1 Readings, Assignments, Labs, and ToDoIndex

• Read (at least) these things (All The Words):
  • Week 08 Notes HTML - This File - ** Read All The Words **
  • Symbolic Links - Soft Links - Symlinks
  • Unix Modes and Permissions
  • Umask and Permissions
  • List of Commands
• Read (All The Words), Do, and Save (but not for hand-in):
  • Lab Worksheet #07 ODT
  • Lab Worksheet #07 PDF
  • Lab Worksheet #09 ODT
  • Lab Worksheet #09 PDF
  • Quizzes will ask you about your answers in your saved worksheets.
• Read (All The Words), Do, and then Submit via Blackboard:
  • Assignment #07
  • Assignment #08
  • Assignment #09
• See the information about the November 5 Midterm Test in this file.
• Write down the dates of your Final Exams from the Course Home Page.
• READ ALL THE WORDS

2 Midterm Test #2 - Week 10 - Monday November 5 - 25%Index

• Midterm test dates are posted on the Course Home Page.
• Midterm Test #2 (Mon Nov 5) covers:
  • anything from the previous midterm test, especially questions that were not answered correctly, plus:
  • Week 04 Notes HTML
  • Week 05 Notes HTML
  • Week 06 Notes HTML
  • Week 07 Notes HTML
  • Week 08 Notes HTML
  • Assignment #05
  • Assignment #07
  • Assignment #08
  • Assignment #09
  • Lab Worksheet #05 ODT Lab Worksheet #05 PDF
  • Lab Worksheet #07 ODT Lab Worksheet #07 PDF
  • Lab Worksheet #09 ODT Lab Worksheet #09 PDF
• See the Practice Test #2 PDF and answer file in the Class Notes.
• You must read the Test Instructions before the test for important directions on how to enter your answers and the test version number on the mark-sense forms.
• You must know which Lab Section Number you attend, and write that number on your question sheet. (NOT your lecture section number!)
• The first 50 minutes of the two-hour class is for questions; the last 45 minutes are for the midterm test. There may be more questions on the test than you can answer in the time allowed; answer the ones you know, first.

3 Final Exam Schedule is PostedIndex

Your Final Exam schedule is posted in the ICT office and on the Course Home Page.

4 Lecture Notes for This WeekIndex

• Review last week. Did you do everything assigned last week?

• Send me the Rap video! If you license it for public view, I’ll post it.
  • videos published: CST8207 Rap Videos
  • any more?

$ touch lab5.3b
$ rm lab5.[3b]

$ ls -dils /bin/*sh                                       
524294 936 -rwxr-xr-x 1 root root 955024 Apr  3  2012 /bin/bash
524318 108 -rwxr-xr-x 1 root root 109768 Mar 29  2012 /bin/dash
524419   0 lrwxrwxrwx 1 root root      4 Sep  7 00:22 /bin/rbash -> bash
524434   0 lrwxrwxrwx 1 root root      4 Sep  7 00:22 /bin/sh -> dash
524438   0 lrwxrwxrwx 1 root root      7 Sep  7 00:22 /bin/static-sh -> busybox
$ ls -dilsL /bin/*sh
524294  936 -rwxr-xr-x 1 root root  955024 Apr  3  2012 /bin/bash
524318  108 -rwxr-xr-x 1 root root  109768 Mar 29  2012 /bin/dash
524294  936 -rwxr-xr-x 1 root root  955024 Apr  3  2012 /bin/rbash
524318  108 -rwxr-xr-x 1 root root  109768 Mar 29  2012 /bin/sh
524297 1788 -rwxr-xr-x 1 root root 1827920 Apr 13  2012 /bin/static-sh
$ ls -dilsL /bin/*sh | sort
524294  936 -rwxr-xr-x 1 root root  955024 Apr  3  2012 /bin/bash
524294  936 -rwxr-xr-x 1 root root  955024 Apr  3  2012 /bin/rbash
524297 1788 -rwxr-xr-x 1 root root 1827920 Apr 13  2012 /bin/static-sh
524318  108 -rwxr-xr-x 1 root root  109768 Mar 29  2012 /bin/dash
524318  108 -rwxr-xr-x 1 root root  109768 Mar 29  2012 /bin/sh

5 Real Sysadmin WorkIndex

Changes by Ubuntu to the basic Unix security model for symlinks and hard links:

• Overview: http://utcc.utoronto.ca/~cks/space/blog/linux/Ubuntu1204Symlinks
  • “In the standard kernel, this […] blocks hardlinks to devices, setuid files, executable setgid files, and files that the UID making the link cannot read or write to (except that the owner of a file is always allowed to make hardlinks to it). Note that this blocks hardlinks to other people’s world-readable files if you can’t write to them.”
• http://lwn.net/Articles/390323/
  • “But some kernel hackers are not convinced that the core kernel should be fixing badly written applications.”
• http://utcc.utoronto.ca/~cks/space/blog/linux/Ubuntu1204Symlinks
  • “Both the Ubuntu Yama LSM and the new standard kernel code for this stuff include a second restriction, this time on what can be hardlinked.”
• Code patch and descriptions: http://lwn.net/Articles/393012/
  • “Normally, hardlinks can be created to files that a given user does not have access to. This can create security problems where privileged processes act on files that only they have access to, but have been put places unexpectedly by an attacker. This option limits the creation of hardlinks to files that a given user would be unable to read and write originally, or are not otherwise sensitive.”
• Change behaviour: sysctl -w kernel.yama.protected_sticky_symlinks=0
• Change behaviour: sysctl -w kernel.yama.protected_nonaccess_hardlinks=0

6 More Ubuntu Linux on your PhoneIndex

See Here