Checks set_loopback_traffic.sh and set_ipv6_loopback_traffic.sh use incorrect regex for parsing the output of `iptables -L INPUT -v -n`

[Przemyslaw Hausman]

usg version: 22.04.6

The following checks incorrectly parse the output of `ip6tables -L INPUT -v -n`:
-/usr/share/ubuntu-scap-security-guides/1/benchmarks/ubuntu2204/checks/sce/set_loopback_traffic.sh
-/usr/share/ubuntu-scap-security-guides/1/benchmarks/ubuntu2204/checks/sce/set_ipv6_loopback_traffic.sh

As a result, these checks return incorrect return value, marking the rule failed.

I have the system with the following rules:

```
# iptables -L INPUT -v -n
Chain INPUT (policy DROP 0 packets, 0 bytes)
 pkts bytes target prot opt in out source destination
 433K 94M ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
    8 480 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 ctstate NEW
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:17070 ctstate NEW
41174 2411K ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
    0 0 DROP all -- * * 127.0.0.0/8 0.0.0.0/0
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpts:49152:49261 ctstate NEW
    0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:11211
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:3306
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:3307
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:3308
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:3309
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:53
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8888
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:9856
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:9866
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:9876
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:41142
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:48922
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:52970
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:5672
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:6641
    0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:6642
    0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:34207
    0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:5405
    0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:5555
    0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:6081
  182 37934 LOGGING all -- * * 0.0.0.0/0 0.0.0.0/0
```

Regular expression used in checks do not take into account letter "K" in the "bytes" column. As a result the check fails but it should be successful.

This is the regex currently implemented in scripts:
```
regex="\s+[0-9]+\s+[0-9]+\s+ACCEPT\s+all\s+--\s+lo\s+\*\s+0\.0\.0\.0\/0\s+0\.0\.0\.0\/0[[:space:]]+[0-9]+\s+[0-9]+\s+DROP\s+all\s+--\s+\*\s+\*\s+127\.0\.0\.0\/8\s+0\.0\.0\.0\/0"
```

[Miha Purg (mihap)]

Hi Przemyslaw, thanks for reporting this!

As you point out the regex doesn't seem to account for the human readable format of packet counts and bytes. Adding the -x flag to iptables/ip6tables solves the issue.

I'll add the fix to the next release of usg for jammy (22.04.7).

[Przemyslaw Hausman (phausman)]

Thank you, @mihap, adding `-x` seems like a nice fix!