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2019 oplossingen Testexamen - Lars Lemmens

Met dank aan de Github van Martijn en natuurlijk Lars Lemmens

Exercise 1

Create a CLI oneliner to match all words with 14, 15 or 16 unique letters. The output shouldlook like:

Words with 14 letters: EHBO-diploma's bruiloftsdagen katrolschijven verontschuldig ...
Words with 15 letters: dampkringslucht sandwichformule ...
Words with 16 letters: ...

'user@:~$' • for foo in 14 15 16; do echo "Words with $foo letters:" $(grep -vP '(.).*\1' /usr/ share/dict/dutch | grep -P "^.{$foo}$");done
  • for name [ [ in [ word ... ] ] ; ] do list ; done The list of words following in is expanded, generating a list of items. The variable name is set to each element of this list in turn, and list is executed each time. If the in word is omitted, the for command executes list once for each positional parameter that is set (see PARAMETERS below). The return status is the exit status of the last command that executes. If the expansion of the items following in results in an empty list, no commands are executed, and the return status is 0.
  • echo displays a line of text

Exercise 2

Create a linux CLI oneliner to extract an overview of the different FTP usernames in the file ftp_bruteforce.pcap. Only the commands tshark and sort are allowed.

'user@:~$' • tshark -r ftp_bruteforce.pcap -Y 'ftp.request.command == USER' -T fields -e ftp.request.arg |sort -u
  • The -r command opens the recording
  • The -Y command is used for displaying the filter
  • The -T fields -e is used to specify the fields you want to show
  • The sort command is used to sort lines of text files
  • The -u command is used to show the output of only the first of an equal run

Exercise 3

Create a oneliner to show ‘Time = 15:44:25 (11/10/1901)' or 'Time = 15:44:25 (11-10-1901)’ each time with the current time and date.

'user@:~$' • date '+Time = %X (%x)'
  • The date command prints or sets the system date and time
  • The +Time is used to set time
  • The %X command is used to set the systems time
  • The %x command is used to set the date -> with () is used to put () around the date

Exercise 4

Create a linux CLI oneliner to decode the following string ‘RGUgcHVudGVuIG9wIGRlemUgdnJhYWcgemlqbiBhbCBiaW5uZW4uCg==’. (/home/logs/secret)

'user@:~$' • cat /home/logs/secret | openssl enc -a -d
  • The cat command is used to concatenate files and print on the standard output
  • The enc command is used to encrypt or decrypt a file
  • The -a command is used if encryption is taking place the data is base64 encoded after encryption. If decryption is set then the input data is base64 decoded before being decrypted
  • The -d command is used to decrypt

Exercise 5

Create a CLI oneliner using openssl to retrieve the certificate of the server wiki.uclllabs.beand to display only it’s fingerprint, serial and public key.Sample output:

SHA1 Fingerprint=8C:CB:D9:A1:F3:3C:78:C2:2E:F6:EB:1C:CD:4B:F3:39:1B:9A:EE:4Eserial=0966DB4115B74092EE07D6DA585547D8-----BEGIN PUBLIC KEY-----MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE2NHdNb3iWbb7mx9UFYzbv05YvUe+uBD8IunSnpj4SSol+5RG5EKZhFAcXwH9FCUxXE7ZZP3FDLNG0qG8cLSHjg==-----END PUBLIC KEY-----

'user@:~$' • echo | openssl s_client -connect wiki.uclllabs.be:443 2>/dev/null | openssl x509 -noout -fingerprint -serial -pubkey
  • The s_client command implements a generic SSL/TLS server which accepts connections from remote clients speaking SSL/TLS
  • The x509 command outputs a self signed certificate instead of a certificate request.
  • The -noout command is used to prevent output of the encoded version of the request
  • The -fingerprint command is used to show the fingerprint
  • The -serial command outputs the certificate serial number.
  • The -pubkey command outputs the the certificate's SubjectPublicKeyInfo block in PEM format.
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