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#include "ObjCActivity.h"
#include "lowlevelilinstruction.h"
// TODO: Consolidate this with the Obj-C workflow at some point https://github.com/Vector35/workflow_objc
using namespace BinaryNinja;
void ObjCActivity::Register(Workflow &workflow)
{
workflow.RegisterActivity(new Activity(R"({
"name": "core.analysis.sharedCache.objc.adjustCallType",
"eligibility": {
"predicates": [
{
"type": "viewType",
"operator": "in",
"value": [
"DSCView"
]
}
]
}
})", &AdjustCallType));
workflow.Insert("core.function.analyzeTailCalls", "core.analysis.sharedCache.objc.adjustCallType");
}
std::vector<std::string> splitSelector(const std::string& selector) {
std::vector<std::string> components;
std::istringstream stream(selector);
std::string component;
while (std::getline(stream, component, ':')) {
if (!component.empty()) {
components.push_back(component);
}
}
return components;
}
std::vector<std::string> generateArgumentNames(const std::vector<std::string>& components) {
std::vector<std::string> argumentNames;
for (const std::string& component : components) {
size_t startPos = component.find_last_of(' ');
std::string argumentName = (startPos == std::string::npos) ? component : component.substr(startPos + 1);
argumentNames.push_back(argumentName);
}
return argumentNames;
}
void ObjCActivity::AdjustCallType(Ref<AnalysisContext> ctx)
{
const auto func = ctx->GetFunction();
const auto arch = func->GetArchitecture();
const auto bv = func->GetView();
const auto baseAddr = bv->GetStart();
const auto llil = ctx->GetLowLevelILFunction();
if (!llil) {
return;
}
const auto ssa = llil->GetSSAForm();
if (!ssa) {
return;
}
const auto rewriteIfEligible = [bv, ssa, baseAddr](size_t insnIndex) {
auto insn = ssa->GetInstruction(insnIndex);
if (insn.operation != LLIL_CALL_SSA && insn.operation != LLIL_TAILCALL_SSA)
return;
enum class MessageSendType {
Normal,
Super,
};
MessageSendType messageSendType = MessageSendType::Normal;
// Filter out calls that aren't to `objc_msgSend`, `objc_msgSendSuper`, or `objc_msgSendSuper2`.
auto callExpr = insn.GetDestExpr();
if (auto symbol = bv->GetSymbolByAddress(callExpr.GetValue().value))
{
std::string_view symbolName = symbol->GetRawNameRef();
if (symbolName == "_objc_msgSend")
messageSendType = MessageSendType::Normal;
else if (symbolName == "_objc_msgSendSuper2" || symbolName == "_objc_msgSendSuper")
messageSendType = MessageSendType::Super;
else
return;
}
const auto params = insn.GetParameterExprs();
// The second parameter passed to the objc_msgSend call is the address of
// either the selector reference or the method's name, which in both cases
// is dereferenced to retrieve a selector.
if (params.size() < 2)
return;
uint64_t rawSelector = 0;
if (params[1].operation == LLIL_REG_SSA)
{
const auto selectorRegister = params[1].GetSourceSSARegister<LLIL_REG_SSA>();
rawSelector = ssa->GetSSARegisterValue(selectorRegister).value;
}
else if (params[0].operation == LLIL_SEPARATE_PARAM_LIST_SSA)
{
if (params[0].GetParameterExprs<LLIL_SEPARATE_PARAM_LIST_SSA>().size() == 0)
return;
const auto selectorRegister = params[0].GetParameterExprs<LLIL_SEPARATE_PARAM_LIST_SSA>()[1].GetSourceSSARegister<LLIL_REG_SSA>();
rawSelector = ssa->GetSSARegisterValue(selectorRegister).value;
}
// Skip if we don't have a
if (!rawSelector || rawSelector < baseAddr)
return;
std::string selector;
if (bv->IsValidOffset(rawSelector)) {
BinaryReader reader(bv);
reader.Seek(rawSelector);
selector = reader.ReadCString(500);
} else {
// Look for the `sel_` symbols that ObjCProcessor adds to represent selectors
// whose backing regions have not yet been loaded into the view.
constexpr std::string_view SelectorPrefix = "sel_";
auto symbol = bv->GetSymbolByAddress(rawSelector);
if (!symbol)
return;
std::string_view name = symbol->GetRawNameRef();
if (name.find(SelectorPrefix) != 0)
return;
selector = name.substr(SelectorPrefix.length());
}
// -- Do callsite override
auto additionalArgumentCount = std::count(selector.begin(), selector.end(), ':');
auto retType = bv->GetTypeByName({ "id" });
if (!retType)
retType = Type::PointerType(ssa->GetArchitecture(), Type::VoidType());
std::vector<FunctionParameter> callTypeParams;
auto cc = bv->GetDefaultPlatform()->GetDefaultCallingConvention();
if (messageSendType == MessageSendType::Normal)
callTypeParams.emplace_back("self", retType, true, Variable());
else
{
auto superType = bv->GetTypeByName({ "objc_super" });
if (!superType)
superType = Type::PointerType(ssa->GetArchitecture(), Type::VoidType());
callTypeParams.emplace_back("super", Type::PointerType(ssa->GetArchitecture(), superType), true, Variable());
}
auto selType = bv->GetTypeByName({ "SEL" });
if (!selType)
selType = Type::PointerType(ssa->GetArchitecture(), Type::IntegerType(1, true));
callTypeParams.emplace_back("sel", selType, true, Variable());
std::vector<std::string> selectorComponents = splitSelector(selector);
std::vector<std::string> argumentNames = generateArgumentNames(selectorComponents);
for (size_t i = 0; i < additionalArgumentCount; i++)
{
auto argType = Type::IntegerType(bv->GetAddressSize(), true);
if (argumentNames.size() > i && !argumentNames[i].empty())
callTypeParams.emplace_back(argumentNames[i], argType, true, Variable());
else
callTypeParams.emplace_back("arg" + std::to_string(i), argType, true, Variable());
}
auto funcType = Type::FunctionType(retType, cc, callTypeParams);
ssa->GetFunction()->SetAutoCallTypeAdjustment(ssa->GetFunction()->GetArchitecture(), insn.address, {funcType, BN_DEFAULT_CONFIDENCE});
// --
};
for (const auto& block : ssa->GetBasicBlocks())
for (size_t i = block->GetStart(), end = block->GetEnd(); i < end; ++i)
rewriteIfEligible(i);
}
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