Function randomString

middleware/util.go:63–107

(length uint8)

var randStringScratchPool = sync.Pool{New: func() any { return new(randStringScratch) }}

func randomString(length uint8) string {
	reader := randomReaderPool.Get().(*bufio.Reader)
	defer randomReaderPool.Put(reader)
	sc := randStringScratchPool.Get().(*randStringScratch)
	defer randStringScratchPool.Put(sc)

	n := int(length)
	if cap(sc.b) < n {
		sc.b = make([]byte, n)
	} else {
		sc.b = sc.b[:n]
	}
	rlen := n + n/4 // perf: avoid read from rand.Reader many times
	if cap(sc.r) < rlen {
		sc.r = make([]byte, rlen)
	} else {
		sc.r = sc.r[:rlen]
	}
	b, r := sc.b, sc.r
	var i uint8 = 0

	// security note:
	// we can't just simply do b[i]=randomStringCharset[rb%len(randomStringCharset)],
	// len(len(randomStringCharset)) is 52, and rb is [0, 255], 256 = 52 * 4 + 48.
	// make the first 48 characters more possibly to be generated then others.
	// So we have to skip bytes when rb > randomStringMaxByt

	for {
		_, err := io.ReadFull(reader, r)
		if err != nil {
			panic("unexpected error happened when reading from bufio.NewReader(crypto/rand.Reader)")
		}
		for _, rb := range r {
			if rb > randomStringMaxByte {
				// Skip this number to avoid bias.
				continue
			}
			b[i] = randomStringCharset[rb%randomStringCharsetLen]
			i++
			if i == length {
				return string(b[:length])
			}
		}
	}
}

func validateOrigins(origins []string, what string) error {
	for _, o := range origins {