From 8f30ed9209d0b44dcbf802546c84b593bc9f2a1e Mon Sep 17 00:00:00 2001
From: Garrett Dickinson <dickinsongarrett@gmail.com>
Date: Thu, 26 Jan 2023 15:24:55 -0600
Subject: [PATCH] Add offset constants for header and section table

---
 README.md   |  5 ++---
 src/main.rs | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index eec7569..01614fb 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,7 @@
 # chisel
-`chisel` is a tool for decompiling *nix ELF programs for binary analysis and reverse engineering. This project is being developed alongside coursework for **Auburn University's COMP5970 Binary Program Analysis**.
+`chisel` is a tool for decompiling *nix ELF programs for binary analysis and reverse engineering. This project is being developed for assignments pertaining to Auburn University's **COMP5970 Binary Program Analysis** course.
 
 
 ## Supported Binary formats
 
-`chisel` supports binaries compiled to the [ELF format](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) from most x86 *nix systems, and *does not* currently support macOS Mach-O or Windows PE binaries.
-
+`chisel` supports binaries compiled to the [ELF format](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) from most x86/x64 *nix systems, and __does not__ currently support macOS Mach-O or Windows PE binaries.
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 9931cda..ca6a4e5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,40 @@
+// main.rs
+// Author: Garrett Dickinson
+// Created: 01/23/2023
+// Description: Main entrypoint script for chisel. Contains basic procedures
+//              for gathering ELF file data.
+
+
 use std::path;
 use std::env;
 use std::fs;
 use std::process::exit;
 
+// Generic ELF information offsets.
+
 const ELF_MAGIC_NUMBER: &[u8] = &[0x7F,0x45,0x4C,0x46];
+const ELF_ARCH_OFFSET: u8 = 0x04;       // x86 or x64 indiicator; 1 byte
+const ELF_ENDIAN_OFFSET: u8 = 0x05;     // Endian offset (1 - little, 2 - big); 1 byte
+const ELF_ABI_OFFSET: u8 = 0x07;        // ABI identifier; 1 byte
+const ELF_TYPE_OFFSET: u8 = 0x10;       // Object type identifier; 2 bytes
+const ELF_MACHINE_OFFSET: u8 = 0x12;    // Instruction set type; 2 bytes
+
+
+// Entry points and program header table inforamtion.
+// Tupled offset are split by architecture:
+//      0 : x86
+//      1 : x86_64
+
+const ELF_ENTRYPOINT_OFFSET: u8 = 0x18;
+const ELF_PHOFF_OFFSET: (u8, u8) = (0x1C, 0x20);        // Program header table pointer; 2 bytes
+const ELF_SHOFF_OFFSET: (u8, u8) = (0x20, 0x28);        // Section table pointer; 2 bytes
+const ELF_EHSIZE_OFFSET: (u8, u8) = (0x28, 0x34);       // Program header table entry size pointer; 2 bytes
+const ELF_PHENTSIZE_OFFSET: (u8, u8) = (0x28, 0x34);    // Section table pointer; 2 bytes
+const ELF_PHNUM_OFFSET: (u8, u8) = (0x2C, 0x38);
+const ELF_SHENTSIZE_OFFSET: (u8, u8) = (0x2E, 0x3A);
+const ELF_SHNUM_OFFSET: (u8, u8) = (0x30, 0x3C);
+const ELF_SHSTRNDX_OFFSET: (u8, u8) = (0x32, 0x3E);
+
 
 fn main() {
     // Collect our execution args
@@ -24,7 +55,7 @@ fn main() {
             if magic_num == ELF_MAGIC_NUMBER {
                 println!("Found ELF Magic Number!");
             } else {
-                println!("[Error] Could not find magic number, is this an executable?")
+                println!("[Error] Could not find magic number, is this an ELF executable?")
             }
         }
     } else {