execveCmdLine improperly hex-decodes values which are not hex encoded about go-libaudit HOT 3 CLOSED

func hexToASCII(h string) (string, error) {

	output, err := hex.DecodeString(h)

	nullTerm := bytes.Index(output, []byte{0})
	if nullTerm != -1 {
		output = output[:nullTerm]
	}

	acceptChar := func(r rune) bool {
		return !unicode.IsLetter(r) && !unicode.IsDigit(r) && !unicode.IsPunct(r) && !unicode.IsSpace(r) && !unicode.IsControl(r)
	}

	s_res := strings.IndexFunc(string(output), acceptChar)
	if s_res != -1 {
		return h, errors.New("Not Hex Encoded")
	} else {
		return string(output), err
	}
}

type=EXECVE msg=audit(1491863086.221:1050925): argc=5 a0="grep" a1="--color=auto" a2="-e" a3="[:alpha:]" a4="/etc/passwd"
type=EXECVE msg=audit(1491946471.575:1075898): argc=3 a0="jq" a1="." a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