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mr-tz authored Sep 9, 2024
2 parents 7b7a680 + 44e6594 commit 963013c
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9 changes: 7 additions & 2 deletions .justfile
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@deptry:
pre-commit run deptry --hook-stage manual --all-files

lint: isort black ruff flake8 mypy deptry

@lint:
-just isort
-just black
-just ruff
-just flake8
-just mypy
-just deptry
6 changes: 5 additions & 1 deletion CHANGELOG.md
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## master (unreleased)

### New Features
Unlock powerful malware analysis with capa's new [VMRay sandbox](https://www.vmray.com/) integration! Simply provide a VMRay analysis archive, and capa will automatically extract and match capabilties, streamlining your workflow.

### New Features
- regenerate ruleset cache automatically on source change (only in dev mode) #2133 @s-ff
- add landing page https://mandiant.github.io/capa/ @williballenthin #2310
- add rules website https://mandiant.github.io/capa/rules @DeeyaSingh #2310
- add .justfile @williballenthin #2325
- dynamic: add support for VMRay dynamic sandbox traces #2208 @mike-hunhoff @r-sm2024 @mr-tz
- cli: use modern terminal features to hyperlink to the rules website #2337 @williballenthin
- support analyzing BinExport2 files generated by Ghidra #1950 @williballenthin @mehunhoff @mr-tz
- add support for Android OS #1950 @williballenthin @mehunhoff @mr-tz
- add support for aarch64 architecture via BinExport2 backend #1950 @williballenthin @mehunhoff @mr-tz
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22 changes: 12 additions & 10 deletions README.md
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Expand Up @@ -28,7 +28,7 @@ capa detects capabilities in executable files.
You run it against a PE, ELF, .NET module, shellcode file, or a sandbox report and it tells you what it thinks the program can do.
For example, it might suggest that the file is a backdoor, is capable of installing services, or relies on HTTP to communicate.

To interactively inspect capa results in your browser use the [capa web explorer](https://mandiant.github.io/capa/explorer/).
To interactively inspect capa results in your browser use the [capa explorer web](https://mandiant.github.io/capa/explorer/).

If you want to inspect or write capa rules, head on over to the [capa-rules repository](https://github.com/mandiant/capa-rules). Otherwise, keep reading.

Expand Down Expand Up @@ -89,12 +89,12 @@ Download stable releases of the standalone capa binaries [here](https://github.c

To use capa as a library or integrate with another tool, see [doc/installation.md](https://github.com/mandiant/capa/blob/master/doc/installation.md) for further setup instructions.

# web explorer
The [capa web explorer](https://mandiant.github.io/capa/explorer/) enables you to interactively explore capa results in your web browser. Besides the online version you can download a standalone HTML file for local offline usage.
# capa explorer web
The [capa explorer web](https://mandiant.github.io/capa/explorer/) enables you to interactively explore capa results in your web browser. Besides the online version you can download a standalone HTML file for local offline usage.

![capa web explorer screenshot](https://github.com/mandiant/capa/blob/master/doc/img/capa_web_explorer.png)
![capa explorer web screenshot](https://github.com/mandiant/capa/blob/master/doc/img/capa_web_explorer.png)

More details on the web UI is available in the [capa web explorer README](https://github.com/mandiant/capa/blob/master/web/explorer/README.md).
More details on the web UI is available in the [capa explorer web README](https://github.com/mandiant/capa/blob/master/web/explorer/README.md).

# example

Expand Down Expand Up @@ -150,13 +150,15 @@ function @ 0x4011C0
...
```

## analyzing sandbox reports
Additionally, capa also supports analyzing sandbox reports for dynamic capability extraction.
In order to use this, you first submit your sample to one of supported sandboxes for analysis, and then run capa against the generated report file.
capa also supports dynamic capabilities detection for multiple sandboxes including:
* [CAPE](https://github.com/kevoreilly/CAPEv2) (supported report formats: `.json`, `.json_`, `.json.gz`)
* [DRAKVUF](https://github.com/CERT-Polska/drakvuf-sandbox/) (supported report formats: `.log`, `.log.gz`)
* [VMRay](https://www.vmray.com/) (supported report formats: analysis archive `.zip`)

Currently, capa supports the [CAPE sandbox](https://github.com/kevoreilly/CAPEv2) and the [DRAKVUF sandbox](https://github.com/CERT-Polska/drakvuf-sandbox/). In order to use either, simply run capa against the generated file (JSON for CAPE or LOG for DRAKVUF sandbox) and it will automatically detect the sandbox and extract capabilities from it.

Here's an example of running capa against a packed binary, and then running capa against the CAPE report of that binary:
To use this feature, submit your file to a supported sandbox and then download and run capa against the generated report file. This feature enables capa to match capabilities against dynamic and static features that the sandbox captured during execution.

Here's an example of running capa against a packed file, and then running capa against the CAPE report generated for the same packed file:

```yaml
$ capa 05be49819139a3fdcdbddbdefd298398779521f3d68daa25275cc77508e42310.exe
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2 changes: 2 additions & 0 deletions capa/features/common.py
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Expand Up @@ -463,6 +463,7 @@ def evaluate(self, features: "capa.engine.FeatureSet", short_circuit=True):
FORMAT_SC64 = "sc64"
FORMAT_CAPE = "cape"
FORMAT_DRAKVUF = "drakvuf"
FORMAT_VMRAY = "vmray"
FORMAT_BINEXPORT2 = "binexport2"
FORMAT_FREEZE = "freeze"
FORMAT_RESULT = "result"
Expand All @@ -479,6 +480,7 @@ def evaluate(self, features: "capa.engine.FeatureSet", short_circuit=True):
DYNAMIC_FORMATS = {
FORMAT_CAPE,
FORMAT_DRAKVUF,
FORMAT_VMRAY,
FORMAT_FREEZE,
FORMAT_RESULT,
}
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161 changes: 161 additions & 0 deletions capa/features/extractors/vmray/__init__.py
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# Copyright (C) 2024 Mandiant, Inc. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at: [package root]/LICENSE.txt
# Unless required by applicable law or agreed to in writing, software distributed under the License
# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and limitations under the License.
import logging
from typing import Dict, List, Tuple, Optional
from pathlib import Path
from zipfile import ZipFile
from collections import defaultdict

from capa.exceptions import UnsupportedFormatError
from capa.features.extractors.vmray.models import File, Flog, SummaryV2, StaticData, FunctionCall, xml_to_dict

logger = logging.getLogger(__name__)

DEFAULT_ARCHIVE_PASSWORD = b"infected"

SUPPORTED_FLOG_VERSIONS = ("2",)


class VMRayAnalysis:
def __init__(self, zipfile_path: Path):
self.zipfile = ZipFile(zipfile_path, "r")

# summary_v2.json is the entry point to the entire VMRay archive and
# we use its data to find everything else that we need for capa
self.sv2 = SummaryV2.model_validate_json(
self.zipfile.read("logs/summary_v2.json", pwd=DEFAULT_ARCHIVE_PASSWORD)
)
self.file_type: str = self.sv2.analysis_metadata.sample_type

# flog.xml contains all of the call information that VMRay captured during execution
flog_xml = self.zipfile.read("logs/flog.xml", pwd=DEFAULT_ARCHIVE_PASSWORD)
flog_dict = xml_to_dict(flog_xml)
self.flog = Flog.model_validate(flog_dict)

if self.flog.analysis.log_version not in SUPPORTED_FLOG_VERSIONS:
raise UnsupportedFormatError(
"VMRay feature extractor does not support flog version %s" % self.flog.analysis.log_version
)

self.exports: Dict[int, str] = {}
self.imports: Dict[int, Tuple[str, str]] = {}
self.sections: Dict[int, str] = {}
self.process_ids: Dict[int, int] = {}
self.process_threads: Dict[int, List[int]] = defaultdict(list)
self.process_calls: Dict[int, Dict[int, List[FunctionCall]]] = defaultdict(lambda: defaultdict(list))
self.base_address: int

self.sample_file_name: Optional[str] = None
self.sample_file_analysis: Optional[File] = None
self.sample_file_static_data: Optional[StaticData] = None

self._find_sample_file()

# VMRay analysis archives in various shapes and sizes and file type does not definitively tell us what data
# we can expect to find in the archive, so to be explicit we check for the various pieces that we need at
# minimum to run capa analysis
if self.sample_file_name is None or self.sample_file_analysis is None:
raise UnsupportedFormatError("VMRay archive does not contain sample file (file_type: %s)" % self.file_type)

if not self.sample_file_static_data:
raise UnsupportedFormatError("VMRay archive does not contain static data (file_type: %s)" % self.file_type)

if not self.sample_file_static_data.pe and not self.sample_file_static_data.elf:
raise UnsupportedFormatError(
"VMRay feature extractor only supports PE and ELF at this time (file_type: %s)" % self.file_type
)

# VMRay does not store static strings for the sample file so we must use the source file
# stored in the archive
sample_sha256: str = self.sample_file_analysis.hash_values.sha256.lower()
sample_file_path: str = f"internal/static_analyses/{sample_sha256}/objects/files/{sample_sha256}"

logger.debug("file_type: %s, file_path: %s", self.file_type, sample_file_path)

self.sample_file_buf: bytes = self.zipfile.read(sample_file_path, pwd=DEFAULT_ARCHIVE_PASSWORD)

self._compute_base_address()
self._compute_imports()
self._compute_exports()
self._compute_sections()
self._compute_process_ids()
self._compute_process_threads()
self._compute_process_calls()

def _find_sample_file(self):
for file_name, file_analysis in self.sv2.files.items():
if file_analysis.is_sample:
# target the sample submitted for analysis
self.sample_file_name = file_name
self.sample_file_analysis = file_analysis

if file_analysis.ref_static_data:
# like "path": ["static_data","static_data_0"] where "static_data_0" is the summary_v2 static data
# key for the file's static data
self.sample_file_static_data = self.sv2.static_data[file_analysis.ref_static_data.path[1]]

break

def _compute_base_address(self):
assert self.sample_file_static_data is not None
if self.sample_file_static_data.pe:
self.base_address = self.sample_file_static_data.pe.basic_info.image_base

def _compute_exports(self):
assert self.sample_file_static_data is not None
if self.sample_file_static_data.pe:
for export in self.sample_file_static_data.pe.exports:
self.exports[export.address] = export.api.name

def _compute_imports(self):
assert self.sample_file_static_data is not None
if self.sample_file_static_data.pe:
for module in self.sample_file_static_data.pe.imports:
for api in module.apis:
self.imports[api.address] = (module.dll, api.api.name)

def _compute_sections(self):
assert self.sample_file_static_data is not None
if self.sample_file_static_data.pe:
for pefile_section in self.sample_file_static_data.pe.sections:
self.sections[pefile_section.virtual_address] = pefile_section.name
elif self.sample_file_static_data.elf:
for elffile_section in self.sample_file_static_data.elf.sections:
self.sections[elffile_section.header.sh_addr] = elffile_section.header.sh_name

def _compute_process_ids(self):
for process in self.sv2.processes.values():
# we expect VMRay's monitor IDs to be unique, but OS PIDs may be reused
assert process.monitor_id not in self.process_ids.keys()
self.process_ids[process.monitor_id] = process.os_pid

def _compute_process_threads(self):
# logs/flog.xml appears to be the only file that contains thread-related data
# so we use it here to map processes to threads
for function_call in self.flog.analysis.function_calls:
pid: int = self.get_process_os_pid(function_call.process_id) # flog.xml uses process monitor ID, not OS PID
tid: int = function_call.thread_id

assert isinstance(pid, int)
assert isinstance(tid, int)

if tid not in self.process_threads[pid]:
self.process_threads[pid].append(tid)

def _compute_process_calls(self):
for function_call in self.flog.analysis.function_calls:
pid: int = self.get_process_os_pid(function_call.process_id) # flog.xml uses process monitor ID, not OS PID
tid: int = function_call.thread_id

assert isinstance(pid, int)
assert isinstance(tid, int)

self.process_calls[pid][tid].append(function_call)

def get_process_os_pid(self, monitor_id: int) -> int:
return self.process_ids[monitor_id]
53 changes: 53 additions & 0 deletions capa/features/extractors/vmray/call.py
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# Copyright (C) 2024 Mandiant, Inc. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at: [package root]/LICENSE.txt
# Unless required by applicable law or agreed to in writing, software distributed under the License
# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and limitations under the License.
import logging
from typing import Tuple, Iterator

from capa.features.insn import API, Number
from capa.features.common import String, Feature
from capa.features.address import Address
from capa.features.extractors.vmray.models import PARAM_TYPE_INT, PARAM_TYPE_STR, Param, FunctionCall, hexint
from capa.features.extractors.base_extractor import CallHandle, ThreadHandle, ProcessHandle

logger = logging.getLogger(__name__)


def get_call_param_features(param: Param, ch: CallHandle) -> Iterator[Tuple[Feature, Address]]:
if param.deref is not None:
# pointer types contain a special "deref" member that stores the deref'd value
# so we check for this first and ignore Param.value as this always contains the
# deref'd pointer value
if param.deref.value is not None:
if param.deref.type_ in PARAM_TYPE_INT:
yield Number(hexint(param.deref.value)), ch.address
elif param.deref.type_ in PARAM_TYPE_STR:
yield String(param.deref.value), ch.address
else:
logger.debug("skipping deref param type %s", param.deref.type_)
elif param.value is not None:
if param.type_ in PARAM_TYPE_INT:
yield Number(hexint(param.value)), ch.address


def extract_call_features(ph: ProcessHandle, th: ThreadHandle, ch: CallHandle) -> Iterator[Tuple[Feature, Address]]:
call: FunctionCall = ch.inner

if call.params_in:
for param in call.params_in.params:
yield from get_call_param_features(param, ch)

yield API(call.name), ch.address


def extract_features(ph: ProcessHandle, th: ThreadHandle, ch: CallHandle) -> Iterator[Tuple[Feature, Address]]:
for handler in CALL_HANDLERS:
for feature, addr in handler(ph, th, ch):
yield feature, addr


CALL_HANDLERS = (extract_call_features,)
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