CENG200 - Lab 2: Security, Simple Web Pages

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1 Out: Sept 12, 2016 Due: Sept 26, 2016 (start of lecture) Preliminary Steps CENG200 - Lab 2: Security, Simple Web Pages A. When you log in for this lab, perform the following actions (one time only) chmod a+x. public_html This makes your public_html directory navigable as a web site - which you need in exercise 3. B. Add the following command to your.bashrc file set -o vim #This lets you use vim commands to edit the command line Save and exit vim. Then rerun the.bashrc file using the following command: source ~/.bashrc C. Create a new directories perms1 and ps2. Use the touch command to create files filea through filef in both directories. D. Use the id command and record your alternate group at the top of your report. It should be one of: sharks minnows or dolphins According to the system there are 8 sharks, 5 minnows and 13 minnows in the class. If you are a shark or a minnow find a partner who is a dolphin. You will need them for exercises #5 & 6. Next to your group record the real name and user ID of your partner. [Anyone who does not have a partner, please notify me by !!!] There are 27 available marks in this assignment. It is marked out of 25. Lab Exercises 1. The following exercise was moved from Lab 1 to Lab 2 through an announcement during last week s class. If you handed in your answers with Lab 1 there is no need to hand this in again I ll credit your Lab 2 mark. Wildcards (globbing) in the Bash shell (1 mark each/6 marks)

2 Create a wildcard pattern to select the specified files from the /usr/bin directory on munro. Verify visually that your command selected the appropriate files, then pipe the result through wc command to count the # of results. Record the pattern that you used and the number of files matched. (I am not looking for an actual list of files and will deduct a mark if you give me full lists) eg (for all files): ls * wc -l a) list the name of all the files in the /usr/bin directory that start with ls. b) list the name of all the files in the /usr/bin directory that end with ls c) list the name of all the files that start with the letter q and end with the number 3 d) list the name of all the files that consist of 2 letters where the 1 st letter is in the range from d to p. e) List the name of all the files that start and end with a vowel. f) List the name of all the files that start and end with a vowel where the whole file name is only 4 characters long. 2. Using chmod with symbolic operators (6 marks) Use chmod using the symbols: ugo+-rwx, alter the permissions on the files in perms1 as follows. You are not allowed to use the = symbol - that would be too easy!) If you set the permissions to a file incorrectly either remove and recreate the file so that it has it s default permissions or reset the permissions to rw using the = option. (6 marks) a. The filea should only be writeable by you and your group b. The fileb should be readable by everyone and executable by you. c. The filec should be readable and writable only by others, not by you or members of your group. d. The filed should have all permissions turned on except it should not be writeable by members of your group or others. e. The filee should be executable by you and others, but not members of your group f. The file f should have all file permissions turned on, except you can t read it. When you run ls -l on the files the permissions should appear as follows: --w- -w filea -r-x r-- r-- fileb rw- filec -rwx r-x r-x filed ---x x filee --wx rwx rwx filef

3 3. Using chmod with octal codes (6 marks) Repeat exercise 1 on the files in your directory perm2 but use the chmod command using octal values instead of symbols. Record the commands used. (6 marks) 4. Creating a really really simple web page hello.txt (2 marks) In your public_html directory create a file hello.txt containing a short joke or semi-famous quote. Make sure that the following is true: a. The file hello.txt is readable by others b. Your public_html directory is executable (navigable) by others c. Your home directory is executable by others Test that your web page is visible to the outside world by bringing it up on a browser on a different machine There is no need to hand anything in. To check the status of your web page, view the following web page which is actually a script: Everyone should have a simple web page by the end of the Sept 12 th lab. You ll need it to do the last exercise. 5) The finger command: Applying Access Permissions (4 marks) Your userid and current group determine what files you can look at. In this exercise you will change only the read permissions of two special files:.plan and.project and work with a partner in a different group. For this exercise pick a partner with who is in a group that you are not a member of. In this section there are 13 dolphins, 5 minnows and 8 sharks. If everyone who is a minnow or a shark picks a dolphin as a partner we should be OK. a) Each of you should create a.project and a.plan file in your home directories. In.project describe some project that you are currently working on. In.plan describe a long term

4 goal that you might have. The finger command is: finger userid finger yourself to verify that your.plan and.project show up. b) Set the access permissions of your.plan and.project file so that only other members of your group can read the file and so that you are not allowed to read your own files nor can others. At this point both you and your partner are members of the group student. i) Can you finger yourself and see the.project and.plan files? ii) Can your partner do the same? c) Change the group membership of the.plan and.project files to your alternate groups using the chgrp command. ie: chgrp whales.plan.project Both you and your partner i) Can you still finger yourself? ii) Can your partner use finger to see your.project and.plan? d) Change the permissions of the.plan and.project files so that others can read the file but neither you nor anyone else in your group. Record the chmod command used. i) Can you still apply the finger command to each other and see the.plan and.project files? ii) Can your partner? 6) The setfacl and getfacl commands (5 marks) Access Control Lists (ACLs) are a form of granting permissions to specific individuals or groups. Because they are not available on munro, you and your partner will have to log into apollo. Your userid and password are the same. The getfacl command merely retrieves the current permissions of a file or file list getfacl file1 file2 file3... The setfacl command is used to set permissions. We are only going to consider the -m (modify) flag: setfacl -m acl-specification filelist Where the acl-specification is one or more of the following, separated by commas u:userid:rwx user:userid:rwx The permissions can be in any order. A - (dash) means all perms off.

5 u::rwx The permissions are for the current user only g:groupname:rwx You can only use existing group names such as sharks, students group:groupname:rxx g::rwx Permissions apply to the group that owns the file o::rwx Permission applies to everyone not specified in the ACL other::rwx default:user: king:rwx Only valid when used with a directory. All new files in the default:group:whales:rx the directory will have the stated permissions. example: setfacl -m u:king:rx,group:ceng:rw,o::-,g::r file1 file2 file3 a) You and your partner should create a.project and a.plan file in your home directories on apollo. Set the group ownership to your 2ndary group (ie: sharks, minnows or dolphins) Show the files in your directories and use newgrp to make your current group your secondary group. State whether or not you can finger each other. b) Use setfacl to grant your partner access to your.plan and.project files. Record the command used and use getfacl to display the result. Can your partner successfully finger your.plan and.project files? c) Remove the permissions that you created in b, then grant permission to your partner s group to access your.plan and.project files. Record the commands used and use getfacl to display the result. Can your partner successfully finger your.project and.plan files now? d) Use setfacl to set the default permissions on your public_html directory so that the user apache can read any new files. Create a file hello2.html and put a short note to your parents in the file. Use getfacl to verify that hello2.html has inherited apache s permissions and hand in the output of the getfacl command. Verify that your web page on apollo is visible in a web browser.