1 Introduction to GNU/Linux & TCP/IP Basics

Transcription

1 2 Toegepaste Informatica, reeks 1B Computernetwerken, deel 2 Opdracht: Oplossingen Labo s Student: Y. Reekmans 1 Introduction to GNU/Linux & TCP/IP Basics Server: debbie.nwlab.khleuven.be Port: Exercises Opdracht 2 man ls man cp man rm man mv... mkdir - p exercise/dir1/dir4 touch excercise/dir1/dir4/file4 touch exercise/dir1/file3 mkdir exercise/dir2 mkdir exercise/dir3 touch exercise/file1 touch exercise/file2 rm -r exercise du -h /var Text editing Opdracht 7 vi me.txt <i> Joske Vermeulen <esc> :wq pg. 1 van 10 KHLeuven, dept. G&T, 2TI

2 Opdracht 8 cp me.txt we.txt vi we.txt <i> Meer namen <esc> :wq Network commands Opdracht 9 ifconfig 0 ping -c 10 1 traceroute 2 netstat -tl 3 netstat 6 nc -l -p nc localhost nc -l -p Firefox: debbie: pg. 2 van 10 KHLeuven, dept. G&T, 2TI

3 2 Introduction to GNU/Linux 2 Your homedirectory pscp -P @debbie.nwlab.khleuven.be:test.txt C:\ pscp -P C:\test.txt @debbie.nwlab.khleuven.be:test.txt Permissions Opdracht 2 chmod u=rwx,g=rwx,o=rwx file1 chmod u=rw,g=r,o=r file2 chmod u=rw,g=,o= file3... of ook: chmod 777 file1 chmod 644 file2 chmod 600 file3... mkdir public chmod 755 public Neen, de permissies zijn niet overgedragen op de kopie. Door het gebruiken van de -p flag: cp -p file file_copy history less Improving efficiently Opdracht 6 less /.bash_history history Opdracht 9 touch file_$(date +%Y.%m.%d) 0 alias dua='du --max-depth=1 -B KB;du --max-depth=1 -B MB;du --max-depth=1 -B GB' dua pg. 3 van 10 KHLeuven, dept. G&T, 2TI

4 3 Introduction to GNU/Linux 3 man sort man head man tail... User 1: - mkfifo /tmp/pipe - cat > /tmp/pipe User 2: - cat /tmp/pipe User 1: rm /tmp/pipe echo "text1" > file1.txt;echo "text2" > file2.txt;cat file1.txt file2.txt > file3.txt ls -l grep -v rwx Opdracht 6 cat /usr/share/dict/dutch grep rare Opdracht 7 ls -l tr -s ' ' cut -d ' ' -f1,8 Opdracht 8 cat /usr/share/dict/dutch grep rare sort -d -r Applied exercises Opdracht 9 last.log cat last.log grep -E 'ˆ([0-9]{6})' cut -d ' ' -f1 sort -u wc -l cat last.log grep -E 'ˆ([0-9]{6})' cut -d ' ' -f1 sort uniq -c sort -nr head -n 1 cat last.log grep -E 'ˆ([0-9]{6})' tr -s ' ' cut -d ' ' -f1,10 sort -k 2 -r head -n 5 0 ftpd.log pg. 4 van 10 KHLeuven, dept. G&T, 2TI

5 cat ftpd.log wc -l cat ftpd.log grep "Feb" grep "RETR " cut -d "\"" -f2 cut -d " " -f2 cat ftpd.log grep "USER usery" wc -l cat ftpd.log grep "Feb" grep "USER usery" cut -d " " -f1 sort uniq A bruteforce attack checking common used logins Nope traceroute DSL bb.netvision.net.il (Israel --> Provider netvision -->...) cat ftpd.log grep "06/Feb" grep "netvision.net" grep "USER " cut -d "\"" -f2 cut -d " " cat ftpd.log grep "06/Feb" grep "netvision.net" grep "PASS " wc -l cat ftpd.log cut -d " " -f1 sort uniq -c sort -nr head -n 10 1 portscan tcpdump.log and portscan firewalled tcpdump.log Checking on every port (udp/tcp) of a connection whether it is open or not Attacker: & Victim: cat portscan_tcpdump.log grep ack cut -d " " -f3 cut -d "." -f5 sort -n 2 apache google.log Visits from google's bot and those from regular users using google as search engine Bot(cat apache_google.log grep "bot" wc -l): Regular(cat apache_google.log grep -v "bot" wc -l): (cat apache_google.log grep "bot" cut -d " " -f1 sort uniq wc -l) None cat apache_google.log grep -v "bot" cut -d "\"" -f4 cut -d "/" -f pg. 5 van 10 KHLeuven, dept. G&T, 2TI

6 4 Regular Expressions grep -E '[aeiou]{4,5}' /usr/share/dict/dutch Opdracht 2 grep -E "([0-9]{1,3}[\.,-]){4}\.*\.*" ftpd.log grep -oe "Firefox/2.0.0.([0-9])*" apache_google.log sort uniq grep -oe "Firefox/([0-9]+\.)*[0-9]" apache_google.log sort uniq grep -E 'ˆver(.)*en$' /usr/share/dict/dutch wc -l grep -E 'ˆ[enrtiscau]{7}v[enrtiscau]{15}$' /usr/share/dict/dutch Opdracht 6 Correct? grep -E "ˆ([zrtypqsdfghjklmwxcvbn]?[aeiou]){2}*$" /usr/share/dict/dutch Opdracht 7?? pg. 6 van 10 KHLeuven, dept. G&T, 2TI

7 5 Extra practice cat /etc/debconf.conf grep -v '#' Opdracht 2 last -i grep -v "10." grep -v "root" grep -v " " wc -l last -i grep -v "10." grep -v "root" grep -v " " cut -d " " -f1 sort uniq so echo Time = $(date +"%H:%M:%S (%d/%m/%y)") date "+Time = %H:%M:%S (%d/%m/%y)" echo "Logged in users = $(who cut -d " " -f1 sort uniq wc -l)" Opdracht 6 echo "Open TCP connections = $(netstat -t wc -l)" Opdracht 7 echo "Free memory = $(free -m grep Mem: tr -s " " cut -d " " -f4) MB" Opdracht 8 echo "Free Disk Space = $(df / -B G grep / tr -s " " cut -d " " -f4)b" Opdracht 9 echo "CPU =$(cat /proc/cpuinfo grep "model name" cut -d ":" -f2)" 0 echo "System load = $(uptime tr -s " " cut -d " " -f9,10,11)" 1?? 2?? 3?? pg. 7 van 10 KHLeuven, dept. G&T, 2TI

8 ?? 5?? pg. 8 van 10 KHLeuven, dept. G&T, 2TI

9 6 Some Notes openssl enc -aes-128-cbc -in secret.txt -out secret.txt.aes openssl enc -d -aes-128-cbc -in secret.txt.aes openssl enc -des3 -in secret.txt -out secret.txt.aes openssl enc -d -des3 -in secret.txt.aes pg. 9 van 10 KHLeuven, dept. G&T, 2TI

10 7 Stappenplan gpg --gen-key Opdracht 2 bestandje maken Export your asciiencoded key to a file username.pub in your home directory, and make sure all other users can read this file (only read access of course!). gpg --output <file> --export < > (eigen ) Now import some keys from classmates: gpg --import <file> een bestand encrypteren: gpg --encrypt --armor --output <encrypted filename> --recipient < > Opdracht 6 Keys are identified by the corresponding address. If you look at this file, you will see it contains binary data1. To get the output in an ascii format, use the armor option: Opdracht 7 Decrypteren: gpg --decrypt --output <ontcijferd geencrypteerd> pg. 10 van 10 KHLeuven, dept. G&T, 2TI