Challenge_06

1. Create a file as a non-previleged user, show it's permissions and change them to -:
   User (Owner)-:  Write & Execute
   Group (Group Owner) -: Read & Execute
   Others -: Null
   using both symbolic and octal notations.
Sol.
touch flip.txt
ls flip.txt
chmod u=wx,g=rx,o= flip.txt
OR
chmod 350 flip.txt


2. A non-previleged user cannot view the contents of the shadow file USING CAT command, without using less command or without becoming root how can he access and 
   view it's content.
Sol. 
By setting the SUID bit for the file.
sudo chmod 4755 /usr/bin/cat


3. Create a shared directory, "programming" for a group "programmers" provided that no user no other can use it and the owner of the directory is one of the 
   programmers and the group owner as the programmers group.
Sol. 
groupadd programmers
useradd -aG programmers pr1
usermod -aG programmers pr2
mkdir /programming
chown pr1:programmers /programming
chmod 770 /programming
su pr1
cd /programming
touch source1.cpp
ls -l source1.cpp=> THE GROUP OWNER OF THE FILE IS THE PRIMARY GROUP OF THE CREATOR (pr1) & THE OTHER USERS IN THE SAME GROUP WON'T BE ABLE TO WORK ON IT. 
                    Sol. Set SGID bit
exit
chmod 2770 /programming
su pr2
cd /programming
touch source2.cpp
ls -l source2.cpp => THE GROUP OWNER OF THE FILE IS THE GROUP OF THE PARENT DIRECTORY ISTEAD OF THE PRIMARY GROUP OF THE CREATOR (pr2) AND OTHER MEMBERS OF THE
                     GROUP CAN ONLY WORK ON IT.
                     
                     
4. Create a shared directory in which no user can delete other user's file.
Sol.
su
mkdir /temp
chmod 777 /temp
ls -l /temp => Owner and Group Owner both = root
su user1
cd /temp
touch f1.txt f2.txt
chmod 600 f*
ls -l => rw------- (for both files). THE FILE PERMISSION DOES NOT ALLOWS TO READ OR WRITE THE FILE BUT THE PARENT DIRECTORY'S PERMISSION PERMITS IT.
su user2
rm -rf f1.txt => REMOVED (!!!!!!!!). Sol. Set Sticky bit
sudo chmod 1777 /temop
su user2
rm -rf f2.txt => NOT ALLOWED :)

SUID -: TO CHANGE THE OWNER OF THE FILE
SGID -: TO CHANGE THE GROUP OWNER OF THE FILE
STICKY -: TO CHANGE THE DELETION PERMISSION OF THE FILE