怎么分析CobaltStrike3.12,针对这个问题,这篇文章详细介绍了相对应的分析和解答,希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。
CobaltStrike是一款内网渗透的商业远控软件,支持自定义脚本扩展,功能非常强大。前段时间Github上有好心人放出了CobaltStrike3.12的试用版,接着Lz1y很快就放出了Patch版,加上热心老哥提供了的xor64.bin(试用版中没有这个文件),一个比较完美的最新可用版本诞生了。下面我们看下最新试用版是如何被完美Patch的。
CobaltStrike(下面简称CS)主体代码是用Java开发的,逆起来比较友好。用jd-gui反编译cobaltstrike.jar文件,可以看到代码几乎没有做加固。Java源码没有任何混淆。但是查看反编译的源码时,很多地方出现了// INTERNAL ERROR //
,这里我推荐一款Java反编译工具luyten
,几乎可以100%反编译获得cobaltstrike.jar源码。
CS的License处理逻辑在common/License.java
文件中:
package common; import aggressor.*; import javax.swing.*; import java.awt.*; public class License { private static long life; private static long today; private static long start; private static long difference; private static long getTimeSinceStart() { final Prefs options = Prefs.getPreferences(); License.today = System.currentTimeMillis(); License.start = options.getLongNumber("cobaltstrike.start.int", 0L); if (License.start == 0L) { options.set("cobaltstrike.start.int", License.today + ""); options.save(); License.start = License.today; } return License.difference = (License.today - License.start) / 86400000L; } public static void checkLicenseGUI(final Authorization auth) { getTimeSinceStart(); if (License.difference > License.life || License.today - License.start < 0L) { JOptionPane.showMessageDialog(null, "Your Cobalt Strike trial is now expired.\nPlease purchase a license and use the\nsoftware update feature to continue.\n\nFor details, visit:\nhttps://www.cobaltstrike.com/", null, 0); System.exit(0); } else { final long left = License.life - License.difference; String form = left + " day"; if (left != 1L) { form += "s"; } CommonUtils.print_warn("This is a trial version of Cobalt Strike. You have " + form + " left of your trial. If you purchased Cobalt Strike. Run the Update program and enter your license."); CommonUtils.print_trial("WARNING! This trial is *built* to get caught by standard defenses. The licensed product does not have these restrictions. See: http://blog.cobaltstrike.com/2015/10/14/the-cobalt-strike-trials-evil-bit/"); JOptionPane.showMessageDialog(null, "This is a trial version of Cobalt Strike.\nYou have " + form + " left of your trial.\n\nIf you purchased Cobalt Strike. Run the\nUpdate program and enter your license.", null, 1); } } public static boolean isTrial() { return true; } public static void checkLicenseConsole(final Authorization auth) { getTimeSinceStart(); if (License.difference > License.life || License.today - License.start < 0L) { CommonUtils.print_error("Your Cobalt Strike trial is now expired. Please purchase a license and use the software update feature to continue. For details, visit: https://www.cobaltstrike.com/"); System.exit(0); } else { final long left = License.life - License.difference; String form = left + " day"; if (left != 1L) { form += "s"; } CommonUtils.print_warn("This is a trial version of Cobalt Strike. You have " + form + " left of your trial. If you purchased Cobalt Strike. Run the Update program and enter your license."); CommonUtils.print_trial("WARNING! This trial is *built* to get caught by standard defenses. The licensed product does not have these restrictions. See: http://blog.cobaltstrike.com/2015/10/14/the-cobalt-strike-trials-evil-bit/"); } } static { License.life = 21L; License.today = 0L; License.start = 0L; License.difference = 0L; } }
代码逻辑很清晰,这里我们有两个方向进行patch:
修改License.life
无限延长试用
修改isTrial()
返回值,伪造成正式版
因为CS很多地方的试用版和正式版处理逻辑不同,所以修改了isTrial()
返回值之后,我们还需要修改所有调用了isTrial()
函数的地方,对代码进行调整。另外试用版CS留了一些特征指纹和限制,我们也需要去除相应的特征代码。
既然知道了破解思路,我们看下如何动手操作去修改源码并重编译。Java编程中我们可以使用jar
工具将一系列的.class文件打包成jar包,供其他java程序使用。我们也可以修改jar包中.class文件的内容,并重新编译打包。比如修改demo.jar中的kingx.class并重新编译的过程如下:
使用jd-gui、luyten等工具把demo.jar包中的class反编译成源码,从中提取得到kingx.java
执行jar xvf demo.jar
解压demo.jar得到jar包的子文件(注意会解压到当前目录),将kingx.java文件放置到与example.class文件同一目录
执行javac -cp a.jar;b.jar;c.jar kingx.java
重新编译。(或者javac -cp demo.jar kingx.java)得到新的kingx.class文件。
其中a.jar、b.jar、c.jar是依赖包,一般直接依赖一个原始解压的demo.jar包即可
确保编译后的kingx.class替换了原来的kingx.class文件(可以通过jd-gui反编译查看)
执行jar -uvf demo.jar com/some/path/kingx.class
更新demo.jar包
更新jar包中的class文件时,新的class文件目录路径需要与原package路径保持一致。比如修改了aggressor.AggressorClient.java
并重新编译之后,更新jar包的命令如下:
17:16 KINGX modified_java_files >jar -uvf cobaltstrike-with-xor64.jar aggressor/AggressorClient*.class 正在添加: aggressor/AggressorClient$1.class(输入 = 650) (输出 = 403)(压缩了 38%) 正在添加: aggressor/AggressorClient$2.class(输入 = 1263) (输出 = 704)(压缩了 44%) 正在添加: aggressor/AggressorClient.class(输入 = 11115) (输出 = 5196)(压缩了 53%)
修改后的java文件在重新编译为class文件时,可能会遇到很多奇怪的报错。有时候是因为反编译出的源码存在错误导致的,这个时候我们可以将luyten、jad、jd-gui等反编译工具结合使用,尽量还原成正确的源码,再重新编译。
比如:AggressorClient.java,jad aggressor/AggressorClient*.class
和luyten
反编译得到的源码是不一样的。
Tips: 以下代码片段中行首的 - 代表删除,+ 代表新增
修改common.License,去掉checkLicenseGUI()、checkLicenseConsole()函数体,修改isTrial()返回值为true
aggressor.AggressorClient,修改getTitle()函数
一个teamserver默认只能监听一个listener,可以通过修改代码去除限制。
aggressor.dialogs.ListenerDialog,去除以下代码:
... else if (Listener.isEgressBeacon(payload) && DataUtils.isBeaconDefined(this.datal) && !name.equals(DataUtils.getEgressBeaconListener(this.datal))) { DialogUtils.showError("You may only define one egress Beacon per team server.\nThere are a few things I need to sort before you can\nput multiple Beacon HTTP/DNS listeners on one server.\nSpin up a new team server and add your listener there."); } ...
试用版有几个地方存在EICAR特征字符:X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*
,都需要进行清理:
修改pad()函数:
- result.append("5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*\u0000"); + result.append("123\u0000");
- $eicar = 'X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*' + $eicar = ''
- c2profile.addCommand(".http-get.server", "!header", "X-Malware: X5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*"); - c2profile.addCommand(".http-post.server", "!header", "X-Malware: X5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*"); - c2profile.addCommand(".http-stager.server", "!header", "X-Malware: X5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*"); - c2profile.addCommand(".stage.transform-x86", "append", "X5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*"); - c2profile.addCommand(".stage.transform-x64", "append", "X5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*");
因为已经修改了License.isTrial()返回值为false,所以下面这段改不改也没什么影响。
if (License.isTrial()) { packer.addString("X5O!P%@AP[4\\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*"); CommonUtils.print_trial("Added EICAR string to " + s); }
生成payload时,会调用common.ArtifactUtils中的XorEncode()进行编码:
public static byte[] _XorEncode(final byte[] data, final String arch) { AssertUtils.TestArch(arch); if ("x86".equals(arch)) { final byte[] decoder = XorStub(); final byte[] payload = XorEncoder.encode(data); return CommonUtils.join(decoder, payload); } if ("x64".equals(arch)) { final byte[] decoder = CommonUtils.readResource("resources/xor64.bin"); final byte[] payload = XorEncoder.encode(data); return CommonUtils.join(decoder, payload); } return new byte[0]; } public static byte[] XorEncode(final byte[] data, final String arch) { if (License.isTrial()) { CommonUtils.print_trial("Disabled " + arch + " payload stage encoding."); return data; } AssertUtils.Test(data.length > 16384, "XorEncode used on a stager (or some other small thing)"); return _XorEncode(data, arch); }
试用版不会进行payload stage encoding
,所以试用版软件包中并没有带xor.bin/xor64.bin文件,如果有这两个文件的话,可以添加到resources/xor.bin
、resources/xor64.bin
路径下。
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