127.0.0.1：/* Volga Quals CTF 2014: Reverse 100 */

2023-07-02T08:20:47Z

Volga Quals CTF 2014: Reverse 100

←上一版本		2023年7月2日 (日) 16:20的版本
第56行：		第56行：

	<pre>RDDRRRRRRRRRRRRRRRRRRDDDDDDDDDDRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRUUUUUULLLLLLLLLDDRRRRRRDDLLLLLLLLLLLLLUURRRUUUUURRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDDDDDDDDDDRRRRRRRRRRRRRRRRUUUUUUUUUUUUULLLLLLLUUUURRRRRRRRRRRRDDDDDDDDDDDDDDDDDDDLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLUUUURRRRRRRRRRRRRRRRRRRRRDRRRRRRRRRRRRRRUUULLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLDDDDDRRRRRUUURRRRDDDDDLLLLLLLLLDDDDRRRRRRRRRRUUURRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDRRRRRRRRRRRRRRRRRRRRRRRRRRRR</pre>		<pre>RDDRRRRRRRRRRRRRRRRRRDDDDDDDDDDRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRUUUUUULLLLLLLLLDDRRRRRRDDLLLLLLLLLLLLLUURRRUUUUURRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDDDDDDDDDDRRRRRRRRRRRRRRRRUUUUUUUUUUUUULLLLLLLUUUURRRRRRRRRRRRDDDDDDDDDDDDDDDDDDDLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLUUUURRRRRRRRRRRRRRRRRRRRRDRRRRRRRRRRRRRRUUULLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLDDDDDRRRRRUUURRRRDDDDDLLLLLLLLLDDDDRRRRRRRRRRUUURRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDRRRRRRRRRRRRRRRRRRRRRRRRRRRR</pre>

	== 参考链接 ==		== 参考链接 ==

127.0.0.1：创建页面，内容为“{{Ctf_Wiki}} = 迷宫问题 = 迷宫问题有以下特点: * 在内存中布置一张"地图" * 将用户输入限制在少数几个字符范围内. * 一般只有一个迷宫入口和一个迷宫出口布置的地图可以由可显字符(比如`#`和`*`)组合而成(这非常明显, 查看字符串基本就知道这是个迷宫题了.), 也可以单纯用不可显的十六进制值进行表示. 可以将地图直接组成一…”

2023-07-02T08:19:41Z

创建页面，内容为“{{Ctf_Wiki}} = 迷宫问题 = 迷宫问题有以下特点: * 在内存中布置一张"地图" * 将用户输入限制在少数几个字符范围内. * 一般只有一个迷宫入口和一个迷宫出口布置的地图可以由可显字符(比如<code>#</code>和<code>*</code>)组合而成(这非常明显, 查看字符串基本就知道这是个迷宫题了.), 也可以单纯用不可显的十六进制值进行表示. 可以将地图直接组成一…”

新页面

{{Ctf_Wiki}}
= 迷宫问题 =

迷宫问题有以下特点:

* 在内存中布置一张"地图"
* 将用户输入限制在少数几个字符范围内.
* 一般只有一个迷宫入口和一个迷宫出口

布置的地图可以由可显字符(比如<code>#</code>和<code>*</code>)组合而成(这非常明显, 查看字符串基本就知道这是个迷宫题了.), 也可以单纯用不可显的十六进制值进行表示. 可以将地图直接组成一条非常长的字符串, 或是一行一行分开布置. 如果是一行一行分开布置的话, 因为迷宫一般都会比较大, 所以用于按行(注意, 布置并非按顺序布置, 每行都对应一个具体的行号, 你需要确定行号才能还原迷宫地图)布置迷宫的函数会明显重复多次.

而被限制的字符通常会是一些方便记忆的组合(不是也没办法), 比如<code>w/s/a/d</code>, <code>h/j/k/l</code>, <code>l/r/u/d</code>这样的类似组合. 当然各个键具体的操作需要经过分析判断(像那种只用一条字符串表示迷宫的, 就可以用<code>t</code>键表示向右移动<code>12</code>个字符这样). 对于二维的地图, 一般作者都会设置一个<code>X坐标</code>和一个<code>Y坐标</code>用于保存当前位置. 我们也可以根据这个特点来入手分析.

一般情况下, 迷宫是只有1个入口和1个出口, 像入口在最左上角<code>(0, 0)</code>位置, 而出口在最右下角<code>(max_X, max_Y)</code>处. 但也有可能是出口在迷宫的正中心, 用一个<code>Y</code>字符表示等等. 解答迷宫题的条件也是需要根据具体情况判断的.

当然迷宫的走法可能不止1条, 也有情况是有多条走法, 但是要求某一个走法比如说代价最小. 那么这就可以变相为一个算法问题.

<span id="volga-quals-ctf-2014-reverse-100"></span>
== Volga Quals CTF 2014: Reverse 100 ==

接下来我们以这道题进行示例, 这是一道简单的迷宫题. 该题对地图按行乱序布置, 使用的字符是<code>#</code>和<code>*</code>.

对应的<code>crackme</code>可以点击此处下载: [https://github.com/ctf-wiki/ctf-challenges/blob/master/reverse/maze/2014_volga_quals/rev100 rev100]

对应的<code>idb</code>可以点击此处下载: [https://github.com/ctf-wiki/ctf-challenges/blob/master/reverse/maze/2014_volga_quals/rev100.i64 rev100.i64]

[[File:./figure/setmaze.png|setmaze.png]]

我们可以到<code>.rodata</code>段用光标选择所有的地图字符串, 按下<code>shift+E</code>提取所有的地图数据.

[[File:./figure/extract_maze.png|extract_maze.png]]

但是目前提取到的地图字符串, 从上往下并非是按顺序的, 因此我们需要回到IDA生成的伪C代码, 获取行号并重新排序组合起来.

最后得到的完整地图如下:

对应的<code>迷宫地图文件</code>可以点击此处下载: [https://github.com/ctf-wiki/ctf-challenges/blob/master/reverse/maze/2014_volga_quals/maze_array.txt maze_array.txt]

[[File:./figure/maze_origin.png|maze_origin.png]]

再来看迷宫移动所需要的字符:

[[File:./figure/choice.png|choice.png]]

这里我们知道, 可以使用的字符有<code>L/R/U/D</code>, 分别对应于<code>左/右/上/下</code>.

再往下看

[[File:./figure/check.png|check.png]]

通过调试是可以知道, 这里其实是每次在用户输入<code>L/R/U/D</code>后, 先打印一次你的输入, 然后打印对应的<code>X/Y坐标</code>. 而最后的判定成功的条件, 就是当<code>pos_x == 89 && pos_y == 28</code>. 那么我们就可以根据上述信息, 获得走出迷宫的路径.

[[File:./figure/maze.jpg|maze.jpg]]

最后得到的迷宫路径就是

<pre>RDDRRRRRRRRRRRRRRRRRRDDDDDDDDDDRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRUUUUUULLLLLLLLLDDRRRRRRDDLLLLLLLLLLLLLUURRRUUUUURRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDDDDDDDDDDRRRRRRRRRRRRRRRRUUUUUUUUUUUUULLLLLLLUUUURRRRRRRRRRRRDDDDDDDDDDDDDDDDDDDLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLUUUURRRRRRRRRRRRRRRRRRRRRDRRRRRRRRRRRRRRUUULLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLDDDDDRRRRRUUURRRRDDDDDLLLLLLLLLDDDDRRRRRRRRRRUUURRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDRRRRRRRRRRRRRRRRRRRRRRRRRRRR</pre>
== 参考链接 ==

* [<nowiki/>[https://singularityctf.blogspot.com/2014/03/volgactf-quals-2014-writeup-reverse-100.html VolgaCTF Quals 2014 writeup - Reverse-100]]

[[Category: Reverse_Overview]]

迷宫问题 - 版本历史

127.0.0.1：​/* Volga Quals CTF 2014: Reverse 100 */

127.0.0.1：/* Volga Quals CTF 2014: Reverse 100 */