Topic: Operating Systems Security
Part -1
Cloud Computing
Google Cloud
Setting up Google cloud account
Creating project
Creating virtual machine (host computer without any OS)
Installing image (installing an OS)
Starting command shell via SHH
Testing shell commands
Writing shell script
Making shell script executable
Running shell script
Use Google Cloud Starting Page
Use Free Use Option
Register as Paying User
Use Home Menu Option
Create New Machine
Create VM Machine/Instance
Instance Creation Shell Commands
Cloud Instance Creation Shell Cmmand
Install OS (Use Ready OS Image)
Install Red Hat Linux
Shell Script
Use vi editor and create shell script that prints some table in the C-like format style.
Try to execute newly created shell script file without an x flag.
The file cannot be found by the shell program.
Verify script file content using cat command.
Part - 2:
Cloud Computing
UNIX/Linux PATH Variable
Google Cloud
Reading PATH variable value
adding directory to the PATH string values
Using PATH to run programs as commands
Using PATH to select version of the same program as default
Possible hacks using PATH variable.
Reading PATH Variable
PATH string value helps shell and file system find program files.
Using PATH to Run Program
PATH values list possible directories where program file may be found/located.
Precise Program File Location
Absolute or relative program file directory location can be explicitly used to provide the file to the shell.
Same Files with Different Programs
Create new subdirectory and create in it another shell script with the same name script01.
New Working Directory
Create new/another shell script with the same name script01 in the new working directory.
New Shell Script
Use vi editor and make new shell script in the new working directory.
New Script Access Permissions
Change new script file access permission to become executable.
Modifying PATH Variable
Add two working directories to the PATH variable string using shell variable $ dereferencing operator.
Verify Script File Access Permissions
Verify that two script files with the same name script01 are executable.
Scripts as Commands
The first directory listed in the PATH string that contains needed script file is used.
Question: Scripts as Commands
The first directory listed in the PATH string that contains needed script file is used.
How can be PATH variable be used to trick user to execute viral program that has the same name as the commonly used application/utility program?