SandBlaster: Reversing the Apple Sandbox
Cellebrite Fork
This fork was updated to work on iOS 16.5 and iOS 17 beta.
Authored by Yarden Hamami of Cellebrite Labs.
Description
SandBlaster is a tool for reversing (decompiling) binary Apple sandbox profiles. Apple sandbox profiles are written in SBPL (Sandbox Profile Language), a Scheme-like language, and are then compiled into an undocumented binary format and shipped. Primarily used on iOS, sandbox profiles are present on macOS as well. SandBlaster is, to our knowledge, the first tool that reverses binary sandbox profiles to their original SBPL format. SandBlaster works on iOS from version 7 onwards including iOS 11. This fork only supports iOS 16.5 and iOS 17 beta.
The technical report SandBlaster: Reversing the Apple Sandbox presents extensive (though a bit outdated) information on SandBlaster internals.
SandBlaster relied on previous work by Dionysus Blazakis and Stefan Esser's code and slides.
The reverser (in the reverse-sandbox/
folder) runs on any Python running platform.
Installation
SandBlaster requires Python3 for the reverser (in reverse-sandbox/
).
Usage
In order to use SandBlaster you need access to the binary sandbox profiles and the sandbox operations, a set of strings that define sandbox-specific actions. Sandbox profiles and sandbox operations are extracted from the kernel sandbox extension.
# Reverse all binary sandbox profiles.
cd ../reverse-sandbox/
mkdir iPad2,1_8.4.1_12H321.reversed_profiles
python3 reverse_sandbox.py -r 17 -o sandbox_operations sandbox_binary_profile -d output_directory/
The -psb
option for reverse_sandbox.py
prints out the sandbox profiles part of a sandbox bundle without doing the actual reversing.
The reverse_sandbox.py
script needs to be run in its directory (reverse-sandbox/
) since it needs the other Python modules and the logger.config
file.
Internals
The actual reverser is part of the reverse-sandbox/
folder. Files here can be categorized as follows:
- The main script is
reverse_sandbox.py
. It parses the command line arguments, does basic parsing of the input binary file (extracts sections) and calls the appropriate functions from the other modules. - The core of the implementation is
operation_node.py
. It provides functions to build the rules graph corresponding to the sandbox profile and to convert the graph to SBPL. It is called byreverse_sandbox.py
. - Sandbox filters (i.e. match rules inside sandbox profiles) are handled by the implementation in
sandbox_filter.py
and the configuration infilters.json
,filter_list.py
andfilters.py
. Filter specific functions are called byoperation_node.py
. - Regular expression reversing is handled by
sandbox_regex.py
andregex_parse.py
.regex_parse.py
is the back end parser that converts the binary representation to a basic graph.sandbox_regex.py
converts the graph representation (an automaton) to an actual regular expression (i.e. a string of characters and metacharacters). It is called byreverse_sandbox.py
for parsing regular expressions, with the resulting regular expression list being passed to the functions exposed byoperation_node.py
;operation_node.py
passes them on to sandbox filter handling files. - The new format for storing strings since iOS 10 is handled by
reverse_string.py
. The primarySandboxString
class inreverse_string.py
is used insandbox_filter.py
. - Logging is configured in the
logger.config
file. By default,INFO
and higher level messages are printed to the console, whileDEBUG
and higher level messages are printed to thereverse.log
file.
Supported iOS Versions
This fork only supports iOS 16.5 and iOS 17 sandbox format.