Skip to content

Assignment 3

Jump to bottom
WMX66666 edited this page May 20, 2025 · 35 revisions

Assignment-3 folder layout

../Assignment-3/
|-- CPP
|   |-- Assignment-3-Helper.cpp
|   |-- Assignment-3-Helper.h
|   |-- Assignment-3.cpp
|   |-- Assignment-3.h
|   |-- CMakeLists.txt
|   `-- test-ae.cpp
|-- Python
|   |-- Ass3_helper.py
|   |-- Assignment3.py
|   |-- CMakeLists.txt
|   |-- Main.py
|   |-- Test.py
`-- Tests
    |-- ae
    |   |-- test1.c
    |   |-- test1.ll
    |   |-- test2.c
    |   |-- test2.ll
    |   |-- test3.c
    |   |-- test3.ll
    |   |-- test4.c
    |   `-- test4.ll
    `-- buf
        |-- test1.c
        |-- test1.ll
        |-- test2.c
        |-- test2.ll
        |-- test3.c
        |-- test3.ll
        |-- test4.c
        |-- test4.ll
        |-- test5.c
        `-- test5.ll

1. Get the latest code template

* Before coding, please type cd $HOME/Software-Security-Analysis and git pull in your terminal to make sure you always have the latest version of the code template before each assignment.

Make sure to switch your program to ass3 before coding.

2. Assignment 3 task

Method Description
updateStateOnCopy Handle COPYStmt
updateStateOnStore Handle StoreStmt
updateStateOnLoad Handle LoadStmt
updateStateOnGep Handle GepStmt
updateStateOnBinary Handle BinaryStmt.
updateStateOnPhi Handle PhiStmt.
bufOverflowDetection Check buffer overflow at GepStmt.
handleCycleWTO Widening and narrowing for loops.
updateStateOnExtCall handle External APIs.
  1. Implement the above methods of class AbstractExecution in Assignment_3.cpp or Assignment_3.py

2.1 Implementing updateState

The updateStateOnStore function should store the RHS value at the memory address corresponding to the LHS value in AEState which is from calling getAbsStateFromTrace. Note that the RHS variable can be either IntervalValue or AddressValue.

The updateStateOnGep function aims to compute the virtual address by adding an offset to the base pointer and then store the updated state in LHS value in AEState which is from calling getAbsStateFromTrace.

The updateStateOnCopy function should copy the RHS value to the LHS value in AEState which is from calling getAbsStateFromTrace.

The updateStateOnBinary function should perform the binary operation specified by the BinaryStmt and store the result in the LHS value in AEState which is from calling getAbsStateFromTrace.

The updateStateOnLoad function should load the value from the memory address corresponding to the RHS value and store it in the LHS value in AEState which is from calling getAbsStateFromTrace.

The updateStateOnPhi function should merge the values from the predecessor blocks and store the merged value in the LHS value in AEState which is from calling getAbsStateFromTrace.

2.2 Implementing handleCycleWTO

The handleCycleWTO function needs to include widening and narrowing logic. This will enable the function to handle loop bounds efficiently (e.g., for i = 0; i < 10000; ++i), allowing it to exit the loop after several iterations and determine the correct value of i.

2.3 Implementing bufOverflowDetection

This function takes an SVFStmt as input. If the statement is a GepStmt, it indicates an attempt to access an offset of a pointer or array. An overflow checking is needed to make sure the access offset is smaller than the size of the underlying object.

The provided framework already includes the following steps:

  1. Identifying if the statement is a GepStmt.
  2. Using the updateGepObjOffsetFromBase function to update the offsets for the GEP objects.

You need to complete the following tasks:

  1. Check Object Sizes and Access Offsets: After updating the offsets using updateGepObjOffsetFromBase, you need to check if the access offset exceeds the effective byte size of the object.
  2. Report Buffer Overflow: If an access offset is found to exceed the object's size, you should report a buffer overflow.

Specifically, in the bufOverflowDetection function, you need to:

  • Retrieve the base address and size of the object.
  • Get the access offset.
  • Compare the access offset with the object's size. If the offset exceeds the size, report a buffer overflow.

Ensure you use the provided tools and functions correctly to perform these checks and report any buffer overflows.

It is important to note that a buffer overflow bug may occur during a GepStmt. For example:

int arr[5];
arr[10] = 1;

A buffer overflow might also occur after multiple GepStmts, such as:

int arr[5];
int* ptr = arr + 3;
ptr[4] = 1;

Therefore, each GepStmt must be checked to ensure that the RHS variable's effective length still supports the current offset. If a bug is detected, invoke reportBufOverflow to report a bug.

2.4 Implementing updateStateOnExtCall

The updateStateOnExtCall function is responsible for handling external function calls within the abstract execution framework. This function ensures that operations involving external calls, such as buffer manipulations, are safely executed without causing buffer overflows.

Key Responsibilities

  • Memory Insertion (mem_insert): This function checks whether the buffer has sufficient space to accommodate the data being inserted at a specified position.

    • Check: Ensure sizeof(buffer) > position + data_size.
    • Action: If the check fails, invoke reportBufOverflow to report a potential buffer overflow.

  • String Insertion (str_insert): Similar to mem_insert, but involves inserting a string into a buffer.

    • Check: Ensure sizeof(buffer) > position + strlen(data).
    • Action: If the check fails, invoke reportBufOverflow.

Implementation Details

For each external call, the function retrieves the relevant arguments and performs the necessary checks:

  • Buffer Size Retrieval: For each buffer address, determine the object's byte size using svfir->getBaseObj(objId)->getByteSizeOfObj().
  • Offset Calculation: Calculate the access offset by adding the position and data size or string length.
  • Overflow Detection: Compare the calculated access offset with the buffer size. If the offset exceeds the size, report a buffer overflow using reportBufOverflow.

This function ensures robust handling of external calls, preventing unsafe memory operations that could lead to vulnerabilities.

Run Tests

Upload Your Solution

3. Configuration and Debugging

Clone this wiki locally