NPTEL Introduction to Operating Systems Week 8 Assignment Answers 2024
1. State True/ False.
A user with confidential clearance has read only rights to a top secret file. He decides to save a copy of the file and email it to all his friends on Facebook. This breach of information can be prevented by implementing Bell-la-Padula model.
- True
- False
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2. Your project manager asks you to ensure that a particular source code is free from buffer overflow vulnerabilities. Which of the following would you need to look out for?
- scanf in the code
- strcpy in the code
- For loops that manipulate arrays
- All of the above
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3. State True/False.
Address Space Layout Randomization randomizes the size of all arrays and thereby makes it difficult to overflow buffers.
- True
- False
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4. Arrange the following, based on the order parameters are pushed onto the stack
a) Return address is pushed
b) Local variables are allocated
c) Previous frame pointers
d) The function call parameters
- a, b, c, d
- b, c, d, a
- b, a , c, d
- d, a, c, b
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5. State True/False:
Gadgets are short sequences of instructions that ends with return instruction.
- True
- False
Answer :-
6. An ROP attack can potentially be detected at run-time by
- Canaries
- The number of return statements executed in the processor
- The number of return statements present in the executable
- By a non-executable stack
Answer :-
7. State True/False.
The number of gadgets present in an implementation depends on the number of return instructions in the machine code.
- True
- False
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8. Programmer X has found that the source code has a buffer overflow vulnerability caused by strcpy instruction. He then used strncpy in place of strcpy to prevent buffer overflow vulnerabilities. Which of the following is true?
- Buffer overflow vulnerabilities caused due to strcpy is avoided due to bounds check
- This will not make any changes in the source code
- Buffer overflow attack will not occur in this source code
- None of these
Answer :-
9. Match the following:
a) Secrecy 1)Limits the resource usage
b) Integrity 2)Unauthorized modification
c) Availability 3)Unauthorized disclosure
- a-1, b-2, c-3
- a-2, b-3, c-1
- a-3, b-2, c-1
- None of these
Answer :-
10. State True/ False.
A gadget that ends with a branch instruction can never be used for an ROP attack.
- True
- False
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