delphi程序crackme分析1

本文通过使用PeiD和DelphiDecompiler等工具分析了一个软件的注册码生成和验证过程。详细介绍了如何找到注册码的生成算法,并给出了爆破思路。

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拿到exe文件,先用PeiD查一下有没有壳,什么语言写的:
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确定了是delphi写的之后,放到Delhpi Decompiler反编译分析:
点击Procedures,再双击CKM
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注意到chkcode那个函数,怀疑是检测代码,ida跟进去看看:
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函数前面部分是根据输入的用户名,计算出一个注册码:
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所以连接后的字符串为:”黑头Sun Bird”+(用户名长度+5)+”dseloffc-012-OK”+用户名,这个也就是注册码了

中间的部分是垃圾代码,没有实际作用:
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后面的部分是比较输入的注册码和计算注册码是否相等:
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这个函数就分析完成了,要爆破的话就吧0x457d3a的jnz short failed指令nop掉就ok

那么是在那里检查赋给[ebx+0x30c]的值呢?分析发现是在Panel1Click函数里面检查的(Panel1Cilck函数在Delhpi Decompiler反编译时就发现了):
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我把下面的已经nop掉了,源程序不是这样的

Version 1.7 build 929 (24.04.2014) * Fixed critical errors in the DCUDumper Version 1.6 build 911 (23.04.2014) * Added decopilation DCU for Delphi XE-X5 Version 1.5 build 888 (2012-07-24) * Fixed a critical errors in dumping of programs compiled in Delphi 2010,XE ?XE2 * Fixed minor bugs in the window "Select Process" Version 1.4 build 808 (2012-07-19) * Fixed a critical error in getting the process list in the "Select Process" window + Added detection of programs compiled with Delphi XE2 Version 1.3 build 777 (2012-07-18) * This version for test only + Partial support Delphi XE and Delphi XE2 + Fully supported DCU decompiling for Delphi XE and Delphi XE2 + Full refactoring the program interface - Removed languages support, now only English * Fixed many bugs in the "Select Process" window + Added debug privilege * Fixed other many bugs Version 1.1 build 211 (2010-03-26) * Fixed the definition of programs compiled in Delphi 7 + Added ability to drag files to the main window (drag & drop) Version 1.1 build 195 (2010-03-04) + Updated the DSF Editor * Fixed loss of DSF editor when parsing + In DSF editor adds support for Delphi 2007, 2009, 2010 (so far works only for parsing. Bpl) * Optimized code for rendering assembly code * Full reconstruction project to accelerate work on a batch of assemblies and the subsequent testing Version 1.1 build 191 + Updated the PE Editor + Improved the window "Options" + Added ability to change fonts: - In the DFM Editor - Lists ListView - In disassembler * Reduced the delay timer on the window screen saver Version 1.1 build 187 * Fixed a PE editor + Added saving of projects Delphi 2007 + Added saving of projects Delphi 2009 + Added saving of projects Delphi 2010 Version 1.1 build 180 + The project status has changed to "beta" Version 1.1 build 177 + Rewritten engine decompilation DCU + Rewrote the analysis engine EXE + New format DOI and DSF
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