Anna Zaks | df18c5a | 2011-11-16 19:58:13 +0000 | [diff] [blame^] | 1 | //== GenericTaintChecker.cpp ----------------------------------- -*- C++ -*--=// |
| 2 | // |
| 3 | // The LLVM Compiler Infrastructure |
| 4 | // |
| 5 | // This file is distributed under the University of Illinois Open Source |
| 6 | // License. See LICENSE.TXT for details. |
| 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | // |
| 10 | // This checker defines the attack surface for generic taint propagation. |
| 11 | // |
| 12 | // The taint information produced by it might be useful to other checkers. For |
| 13 | // example, checkers should report errors which involve tainted data more |
| 14 | // aggressively, even if the involved symbols are under constrained. |
| 15 | // |
| 16 | //===----------------------------------------------------------------------===// |
| 17 | #include "ClangSACheckers.h" |
| 18 | #include "clang/StaticAnalyzer/Core/Checker.h" |
| 19 | #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| 20 | #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| 21 | #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| 22 | |
| 23 | using namespace clang; |
| 24 | using namespace ento; |
| 25 | |
| 26 | namespace { |
| 27 | class GenericTaintChecker : public Checker< check::PostStmt<CallExpr> > { |
| 28 | |
| 29 | mutable llvm::OwningPtr<BuiltinBug> BT; |
| 30 | |
| 31 | /// Functions defining the attacke surface. |
| 32 | typedef void (GenericTaintChecker::*FnCheck)(const CallExpr *, |
| 33 | CheckerContext &C) const; |
| 34 | void processScanf(const CallExpr *CE, CheckerContext &C) const; |
| 35 | void processRetTaint(const CallExpr *CE, CheckerContext &C) const; |
| 36 | |
| 37 | public: |
| 38 | void checkPostStmt(const CallExpr *CE, CheckerContext &C) const; |
| 39 | }; |
| 40 | } |
| 41 | |
| 42 | void GenericTaintChecker::checkPostStmt(const CallExpr *CE, |
| 43 | CheckerContext &C) const { |
| 44 | if (!C.getState()) |
| 45 | return; |
| 46 | |
| 47 | StringRef Name = C.getCalleeName(CE); |
| 48 | |
| 49 | // Define the attack surface. |
| 50 | // Set the evaluation function by switching on the callee name. |
| 51 | FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) |
| 52 | .Case("scanf", &GenericTaintChecker::processScanf) |
| 53 | .Case("getchar", &GenericTaintChecker::processRetTaint) |
| 54 | .Default(NULL); |
| 55 | |
| 56 | // If the callee isn't defined, it is not of security concern. |
| 57 | // Check and evaluate the call. |
| 58 | if (evalFunction) |
| 59 | (this->*evalFunction)(CE, C); |
| 60 | |
| 61 | } |
| 62 | static SymbolRef getPointedToSymbol(const ProgramState *State, |
| 63 | const Expr* Arg) { |
| 64 | SVal AddrVal = State->getSVal(Arg->IgnoreParenCasts()); |
| 65 | Loc *AddrLoc = dyn_cast<Loc>(&AddrVal); |
| 66 | SVal Val = State->getSVal(*AddrLoc); |
| 67 | return Val.getAsSymbol(); |
| 68 | } |
| 69 | |
| 70 | |
| 71 | void GenericTaintChecker::processScanf(const CallExpr *CE, |
| 72 | CheckerContext &C) const { |
| 73 | const ProgramState *State = C.getState(); |
| 74 | assert(CE->getNumArgs() == 2); |
| 75 | SVal x = State->getSVal(CE->getArg(1)); |
| 76 | // All arguments except for the very first one should get taint. |
| 77 | for (unsigned int i = 1; i < CE->getNumArgs(); ++i) { |
| 78 | // The arguments are pointer arguments. The data they are pointing at is |
| 79 | // tainted after the call. |
| 80 | const Expr* Arg = CE->getArg(i); |
| 81 | SymbolRef Sym = getPointedToSymbol(State, Arg); |
| 82 | if (Sym) |
| 83 | State = State->addTaint(Sym); |
| 84 | } |
| 85 | C.addTransition(State); |
| 86 | |
| 87 | } |
| 88 | |
| 89 | void GenericTaintChecker::processRetTaint(const CallExpr *CE, |
| 90 | CheckerContext &C) const { |
| 91 | const ProgramState *NewState = C.getState()->addTaint(CE); |
| 92 | C.addTransition(NewState); |
| 93 | } |
| 94 | |
| 95 | void ento::registerGenericTaintChecker(CheckerManager &mgr) { |
| 96 | mgr.registerChecker<GenericTaintChecker>(); |
| 97 | } |