def generate_api_features(apiname, va):
"""
for a given function name and address, generate API names.
we over-generate features to make matching easier.
these include:
- kernel32.CreateFileA
- kernel32.CreateFile
- CreateFileA
- CreateFile
"""
# (kernel32.CreateFileA, 0x401000)
yield API(apiname), va
if is_aw_function(apiname):
# (kernel32.CreateFile, 0x401000)
yield API(apiname[:-1]), va
if "." in apiname:
modname, impname = apiname.split(".")
# strip modname to support importname-only matching
# (CreateFileA, 0x401000)
yield API(impname), va
if is_aw_function(impname):
# (CreateFile, 0x401000)
yield API(impname[:-1]), va
def extract_insn_api_features(f, bb, insn):
"""parse API features from the given instruction."""
if insn.offset in f.apirefs:
api_entry = f.apirefs[insn.offset]
# reformat
dll_name, api_name = api_entry.split("!")
dll_name = dll_name.split(".")[0]
dll_name = dll_name.lower()
for name in capa.features.extractors.helpers.generate_symbols(dll_name, api_name):
yield API(name), insn.offset
elif insn.offset in f.outrefs:
current_function = f
current_instruction = insn
for index in range(THUNK_CHAIN_DEPTH_DELTA):
if current_function and len(current_function.outrefs[current_instruction.offset]) == 1:
target = current_function.outrefs[current_instruction.offset][0]
referenced_function = current_function.smda_report.getFunction(target)
if referenced_function:
# TODO SMDA: implement this function for both jmp and call, checking if function has 1 instruction which refs an API
if referenced_function.isApiThunk():
api_entry = (
referenced_function.apirefs[target] if target in referenced_function.apirefs else None
)
if api_entry:
# reformat
dll_name, api_name = api_entry.split("!")
dll_name = dll_name.split(".")[0]
dll_name = dll_name.lower()
for name in capa.features.extractors.helpers.generate_symbols(dll_name, api_name):
yield API(name), insn.offset
elif referenced_function.num_instructions == 1 and referenced_function.num_outrefs == 1:
current_function = referenced_function
current_instruction = [i for i in referenced_function.getInstructions()][0]
else:
return
def extract_insn_api_features(f, bb, insn):
"""parse instruction API features
args:
f (IDA func_t)
bb (IDA BasicBlock)
insn (IDA insn_t)
example:
call dword [0x00473038]
"""
if not insn.get_canon_mnem() in ("call", "jmp"):
return
for api in check_for_api_call(f.ctx, insn):
dll, _, symbol = api.rpartition(".")
for name in capa.features.extractors.helpers.generate_symbols(dll, symbol):
yield API(name), insn.ea
# extract IDA/FLIRT recognized API functions
targets = tuple(idautils.CodeRefsFrom(insn.ea, False))
if not targets:
return
target = targets[0]
target_func = idaapi.get_func(target)
if not target_func or target_func.start_ea != target:
# not a function (start)
return
if target_func.flags & idaapi.FUNC_LIB:
name = idaapi.get_name(target_func.start_ea)
yield API(name), insn.ea
def extract_insn_api_features(f, bb, insn):
"""parse instruction API features
args:
f (IDA func_t)
bb (IDA BasicBlock)
insn (IDA insn_t)
example:
call dword [0x00473038]
"""
unit: DataUnit = f.unit
if insn.mne in unit.syntax.operations:
if not unit.syntax.operations[insn.mne].jmp:
return
for c in insn.cr + insn.dr:
if str(c) in unit.obj.bin.import_functions:
module, func, _ = unit.obj.bin.import_functions[str(c)]
if '.dll' in module:
module = module.replace('.dll', '')
for symbol in helpers.generate_symbols(module, func):
yield API(symbol), insn.ea
# THUNK!!
depth = 0
_next = c
while depth < THUNK_CHAIN_DEPTH_DELTA:
if _next not in unit.map_f:
break
c_f = unit.map_f[_next]
if len(c_f.blocks) != 1:
break
if len(c_f.blocks[0].ins) != 1:
break
if len(c_f.blocks[0].ins[0].cr) == 1:
# code reference of thunked function to the symbol
_next = c_f.blocks[0].ins[0].cr[0]
elif len(c_f.blocks[0].ins[0].dr) == 1:
# data reference of thunked function to the symbol
_next = c_f.blocks[0].ins[0].dr[0]
else:
break
if str(_next) in unit.obj.bin.import_functions:
module, func, _ = unit.obj.bin.import_functions[str(_next)]
if '.dll' in module:
module = module.replace('.dll', '')
for symbol in helpers.generate_symbols(module, func):
yield API(symbol), insn.ea
depth += 1
def extract_insn_api_features(f: CilMethodBody, bb: CilMethodBody,
insn: Instruction) -> Iterator[Tuple[API, int]]:
"""parse instruction API features"""
if insn.opcode not in (OpCodes.Call, OpCodes.Callvirt, OpCodes.Jmp,
OpCodes.Calli):
return
name: str = get_imports(f.ctx).get(insn.operand.value, "")
if not name:
return
if "::" in name:
# like System.IO.File::OpenRead
yield API(name), insn.offset
else:
# like kernel32.CreateFileA
dll, _, symbol = name.rpartition(".")
for name_variant in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name_variant), insn.offset
def extract_insn_api_features(f, bb, insn):
"""parse instruction API features
args:
f (IDA func_t)
bb (IDA BasicBlock)
insn (IDA insn_t)
example:
call dword [0x00473038]
"""
if not insn.get_canon_mnem() in ("call", "jmp"):
return
for api in check_for_api_call(f.ctx, insn):
dll, _, symbol = api.rpartition(".")
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.ea
# extract IDA/FLIRT recognized API functions
targets = tuple(idautils.CodeRefsFrom(insn.ea, False))
if not targets:
return
target = targets[0]
target_func = idaapi.get_func(target)
if not target_func or target_func.start_ea != target:
# not a function (start)
return
if target_func.flags & idaapi.FUNC_LIB:
name = idaapi.get_name(target_func.start_ea)
yield API(name), insn.ea
if name.startswith("_"):
# some linkers may prefix linked routines with a `_` to avoid name collisions.
# extract features for both the mangled and un-mangled representations.
# e.g. `_fwrite` -> `fwrite`
# see: https://stackoverflow.com/a/2628384/87207
yield API(name[1:]), insn.ea
def extract_insn_api_features(f, bb, insn):
"""parse instruction API features
args:
f (IDA func_t)
bb (IDA BasicBlock)
insn (IDA insn_t)
example:
call dword [0x00473038]
"""
for api in check_for_api_call(f.ctx, insn):
dll, _, symbol = api.rpartition(".")
for name in capa.features.extractors.helpers.generate_symbols(dll, symbol):
yield API(name), insn.ea
def extract_insn_api_features(f, bb, insn):
"""parse API features from the given instruction."""
# example:
#
# call dword [0x00473038]
if insn.mnem != "call":
return
# traditional call via IAT
if isinstance(insn.opers[0], envi.archs.i386.disasm.i386ImmMemOper):
oper = insn.opers[0]
target = oper.getOperAddr(insn)
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
# call via thunk on x86,
# see 9324d1a8ae37a36ae560c37448c9705a at 0x407985
#
# this is also how calls to internal functions may be decoded on x64.
# see Lab21-01.exe_:0x140001178
elif isinstance(insn.opers[0], envi.archs.i386.disasm.i386PcRelOper):
target = insn.opers[0].getOperValue(insn)
try:
thunk = f.vw.getFunctionMeta(target, "Thunk")
except vivisect.exc.InvalidFunction:
return
else:
if thunk:
dll, _, symbol = thunk.rpartition(".")
if symbol.startswith("ord"):
symbol = "#" + symbol[len("ord"):]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
# call via import on x64
# see Lab21-01.exe_:0x14000118C
elif isinstance(insn.opers[0], envi.archs.amd64.disasm.Amd64RipRelOper):
op = insn.opers[0]
target = op.getOperAddr(insn)
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
elif isinstance(insn.opers[0], envi.archs.i386.disasm.i386RegOper):
try:
(_, target) = resolve_indirect_call(f.vw, insn.va, insn=insn)
except NotFoundError:
# not able to resolve the indirect call, sorry
return
if target is None:
# not able to resolve the indirect call, sorry
return
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
def extract_insn_api_features(f, bb, insn):
"""parse API features from the given instruction."""
# example:
#
# call dword [0x00473038]
if insn.mnem not in ("call", "jmp"):
return
if insn.mnem == "jmp":
if f.vw.getFunctionMeta(f.va, "Thunk"):
return
# traditional call via IAT
if isinstance(insn.opers[0], envi.archs.i386.disasm.i386ImmMemOper):
oper = insn.opers[0]
target = oper.getOperAddr(insn)
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
# call via thunk on x86,
# see 9324d1a8ae37a36ae560c37448c9705a at 0x407985
#
# this is also how calls to internal functions may be decoded on x64.
# see Lab21-01.exe_:0x140001178
#
# follow chained thunks, e.g. in 82bf6347acf15e5d883715dc289d8a2b at 0x14005E0FF in
# 0x140059342 (viv) / 0x14005E0C0 (IDA)
# 14005E0FF call j_ElfClearEventLogFileW (14005AAF8)
# 14005AAF8 jmp ElfClearEventLogFileW (14005E196)
# 14005E196 jmp cs:__imp_ElfClearEventLogFileW
elif isinstance(insn.opers[0], envi.archs.i386.disasm.i386PcRelOper):
imports = get_imports(f.vw)
target = capa.features.extractors.viv.helpers.get_coderef_from(
f.vw, insn.va)
if not target:
return
for _ in range(THUNK_CHAIN_DEPTH_DELTA):
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
target = capa.features.extractors.viv.helpers.get_coderef_from(
f.vw, target)
if not target:
return
# call via import on x64
# see Lab21-01.exe_:0x14000118C
elif isinstance(insn.opers[0], envi.archs.amd64.disasm.Amd64RipRelOper):
op = insn.opers[0]
target = op.getOperAddr(insn)
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
elif isinstance(insn.opers[0], envi.archs.i386.disasm.i386RegOper):
try:
(_, target) = resolve_indirect_call(f.vw, insn.va, insn=insn)
except NotFoundError:
# not able to resolve the indirect call, sorry
return
if target is None:
# not able to resolve the indirect call, sorry
return
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
def extract_insn_api_features(f, bb, insn):
"""parse API features from the given instruction."""
# example:
#
# call dword [0x00473038]
if insn.mnem not in ("call", "jmp"):
return
if insn.mnem == "jmp":
if f.vw.getFunctionMeta(f.va, "Thunk"):
return
# traditional call via IAT
if isinstance(insn.opers[0], envi.archs.i386.disasm.i386ImmMemOper):
oper = insn.opers[0]
target = oper.getOperAddr(insn)
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
# call via thunk on x86,
# see 9324d1a8ae37a36ae560c37448c9705a at 0x407985
#
# this is also how calls to internal functions may be decoded on x32 and x64.
# see Lab21-01.exe_:0x140001178
#
# follow chained thunks, e.g. in 82bf6347acf15e5d883715dc289d8a2b at 0x14005E0FF in
# 0x140059342 (viv) / 0x14005E0C0 (IDA)
# 14005E0FF call j_ElfClearEventLogFileW (14005AAF8)
# 14005AAF8 jmp ElfClearEventLogFileW (14005E196)
# 14005E196 jmp cs:__imp_ElfClearEventLogFileW
elif isinstance(insn.opers[0], envi.archs.i386.disasm.i386PcRelOper):
imports = get_imports(f.vw)
target = capa.features.extractors.viv.helpers.get_coderef_from(
f.vw, insn.va)
if not target:
return
if viv_utils.flirt.is_library_function(f.vw, target):
name = viv_utils.get_function_name(f.vw, target)
yield API(name), insn.va
if name.startswith("_"):
# some linkers may prefix linked routines with a `_` to avoid name collisions.
# extract features for both the mangled and un-mangled representations.
# e.g. `_fwrite` -> `fwrite`
# see: https://stackoverflow.com/a/2628384/87207
yield API(name[1:]), insn.va
return
for _ in range(THUNK_CHAIN_DEPTH_DELTA):
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
# if jump leads to an ENDBRANCH instruction, skip it
if f.vw.getByteDef(target)[1].startswith(b"\xf3\x0f\x1e"):
target += 4
target = capa.features.extractors.viv.helpers.get_coderef_from(
f.vw, target)
if not target:
return
# call via import on x64
# see Lab21-01.exe_:0x14000118C
elif isinstance(insn.opers[0], envi.archs.amd64.disasm.Amd64RipRelOper):
op = insn.opers[0]
target = op.getOperAddr(insn)
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
elif isinstance(insn.opers[0], envi.archs.i386.disasm.i386RegOper):
try:
(_, target) = resolve_indirect_call(f.vw, insn.va, insn=insn)
except NotFoundError:
# not able to resolve the indirect call, sorry
return
if target is None:
# not able to resolve the indirect call, sorry
return
imports = get_imports(f.vw)
if target in imports:
dll, symbol = imports[target]
for name in capa.features.extractors.helpers.generate_symbols(
dll, symbol):
yield API(name), insn.va
