Lab 2- Marble Pre-Processor

CS320: Marble
Marble Pre-Processor

Amount: +25%
1 Overview
In his Future of Programming lecture, Robert Martin briefly touches on the
early development of both C++ and Objective-C. In each case, developers
used the tools they had to build the ones they wanted. This technique
persists in modern programming, as several intelligence leaks confirm, for the
Central Intelligence Agency built frameworks 1 around the C++ language
to simplify development and deployment of sensitive tools.
In this assignment, students shall follow in these footsteps and create a
specialized pre-processor designed to help conceal strings in executable files
using the C++11 programming language. This extensive project requires
students create both a unique class to represent strings, but they must also
build the application which modifies arbitrary C++ input files by replacing
certain string calls with calls to the student-generated class.
2 Requirements
This project requires students submit multiple C++11 source files: The
marble string object and the program that swaps it into source files. Students must use the object-oriented model when building the string marble
object.
2.1 Marble Class
Each submission must include its unique implementation of a marble character object in its own file. This class shall include the following functionality:
• A constructor accepting a string-literal as its only required parameter.
• Override the << operator such that the marble object returns the
unscrambled version of the string.
• Implement a size() method which returns the true size of the concealed string.
1Allegedly.
CS 320: Marble Summer 2019
Original Modified
char data[] = "abc"; MarbleString data = "bcd";
char stuff[ ]="rEd" ; MarbleString stuff = "sFe";
Figure 1: Example of a modified declaration statement. The trivial marbling
algorithm simply adds one to each character.
• Store the concealed string on the stack in a char array.
The particular algorithm students use to conceal the original stringliteral remains up to the implementer. Trivially, as shown in the examples
in this document, one might add one to the original value. This facilitates
simple error discovery during development. Alternatively, students may
attempt a more complicated approach. Consider bit shifting and adding to
the original characters, for one may rapidly reverse these modifications. In
any event, the marble class shall not store the original string literal in an
unmodified form, and the transformation must be reversible.
When printed, instead of displaying the marbled text, the marble class
object shall override the << operator such that it produces the original
string. Consequently, the class must use a reversible algorithm when concealing the string. For example, one could hard-code in an 8-bit key to
use, and then exclusive-OR each byte of the string literal with this value to
produce the concealed string. When it comes time to print this string, one
simply performs the exclusive-OR operation a second time to recover the
original text.
At run-time, the program can recreate the string, but it shall not appear
in the original text.
2.2 Driver Application
The driver application scans an input source file for character array declaration statements matching a particular from, and it then replaces them with
calls to a custom class. Additionally, for files it modifies, the application
must also include a pre-processor directive inserting the custom class in the
modified input file.
The modified call replaces the original string literal with a scrambled
version in the modified output source file. Consequently, after compiling
the modified source file, the original string literal will not leap out in plain
text.
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CS 320: Marble Summer 2019
2.2.1 Replaced Strings
Although one may insert string literals in source code several ways, the driver
application implemented in this assignment shall only replace character array, string-literal in an assignment, declaration statement. Simple character
array declarations, without an accompanying string literal assignment, shall
remain untouched. Figure 1 provides examples of the replacement.
Spaces may appear throughout the declaration, and the driver application must accommodate these accordingly, but it need not preserve them in
the final substitution. That is, a declaration without a space in the original
may insert one in the modified version.
2.2.2 Output File
After replacing the standard calls in the original source file with calls to
the custom class, the program shall store the modified output in a new file.
The new output file shall use the same path and basic name as the original
file, but it shall append a mbl- prefix to the name. For example, if the user
identified cryptic.cpp as the input file, then mbl-cryptic.cpp will hold
the modified output.
2.3 Coding Style
Software quality strengthens program security, reliability, and maintainability. In general, all submitted software must:
• Adhere to a consistent naming convention and follow best practices
for variable naming.
• Use private, or protected, internal methods to help clean the code.
• Remain free of commented out blocks of code.
• Use consistent formatting.
• The maximum column width is 80 characters.
The graders may elect to subtract points as they deem necessary for
coding style and naming convention violations.
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CS 320: Marble Summer 2019
2.3.1 Input File Format
This driver application scans C++ source files for certain character array
declaration statements and substitutes in a custom object.
It operates on a single, user-supplied source file with each program activation, so solutions need not scan recursively for all files in the project.
The driver assumes the input file complies with the syntax and formatting
defined
3 Delivery
At the start of class on the due date, students shall submit a legible, physical
ASCII printout of their source code. Do not submit screen-shots of source
code or the development environment. Do not copy the source into a wordprocessor. Simply print the source file, which is ASCII, directly. The 80
character line limit in defined in the coding standard ensures that the source
file prints as it appears on screen.
For extra credit, students shall submit a fully-compliant solution on the
earlier due date identified in the prompt header. Students seeking this approach shall not receive additional, priority, or expiated assistance from the
teaching assistants or instructors.
4 Grading
In general, all submissions must meet every requirement in this specification.
Requirement Points
Coding Style 10
Application 20
Marble Class 70
5 Other Notes
The instructor and teaching assistants remain available to assist students
with questions that arise during the application’s development and design.
Due to high demand, however, students may not receive attention.
For an example of some advanced algorithms to use, feel free to explore
https://wikileaks.org/vault7/document/Marble/.
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