rp)
if err != nil {
return rs.String(), err
}
c, r = binary.BigEndian.Uint64(rp), letterIdxMax
}
if idx := int(c & letterIdxMask); idx < crl {
rs.WriteByte(cr[idx])
i--
}
c >>= letterIdxBits
r--
}
return rs.String(), nil
}
// randNum returns a random number with a maximum value of n
func randNum(n int) (int, error) {
if n <= 0 {
return 0, fmt.Errorf("provided number is <= 0: %d", n)
}
mbi := big.NewInt(int64(n))
if !mbi.IsUint64() {
return 0, fmt.Errorf("big.NewInt() generation returned negative value: %d", mbi)
}
rn64, err := rand.Int(rand.Reader, mbi)
if err != nil {
return 0, err
}
rn := int(rn64.Int64())
if rn < 0 {
return 0, fmt.Errorf("generated random number does not fit as int64: %d", rn64)
}
return rn, nil
}