Windows Reverse Engineering - Debuggers (Page 4 of 9 )
+Fravia calls SoftICE (http://www.numega.com) the “Alpha and the Omega” of debuggers. However, what many modern reverse engineers are too young to remember (unless your hair is as grey as that of the authors) is that the forefather of SoftICE itself, known as ICE-86, was actually a hardware-based in-circuit emulator from Intel, designed to debug their seminal 8086 processor. A full description of this hardware can be found in the classic 8086 Family User’s Manual published by Intel in 1979.
SoftICE allows you to single-step through program code and to edit memory, registers, variables and flags on the fly as the program executes. The following function keys let you step through code and edit memory in SoftICE:
F8 - Single-step.
F10 - Program step.
F11 - Return to a routine from a call.
F12 - Forward to next Return.
D - Display memory contents.
S - Search memory for a string.
WW - Watch a register.
Once you have SoftICE installed, your system will boot WINICE.EXE along with Windows. SoftICE is integrated with the Windows operating system itself, at Ring 0, which is what makes it so powerful. SoftICE is configured by editing the WINICE.DAT file. Remove the semicolons in WINICE.DAT to uncomment the particular features that you need. For example, if you are editing WINICE.DAT to include 32-bit calls (recommended), uncomment the following lines:
gdi32.dll
kernel32.dll
user32.dll
SoftICE is a complex application. In fact, it comes with a large, two-volume user’s manual just to help get you started with the basics of its use. However, the most difficult part of using SoftICE is remembering the command shortcuts. If you are performing RCE with SoftICE, you will need a reference list that you can keep handy while you are cracking. Even the official user’s manual for SoftICE doesn’t list these critical breakpoints. For this reason, we have included a basic list of useful SoftICE commands and breakpoints in the Appendix. We also recommend that you read through the SoftICE user’s manual at least once before working the examples at the end of this chapter.
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