SnakeAppleSecurityFiles/README.md

Snake & Apple

The code repository for the Snake&Apple article series, which documents my research about macOS security.

Each article directory contains three subdirectories:

• mac - source code of macOS for references.
• custom - code, for example, programs written for articles.
• python - contains the latest CrimsonUroboros and other Python scripts created during research.

ARTICLES

• ☑ I. Mach-O
• ☑ II. Code Signing
• ☑ III. Checksec
• ☑ IV. Dylibs
• ☐ V. Dyld
  • ☑ DYLD — Do You Like Death? (I)
  • ☑ DYLD — Do You Like Death? (II)
  • ☑ DYLD — Do You Like Death? (III)

TOOLS

CrimsonUroboros • MachOFileFinder • TrustCacheParser • SignatureReader • extract_cms.sh • ModifyMachOFlags • LCFinder • MachODylibLoadCommandsFinder

---

CrimsonUroboros

Core program resulting from the Snake&Apple article series for binary analysis. You may find older versions of this script in each article directory in this repository.

• Usage

usage: CrimsonUroboros [-h] -p PATH [--file_type] [--header_flags] [--endian] [--header] [--load_commands] [--segments] [--sections] [--symbols] [--chained_fixups] [--exports_trie]
                       [--uuid] [--main] [--encryption_info [(optional) save_path.bytes]] [--strings_section] [--all_strings] [--save_strings all_strings.txt] [--info]
                       [--verify_signature] [--cd_info] [--cd_requirements] [--entitlements [human|xml|var]] [--extract_cms cms_signature.der]
                       [--extract_certificates certificate_name] [--remove_sig unsigned_binary] [--sign_binary [adhoc|identity_number]] [--has_pie] [--has_arc] [--is_stripped]
                       [--has_canary] [--has_nx_stack] [--has_nx_heap] [--has_xn] [--is_notarized] [--is_encrypted] [--has_restrict] [--is_hr] [--is_as] [--is_fort] [--has_rpath]
                       [--has_lv] [--checksec] [--dylibs] [--rpaths] [--rpaths_u] [--dylibs_paths] [--dylibs_paths_u] [--broken_relative_paths]
                       [--dylibtree [cache_path,output_path,is_extracted]] [--dylib_id] [--reexport_paths] [--hijack_sec] [--dylib_hijacking [cache_path]]
                       [--dylib_hijacking_a [cache_path]] [--prepare_dylib [target_dylib_path]]

Mach-O files parser for binary analysis

options:
  -h, --help            show this help message and exit
  -p PATH, --path PATH  Path to the Mach-O file

MACH-O ARGS:
  --file_type           Print binary file type
  --header_flags        Print binary header flags
  --endian              Print binary endianess
  --header              Print binary header
  --load_commands       Print binary load commands names
  --segments            Print binary segments in human-friendly form
  --sections            Print binary sections in human-friendly form
  --symbols             Print all binary symbols
  --chained_fixups      Print Chained Fixups information
  --exports_trie        Print Export Trie information
  --uuid                Print UUID
  --main                Print entry point and stack size
  --encryption_info [(optional) save_path.bytes]
                        Print encryption info if any. Optionally specify an output path to dump the encrypted data (if cryptid=0, data will be in plain text)
  --strings_section     Print strings from __cstring section
  --all_strings         Print strings from all sections
  --save_strings all_strings.txt
                        Parse all sections, detect strings, and save them to a file
  --info                Print header, load commands, segments, sections, symbols, and strings

CODE SIGNING ARGS:
  --verify_signature    Code Signature verification (if the contents of the binary have been modified)
  --cd_info             Print Code Signature information
  --cd_requirements     Print Code Signature Requirements
  --entitlements [human|xml|var]
                        Print Entitlements in a human-readable, XML, or DER format (default: human)
  --extract_cms cms_signature.der
                        Extract CMS Signature from the Code Signature and save it to a given file
  --extract_certificates certificate_name
                        Extract Certificates and save them to a given file. To each filename will be added an index at the end: _0 for signing, _1 for intermediate, and _2 for root CA
                        certificate
  --remove_sig unsigned_binary
                        Save the new file on a disk with removed signature
  --sign_binary [adhoc|identity_number]
                        Sign binary using specified identity - use : 'security find-identity -v -p codesigning' to get the identity (default: adhoc)

CHECKSEC ARGS:
  --has_pie             Check if Position-Independent Executable (PIE) is set
  --has_arc             Check if Automatic Reference Counting (ARC) is in use (can be false positive)
  --is_stripped         Check if binary is stripped
  --has_canary          Check if Stack Canary is in use (can be false positive)
  --has_nx_stack        Check if stack is non-executable (NX stack)
  --has_nx_heap         Check if heap is non-executable (NX heap)
  --has_xn              Check if binary is protected by eXecute Never (XN) ARM protection
  --is_notarized        Check if the application is notarized and can pass the Gatekeeper verification
  --is_encrypted        Check if the application is encrypted (has LC_ENCRYPTION_INFO(_64) and cryptid set to 1)
  --has_restrict        Check if binary has __RESTRICT segment
  --is_hr               Check if the Hardened Runtime is in use
  --is_as               Check if the App Sandbox is in use
  --is_fort             Check if the binary is fortified
  --has_rpath           Check if the binary utilise any @rpath variables
  --has_lv              Check if the binary has Library Validation (protection against Dylib Hijacking)
  --checksec            Run all checksec module options on the binary

DYLIBS ARGS:
  --dylibs              Print shared libraries used by specified binary with compatibility and the current version (loading paths unresolved, like @rpath/example.dylib)
  --rpaths              Print all paths (resolved) that @rpath can be resolved to
  --rpaths_u            Print all paths (unresolved) that @rpath can be resolved to
  --dylibs_paths        Print absolute dylib loading paths (resolved @rpath|@executable_path|@loader_path) in order they are searched for
  --dylibs_paths_u      Print unresolved dylib loading paths.
  --broken_relative_paths
                        Print 'broken' relative paths from the binary (cases where the dylib source is specified for an executable directory without @executable_path)
  --dylibtree [cache_path,output_path,is_extracted]
                        Print the dynamic dependencies of a Mach-O binary recursively. You can specify the Dyld Shared Cache path in the first argument, the output directory as the
                        2nd argument, and if you have already extracted DSC in the 3rd argument (0 or 1). The output_path will be used as a base for dylibtree. For example, to not
                        extract DSC, use: --dylibs ",,1", or to extract from default to default use just --dylibs or --dylibs ",,0" which will extract DSC to
                        extracted_dyld_share_cache/ in the current directory
  --dylib_id            Print path from LC_ID_DYLIB
  --reexport_paths      Print paths from LC_REEXPORT_DLIB
  --hijack_sec          Check if binary is protected against Dylib Hijacking
  --dylib_hijacking [cache_path]
                        Check for possible Direct and Indirect Dylib Hijacking loading paths. The output is printed to console and saved in JSON format to
                        /tmp/dylib_hijacking_log.json(append mode). (optional)Specify the path to the Dyld Shared Cache
  --dylib_hijacking_a [cache_path]
                        Like --dylib_hijacking, but shows only possible vectors (without protected binaries)
  --prepare_dylib [target_dylib_path]
                        Compile rogue dylib. (optional) Specify target_dylib_path, it will search for the imported symbols from it in the dylib specified in the --path argument and
                        automatically add it to the source code of the rogue lib. Example: --path lib1.dylib --prepare_dylib /path/to/lib2.dylib

• Example:

CrimsonUroboros.py -p PATH --info

---

MachOFileFinder

Designed to find ARM64 Mach-O binaries within a specified directory and print their file type.

• Usage:

python MachOFileFinder.py PATH

• Example:

python MachOFileFinder.py . -r 2>/dev/null
EXECUTE:/Users/karmaz95/t/pingsender
DYLIB:/Users/karmaz95/t/dylibs/use_dylib_app/customs/custom.dylib
BUNDLE:/Users/karmaz95/t/bundles/MyBundle

---

TrustCacheParser

Designed to parse trust caches and print it in human readable form (based on PyIMG4 and trustcache)

• Usage:

usage: TrustCacheParser [-h] [--dst DST] [--parse_img] [--parse_tc] [--print_tc] [--all]

Copy Trust Cache files to a specified destination.

options:
  -h, --help         show this help message and exit
  --dst DST, -d DST  Destination directory to copy Trust Cache files to.
  --parse_img        Parse copied Image4 to extract payload data.
  --parse_tc         Parse extract payload data to human-readable form trust cache using
                     trustcache.
  --print_tc         Print the contents of trust_cache (files must be in the current
                     directory and ends with .trust_cache)
  --all              parse_img -> parse_tc -> print_tc

---

SignatureReader

Designed to parse extracted cms sginature from Mach-O files.

• Usage:

# First extract CMS Signature using CrimsonUroboros 
CrimsonUroboros -p target_binary --extract_cms cms_sign
# or using extract_cms.sh script
./extract_cms.sh target_binary cms_sign

usage: SignatureReader [-h] [--load_cms cms_signature.der]
                       [--extract_signature cms_signature.der]
                       [--extract_pubkey cert_0] [--human]

CMS Signature Loader

options:
  -h, --help            show this help message and exit
  --load_cms cms_signature.der
                        Load the DER encoded CMS Signature from the filesystem
                        and print it
  --extract_signature cms_signature.der
                        Extract and print the signature part from the DER
                        encoded CMS Signature
  --extract_pubkey cert_0
                        Extract public key from the given certificate and save
                        it to extracted_pubkey.pem
  --human               Print in human-readable format
❯ CrimsonUroboros -p signed_ad_hoc_example --extract_cms cms_sign

• Example:

SignatureReader --extract_signature cms_sign --human
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

---

extract_cms.sh

Designed to extract cms sginature from Mach-O files (bash alternative to SingatureReader --extract_signature).

• Example:

./extract_cms.sh target_binary cms_sign

---

ModifyMachOFlags

Designed to change Mach-O header flags.

• Usage:

usage: ModifyMachOFlags [-h] -i INPUT -o OUT [--flag FLAG] [--sign_binary [adhoc|identity_number]]

Modify the Mach-O binary flags.

options:
  -h, --help            show this help message and exit
  -i INPUT, --input INPUT
                        Path to the Mach-O file.
  -o OUT, --out OUT     Where to save a modified file.
  --flag FLAG           Specify the flag constant name and value (e.g., NO_HEAP_EXECUTION=1). Can be used multiple times. Available
                        flags: NOUNDEFS, INCRLINK, DYLDLINK, BINDATLOAD, PREBOUND, SPLIT_SEGS, LAZY_INIT, TWOLEVEL, FORCE_FLAT,
                        NOMULTIDEFS, NOFIXPREBINDING, PREBINDABLE, ALLMODSBOUND, SUBSECTIONS_VIA_SYMBOLS, CANONICAL, WEAK_DEFINES,
                        BINDS_TO_WEAK, ALLOW_STACK_EXECUTION, ROOT_SAFE, SETUID_SAFE, NO_REEXPORTED_DYLIBS, PIE,
                        DEAD_STRIPPABLE_DYLIB, HAS_TLV_DESCRIPTORS, NO_HEAP_EXECUTION, APP_EXTENSION_SAFE,
                        NLIST_OUTOFSYNC_WITH_DYLDINFO, SIM_SUPPORT, DYLIB_IN_CACHE
  --sign_binary [adhoc|identity_number]
                        Sign binary using specified identity - use : 'security find-identity -v -p codesigning' to get the
                        identity. (default: adhoc)

• Example:

ModifyMachOFlags -i hello -o hello_modified --flag NO_HEAP_EXECUTION=1 --sign_binary

---

LCFinder

Designed to find if specified Load Command exist in the binary or list of binaries.

• Usage:

usage: LCFinder [-h] [--path PATH] [--list_path LIST_PATH] --lc LC

Check for a specific load command in Mach-O binaries.

options:
  -h, --help            show this help message and exit
  --path PATH, -p PATH  Absolute path to the valid MachO binary.
  --list_path LIST_PATH, -l LIST_PATH
                        Path to a wordlist file containing absolute paths.
  --lc LC               The load command to check for.

• Example:

LCFinder -l macho_paths.txt --lc SEGMENT_64 2>/dev/null
LCFinder -p hello --lc lc_segment_64 2>/dev/null

---

MachODylibLoadCommandsFinder

Designed to Recursively crawl the system and parse Mach-O files to find DYLIB related load commands. Print the total Mach-O files analyzed and how many DYLIB-related LCs existed

• Usage:

MachODylibLoadCommandsFinder 2>/dev/null

INSTALL

pip3 install -r requirements.txt
wget https://github.com/CRKatri/trustcache/releases/download/v2.0/trustcache_macos_arm64 -O /usr/local/bin/trustcache
chmod +x /usr/local/bin/trustcache
xattr -d com.apple.quarantine /usr/local/bin/trustcache
brew install keith/formulae/dyld-shared-cache-extractor
brew install blacktop/tap/ipsw

LIMITATIONS

• Codesigning module(codesign wrapper) works only on macOS.
• --dylib_hijacking needs ipsw to be installed.
• --dylibtree needs the dyld-shared-cache-extractor to be installed.

WHY UROBOROS?

I will write the code for each article as a class SnakeX, where X will be the article number. To make it easier for the audience to follow. Each Snake class will be a child of the previous one and infinitely "eat itself" (inherit methods of the previous class), like Uroboros.

ADDITIONAL LINKS

• Apple Open Source
• XNU
• dyld

TODO - IDEAS / IMPROVES

• DER Entitlements converter method - currently, only the convert_xml_entitlements_to_dict() method exists. I need to create a Python parser for DER-encoded entitlements.
• SuperBlob parser - to find other blobs in Code Signature.
• Entitlements Blob parser - to check if XML and DER blobs exist.
• Every method in the Snake class that use Entitlements should parse first XML > DER (currently, only XML parser exists)
• After making a SuperBlob parser and CodeDirectory blob parser, modify hasHardenedRuntime to check Runtime flag by using bitmask, instead of string.
• Build Dyld Shared Cache parser and extractor to make SnakeIV independant of dyld-shared-cache-extractor.
• Make testing branch and implement tests, before pushing new updates.
• Create RottenApple.app in another repository and use it for testing.