essay
medium
Understand
setuid-effect
2 points
Question 7. CSCD240-E1-B
What does the setuid bit cause when the file is executed? Use "effective user ID".
Work the drill
Answer on paper or in a terminal before revealing the ideal answer.
Ideal answer
The process runs with the effective user ID of the file's owner (not the invoker). Example: running /usr/bin/passwd as a normal user gives the process root's EUID so it can modify /etc/shadow.
Misconception bank
Each row below is a plausible wrong answer, the thinking that produces it, and the remedy that corrects the misconception. These are the foundation of the multiple-choice framing and the targeted feedback a student receives after answering.
Runs as root
Misconception. Only if owner is root. Not universal.
Remedy. EUID = OWNER UID, whichever that is.
Suspends the process
Misconception. Confused with stop/pause.
Remedy. setuid is about identity, not scheduling.
Authority mappings
Hover any chip for the mapping justification; click to open the authority record.
DCWF roles:
CE-121 Exploitation Analyst
DCWF tasks:
T0250
KU topics:
CD-OSC-T7
Course-artifact links
Lectures
- CSCD240-S26-L05. Permissions part 1: ls -l anatomy, rwx, file types
CTF challenges
- 99 BONUS: Lecture Recall: What Does the S Stand For?