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VMRay and dynamic improvements #2537

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merged 5 commits into from
Dec 17, 2024
Merged

VMRay and dynamic improvements #2537

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893378c
record origin_monitor_id for more reliable process association
mr-tz Dec 12, 2024
55720dd
make more fields optional for more flexible model
mr-tz Dec 12, 2024
06f0012
only check file limitations for static file formats
mr-tz Dec 12, 2024
1f34795
vmray and dynamic updates
mr-tz Dec 12, 2024
51d606b
use default emptry list for ElfFileSection
mr-tz Dec 13, 2024
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10 changes: 5 additions & 5 deletions capa/features/extractors/vmray/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -151,9 +151,8 @@ def _compute_sections(self):
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:
if self.sample_file_static_data.elf.sections:
for elffile_section in self.sample_file_static_data.elf.sections:
self.sections[elffile_section.header.sh_addr] = elffile_section.header.sh_name
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_monitor_processes(self):
for process in self.sv2.processes.values():
Expand Down Expand Up @@ -193,13 +192,14 @@ def _compute_monitor_processes(self):
# for the other fields we've observed cases with slight deviations, e.g.,
# the ppid for a process in flog.xml is not set correctly, all other data is equal
sv2p = self.monitor_processes[monitor_process.process_id]
if self.monitor_processes[monitor_process.process_id] != vmray_monitor_process:
logger.debug("processes differ: %s (sv2) vs. %s (flog)", sv2p, vmray_monitor_process)

assert (sv2p.pid, sv2p.monitor_id, sv2p.origin_monitor_id) == (
vmray_monitor_process.pid,
vmray_monitor_process.monitor_id,
vmray_monitor_process.origin_monitor_id,
)
if self.monitor_processes[monitor_process.process_id] != vmray_monitor_process:
logger.debug("processes differ: %s (sv2) vs. %s (flog)", sv2p, vmray_monitor_process)

def _compute_monitor_threads(self):
for monitor_thread in self.flog.analysis.monitor_threads:
Expand Down
2 changes: 1 addition & 1 deletion capa/features/extractors/vmray/models.py
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Original file line number Diff line number Diff line change
Expand Up @@ -276,7 +276,7 @@ class ElfFileHeader(BaseModel):

class ElfFile(BaseModel):
# file_header: ElfFileHeader
sections: Optional[list[ElfFileSection]] = None
sections: list[ElfFileSection] = []
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incidentally, is this the correct way to set the default value, particularly as a list? i see this pattern used throughout the file.

my worry is that the default value = [] uses the same instance of a mutable list, rather than copies of it. sorta like when you have a kwarg parameter def foo(bar=[]).

in the past, i've used pydantic.Field for these. but maybe pydantic is extra smart and doesn't require this. @mr-tz @mike-hunhoff

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hm, great question, this is how mypy accepted the change and I saw the pattern throughout. Other files use Optional[list[<foo>]] = None or Field, we should cleanup the inconsistencies (separately).

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My understanding is that pydantic handles this correctly (i.e. deep copy) for non-hashable default values (i.e. lists). source: https://docs.pydantic.dev/latest/concepts/models/#fields-with-non-hashable-default-values

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whoa that's cool!

so, looks good to me. and maybe we can update our remaining code to use this pattern.



class StaticData(BaseModel):
Expand Down
4 changes: 2 additions & 2 deletions tests/test_vmray_model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -103,8 +103,8 @@ def test_vmray_model_elffile():
"""
)

assert elffile.sections and elffile.sections[0].header.sh_name == "abcd1234"
assert elffile.sections and elffile.sections[0].header.sh_addr == 2863311530
assert elffile.sections[0].header.sh_name == "abcd1234"
assert elffile.sections[0].header.sh_addr == 2863311530


def test_vmray_model_pefile():
Expand Down
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