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| macos-sandbox-debug-and-bypass.md | ||
| README.md | ||
macOS Sandbox
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Basic Information
MacOS Sandbox (initially called Seatbelt) limits applications running inside the sandbox to the allowed actions specified in the Sandbox profile the app is running with. This helps to ensure that the application will be accessing only expected resources.
Any app with the entitlement com.apple.security.app-sandbox will be executed inside the sandbox. Apple binaries are usually executed inside a Sanbox and in order to publish inside the App Store, this entitlement is mandatory. So most applications will be executed inside the sandbox.
In order to control what a process can or cannot do the Sandbox has hooks in all syscalls across the kernel. Depending on the entitlements of the app the Sandbox will allow certain actions.
Some important components of the Sandbox are:
- The kernel extension
/System/Library/Extensions/Sandbox.kext - The private framework
/System/Library/PrivateFrameworks/AppSandbox.framework - A daemon running in userland
/usr/libexec/sandboxd - The containers
~/Library/Containers
Inside the containers folder you can find a folder for each app executed sanboxed with the name of the bundle id:
ls -l ~/Library/Containers
total 0
drwx------@ 4 username staff 128 May 23 20:20 com.apple.AMPArtworkAgent
drwx------@ 4 username staff 128 May 23 20:13 com.apple.AMPDeviceDiscoveryAgent
drwx------@ 4 username staff 128 Mar 24 18:03 com.apple.AVConference.Diagnostic
drwx------@ 4 username staff 128 Mar 25 14:14 com.apple.Accessibility-Settings.extension
drwx------@ 4 username staff 128 Mar 25 14:10 com.apple.ActionKit.BundledIntentHandler
[...]
Inside each bundle id folder you can find the plist and the Data directory of the App:
cd /Users/username/Library/Containers/com.apple.Safari
ls -la
total 104
drwx------@ 4 username staff 128 Mar 24 18:08 .
drwx------ 348 username staff 11136 May 23 20:57 ..
-rw-r--r-- 1 username staff 50214 Mar 24 18:08 .com.apple.containermanagerd.metadata.plist
drwx------ 13 username staff 416 Mar 24 18:05 Data
ls -l Data
total 0
drwxr-xr-x@ 8 username staff 256 Mar 24 18:08 CloudKit
lrwxr-xr-x 1 username staff 19 Mar 24 18:02 Desktop -> ../../../../Desktop
drwx------ 2 username staff 64 Mar 24 18:02 Documents
lrwxr-xr-x 1 username staff 21 Mar 24 18:02 Downloads -> ../../../../Downloads
drwx------ 35 username staff 1120 Mar 24 18:08 Library
lrwxr-xr-x 1 username staff 18 Mar 24 18:02 Movies -> ../../../../Movies
lrwxr-xr-x 1 username staff 17 Mar 24 18:02 Music -> ../../../../Music
lrwxr-xr-x 1 username staff 20 Mar 24 18:02 Pictures -> ../../../../Pictures
drwx------ 2 username staff 64 Mar 24 18:02 SystemData
drwx------ 2 username staff 64 Mar 24 18:02 tmp
{% hint style="danger" %}
Note that even if the symlinks are there to "escape" from the Sandbox and access other folders, the App still needs to have permissions to access them. These permissions are inside the .plist.
{% endhint %}
# Get permissions
plutil -convert xml1 .com.apple.containermanagerd.metadata.plist -o -
# In this file you can find the entitlements:
<key>Entitlements</key>
<dict>
<key>com.apple.MobileAsset.PhishingImageClassifier2</key>
<true/>
<key>com.apple.accounts.appleaccount.fullaccess</key>
<true/>
<key>com.apple.appattest.spi</key>
<true/>
[...]
# Some parameters
<key>Parameters</key>
<dict>
<key>_HOME</key>
<string>/Users/username</string>
<key>_UID</key>
<string>501</string>
<key>_USER</key>
<string>username</string>
[...]
# The paths it can access
<key>RedirectablePaths</key>
<array>
<string>/Users/username/Downloads</string>
<string>/Users/username/Documents</string>
<string>/Users/username/Library/Calendars</string>
<string>/Users/username/Desktop</string>
[...]
Sandbox Profiles
The Sandbox profiles are configuration files that indicates what is going to be allowed/forbidden in that Sandbox. It uses the Sandbox Profile Language (SBPL), which uses the Scheme programming language.
Here you can find an example:
(version 1) ; First you get the version
(deny default) ; Then you shuold indicate the default action when no rule applies
(allow network*) ; You can use wildcards and allow everything
(allow file-read* ; You can specify where to apply the rule
(subpath "/Users/username/")
(literal "/tmp/afile")
(regex #"^/private/etc/.*")
)
(allow mach-lookup
(global-name "com.apple.analyticsd")
)
{% hint style="success" %} Check this research to check more actions that could be allowed or denied. {% endhint %}
Important system services also run inside their own custom sandbox such as the mdnsresponder service. You can view these custom sandbox profiles inside:
/usr/share/sandbox/System/Library/Sandbox/Profiles- Other sandbox profiles can be checked in https://github.com/s7ephen/OSX-Sandbox--Seatbelt--Profiles.
App Store apps use the profile /System/Library/Sandbox/Profiles/application.sb. You can check in this profile how entitlements such as com.apple.security.network.server allows a process to use the network.
SIP is a Sandbox profile called platform_profile in /System/Library/Sandbox/rootless.conf
Sandbox Profile Examples
To start an application with an specific sandbox profile you can use:
sandbox-exec -f example.sb /Path/To/The/Application
{% tabs %} {% tab title="touch" %} {% code title="touch.sb" %}
(version 1)
(deny default)
(allow file* (literal "/tmp/hacktricks.txt"))
{% endcode %}
# This will fail because default is denied, so it cannot execute touch
sandbox-exec -f touch.sb touch /tmp/hacktricks.txt
# Check logs
log show --style syslog --predicate 'eventMessage contains[c] "sandbox"' --last 30s
[...]
2023-05-26 13:42:44.136082+0200 localhost kernel[0]: (Sandbox) Sandbox: sandbox-exec(41398) deny(1) process-exec* /usr/bin/touch
2023-05-26 13:42:44.136100+0200 localhost kernel[0]: (Sandbox) Sandbox: sandbox-exec(41398) deny(1) file-read-metadata /usr/bin/touch
2023-05-26 13:42:44.136321+0200 localhost kernel[0]: (Sandbox) Sandbox: sandbox-exec(41398) deny(1) file-read-metadata /var
2023-05-26 13:42:52.701382+0200 localhost kernel[0]: (Sandbox) 5 duplicate reports for Sandbox: sandbox-exec(41398) deny(1) file-read-metadata /var
[...]
{% code title="touch2.sb" %}
(version 1)
(deny default)
(allow file* (literal "/tmp/hacktricks.txt"))
(allow process* (literal "/usr/bin/touch"))
; This will also fail because:
; 2023-05-26 13:44:59.840002+0200 localhost kernel[0]: (Sandbox) Sandbox: touch(41575) deny(1) file-read-metadata /usr/bin/touch
; 2023-05-26 13:44:59.840016+0200 localhost kernel[0]: (Sandbox) Sandbox: touch(41575) deny(1) file-read-data /usr/bin/touch
; 2023-05-26 13:44:59.840028+0200 localhost kernel[0]: (Sandbox) Sandbox: touch(41575) deny(1) file-read-data /usr/bin
; 2023-05-26 13:44:59.840034+0200 localhost kernel[0]: (Sandbox) Sandbox: touch(41575) deny(1) file-read-metadata /usr/lib/dyld
; 2023-05-26 13:44:59.840050+0200 localhost kernel[0]: (Sandbox) Sandbox: touch(41575) deny(1) sysctl-read kern.bootargs
; 2023-05-26 13:44:59.840061+0200 localhost kernel[0]: (Sandbox) Sandbox: touch(41575) deny(1) file-read-data /
{% endcode %}
{% code title="touch3.sb" %}
(version 1)
(deny default)
(allow file* (literal "/private/tmp/hacktricks.txt"))
(allow process* (literal "/usr/bin/touch"))
(allow file-read-data (literal "/"))
; This one will work
{% endcode %} {% endtab %} {% endtabs %}
{% hint style="info" %} Note that the Apple-authored software that runs on Windows doesn’t have additional security precautions, such as application sandboxing. {% endhint %}
Bypasses examples:
- https://lapcatsoftware.com/articles/sandbox-escape.html
- https://desi-jarvis.medium.com/office365-macos-sandbox-escape-fcce4fa4123c (they are able to write files outside the sandbox whose name starts with
~$).
Debug & Bypass Sandbox
Processes are not born sandboxed on macOS: unlike iOS, where the sandbox is applied by the kernel before the first instruction of a program executes, on macOS a process must elect to place itself into the sandbox.
Processes are automatically Sandboxed from userland when they start if they have the entitlement: com.apple.security.app-sandbox. For a detailed explanation of this process check:
{% content-ref url="macos-sandbox-debug-and-bypass.md" %} macos-sandbox-debug-and-bypass.md {% endcontent-ref %}
Check PID Privileges
According to this, the sandbox_check (it's a __mac_syscall), can check if an operation is allowed or not by the sandbox in a certain PID.
The tool sbtool can check if a PID can perform a certain action:
sbtool <pid> mach #Check mac-ports (got from launchd with an api)
sbtool <pid> file /tmp #Check file access
sbtool <pid> inspect #Gives you an explaination of the sandbox profile
sbtool <pid> all
Custom SBPL in App Store apps
It could be possible for companies to make their apps run with custom Sandbox profiles (instead of with the default one). They need to use the entitlement com.apple.security.temporary-exception.sbpl which needs to be authorized by Apple.
It's possible to check the definition of this entitlement in /System/Library/Sandbox/Profiles/application.sb:
(sandbox-array-entitlement
"com.apple.security.temporary-exception.sbpl"
(lambda (string)
(let* ((port (open-input-string string)) (sbpl (read port)))
(with-transparent-redirection (eval sbpl)))))
This will eval the string after this entitlement as an Sandbox profile.
☁️ HackTricks Cloud ☁️ -🐦 Twitter 🐦 - 🎙️ Twitch 🎙️ - 🎥 Youtube 🎥
- Do you work in a cybersecurity company? Do you want to see your company advertised in HackTricks? or do you want to have access to the latest version of the PEASS or download HackTricks in PDF? Check the SUBSCRIPTION PLANS!
- Discover The PEASS Family, our collection of exclusive NFTs
- Get the official PEASS & HackTricks swag
- Join the 💬 Discord group or the telegram group or follow me on Twitter 🐦@carlospolopm.
- Share your hacking tricks by submitting PRs to the hacktricks repo and hacktricks-cloud repo.