vmray: loosen file checks to enable processing of additional file types

CHANGELOG.md

@@ -17,8 +17,9 @@
 - vmray: load more analysis archives @mr-tz
 - dynamic: only check file limitations for static file formats @mr-tz
 - vmray: skip non-printable strings @mike-hunhoff
-- strings: add type hints and fix uncovered bugs @williballenthin @2555
+- strings: add type hints and fix uncovered bugs @williballenthin #2555
 - elffile: handle symbols without a name @williballenthin #2553
+- vmray: loosen file checks to enable processing more file types @mike-hunhoff #2571
 
 ### capa Explorer Web
 

capa/features/extractors/vmray/__init__.py

@@ -56,7 +56,8 @@ def __init__(self, zipfile_path: Path):
         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
+        self.submission_type: str = self.sv2.analysis_metadata.sample_type
+        self.submission_name: str = self.sv2.analysis_metadata.submission_filename
 
         # 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)
@@ -80,36 +81,54 @@ def __init__(self, zipfile_path: Path):
         # map function calls to their associated monitor thread ID mapped to its associated monitor process ID
         self.monitor_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.submission_base_address: Optional[int] = None
+        self.submission_sha256: Optional[str] = None
+        self.submission_meta: Optional[File] = None
+        self.submission_static: Optional[StaticData] = None
 
+        # order matters, call this before attempting the analysis that follows
         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:
+        # something bad must have happened if there is no submission analysis
+        if self.submission_meta is None:
             raise UnsupportedFormatError(
-                "VMRay feature extractor only supports PE and ELF at this time (file_type: %s)" % self.file_type
+                "archive does not contain submission analysis (submission_name: %s, submission_type: %s)"
+                % (self.submission_name, self.submission_type)
+            )
+
+        if self.submission_static is not None:
+            if self.submission_static.pe is None and self.submission_static.elf is None:
+                # we only support static analysis for PE and ELF files for now
+                raise UnsupportedFormatError(
+                    "archive does not contain a supported file format (submission_name: %s, submission_type: %s)"
+                    % (self.submission_name, self.submission_type)
+                )
+        else:
+            # VMRay may not record static analysis for certain file types, e.g. MSI, but we'd still like to match dynamic
+            # execution so we continue without and accept that the results may be incomplete
+            logger.warning(
+                "archive does not contain submission static data analysis, results may be incomplete (submission_name: %s, submission_type: %s)",
+                self.submission_name,
+                self.submission_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}"
+        submission_path: str = (
+            f"internal/static_analyses/{self.submission_sha256}/objects/files/{self.submission_sha256}"
+        )
+
+        logger.debug(
+            "\nsubmission_name: %s\nsubmission_type: %s\nsubmission_sha256: %s\nsubmission_zip_path: %s",
+            self.submission_name,
+            self.submission_type,
+            self.submission_sha256,
+            submission_path,
+        )
 
-        logger.debug("file_type: %s, file_path: %s", self.file_type, sample_file_path)
+        self.submission_bytes: bytes = self.zipfile.read(submission_path, pwd=DEFAULT_ARCHIVE_PASSWORD)
 
-        self.sample_file_buf: bytes = self.zipfile.read(sample_file_path, pwd=DEFAULT_ARCHIVE_PASSWORD)
+        logger.debug("submission_bytes: %s", self.submission_bytes[:10])
 
         # do not change order, it matters
         self._compute_base_address()
@@ -121,45 +140,52 @@ def __init__(self, zipfile_path: Path):
         self._compute_monitor_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
+        logger.debug("searching archive for submission")
+
+        # VMRay may mark more than one file as the submission, e.g., when a compound ZIP file is used
+        # both the ZIP file and embedded target file are marked as submissions. We have yet to find a
+        # guarenteed way to differentiate which is the actual submission, so we opt to choose the last
+        # file that is marked as the submission for now
+        for file_analysis in self.sv2.files.values():
+            if not file_analysis.is_sample:
+                continue
+
+            self.submission_meta = file_analysis
+            self.submission_sha256 = self.submission_meta.hash_values.sha256
 
-                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]]
+            logger.debug("sha256: %s marked as submission", self.submission_sha256)
 
-                break
+            if file_analysis.ref_static_data is not None:
+                # 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.submission_static = self.sv2.static_data[file_analysis.ref_static_data.path[1]]
 
     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
+        if self.submission_static is not None:
+            if self.submission_static.pe:
+                self.submission_base_address = self.submission_static.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
+        if self.submission_static is not None:
+            if self.submission_static.pe:
+                for export in self.submission_static.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)
+        if self.submission_static is not None:
+            if self.submission_static.pe:
+                for module in self.submission_static.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
+        if self.submission_static is not None:
+            if self.submission_static.pe:
+                for pefile_section in self.submission_static.pe.sections:
+                    self.sections[pefile_section.virtual_address] = pefile_section.name
+            elif self.submission_static.elf:
+                for elffile_section in self.submission_static.elf.sections:
+                    self.sections[elffile_section.header.sh_addr] = elffile_section.header.sh_name
 
     def _compute_monitor_processes(self):
         for process in self.sv2.processes.values():

capa/features/extractors/vmray/extractor.py

@@ -20,7 +20,7 @@
 import capa.features.extractors.vmray.call
 import capa.features.extractors.vmray.file
 import capa.features.extractors.vmray.global_
-from capa.features.common import Feature, Characteristic
+from capa.features.common import Feature
 from capa.features.address import (
     NO_ADDRESS,
     Address,
@@ -56,13 +56,13 @@ def get_formatted_params(params: ParamList) -> list[str]:
 
 class VMRayExtractor(DynamicFeatureExtractor):
     def __init__(self, analysis: VMRayAnalysis):
-        assert analysis.sample_file_analysis is not None
+        assert analysis.submission_meta is not None
 
         super().__init__(
             hashes=SampleHashes(
-                md5=analysis.sample_file_analysis.hash_values.md5.lower(),
-                sha1=analysis.sample_file_analysis.hash_values.sha1.lower(),
-                sha256=analysis.sample_file_analysis.hash_values.sha256.lower(),
+                md5=analysis.submission_meta.hash_values.md5.lower(),
+                sha1=analysis.submission_meta.hash_values.sha1.lower(),
+                sha256=analysis.submission_meta.hash_values.sha256.lower(),
             )
         )
 
@@ -72,8 +72,12 @@ def __init__(self, analysis: VMRayAnalysis):
         self.global_features = list(capa.features.extractors.vmray.global_.extract_features(self.analysis))
 
     def get_base_address(self) -> Address:
-        # value according to the PE header, the actual trace may use a different imagebase
-        return AbsoluteVirtualAddress(self.analysis.base_address)
+        # value according to submission file header, the actual trace may use a different imagebase
+        # value may not exist for certain submission file types, e.g. PS1
+        if self.analysis.submission_base_address is None:
+            return NO_ADDRESS
+        else:
+            return AbsoluteVirtualAddress(self.analysis.submission_base_address)
 
     def extract_file_features(self) -> Iterator[tuple[Feature, Address]]:
         yield from capa.features.extractors.vmray.file.extract_features(self.analysis)
@@ -102,11 +106,8 @@ def get_threads(self, ph: ProcessHandle) -> Iterator[ThreadHandle]:
             yield ThreadHandle(address=address, inner=monitor_thread)
 
     def extract_thread_features(self, ph: ProcessHandle, th: ThreadHandle) -> Iterator[tuple[Feature, Address]]:
-        if False:
-            # force this routine to be a generator,
-            # but we don't actually have any elements to generate.
-            yield Characteristic("never"), NO_ADDRESS
-        return
+        # we have not identified thread-specific features for VMRay yet
+        yield from []
 
     def get_calls(self, ph: ProcessHandle, th: ThreadHandle) -> Iterator[CallHandle]:
         for function_call in self.analysis.monitor_process_calls[ph.inner.monitor_id][th.inner.monitor_id]:

capa/features/extractors/vmray/file.py

@@ -67,7 +67,8 @@ def extract_referenced_registry_key_names(analysis: VMRayAnalysis) -> Iterator[t
 
 
 def extract_file_strings(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:
-    yield from capa.features.extractors.common.extract_file_strings(analysis.sample_file_buf)
+    if analysis.submission_static is not None:
+        yield from capa.features.extractors.common.extract_file_strings(analysis.submission_bytes)
 
 
 def extract_features(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:

capa/features/extractors/vmray/global_.py

@@ -18,6 +18,8 @@
 
 from capa.features.common import (
     OS,
+    OS_ANY,
+    ARCH_ANY,
     OS_LINUX,
     ARCH_I386,
     FORMAT_PE,
@@ -35,35 +37,50 @@
 
 
 def extract_arch(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:
-    file_type: str = analysis.file_type
-
-    if "x86-32" in file_type:
+    if "x86-32" in analysis.submission_type:
         yield Arch(ARCH_I386), NO_ADDRESS
-    elif "x86-64" in file_type:
+    elif "x86-64" in analysis.submission_type:
         yield Arch(ARCH_AMD64), NO_ADDRESS
     else:
-        raise ValueError("unrecognized arch from the VMRay report: %s" % file_type)
+        yield Arch(ARCH_ANY), NO_ADDRESS
+
+        logger.debug(
+            "unrecognized arch for submission (filename: %s, file_type: %s)",
+            analysis.submission_name,
+            analysis.submission_type,
+        )
 
 
 def extract_format(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:
-    assert analysis.sample_file_static_data is not None
-    if analysis.sample_file_static_data.pe:
-        yield Format(FORMAT_PE), NO_ADDRESS
-    elif analysis.sample_file_static_data.elf:
-        yield Format(FORMAT_ELF), NO_ADDRESS
+    if analysis.submission_static is not None:
+        if analysis.submission_static.pe:
+            yield Format(FORMAT_PE), NO_ADDRESS
+        elif analysis.submission_static.elf:
+            yield Format(FORMAT_ELF), NO_ADDRESS
     else:
-        raise ValueError("unrecognized file format from the VMRay report: %s" % analysis.file_type)
+        # there is no "FORMAT_ANY" to yield here, but few rules rely on the "format" feature
+        # so this should be fine for now
 
+        logger.debug(
+            "unrecognized format for submission (filename: %s, file_type: %s)",
+            analysis.submission_name,
+            analysis.submission_type,
+        )
 
-def extract_os(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:
-    file_type: str = analysis.file_type
 
-    if "windows" in file_type.lower():
+def extract_os(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:
+    if "windows" in analysis.submission_type.lower():
         yield OS(OS_WINDOWS), NO_ADDRESS
-    elif "linux" in file_type.lower():
+    elif "linux" in analysis.submission_type.lower():
         yield OS(OS_LINUX), NO_ADDRESS
     else:
-        raise ValueError("unrecognized OS from the VMRay report: %s" % file_type)
+        yield OS(OS_ANY), NO_ADDRESS
+
+        logger.debug(
+            "unrecognized os for submission (filename: %s, file_type: %s)",
+            analysis.submission_name,
+            analysis.submission_type,
+        )
 
 
 def extract_features(analysis: VMRayAnalysis) -> Iterator[tuple[Feature, Address]]:

scripts/minimize_vmray_results.py

@@ -49,9 +49,9 @@ def main(argv=None):
     vmra = VMRayAnalysis(analysis_archive)
     sv2_json = vmra.zipfile.read("logs/summary_v2.json", pwd=DEFAULT_ARCHIVE_PASSWORD)
     flog_xml = vmra.zipfile.read("logs/flog.xml", pwd=DEFAULT_ARCHIVE_PASSWORD)
-    sample_file_buf = vmra.sample_file_buf
-    assert vmra.sample_file_analysis is not None
-    sample_sha256: str = vmra.sample_file_analysis.hash_values.sha256.lower()
+    sample_file_buf = vmra.submission_bytes
+    assert vmra.submission_meta is not None
+    sample_sha256: str = vmra.submission_meta.hash_values.sha256.lower()
 
     new_zip_name = f"{analysis_archive.parent / analysis_archive.stem}_min.zip"
     with zipfile.ZipFile(new_zip_name, "w") as new_zip:

tests/fixtures.py

@@ -453,6 +453,14 @@ def get_data_path_by_name(name) -> Path:
             / "vmray"
             / "2f8a79b12a7a989ac7e5f6ec65050036588a92e65aeb6841e08dc228ff0e21b4_min_archive.zip"
         )
+    elif name.startswith("eb1287-vmray"):
+        return (
+            CD
+            / "data"
+            / "dynamic"
+            / "vmray"
+            / "eb12873c0ce3e9ea109c2a447956cbd10ca2c3e86936e526b2c6e28764999f21_min_archive.zip"
+        )
     elif name.startswith("ea2876"):
         return CD / "data" / "ea2876e9175410b6f6719f80ee44b9553960758c7d0f7bed73c0fe9a78d8e669.dll_"
     elif name.startswith("1038a2"):

tests/test_vmray_features.py

@@ -35,6 +35,7 @@
         ("93b2d1-vmray", "process=(2176:0),thread=2420", capa.features.insn.API("DoesNotExist"), False),
         # call/api
         ("93b2d1-vmray", "process=(2176:0),thread=2420,call=2361", capa.features.insn.API("GetAddrInfoW"), True),
+        ("eb1287-vmray", "process=(4968:0),thread=5992,call=10981", capa.features.insn.API("CreateMutexW"), True),
         # call/string argument
         (
             "93b2d1-vmray",