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.
- ☑ I. Mach-O
- ☑ II. Code Signing
- ☑ III. Checksec
- ☑ IV. Dylibs
- ☑ V. Dyld
- ☑ DYLD — Do You Like Death? (I) - Startup | kernArgs | rebaseSelf | initializeLibc | task_self_trap | stack_guard | findArgv | findEnvp | findApple
- ☑ DYLD — Do You Like Death? (II) - handleDyldInCache| isBuiltForSimulator | isTranslated | crossarch_trap | Calling Convention on ARM64v8 | __unused attribute | Dyld Shared Region | thisDyldUuid | hasExistingDyldCache | shared_region_check_np | Carry flag | dynamic data header | dyldInCacheMH
- ☑ DYLD — Do You Like Death? (III) - handleDyldInCache | DYLD_IN_CACHE | restartWithDyldInCache | dyld_all_image_infos | calculating offset for debugging Dyld in Cache
- ☑ DYLD — Do You Like Death? (IV) - RuntimeLocks | MemoryManager | dyld_hw_tpro | Lambda Capture | withWritableMemory | PAC | arm64e_preview_abi | __ptrauth_dyld_tpro0 | WriteProtectionState | previousState | os_compiler_barrier |
- ☑ DYLD — Do You Like Death? (V) - Linker Standard Library | EphemeralAllocator | Dyld Private Memory | PersistentAllocator | vm_allocate | vm_protect | _kernelrpc_mach_vm_allocate_trap | _kernelrpc_mach_vm_protect_trap
- ☑ DYLD — Do You Like Death? (VI) - ProcessConfig | Process::Process | Process::Security | csr_check | CSR_ALLOW_APPLE_INTERNAL | csrctl | syscall_csr_check | AMFI | internalInstall | isRestricted | isFairPlayEncrypted | amfiFlags | amfi_check_dyld_policy_self | ___sandbox_ms | ___mac_syscall | mpo_policy_syscall_t | MAC policy | com.apple.driver.AppleMobileFileIntegrity | _policy_syscall | _check_dyld_policy_internal | macos_Dyld_policy_collect_state | logDyldPolicyData | DYLD_AMFI_FAKE | getAMFI | pruneEnvVars | com.apple.security.cs.allow-dyld-environment-variables
- ☑ DYLD — Do You Like Death? (VII) - ProcessConfig | Process::Logging | Process::dyldCache | DYLD_PRINT_TO_STDERR | DYLD_PRINT_INTERPOSING | allowEnvVarsSharedCache | allowEnvVarsPrint | openLogFile | DYLD_PRINT_TO_FILE | BSD open syscall | DYLD_SHARED_REGION | Shared Library Cache | DYLD_SHARED_CACHE_DIR | dyldCache | CacheFinder | Ignite | ignitionPayload | ignition | open_console | log_init | sysctlbyname | __sysctl | dyld_parse_boot_arg_int | dyld_parse_boot_arg_cstr | libignition | boot_init | stage_fire | getDyldCache | loadDyldCache | mapSplitCachePrivate | reuseExistingCache | mapSplitCacheSystemWide | jettison
- ☑ DYLD — Do You Like Death? (VIII) - ProcessConfig | Process::PathOverrides | Overrides and path fallbacks for Dylibs | security.allowEnvVarsPath | crashMsg | addEnvVar | DYLD_LIBRARY_PATH | DYLD_FRAMEWORK_PATH | DYLD_FALLBACK_FRAMEWORK_PATH | DYLD_FALLBACK_LIBRARY_PATH | DYLD_VERSIONED_FRAMEWORK_PATH | DYLD_VERSIONED_LIBRARY_PATH | DYLD_INSERT_LIBRARIES | DYLD_IMAGE_SUFFIX | DYLD_ROOT_PATH | _dylibPathOverridesExeLC | _dylibPathOverridesEnv | isLC_DYLD_ENV | CRSetCrashLogMessage2 | LC_DYLD_ENVIRONMENT | allowEmbeddedVars | _insertedDylibs | cryptexOSPath | VersionedPaths | processVersionedPaths | checkVersionedPath | LC_ID_DYLIB | sys.getDylibInfo | addPathOverride | dontUsePrebuiltForApp | adjustDevelopmentMode
- ☑ DYLD — Do You Like Death? (IX) - RuntimeState | ProcessConfig | finalizeListTLV | FileManager | _fsUUIDMap | OrderedMap | UUIDs | PermanentRanges | state APIs
- ☑ DYLD — Do You Like Death? (X) - ExternallyViewableState | externallyViewable.init | dyld_all_image_info | exec_prefault_data | task_info | com.apple.security.get-task-allow | get_dyld_info | lsl:Vector | ProcessSnapshot | compact info | makeUnique | release | setDyldState | setInitialExternallyVisibleState | setShareCacheInfo | setDyld | inDyldCache | DYLD_IN_CACHE | recordFromInfo | FileRecord | Image | addImage | _snapshot | addImageInfo | setInitialImageCount | commit | compactInfoData | RemoteNotificationResponder
- ☑ VI. AMFI
CrimsonUroboros • MachOFileFinder • TrustCacheParser • SignatureReader • extract_cms.sh • ModifyMachOFlags • LCFinder • MachODylibLoadCommandsFinder
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] [--has_cmd LC_MAIN]
[--segments] [--has_segment __SEGMENT] [--sections]
[--has_section __SEGMENT,__section] [--symbols]
[--imports] [--exports] [--imported_symbols]
[--chained_fixups] [--exports_trie] [--uuid] [--main]
[--encryption_info [(optional) save_path.bytes]]
[--strings_section] [--all_strings]
[--save_strings all_strings.txt] [--info]
[--dump_data [offset,size,output_path]]
[--calc_offset vm_offset] [--constructors]
[--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]] [--cs_offset]
[--cs_flags] [--has_pie] [--has_arc] [--is_stripped]
[--has_canary] [--has_nx_stack] [--has_nx_heap]
[--has_xn] [--is_notarized] [--is_encrypted]
[--is_restricted] [--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 [(optional) cache_path]]
[--dylib_hijacking_a [cache_path]]
[--prepare_dylib [(optional) target_dylib_name]]
[--is_built_for_sim] [--get_dyld_env]
[--compiled_with_dyld_env] [--has_interposing]
[--interposing_symbols]
[--dump_prelink_info [(optional) out_name]]
[--dump_prelink_text [(optional) out_name]]
[--dump_prelink_kext [kext_name]]
[--kext_prelinkinfo [kext_name]]
[--kmod_info kext_name] [--kext_entry kext_name]
[--kext_exit kext_name] [--mig] [--has_suid]
[--has_sgid] [--has_sticky] [--injectable_dyld]
[--test_insert_dylib] [--test_prune_dyld]
[--test_dyld_print_to_file]
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
--has_cmd LC_MAIN Check of binary has given load command
--segments Print binary segments in human-friendly form
--has_segment __SEGMENT
Check if binary has given '__SEGMENT'
--sections Print binary sections in human-friendly form
--has_section __SEGMENT,__section
Check if binary has given '__SEGMENT,__section'
--symbols Print all binary symbols
--imports Print imported symbols
--exports Print exported symbols
--imported_symbols Print symbols imported from external libraries with
dylib names
--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
--dump_data [offset,size,output_path]
Dump {size} bytes starting from {offset} to a given
{filename} (e.g. '0x1234,0x1000,out.bin')
--calc_offset vm_offset
Calculate the real address (file on disk) of the given
Virtual Memory {vm_offset} (e.g. 0xfffffe000748f580)
--constructors Print binary constructors
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]
Sign binary using specified identity - use : 'security
find-identity -v -p codesigning' to get the identity
(default: adhoc)
--cs_offset Print Code Signature file offset
--cs_flags Print Code Signature flags
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)
--is_restricted Check if binary has __RESTRICT segment or CS_RESTRICT
flag set
--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 [(optional) 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).
Optionally, 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 [(optional) target_dylib_name]
Compile rogue dylib. Optionally, 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
DYLD ARGS:
--is_built_for_sim Check if binary is built for simulator platform.
--get_dyld_env Extract Dyld environment variables from the loader
binary.
--compiled_with_dyld_env
Check if binary was compiled with -dyld_env flag and
print the environment variables and its values.
--has_interposing Check if binary has interposing sections.
--interposing_symbols
Print interposing symbols if any.
AMFI ARGS:
--dump_prelink_info [(optional) out_name]
Dump "__PRELINK_INFO,__info" to a given file (default:
"PRELINK_info.txt")
--dump_prelink_text [(optional) out_name]
Dump "__PRELINK_TEXT,__text" to a given file (default:
"PRELINK_text.txt")
--dump_prelink_kext [kext_name]
Dump prelinked KEXT {kext_name} from decompressed
Kernel Cache PRELINK_TEXT segment to a file named:
prelinked_{kext_name}.bin
--kext_prelinkinfo [kext_name]
Print _Prelink properties from PRELINK_INFO,__info for
a give {kext_name}
--kmod_info kext_name
Parse kmod_info structure for the given {kext_name}
from Kernel Cache
--kext_entry kext_name
Calculate the virtual memory address of the __start
(entrpoint) for the given {kext_name} Kernel Extension
--kext_exit kext_name
Calculate the virtual memory address of the __stop
(exitpoint) for the given {kext_name} Kernel Extension
--mig Search for MIG subsystem and prints message handlers
--has_suid Check if the file has SetUID bit set
--has_sgid Check if the file has SetGID bit set
--has_sticky Check if the file has sticky bit set
--injectable_dyld Check if the binary is injectable using
DYLD_INSERT_LIBRARIES
--test_insert_dylib Check if it is possible to inject dylib using
DYLD_INSERT_LIBRARIES (INVASIVE - the binary is
executed)
--test_prune_dyld Check if Dyld Environment Variables are cleared (using
DYLD_PRINT_INITIALIZERS=1) (INVASIVE - the binary is
executed)
--test_dyld_print_to_file
Check if YLD_PRINT_TO_FILE Dyld Environment Variables
works (INVASIVE - the binary is executed)
- Example:
CrimsonUroboros.py -p PATH --infoDesigned 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/MyBundleDesigned 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_tcDesigned 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_signusage: 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
0x25ca80ad5f11be197dc7a2d53f3db5b6bf463a38224db8c0a17fa4b8fd5ad7e0c60f2be8e8849cf2e581272290991c0db40b0d452b2d2dbf230c0ccab3a6d78e0230bca7bccbc50d379372bcddd8d8542add5ec59180bc3409b2df3bd8995301b9ba1e65ac62420c75104f12cb58b430fde8a177a1cd03940d4b0e77a9d875d65552cf96f03cb63b437c36d9bab12fa727e17603da49fcb870edaec115f90def1ac2ad12c2e9349a5470b5ed2f242b5566cd7ddee785eff8ae5484f145a8464d4dc3891b10a3b2981e9add1e4c0aec31fa80320eb5494d9623400753adf24106efdd07ad657035ed2876e9460219944a4730b0b620954961350ddb1fcf0ea539Designed to extract cms sginature from Mach-O files (bash alternative to SingatureReader --extract_signature).
- Example:
./extract_cms.sh target_binary cms_sign
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_binaryDesigned 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/nullDesigned 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/nullSimple script for calculating amfiFlags (described here in ProcessConfig — AMFI properties)
- Usage:
python3 check_amfi.py 0x1dfpip3 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
- Codesigning module(codesign wrapper) works only on macOS.
--dylib_hijackingneeds ipsw to be installed.--dylibtreeneeds the dyld-shared-cache-extractor to be installed.
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.
- 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.
- Create
RottenApple.appin another repository and use it for testing. - Add Dyld Closure chapter to Snake&Apple V - Dyld
- Move
kext_prelinkinfo,dumpPrelink_infoanddumpPrelink_textto Snake & Apple chapter about Kernel Extensions when ready. - Add kernelcache parser.
- Add
LC_FILESET_ENTRYmethod todumpKernelExtension. - Consider moving methods like
removeNullBytesAlignment,calcTwoComplement64etc. toUtilsclass. - Move
--migoption to Snake & Apple chapter about Mach Kernel when ready. - Make Thread manager class and improve the Threading.thread with tracing methods and
kill().