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//==--- MacOSKeychainAPIChecker.cpp -----------------------------------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// This checker flags misuses of KeyChainAPI. In particular, the password data
// allocated/returned by SecKeychainItemCopyContent,
// SecKeychainFindGenericPassword, SecKeychainFindInternetPassword functions has
// to be freed using a call to SecKeychainItemFreeContent.
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/GRState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/GRStateTrait.h"
using namespace clang;
using namespace ento;
namespace {
class MacOSKeychainAPIChecker : public Checker<check::PreStmt<CallExpr>,
check::PreStmt<ReturnStmt>,
check::PostStmt<CallExpr>,
check::EndPath > {
public:
void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
void checkPostStmt(const CallExpr *S, CheckerContext &C) const;
void checkEndPath(EndOfFunctionNodeBuilder &B, ExprEngine &Eng) const;
private:
static const unsigned InvalidParamVal = 100000;
/// Given the function name, returns the index of the parameter which will
/// be allocated as a result of the call.
unsigned getAllocatingFunctionParam(StringRef Name) const {
if (Name == "SecKeychainItemCopyContent")
return 4;
if (Name == "SecKeychainFindGenericPassword")
return 6;
if (Name == "SecKeychainFindInternetPassword")
return 13;
return InvalidParamVal;
}
/// Given the function name, returns the index of the parameter which will
/// be freed by the function.
unsigned getDeallocatingFunctionParam(StringRef Name) const {
if (Name == "SecKeychainItemFreeContent")
return 1;
return InvalidParamVal;
}
};
}
// GRState traits to store the currently allocated (and not yet freed) symbols.
typedef llvm::ImmutableSet<SymbolRef> AllocatedSetTy;
namespace { struct AllocatedData {}; }
namespace clang { namespace ento {
template<> struct GRStateTrait<AllocatedData>
: public GRStatePartialTrait<AllocatedSetTy > {
static void *GDMIndex() { static int index = 0; return &index; }
};
}}
void MacOSKeychainAPIChecker::checkPreStmt(const CallExpr *CE,
CheckerContext &C) const {
const GRState *State = C.getState();
const Expr *Callee = CE->getCallee();
SVal L = State->getSVal(Callee);
const FunctionDecl *funDecl = L.getAsFunctionDecl();
if (!funDecl)
return;
IdentifierInfo *funI = funDecl->getIdentifier();
if (!funI)
return;
StringRef funName = funI->getName();
// If a value has been freed, remove from the list.
unsigned idx = getDeallocatingFunctionParam(funName);
if (idx != InvalidParamVal) {
SymbolRef Param = State->getSVal(CE->getArg(idx)).getAsSymbol();
if (!Param)
return;
if (!State->contains<AllocatedData>(Param)) {
// TODO: do we care about this?
assert(0 && "Trying to free data which has not been allocated yet.");
}
State = State->remove<AllocatedData>(Param);
C.addTransition(State);
}
}
void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE,
CheckerContext &C) const {
const GRState *State = C.getState();
const Expr *Callee = CE->getCallee();
SVal L = State->getSVal(Callee);
StoreManager& SM = C.getStoreManager();
const FunctionDecl *funDecl = L.getAsFunctionDecl();
if (!funDecl)
return;
IdentifierInfo *funI = funDecl->getIdentifier();
if (!funI)
return;
StringRef funName = funI->getName();
// If a value has been allocated, add it to the set for tracking.
unsigned idx = getAllocatingFunctionParam(funName);
if (idx != InvalidParamVal) {
SVal Param = State->getSVal(CE->getArg(idx));
if (const loc::MemRegionVal *X = dyn_cast<loc::MemRegionVal>(&Param)) {
SymbolRef V = SM.Retrieve (State->getStore(), *X).getAsSymbol();
if (!V)
return;
State = State->add<AllocatedData>(V);
C.addTransition(State);
}
}
}
void MacOSKeychainAPIChecker::checkPreStmt(const ReturnStmt *S,
CheckerContext &C) const {
const Expr *retExpr = S->getRetValue();
if (!retExpr)
return;
// Check if the value is escaping through the return.
const GRState *state = C.getState();
SymbolRef V = state->getSVal(retExpr).getAsSymbol();
if (!V)
return;
state->remove<AllocatedData>(V);
}
void MacOSKeychainAPIChecker::checkEndPath(EndOfFunctionNodeBuilder &B,
ExprEngine &Eng) const {
const GRState *state = B.getState();
AllocatedSetTy AS = state->get<AllocatedData>();
// Anything which has been allocated but not freed (nor escaped) will be
// found here, so report it.
if (!AS.isEmpty()) {
assert(0 && "TODO: Report the bug here.");
}
}
void ento::registerMacOSKeychainAPIChecker(CheckerManager &mgr) {
mgr.registerChecker<MacOSKeychainAPIChecker>();
}
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