anmolsagarwal/cs6332-assignment-1

Assignment 1 for Systems Security and Malicious Code Analysis course - library linking and loading

Assignment 0x1: Linking and Loading

For this assignment, you will be given a library source (memsets.c) that implements different version of memset() functions along with driver sources (driver0.c, driver1.c, ...) for different parts of assignments. You need to implement different ways to link or load library functions by carrying out different parts of assignments.

Prerequisites

This assignment requires access to a machine that has a Linux Operating System. This assignment is run on the Linux terminal command line interface.

Part 0 (0 point - warmup)

This part implements a single source version of memsets testcode. Run the following command to see it running:

$ make part0

Part 1: Building C source with Makefile (2pt)

For this part of assignment, you will follow a standard practice to build an executable from multiple sources by linking object files. Please fill in part1: target from Makefile to carry out the followings.

(1) Compile into objects files (driver1.o, memsets.o), and (2) link them into an output executable (part1).

To run this part, type the following command in the terminal:

$ make part1

Part 2: Creating a static library (2pt)

You can package multiple object files in to a static library, so as any program can copy object files to resolve dependencies and build an output binary. You will fill in part2 target of Makefile.

(1) Compile into objects files, (2) package memsets.o into an archive (libmemsets.a), and (3) link driver1.o object file into an output executable (part2). (4) Run the produced executable.

To run this part, type the following command in the terminal:

$ make part2

Part 3: Creating a dynamic library (3pt)

Now, it is time to build a shared library (libmemsets.so). Please update Makefile (target part3) to carry out the following steps.

(1) Compile into objects files, (2) package memsets.o into an shared library (say libmemsets.so), (3) compile driver1.c into an output executable (part3), and (4) dynamically link shared library to run the program.

To run this part, type the following command in the terminal:

$ make part3

Part 4: Dynamically load a library (3pt)

For this part of assignment, you will modify driver4.c to use functions from [dlfcn.h] to dynamically load necessary functions from shared library (libmemsets.so) from part3 at runtime. Fix driver4.c to replace replace_me to appropriate variables and update Makefile accordingly.

To run this part, type the following command in the terminal:

$ make part4

Part 5: Library interposing with LD_PRELOAD (bonus 5pt)

This assignment is again based on part3. While you run the output executable from part3, you will intercept library loading (LD_PRELOAD) to replace memset() from libc library to something else (e.g., memset1).

To run this part, type the following command in the terminal:

$ make part5