Adding hot patching resources

hot-patching/hot-patch.cpp

@@ -0,0 +1,58 @@
+/*
+*   compile: cl.exe hot-patch.cpp
+*/
+#include <windows.h>
+#include <stdio.h>
+
+int targetFunction() {
+    printf("[!] This is the original function, you should NOT see this output when the hot patch is enabled.\n");
+    return 0;
+}
+
+// The replacement function that patches the bad behavior
+int FixedFunction() {
+    printf("[+] The function was successfully patched and corrected!\n");
+    return 0; 
+}
+
+void PatchLocalFunction(void* targetFunction, void* newFunction) {
+    DWORD oldProtect;
+    
+    // Calculate the relative offset for a JMP instruction (0xE9)
+    // Formula: TargetAddress - CurrentAddress - SizeOfJmpInstruction
+    SIZE_T relativeOffset = (SIZE_T)newFunction - (SIZE_T)targetFunction - 5;
+
+    // Build the 5-byte JMP instruction payload
+    unsigned char jmpPatch[5];
+    jmpPatch[0] = 0xE9; // JMP opcode
+    memcpy(&jmpPatch[1], &relativeOffset, 4);
+
+    // Unprotect the target function memory temporarily
+    VirtualProtect(targetFunction, 5, PAGE_EXECUTE_READWRITE, &oldProtect);
+
+    // Overwrite the first 5 bytes to redirect control flow
+    memcpy(targetFunction, jmpPatch, 5);
+
+    // Restore original protection
+    VirtualProtect(targetFunction, 5, oldProtect, &oldProtect);
+}
+
+int main() {
+    printf("[*] Starting hot patch PoC execution\n");
+    
+    // Call the function before the patch to see original behavior
+    printf("[*] Before Patch\n");
+    int result = targetFunction();
+    printf("[*] Completed with return code: %d.\n", result);
+
+    // Apply the local module patch
+    printf("[*] Applying hot patch...\n");
+    PatchLocalFunction((void*)&targetFunction, (void*)&FixedFunction);
+
+    // Call the function after the patch to see if it redirects
+    printf("[*] After Patch\n");
+    result = targetFunction();
+    
+    printf("[*] Completed with return code: %d. Done, exiting.\n", result);
+    return 0;
+}