CEG 2350

You can use a command in support of your answer, but we are evaluating your written response.

A student runs the commands below to back up their repository. Why isn’t the archive compressed, and what should the tar command have been?
```
$ tar -cvf site-backup.tar.gz ceg2350-lastname-f26
$ file site-backup.tar.gz
site-backup.tar.gz: POSIX tar archive (GNU)
```

A student extracts the site with the command below, but the browser still shows the Apache2 Default Page. Using the tar -t output, why, and what is one way to fix it?

$ sudo tar -xzf simple-site.tar.gz -C /var/www/html
$ tar -tzf simple-site.tar.gz
simple-site/
simple-site/about.html
simple-site/contact.html
simple-site/index.html
simple-site/styles/
simple-site/styles/style.css

From their laptop, a student connects with sftp to download their backup from the AWS instance and sees the output below. Why did it fail, and what command should they have used?
```
sftp> ls
ceg2350-lastname-f26    site-backup.tar.gz
sftp> put site-backup.tar.gz
stat local "site-backup.tar.gz": No such file or directory
```

Given the output below, the browser returns 403 Forbidden when visiting the instance’s public IP. Why, and what should the permissions on /var/www/html be?

$ ls -ld /var/www/html
drwxrwx--- 2 ubuntu ubuntu 4096 Nov 10 09:12 /var/www/html
$ ls -l /var/www/html/index.html
-rw-rw-r-- 1 ubuntu ubuntu 1203 Nov 10 09:14 /var/www/html/index.html

Logged into the instance as ubuntu, a student creates the user kay, runs vim ~/.ssh/authorized_keys, and appends their new public key. From their laptop, ssh -i ~/.ssh/lab11key kay@54.210.33.12 returns Permission denied (publickey), but ssh -i ~/.ssh/lab11key ubuntu@54.210.33.12 works. Why?

Why does ssh refuse to use the key below, and how do you fix it?

$ ssh -i ~/.ssh/lab11key kay@54.210.33.12
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/home/student/.ssh/lab11key' are too open.
This private key will be ignored.

Given the ~/.ssh/config entry below, ssh ceg-kay connects, but ssh kay@54.210.33.12 returns Permission denied (publickey). Why isn’t the config entry used for the second command?
```
Host ceg-kay
 HostName 54.210.33.12
 User kay
 IdentityFile ~/.ssh/lab11key
```
A student commits Closes #4 - sftp table done on the branch part2-sftp and pushes it to GitHub. Issue #4 is still open. Why, and what has to happen for GitHub to close it?

Given the ip a output below from an AWS instance, what is the subnet mask, and why does the instance’s public IP (54.210.33.12) not appear anywhere in the output?

2: ens5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc mq state UP group default qlen 1000
 link/ether 0a:1b:2c:3d:4e:5f brd ff:ff:ff:ff:ff:ff
 inet 172.31.22.45/20 metric 100 brd 172.31.31.255 scope global dynamic ens5

A student’s home public IP is 74.83.12.9. For the SSH rule, they enter 74.83.12.9/16 as the source. Their ssh works, so what is wrong with the rule, and what should it be?
After updating the Security Group, a student can ssh to their instance from home and from campus. At a coffee shop, ssh hangs and eventually prints Connection timed out. Why, and why does it time out instead of saying Connection refused?
From a phone hotspot, a student runs the commands below against their instance. Is the server down? Explain using the Lab 12 Security Group rules. ``` $ ping -c 4 54.210.33.12 4 packets transmitted, 0 received, 100% packet loss $ curl http://54.210.33.12 <!DOCTYPE html>

... ``` 13. A student edits `server.py` to use `HOST = "127.0.0.1"` and runs it on the instance. The client on their laptop gets `Connection refused`, even though port 8080 is allowed in the Security Group. Using the output below, why? ``` $ ss -tln | grep 8080 LISTEN 0 128 127.0.0.1:8080 0.0.0.0:* ``` 14. A student runs `client.py`, sends a few messages, types `quit`, then runs `client.py` again and gets `Connection refused`. Using the server code below, why? ```python with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s: s.bind((HOST, PORT)) s.listen() conn, addr = s.accept() with conn: print(f"Connected by {addr}") while True: data = conn.recv(1024) if not data: break conn.sendall(data) ``` 15. While running `tcpdump` against `wttr.in`, a student can read the weather report in the packets from `curl http://wttr.in`, but the packets from `curl https://wttr.in` are unreadable. Why, and what does this mean for anyone viewing the student's Lab 11 site at `http://`? 16. `nslookup ipinfo.io` returns `34.117.59.81`, but `nslookup 34.117.59.81` does not return `ipinfo.io`. Why can a forward lookup and a reverse lookup of the "same" server give different answers? 17. Given the lines below from `auth_logs.csv`, a student runs the command shown to find the **top 5** IPs by connection attempts. Why does the output show IPs with only 1 attempt, and how do you fix it? ``` kduncan, 108.222.118.252 tester, 106.55.241.103 webmaster, 121.4.55.87 ``` ``` cut -d',' -f2 auth_logs.csv | sort | uniq -c | sort -n | head -5 ```