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Diffstat (limited to 'gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp')
| -rw-r--r-- | gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp | 2453 |
1 files changed, 2453 insertions, 0 deletions
diff --git a/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp b/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp new file mode 100644 index 00000000000..21c4bbc6026 --- /dev/null +++ b/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp @@ -0,0 +1,2453 @@ +//= CStringChecker.cpp - Checks calls to C string functions --------*- C++ -*-// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This defines CStringChecker, which is an assortment of checks on calls +// to functions in <string.h>. +// +//===----------------------------------------------------------------------===// + +#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" +#include "InterCheckerAPI.h" +#include "clang/Basic/CharInfo.h" +#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" +#include "clang/StaticAnalyzer/Core/Checker.h" +#include "clang/StaticAnalyzer/Core/CheckerManager.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/Support/raw_ostream.h" + +using namespace clang; +using namespace ento; + +namespace { +enum class ConcatFnKind { none = 0, strcat = 1, strlcat = 2 }; +class CStringChecker : public Checker< eval::Call, + check::PreStmt<DeclStmt>, + check::LiveSymbols, + check::DeadSymbols, + check::RegionChanges + > { + mutable std::unique_ptr<BugType> BT_Null, BT_Bounds, BT_Overlap, + BT_NotCString, BT_AdditionOverflow; + + mutable const char *CurrentFunctionDescription; + +public: + /// The filter is used to filter out the diagnostics which are not enabled by + /// the user. + struct CStringChecksFilter { + DefaultBool CheckCStringNullArg; + DefaultBool CheckCStringOutOfBounds; + DefaultBool CheckCStringBufferOverlap; + DefaultBool CheckCStringNotNullTerm; + + CheckerNameRef CheckNameCStringNullArg; + CheckerNameRef CheckNameCStringOutOfBounds; + CheckerNameRef CheckNameCStringBufferOverlap; + CheckerNameRef CheckNameCStringNotNullTerm; + }; + + CStringChecksFilter Filter; + + static void *getTag() { static int tag; return &tag; } + + bool evalCall(const CallEvent &Call, CheckerContext &C) const; + void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const; + void checkLiveSymbols(ProgramStateRef state, SymbolReaper &SR) const; + void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const; + + ProgramStateRef + checkRegionChanges(ProgramStateRef state, + const InvalidatedSymbols *, + ArrayRef<const MemRegion *> ExplicitRegions, + ArrayRef<const MemRegion *> Regions, + const LocationContext *LCtx, + const CallEvent *Call) const; + + typedef void (CStringChecker::*FnCheck)(CheckerContext &, + const CallExpr *) const; + CallDescriptionMap<FnCheck> Callbacks = { + {{CDF_MaybeBuiltin, "memcpy", 3}, &CStringChecker::evalMemcpy}, + {{CDF_MaybeBuiltin, "mempcpy", 3}, &CStringChecker::evalMempcpy}, + {{CDF_MaybeBuiltin, "memcmp", 3}, &CStringChecker::evalMemcmp}, + {{CDF_MaybeBuiltin, "memmove", 3}, &CStringChecker::evalMemmove}, + {{CDF_MaybeBuiltin, "memset", 3}, &CStringChecker::evalMemset}, + {{CDF_MaybeBuiltin, "explicit_memset", 3}, &CStringChecker::evalMemset}, + {{CDF_MaybeBuiltin, "strcpy", 2}, &CStringChecker::evalStrcpy}, + {{CDF_MaybeBuiltin, "strncpy", 3}, &CStringChecker::evalStrncpy}, + {{CDF_MaybeBuiltin, "stpcpy", 2}, &CStringChecker::evalStpcpy}, + {{CDF_MaybeBuiltin, "strlcpy", 3}, &CStringChecker::evalStrlcpy}, + {{CDF_MaybeBuiltin, "strcat", 2}, &CStringChecker::evalStrcat}, + {{CDF_MaybeBuiltin, "strncat", 3}, &CStringChecker::evalStrncat}, + {{CDF_MaybeBuiltin, "strlcat", 3}, &CStringChecker::evalStrlcat}, + {{CDF_MaybeBuiltin, "strlen", 1}, &CStringChecker::evalstrLength}, + {{CDF_MaybeBuiltin, "strnlen", 2}, &CStringChecker::evalstrnLength}, + {{CDF_MaybeBuiltin, "strcmp", 2}, &CStringChecker::evalStrcmp}, + {{CDF_MaybeBuiltin, "strncmp", 3}, &CStringChecker::evalStrncmp}, + {{CDF_MaybeBuiltin, "strcasecmp", 2}, &CStringChecker::evalStrcasecmp}, + {{CDF_MaybeBuiltin, "strncasecmp", 3}, &CStringChecker::evalStrncasecmp}, + {{CDF_MaybeBuiltin, "strsep", 2}, &CStringChecker::evalStrsep}, + {{CDF_MaybeBuiltin, "bcopy", 3}, &CStringChecker::evalBcopy}, + {{CDF_MaybeBuiltin, "bcmp", 3}, &CStringChecker::evalMemcmp}, + {{CDF_MaybeBuiltin, "bzero", 2}, &CStringChecker::evalBzero}, + {{CDF_MaybeBuiltin, "explicit_bzero", 2}, &CStringChecker::evalBzero}, + }; + + // These require a bit of special handling. + CallDescription StdCopy{{"std", "copy"}, 3}, + StdCopyBackward{{"std", "copy_backward"}, 3}; + + FnCheck identifyCall(const CallEvent &Call, CheckerContext &C) const; + void evalMemcpy(CheckerContext &C, const CallExpr *CE) const; + void evalMempcpy(CheckerContext &C, const CallExpr *CE) const; + void evalMemmove(CheckerContext &C, const CallExpr *CE) const; + void evalBcopy(CheckerContext &C, const CallExpr *CE) const; + void evalCopyCommon(CheckerContext &C, const CallExpr *CE, + ProgramStateRef state, + const Expr *Size, + const Expr *Source, + const Expr *Dest, + bool Restricted = false, + bool IsMempcpy = false) const; + + void evalMemcmp(CheckerContext &C, const CallExpr *CE) const; + + void evalstrLength(CheckerContext &C, const CallExpr *CE) const; + void evalstrnLength(CheckerContext &C, const CallExpr *CE) const; + void evalstrLengthCommon(CheckerContext &C, + const CallExpr *CE, + bool IsStrnlen = false) const; + + void evalStrcpy(CheckerContext &C, const CallExpr *CE) const; + void evalStrncpy(CheckerContext &C, const CallExpr *CE) const; + void evalStpcpy(CheckerContext &C, const CallExpr *CE) const; + void evalStrlcpy(CheckerContext &C, const CallExpr *CE) const; + void evalStrcpyCommon(CheckerContext &C, const CallExpr *CE, bool ReturnEnd, + bool IsBounded, ConcatFnKind appendK, + bool returnPtr = true) const; + + void evalStrcat(CheckerContext &C, const CallExpr *CE) const; + void evalStrncat(CheckerContext &C, const CallExpr *CE) const; + void evalStrlcat(CheckerContext &C, const CallExpr *CE) const; + + void evalStrcmp(CheckerContext &C, const CallExpr *CE) const; + void evalStrncmp(CheckerContext &C, const CallExpr *CE) const; + void evalStrcasecmp(CheckerContext &C, const CallExpr *CE) const; + void evalStrncasecmp(CheckerContext &C, const CallExpr *CE) const; + void evalStrcmpCommon(CheckerContext &C, + const CallExpr *CE, + bool IsBounded = false, + bool IgnoreCase = false) const; + + void evalStrsep(CheckerContext &C, const CallExpr *CE) const; + + void evalStdCopy(CheckerContext &C, const CallExpr *CE) const; + void evalStdCopyBackward(CheckerContext &C, const CallExpr *CE) const; + void evalStdCopyCommon(CheckerContext &C, const CallExpr *CE) const; + void evalMemset(CheckerContext &C, const CallExpr *CE) const; + void evalBzero(CheckerContext &C, const CallExpr *CE) const; + + // Utility methods + std::pair<ProgramStateRef , ProgramStateRef > + static assumeZero(CheckerContext &C, + ProgramStateRef state, SVal V, QualType Ty); + + static ProgramStateRef setCStringLength(ProgramStateRef state, + const MemRegion *MR, + SVal strLength); + static SVal getCStringLengthForRegion(CheckerContext &C, + ProgramStateRef &state, + const Expr *Ex, + const MemRegion *MR, + bool hypothetical); + SVal getCStringLength(CheckerContext &C, + ProgramStateRef &state, + const Expr *Ex, + SVal Buf, + bool hypothetical = false) const; + + const StringLiteral *getCStringLiteral(CheckerContext &C, + ProgramStateRef &state, + const Expr *expr, + SVal val) const; + + static ProgramStateRef InvalidateBuffer(CheckerContext &C, + ProgramStateRef state, + const Expr *Ex, SVal V, + bool IsSourceBuffer, + const Expr *Size); + + static bool SummarizeRegion(raw_ostream &os, ASTContext &Ctx, + const MemRegion *MR); + + static bool memsetAux(const Expr *DstBuffer, SVal CharE, + const Expr *Size, CheckerContext &C, + ProgramStateRef &State); + + // Re-usable checks + ProgramStateRef checkNonNull(CheckerContext &C, + ProgramStateRef state, + const Expr *S, + SVal l, + unsigned IdxOfArg) const; + ProgramStateRef CheckLocation(CheckerContext &C, + ProgramStateRef state, + const Expr *S, + SVal l, + const char *message = nullptr) const; + ProgramStateRef CheckBufferAccess(CheckerContext &C, + ProgramStateRef state, + const Expr *Size, + const Expr *FirstBuf, + const Expr *SecondBuf, + const char *firstMessage = nullptr, + const char *secondMessage = nullptr, + bool WarnAboutSize = false) const; + + ProgramStateRef CheckBufferAccess(CheckerContext &C, + ProgramStateRef state, + const Expr *Size, + const Expr *Buf, + const char *message = nullptr, + bool WarnAboutSize = false) const { + // This is a convenience overload. + return CheckBufferAccess(C, state, Size, Buf, nullptr, message, nullptr, + WarnAboutSize); + } + ProgramStateRef CheckOverlap(CheckerContext &C, + ProgramStateRef state, + const Expr *Size, + const Expr *First, + const Expr *Second) const; + void emitOverlapBug(CheckerContext &C, + ProgramStateRef state, + const Stmt *First, + const Stmt *Second) const; + + void emitNullArgBug(CheckerContext &C, ProgramStateRef State, const Stmt *S, + StringRef WarningMsg) const; + void emitOutOfBoundsBug(CheckerContext &C, ProgramStateRef State, + const Stmt *S, StringRef WarningMsg) const; + void emitNotCStringBug(CheckerContext &C, ProgramStateRef State, + const Stmt *S, StringRef WarningMsg) const; + void emitAdditionOverflowBug(CheckerContext &C, ProgramStateRef State) const; + + ProgramStateRef checkAdditionOverflow(CheckerContext &C, + ProgramStateRef state, + NonLoc left, + NonLoc right) const; + + // Return true if the destination buffer of the copy function may be in bound. + // Expects SVal of Size to be positive and unsigned. + // Expects SVal of FirstBuf to be a FieldRegion. + static bool IsFirstBufInBound(CheckerContext &C, + ProgramStateRef state, + const Expr *FirstBuf, + const Expr *Size); +}; + +} //end anonymous namespace + +REGISTER_MAP_WITH_PROGRAMSTATE(CStringLength, const MemRegion *, SVal) + +//===----------------------------------------------------------------------===// +// Individual checks and utility methods. +//===----------------------------------------------------------------------===// + +std::pair<ProgramStateRef , ProgramStateRef > +CStringChecker::assumeZero(CheckerContext &C, ProgramStateRef state, SVal V, + QualType Ty) { + Optional<DefinedSVal> val = V.getAs<DefinedSVal>(); + if (!val) + return std::pair<ProgramStateRef , ProgramStateRef >(state, state); + + SValBuilder &svalBuilder = C.getSValBuilder(); + DefinedOrUnknownSVal zero = svalBuilder.makeZeroVal(Ty); + return state->assume(svalBuilder.evalEQ(state, *val, zero)); +} + +ProgramStateRef CStringChecker::checkNonNull(CheckerContext &C, + ProgramStateRef state, + const Expr *S, SVal l, + unsigned IdxOfArg) const { + // If a previous check has failed, propagate the failure. + if (!state) + return nullptr; + + ProgramStateRef stateNull, stateNonNull; + std::tie(stateNull, stateNonNull) = assumeZero(C, state, l, S->getType()); + + if (stateNull && !stateNonNull) { + if (Filter.CheckCStringNullArg) { + SmallString<80> buf; + llvm::raw_svector_ostream OS(buf); + assert(CurrentFunctionDescription); + OS << "Null pointer passed as " << IdxOfArg + << llvm::getOrdinalSuffix(IdxOfArg) << " argument to " + << CurrentFunctionDescription; + + emitNullArgBug(C, stateNull, S, OS.str()); + } + return nullptr; + } + + // From here on, assume that the value is non-null. + assert(stateNonNull); + return stateNonNull; +} + +// FIXME: This was originally copied from ArrayBoundChecker.cpp. Refactor? +ProgramStateRef CStringChecker::CheckLocation(CheckerContext &C, + ProgramStateRef state, + const Expr *S, SVal l, + const char *warningMsg) const { + // If a previous check has failed, propagate the failure. + if (!state) + return nullptr; + + // Check for out of bound array element access. + const MemRegion *R = l.getAsRegion(); + if (!R) + return state; + + const ElementRegion *ER = dyn_cast<ElementRegion>(R); + if (!ER) + return state; + + if (ER->getValueType() != C.getASTContext().CharTy) + return state; + + // Get the size of the array. + const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion()); + SValBuilder &svalBuilder = C.getSValBuilder(); + SVal Extent = + svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder)); + DefinedOrUnknownSVal Size = Extent.castAs<DefinedOrUnknownSVal>(); + + // Get the index of the accessed element. + DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>(); + + ProgramStateRef StInBound = state->assumeInBound(Idx, Size, true); + ProgramStateRef StOutBound = state->assumeInBound(Idx, Size, false); + if (StOutBound && !StInBound) { + // These checks are either enabled by the CString out-of-bounds checker + // explicitly or implicitly by the Malloc checker. + // In the latter case we only do modeling but do not emit warning. + if (!Filter.CheckCStringOutOfBounds) + return nullptr; + // Emit a bug report. + if (warningMsg) { + emitOutOfBoundsBug(C, StOutBound, S, warningMsg); + } else { + assert(CurrentFunctionDescription); + assert(CurrentFunctionDescription[0] != '\0'); + + SmallString<80> buf; + llvm::raw_svector_ostream os(buf); + os << toUppercase(CurrentFunctionDescription[0]) + << &CurrentFunctionDescription[1] + << " accesses out-of-bound array element"; + emitOutOfBoundsBug(C, StOutBound, S, os.str()); + } + return nullptr; + } + + // Array bound check succeeded. From this point forward the array bound + // should always succeed. + return StInBound; +} + +ProgramStateRef CStringChecker::CheckBufferAccess(CheckerContext &C, + ProgramStateRef state, + const Expr *Size, + const Expr *FirstBuf, + const Expr *SecondBuf, + const char *firstMessage, + const char *secondMessage, + bool WarnAboutSize) const { + // If a previous check has failed, propagate the failure. + if (!state) + return nullptr; + + SValBuilder &svalBuilder = C.getSValBuilder(); + ASTContext &Ctx = svalBuilder.getContext(); + const LocationContext *LCtx = C.getLocationContext(); + + QualType sizeTy = Size->getType(); + QualType PtrTy = Ctx.getPointerType(Ctx.CharTy); + + // Check that the first buffer is non-null. + SVal BufVal = C.getSVal(FirstBuf); + state = checkNonNull(C, state, FirstBuf, BufVal, 1); + if (!state) + return nullptr; + + // If out-of-bounds checking is turned off, skip the rest. + if (!Filter.CheckCStringOutOfBounds) + return state; + + // Get the access length and make sure it is known. + // FIXME: This assumes the caller has already checked that the access length + // is positive. And that it's unsigned. + SVal LengthVal = C.getSVal(Size); + Optional<NonLoc> Length = LengthVal.getAs<NonLoc>(); + if (!Length) + return state; + + // Compute the offset of the last element to be accessed: size-1. + NonLoc One = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>(); + SVal Offset = svalBuilder.evalBinOpNN(state, BO_Sub, *Length, One, sizeTy); + if (Offset.isUnknown()) + return nullptr; + NonLoc LastOffset = Offset.castAs<NonLoc>(); + + // Check that the first buffer is sufficiently long. + SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType()); + if (Optional<Loc> BufLoc = BufStart.getAs<Loc>()) { + const Expr *warningExpr = (WarnAboutSize ? Size : FirstBuf); + + SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, + LastOffset, PtrTy); + state = CheckLocation(C, state, warningExpr, BufEnd, firstMessage); + + // If the buffer isn't large enough, abort. + if (!state) + return nullptr; + } + + // If there's a second buffer, check it as well. + if (SecondBuf) { + BufVal = state->getSVal(SecondBuf, LCtx); + state = checkNonNull(C, state, SecondBuf, BufVal, 2); + if (!state) + return nullptr; + + BufStart = svalBuilder.evalCast(BufVal, PtrTy, SecondBuf->getType()); + if (Optional<Loc> BufLoc = BufStart.getAs<Loc>()) { + const Expr *warningExpr = (WarnAboutSize ? Size : SecondBuf); + + SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, + LastOffset, PtrTy); + state = CheckLocation(C, state, warningExpr, BufEnd, secondMessage); + } + } + + // Large enough or not, return this state! + return state; +} + +ProgramStateRef CStringChecker::CheckOverlap(CheckerContext &C, + ProgramStateRef state, + const Expr *Size, + const Expr *First, + const Expr *Second) const { + if (!Filter.CheckCStringBufferOverlap) + return state; + + // Do a simple check for overlap: if the two arguments are from the same + // buffer, see if the end of the first is greater than the start of the second + // or vice versa. + + // If a previous check has failed, propagate the failure. + if (!state) + return nullptr; + + ProgramStateRef stateTrue, stateFalse; + + // Get the buffer values and make sure they're known locations. + const LocationContext *LCtx = C.getLocationContext(); + SVal firstVal = state->getSVal(First, LCtx); + SVal secondVal = state->getSVal(Second, LCtx); + + Optional<Loc> firstLoc = firstVal.getAs<Loc>(); + if (!firstLoc) + return state; + + Optional<Loc> secondLoc = secondVal.getAs<Loc>(); + if (!secondLoc) + return state; + + // Are the two values the same? + SValBuilder &svalBuilder = C.getSValBuilder(); + std::tie(stateTrue, stateFalse) = + state->assume(svalBuilder.evalEQ(state, *firstLoc, *secondLoc)); + + if (stateTrue && !stateFalse) { + // If the values are known to be equal, that's automatically an overlap. + emitOverlapBug(C, stateTrue, First, Second); + return nullptr; + } + + // assume the two expressions are not equal. + assert(stateFalse); + state = stateFalse; + + // Which value comes first? + QualType cmpTy = svalBuilder.getConditionType(); + SVal reverse = svalBuilder.evalBinOpLL(state, BO_GT, + *firstLoc, *secondLoc, cmpTy); + Optional<DefinedOrUnknownSVal> reverseTest = + reverse.getAs<DefinedOrUnknownSVal>(); + if (!reverseTest) + return state; + + std::tie(stateTrue, stateFalse) = state->assume(*reverseTest); + if (stateTrue) { + if (stateFalse) { + // If we don't know which one comes first, we can't perform this test. + return state; + } else { + // Switch the values so that firstVal is before secondVal. + std::swap(firstLoc, secondLoc); + + // Switch the Exprs as well, so that they still correspond. + std::swap(First, Second); + } + } + + // Get the length, and make sure it too is known. + SVal LengthVal = state->getSVal(Size, LCtx); + Optional<NonLoc> Length = LengthVal.getAs<NonLoc>(); + if (!Length) + return state; + + // Convert the first buffer's start address to char*. + // Bail out if the cast fails. + ASTContext &Ctx = svalBuilder.getContext(); + QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy); + SVal FirstStart = svalBuilder.evalCast(*firstLoc, CharPtrTy, + First->getType()); + Optional<Loc> FirstStartLoc = FirstStart.getAs<Loc>(); + if (!FirstStartLoc) + return state; + + // Compute the end of the first buffer. Bail out if THAT fails. + SVal FirstEnd = svalBuilder.evalBinOpLN(state, BO_Add, + *FirstStartLoc, *Length, CharPtrTy); + Optional<Loc> FirstEndLoc = FirstEnd.getAs<Loc>(); + if (!FirstEndLoc) + return state; + + // Is the end of the first buffer past the start of the second buffer? + SVal Overlap = svalBuilder.evalBinOpLL(state, BO_GT, + *FirstEndLoc, *secondLoc, cmpTy); + Optional<DefinedOrUnknownSVal> OverlapTest = + Overlap.getAs<DefinedOrUnknownSVal>(); + if (!OverlapTest) + return state; + + std::tie(stateTrue, stateFalse) = state->assume(*OverlapTest); + + if (stateTrue && !stateFalse) { + // Overlap! + emitOverlapBug(C, stateTrue, First, Second); + return nullptr; + } + + // assume the two expressions don't overlap. + assert(stateFalse); + return stateFalse; +} + +void CStringChecker::emitOverlapBug(CheckerContext &C, ProgramStateRef state, + const Stmt *First, const Stmt *Second) const { + ExplodedNode *N = C.generateErrorNode(state); + if (!N) + return; + + if (!BT_Overlap) + BT_Overlap.reset(new BugType(Filter.CheckNameCStringBufferOverlap, + categories::UnixAPI, "Improper arguments")); + + // Generate a report for this bug. + auto report = std::make_unique<PathSensitiveBugReport>( + *BT_Overlap, "Arguments must not be overlapping buffers", N); + report->addRange(First->getSourceRange()); + report->addRange(Second->getSourceRange()); + + C.emitReport(std::move(report)); +} + +void CStringChecker::emitNullArgBug(CheckerContext &C, ProgramStateRef State, + const Stmt *S, StringRef WarningMsg) const { + if (ExplodedNode *N = C.generateErrorNode(State)) { + if (!BT_Null) + BT_Null.reset(new BuiltinBug( + Filter.CheckNameCStringNullArg, categories::UnixAPI, + "Null pointer argument in call to byte string function")); + + BuiltinBug *BT = static_cast<BuiltinBug *>(BT_Null.get()); + auto Report = std::make_unique<PathSensitiveBugReport>(*BT, WarningMsg, N); + Report->addRange(S->getSourceRange()); + if (const auto *Ex = dyn_cast<Expr>(S)) + bugreporter::trackExpressionValue(N, Ex, *Report); + C.emitReport(std::move(Report)); + } +} + +void CStringChecker::emitOutOfBoundsBug(CheckerContext &C, + ProgramStateRef State, const Stmt *S, + StringRef WarningMsg) const { + if (ExplodedNode *N = C.generateErrorNode(State)) { + if (!BT_Bounds) + BT_Bounds.reset(new BuiltinBug( + Filter.CheckCStringOutOfBounds ? Filter.CheckNameCStringOutOfBounds + : Filter.CheckNameCStringNullArg, + "Out-of-bound array access", + "Byte string function accesses out-of-bound array element")); + + BuiltinBug *BT = static_cast<BuiltinBug *>(BT_Bounds.get()); + + // FIXME: It would be nice to eventually make this diagnostic more clear, + // e.g., by referencing the original declaration or by saying *why* this + // reference is outside the range. + auto Report = std::make_unique<PathSensitiveBugReport>(*BT, WarningMsg, N); + Report->addRange(S->getSourceRange()); + C.emitReport(std::move(Report)); + } +} + +void CStringChecker::emitNotCStringBug(CheckerContext &C, ProgramStateRef State, + const Stmt *S, + StringRef WarningMsg) const { + if (ExplodedNode *N = C.generateNonFatalErrorNode(State)) { + if (!BT_NotCString) + BT_NotCString.reset(new BuiltinBug( + Filter.CheckNameCStringNotNullTerm, categories::UnixAPI, + "Argument is not a null-terminated string.")); + + auto Report = + std::make_unique<PathSensitiveBugReport>(*BT_NotCString, WarningMsg, N); + + Report->addRange(S->getSourceRange()); + C.emitReport(std::move(Report)); + } +} + +void CStringChecker::emitAdditionOverflowBug(CheckerContext &C, + ProgramStateRef State) const { + if (ExplodedNode *N = C.generateErrorNode(State)) { + if (!BT_NotCString) + BT_NotCString.reset( + new BuiltinBug(Filter.CheckNameCStringOutOfBounds, "API", + "Sum of expressions causes overflow.")); + + // This isn't a great error message, but this should never occur in real + // code anyway -- you'd have to create a buffer longer than a size_t can + // represent, which is sort of a contradiction. + const char *WarningMsg = + "This expression will create a string whose length is too big to " + "be represented as a size_t"; + + auto Report = + std::make_unique<PathSensitiveBugReport>(*BT_NotCString, WarningMsg, N); + C.emitReport(std::move(Report)); + } +} + +ProgramStateRef CStringChecker::checkAdditionOverflow(CheckerContext &C, + ProgramStateRef state, + NonLoc left, + NonLoc right) const { + // If out-of-bounds checking is turned off, skip the rest. + if (!Filter.CheckCStringOutOfBounds) + return state; + + // If a previous check has failed, propagate the failure. + if (!state) + return nullptr; + + SValBuilder &svalBuilder = C.getSValBuilder(); + BasicValueFactory &BVF = svalBuilder.getBasicValueFactory(); + + QualType sizeTy = svalBuilder.getContext().getSizeType(); + const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy); + NonLoc maxVal = svalBuilder.makeIntVal(maxValInt); + + SVal maxMinusRight; + if (right.getAs<nonloc::ConcreteInt>()) { + maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, right, + sizeTy); + } else { + // Try switching the operands. (The order of these two assignments is + // important!) + maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, left, + sizeTy); + left = right; + } + + if (Optional<NonLoc> maxMinusRightNL = maxMinusRight.getAs<NonLoc>()) { + QualType cmpTy = svalBuilder.getConditionType(); + // If left > max - right, we have an overflow. + SVal willOverflow = svalBuilder.evalBinOpNN(state, BO_GT, left, + *maxMinusRightNL, cmpTy); + + ProgramStateRef stateOverflow, stateOkay; + std::tie(stateOverflow, stateOkay) = + state->assume(willOverflow.castAs<DefinedOrUnknownSVal>()); + + if (stateOverflow && !stateOkay) { + // We have an overflow. Emit a bug report. + emitAdditionOverflowBug(C, stateOverflow); + return nullptr; + } + + // From now on, assume an overflow didn't occur. + assert(stateOkay); + state = stateOkay; + } + + return state; +} + +ProgramStateRef CStringChecker::setCStringLength(ProgramStateRef state, + const MemRegion *MR, + SVal strLength) { + assert(!strLength.isUndef() && "Attempt to set an undefined string length"); + + MR = MR->StripCasts(); + + switch (MR->getKind()) { + case MemRegion::StringRegionKind: + // FIXME: This can happen if we strcpy() into a string region. This is + // undefined [C99 6.4.5p6], but we should still warn about it. + return state; + + case MemRegion::SymbolicRegionKind: + case MemRegion::AllocaRegionKind: + case MemRegion::VarRegionKind: + case MemRegion::FieldRegionKind: + case MemRegion::ObjCIvarRegionKind: + // These are the types we can currently track string lengths for. + break; + + case MemRegion::ElementRegionKind: + // FIXME: Handle element regions by upper-bounding the parent region's + // string length. + return state; + + default: + // Other regions (mostly non-data) can't have a reliable C string length. + // For now, just ignore the change. + // FIXME: These are rare but not impossible. We should output some kind of + // warning for things like strcpy((char[]){'a', 0}, "b"); + return state; + } + + if (strLength.isUnknown()) + return state->remove<CStringLength>(MR); + + return state->set<CStringLength>(MR, strLength); +} + +SVal CStringChecker::getCStringLengthForRegion(CheckerContext &C, + ProgramStateRef &state, + const Expr *Ex, + const MemRegion *MR, + bool hypothetical) { + if (!hypothetical) { + // If there's a recorded length, go ahead and return it. + const SVal *Recorded = state->get<CStringLength>(MR); + if (Recorded) + return *Recorded; + } + + // Otherwise, get a new symbol and update the state. + SValBuilder &svalBuilder = C.getSValBuilder(); + QualType sizeTy = svalBuilder.getContext().getSizeType(); + SVal strLength = svalBuilder.getMetadataSymbolVal(CStringChecker::getTag(), + MR, Ex, sizeTy, + C.getLocationContext(), + C.blockCount()); + + if (!hypothetical) { + if (Optional<NonLoc> strLn = strLength.getAs<NonLoc>()) { + // In case of unbounded calls strlen etc bound the range to SIZE_MAX/4 + BasicValueFactory &BVF = svalBuilder.getBasicValueFactory(); + const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy); + llvm::APSInt fourInt = APSIntType(maxValInt).getValue(4); + const llvm::APSInt *maxLengthInt = BVF.evalAPSInt(BO_Div, maxValInt, + fourInt); + NonLoc maxLength = svalBuilder.makeIntVal(*maxLengthInt); + SVal evalLength = svalBuilder.evalBinOpNN(state, BO_LE, *strLn, + maxLength, sizeTy); + state = state->assume(evalLength.castAs<DefinedOrUnknownSVal>(), true); + } + state = state->set<CStringLength>(MR, strLength); + } + + return strLength; +} + +SVal CStringChecker::getCStringLength(CheckerContext &C, ProgramStateRef &state, + const Expr *Ex, SVal Buf, + bool hypothetical) const { + const MemRegion *MR = Buf.getAsRegion(); + if (!MR) { + // If we can't get a region, see if it's something we /know/ isn't a + // C string. In the context of locations, the only time we can issue such + // a warning is for labels. + if (Optional<loc::GotoLabel> Label = Buf.getAs<loc::GotoLabel>()) { + if (Filter.CheckCStringNotNullTerm) { + SmallString<120> buf; + llvm::raw_svector_ostream os(buf); + assert(CurrentFunctionDescription); + os << "Argument to " << CurrentFunctionDescription + << " is the address of the label '" << Label->getLabel()->getName() + << "', which is not a null-terminated string"; + + emitNotCStringBug(C, state, Ex, os.str()); + } + return UndefinedVal(); + } + + // If it's not a region and not a label, give up. + return UnknownVal(); + } + + // If we have a region, strip casts from it and see if we can figure out + // its length. For anything we can't figure out, just return UnknownVal. + MR = MR->StripCasts(); + + switch (MR->getKind()) { + case MemRegion::StringRegionKind: { + // Modifying the contents of string regions is undefined [C99 6.4.5p6], + // so we can assume that the byte length is the correct C string length. + SValBuilder &svalBuilder = C.getSValBuilder(); + QualType sizeTy = svalBuilder.getContext().getSizeType(); + const StringLiteral *strLit = cast<StringRegion>(MR)->getStringLiteral(); + return svalBuilder.makeIntVal(strLit->getByteLength(), sizeTy); + } + case MemRegion::SymbolicRegionKind: + case MemRegion::AllocaRegionKind: + case MemRegion::VarRegionKind: + case MemRegion::FieldRegionKind: + case MemRegion::ObjCIvarRegionKind: + return getCStringLengthForRegion(C, state, Ex, MR, hypothetical); + case MemRegion::CompoundLiteralRegionKind: + // FIXME: Can we track this? Is it necessary? + return UnknownVal(); + case MemRegion::ElementRegionKind: + // FIXME: How can we handle this? It's not good enough to subtract the + // offset from the base string length; consider "123\x00567" and &a[5]. + return UnknownVal(); + default: + // Other regions (mostly non-data) can't have a reliable C string length. + // In this case, an error is emitted and UndefinedVal is returned. + // The caller should always be prepared to handle this case. + if (Filter.CheckCStringNotNullTerm) { + SmallString<120> buf; + llvm::raw_svector_ostream os(buf); + + assert(CurrentFunctionDescription); + os << "Argument to " << CurrentFunctionDescription << " is "; + + if (SummarizeRegion(os, C.getASTContext(), MR)) + os << ", which is not a null-terminated string"; + else + os << "not a null-terminated string"; + + emitNotCStringBug(C, state, Ex, os.str()); + } + return UndefinedVal(); + } +} + +const StringLiteral *CStringChecker::getCStringLiteral(CheckerContext &C, + ProgramStateRef &state, const Expr *expr, SVal val) const { + + // Get the memory region pointed to by the val. + const MemRegion *bufRegion = val.getAsRegion(); + if (!bufRegion) + return nullptr; + + // Strip casts off the memory region. + bufRegion = bufRegion->StripCasts(); + + // Cast the memory region to a string region. + const StringRegion *strRegion= dyn_cast<StringRegion>(bufRegion); + if (!strRegion) + return nullptr; + + // Return the actual string in the string region. + return strRegion->getStringLiteral(); +} + +bool CStringChecker::IsFirstBufInBound(CheckerContext &C, + ProgramStateRef state, + const Expr *FirstBuf, + const Expr *Size) { + // If we do not know that the buffer is long enough we return 'true'. + // Otherwise the parent region of this field region would also get + // invalidated, which would lead to warnings based on an unknown state. + + // Originally copied from CheckBufferAccess and CheckLocation. + SValBuilder &svalBuilder = C.getSValBuilder(); + ASTContext &Ctx = svalBuilder.getContext(); + const LocationContext *LCtx = C.getLocationContext(); + + QualType sizeTy = Size->getType(); + QualType PtrTy = Ctx.getPointerType(Ctx.CharTy); + SVal BufVal = state->getSVal(FirstBuf, LCtx); + + SVal LengthVal = state->getSVal(Size, LCtx); + Optional<NonLoc> Length = LengthVal.getAs<NonLoc>(); + if (!Length) + return true; // cf top comment. + + // Compute the offset of the last element to be accessed: size-1. + NonLoc One = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>(); + SVal Offset = svalBuilder.evalBinOpNN(state, BO_Sub, *Length, One, sizeTy); + if (Offset.isUnknown()) + return true; // cf top comment + NonLoc LastOffset = Offset.castAs<NonLoc>(); + + // Check that the first buffer is sufficiently long. + SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType()); + Optional<Loc> BufLoc = BufStart.getAs<Loc>(); + if (!BufLoc) + return true; // cf top comment. + + SVal BufEnd = + svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, LastOffset, PtrTy); + + // Check for out of bound array element access. + const MemRegion *R = BufEnd.getAsRegion(); + if (!R) + return true; // cf top comment. + + const ElementRegion *ER = dyn_cast<ElementRegion>(R); + if (!ER) + return true; // cf top comment. + + // FIXME: Does this crash when a non-standard definition + // of a library function is encountered? + assert(ER->getValueType() == C.getASTContext().CharTy && + "IsFirstBufInBound should only be called with char* ElementRegions"); + + // Get the size of the array. + const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion()); + SVal Extent = + svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder)); + DefinedOrUnknownSVal ExtentSize = Extent.castAs<DefinedOrUnknownSVal>(); + + // Get the index of the accessed element. + DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>(); + + ProgramStateRef StInBound = state->assumeInBound(Idx, ExtentSize, true); + + return static_cast<bool>(StInBound); +} + +ProgramStateRef CStringChecker::InvalidateBuffer(CheckerContext &C, + ProgramStateRef state, + const Expr *E, SVal V, + bool IsSourceBuffer, + const Expr *Size) { + Optional<Loc> L = V.getAs<Loc>(); + if (!L) + return state; + + // FIXME: This is a simplified version of what's in CFRefCount.cpp -- it makes + // some assumptions about the value that CFRefCount can't. Even so, it should + // probably be refactored. + if (Optional<loc::MemRegionVal> MR = L->getAs<loc::MemRegionVal>()) { + const MemRegion *R = MR->getRegion()->StripCasts(); + + // Are we dealing with an ElementRegion? If so, we should be invalidating + // the super-region. + if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) { + R = ER->getSuperRegion(); + // FIXME: What about layers of ElementRegions? + } + + // Invalidate this region. + const LocationContext *LCtx = C.getPredecessor()->getLocationContext(); + + bool CausesPointerEscape = false; + RegionAndSymbolInvalidationTraits ITraits; + // Invalidate and escape only indirect regions accessible through the source + // buffer. + if (IsSourceBuffer) { + ITraits.setTrait(R->getBaseRegion(), + RegionAndSymbolInvalidationTraits::TK_PreserveContents); + ITraits.setTrait(R, RegionAndSymbolInvalidationTraits::TK_SuppressEscape); + CausesPointerEscape = true; + } else { + const MemRegion::Kind& K = R->getKind(); + if (K == MemRegion::FieldRegionKind) + if (Size && IsFirstBufInBound(C, state, E, Size)) { + // If destination buffer is a field region and access is in bound, + // do not invalidate its super region. + ITraits.setTrait( + R, + RegionAndSymbolInvalidationTraits::TK_DoNotInvalidateSuperRegion); + } + } + + return state->invalidateRegions(R, E, C.blockCount(), LCtx, + CausesPointerEscape, nullptr, nullptr, + &ITraits); + } + + // If we have a non-region value by chance, just remove the binding. + // FIXME: is this necessary or correct? This handles the non-Region + // cases. Is it ever valid to store to these? + return state->killBinding(*L); +} + +bool CStringChecker::SummarizeRegion(raw_ostream &os, ASTContext &Ctx, + const MemRegion *MR) { + switch (MR->getKind()) { + case MemRegion::FunctionCodeRegionKind: { + if (const auto *FD = cast<FunctionCodeRegion>(MR)->getDecl()) + os << "the address of the function '" << *FD << '\''; + else + os << "the address of a function"; + return true; + } + case MemRegion::BlockCodeRegionKind: + os << "block text"; + return true; + case MemRegion::BlockDataRegionKind: + os << "a block"; + return true; + case MemRegion::CXXThisRegionKind: + case MemRegion::CXXTempObjectRegionKind: + os << "a C++ temp object of type " + << cast<TypedValueRegion>(MR)->getValueType().getAsString(); + return true; + case MemRegion::VarRegionKind: + os << "a variable of type" + << cast<TypedValueRegion>(MR)->getValueType().getAsString(); + return true; + case MemRegion::FieldRegionKind: + os << "a field of type " + << cast<TypedValueRegion>(MR)->getValueType().getAsString(); + return true; + case MemRegion::ObjCIvarRegionKind: + os << "an instance variable of type " + << cast<TypedValueRegion>(MR)->getValueType().getAsString(); + return true; + default: + return false; + } +} + +bool CStringChecker::memsetAux(const Expr *DstBuffer, SVal CharVal, + const Expr *Size, CheckerContext &C, + ProgramStateRef &State) { + SVal MemVal = C.getSVal(DstBuffer); + SVal SizeVal = C.getSVal(Size); + const MemRegion *MR = MemVal.getAsRegion(); + if (!MR) + return false; + + // We're about to model memset by producing a "default binding" in the Store. + // Our current implementation - RegionStore - doesn't support default bindings + // that don't cover the whole base region. So we should first get the offset + // and the base region to figure out whether the offset of buffer is 0. + RegionOffset Offset = MR->getAsOffset(); + const MemRegion *BR = Offset.getRegion(); + + Optional<NonLoc> SizeNL = SizeVal.getAs<NonLoc>(); + if (!SizeNL) + return false; + + SValBuilder &svalBuilder = C.getSValBuilder(); + ASTContext &Ctx = C.getASTContext(); + + // void *memset(void *dest, int ch, size_t count); + // For now we can only handle the case of offset is 0 and concrete char value. + if (Offset.isValid() && !Offset.hasSymbolicOffset() && + Offset.getOffset() == 0) { + // Get the base region's extent. + auto *SubReg = cast<SubRegion>(BR); + DefinedOrUnknownSVal Extent = SubReg->getExtent(svalBuilder); + + ProgramStateRef StateWholeReg, StateNotWholeReg; + std::tie(StateWholeReg, StateNotWholeReg) = + State->assume(svalBuilder.evalEQ(State, Extent, *SizeNL)); + + // With the semantic of 'memset()', we should convert the CharVal to + // unsigned char. + CharVal = svalBuilder.evalCast(CharVal, Ctx.UnsignedCharTy, Ctx.IntTy); + + ProgramStateRef StateNullChar, StateNonNullChar; + std::tie(StateNullChar, StateNonNullChar) = + assumeZero(C, State, CharVal, Ctx.UnsignedCharTy); + + if (StateWholeReg && !StateNotWholeReg && StateNullChar && + !StateNonNullChar) { + // If the 'memset()' acts on the whole region of destination buffer and + // the value of the second argument of 'memset()' is zero, bind the second + // argument's value to the destination buffer with 'default binding'. + // FIXME: Since there is no perfect way to bind the non-zero character, we + // can only deal with zero value here. In the future, we need to deal with + // the binding of non-zero value in the case of whole region. + State = State->bindDefaultZero(svalBuilder.makeLoc(BR), + C.getLocationContext()); + } else { + // If the destination buffer's extent is not equal to the value of + // third argument, just invalidate buffer. + State = InvalidateBuffer(C, State, DstBuffer, MemVal, + /*IsSourceBuffer*/ false, Size); + } + + if (StateNullChar && !StateNonNullChar) { + // If the value of the second argument of 'memset()' is zero, set the + // string length of destination buffer to 0 directly. + State = setCStringLength(State, MR, + svalBuilder.makeZeroVal(Ctx.getSizeType())); + } else if (!StateNullChar && StateNonNullChar) { + SVal NewStrLen = svalBuilder.getMetadataSymbolVal( + CStringChecker::getTag(), MR, DstBuffer, Ctx.getSizeType(), + C.getLocationContext(), C.blockCount()); + + // If the value of second argument is not zero, then the string length + // is at least the size argument. + SVal NewStrLenGESize = svalBuilder.evalBinOp( + State, BO_GE, NewStrLen, SizeVal, svalBuilder.getConditionType()); + + State = setCStringLength( + State->assume(NewStrLenGESize.castAs<DefinedOrUnknownSVal>(), true), + MR, NewStrLen); + } + } else { + // If the offset is not zero and char value is not concrete, we can do + // nothing but invalidate the buffer. + State = InvalidateBuffer(C, State, DstBuffer, MemVal, + /*IsSourceBuffer*/ false, Size); + } + return true; +} + +//===----------------------------------------------------------------------===// +// evaluation of individual function calls. +//===----------------------------------------------------------------------===// + +void CStringChecker::evalCopyCommon(CheckerContext &C, + const CallExpr *CE, + ProgramStateRef state, + const Expr *Size, const Expr *Dest, + const Expr *Source, bool Restricted, + bool IsMempcpy) const { + CurrentFunctionDescription = "memory copy function"; + + // See if the size argument is zero. + const LocationContext *LCtx = C.getLocationContext(); + SVal sizeVal = state->getSVal(Size, LCtx); + QualType sizeTy = Size->getType(); + + ProgramStateRef stateZeroSize, stateNonZeroSize; + std::tie(stateZeroSize, stateNonZeroSize) = + assumeZero(C, state, sizeVal, sizeTy); + + // Get the value of the Dest. + SVal destVal = state->getSVal(Dest, LCtx); + + // If the size is zero, there won't be any actual memory access, so + // just bind the return value to the destination buffer and return. + if (stateZeroSize && !stateNonZeroSize) { + stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, destVal); + C.addTransition(stateZeroSize); + return; + } + + // If the size can be nonzero, we have to check the other arguments. + if (stateNonZeroSize) { + state = stateNonZeroSize; + + // Ensure the destination is not null. If it is NULL there will be a + // NULL pointer dereference. + state = checkNonNull(C, state, Dest, destVal, 1); + if (!state) + return; + + // Get the value of the Src. + SVal srcVal = state->getSVal(Source, LCtx); + + // Ensure the source is not null. If it is NULL there will be a + // NULL pointer dereference. + state = checkNonNull(C, state, Source, srcVal, 2); + if (!state) + return; + + // Ensure the accesses are valid and that the buffers do not overlap. + const char * const writeWarning = + "Memory copy function overflows destination buffer"; + state = CheckBufferAccess(C, state, Size, Dest, Source, + writeWarning, /* sourceWarning = */ nullptr); + if (Restricted) + state = CheckOverlap(C, state, Size, Dest, Source); + + if (!state) + return; + + // If this is mempcpy, get the byte after the last byte copied and + // bind the expr. + if (IsMempcpy) { + // Get the byte after the last byte copied. + SValBuilder &SvalBuilder = C.getSValBuilder(); + ASTContext &Ctx = SvalBuilder.getContext(); + QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy); + SVal DestRegCharVal = + SvalBuilder.evalCast(destVal, CharPtrTy, Dest->getType()); + SVal lastElement = C.getSValBuilder().evalBinOp( + state, BO_Add, DestRegCharVal, sizeVal, Dest->getType()); + // If we don't know how much we copied, we can at least + // conjure a return value for later. + if (lastElement.isUnknown()) + lastElement = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx, + C.blockCount()); + + // The byte after the last byte copied is the return value. + state = state->BindExpr(CE, LCtx, lastElement); + } else { + // All other copies return the destination buffer. + // (Well, bcopy() has a void return type, but this won't hurt.) + state = state->BindExpr(CE, LCtx, destVal); + } + + // Invalidate the destination (regular invalidation without pointer-escaping + // the address of the top-level region). + // FIXME: Even if we can't perfectly model the copy, we should see if we + // can use LazyCompoundVals to copy the source values into the destination. + // This would probably remove any existing bindings past the end of the + // copied region, but that's still an improvement over blank invalidation. + state = InvalidateBuffer(C, state, Dest, C.getSVal(Dest), + /*IsSourceBuffer*/false, Size); + + // Invalidate the source (const-invalidation without const-pointer-escaping + // the address of the top-level region). + state = InvalidateBuffer(C, state, Source, C.getSVal(Source), + /*IsSourceBuffer*/true, nullptr); + + C.addTransition(state); + } +} + + +void CStringChecker::evalMemcpy(CheckerContext &C, const CallExpr *CE) const { + // void *memcpy(void *restrict dst, const void *restrict src, size_t n); + // The return value is the address of the destination buffer. + const Expr *Dest = CE->getArg(0); + ProgramStateRef state = C.getState(); + + evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true); +} + +void CStringChecker::evalMempcpy(CheckerContext &C, const CallExpr *CE) const { + // void *mempcpy(void *restrict dst, const void *restrict src, size_t n); + // The return value is a pointer to the byte following the last written byte. + const Expr *Dest = CE->getArg(0); + ProgramStateRef state = C.getState(); + + evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true, true); +} + +void CStringChecker::evalMemmove(CheckerContext &C, const CallExpr *CE) const { + // void *memmove(void *dst, const void *src, size_t n); + // The return value is the address of the destination buffer. + const Expr *Dest = CE->getArg(0); + ProgramStateRef state = C.getState(); + + evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1)); +} + +void CStringChecker::evalBcopy(CheckerContext &C, const CallExpr *CE) const { + // void bcopy(const void *src, void *dst, size_t n); + evalCopyCommon(C, CE, C.getState(), + CE->getArg(2), CE->getArg(1), CE->getArg(0)); +} + +void CStringChecker::evalMemcmp(CheckerContext &C, const CallExpr *CE) const { + // int memcmp(const void *s1, const void *s2, size_t n); + CurrentFunctionDescription = "memory comparison function"; + + const Expr *Left = CE->getArg(0); + const Expr *Right = CE->getArg(1); + const Expr *Size = CE->getArg(2); + + ProgramStateRef state = C.getState(); + SValBuilder &svalBuilder = C.getSValBuilder(); + + // See if the size argument is zero. + const LocationContext *LCtx = C.getLocationContext(); + SVal sizeVal = state->getSVal(Size, LCtx); + QualType sizeTy = Size->getType(); + + ProgramStateRef stateZeroSize, stateNonZeroSize; + std::tie(stateZeroSize, stateNonZeroSize) = + assumeZero(C, state, sizeVal, sizeTy); + + // If the size can be zero, the result will be 0 in that case, and we don't + // have to check either of the buffers. + if (stateZeroSize) { + state = stateZeroSize; + state = state->BindExpr(CE, LCtx, + svalBuilder.makeZeroVal(CE->getType())); + C.addTransition(state); + } + + // If the size can be nonzero, we have to check the other arguments. + if (stateNonZeroSize) { + state = stateNonZeroSize; + // If we know the two buffers are the same, we know the result is 0. + // First, get the two buffers' addresses. Another checker will have already + // made sure they're not undefined. + DefinedOrUnknownSVal LV = + state->getSVal(Left, LCtx).castAs<DefinedOrUnknownSVal>(); + DefinedOrUnknownSVal RV = + state->getSVal(Right, LCtx).castAs<DefinedOrUnknownSVal>(); + + // See if they are the same. + DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV); + ProgramStateRef StSameBuf, StNotSameBuf; + std::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf); + + // If the two arguments are the same buffer, we know the result is 0, + // and we only need to check one size. + if (StSameBuf && !StNotSameBuf) { + state = StSameBuf; + state = CheckBufferAccess(C, state, Size, Left); + if (state) { + state = StSameBuf->BindExpr(CE, LCtx, + svalBuilder.makeZeroVal(CE->getType())); + C.addTransition(state); + } + return; + } + + // If the two arguments might be different buffers, we have to check + // the size of both of them. + assert(StNotSameBuf); + state = CheckBufferAccess(C, state, Size, Left, Right); + if (state) { + // The return value is the comparison result, which we don't know. + SVal CmpV = + svalBuilder.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount()); + state = state->BindExpr(CE, LCtx, CmpV); + C.addTransition(state); + } + } +} + +void CStringChecker::evalstrLength(CheckerContext &C, + const CallExpr *CE) const { + // size_t strlen(const char *s); + evalstrLengthCommon(C, CE, /* IsStrnlen = */ false); +} + +void CStringChecker::evalstrnLength(CheckerContext &C, + const CallExpr *CE) const { + // size_t strnlen(const char *s, size_t maxlen); + evalstrLengthCommon(C, CE, /* IsStrnlen = */ true); +} + +void CStringChecker::evalstrLengthCommon(CheckerContext &C, const CallExpr *CE, + bool IsStrnlen) const { + CurrentFunctionDescription = "string length function"; + ProgramStateRef state = C.getState(); + const LocationContext *LCtx = C.getLocationContext(); + + if (IsStrnlen) { + const Expr *maxlenExpr = CE->getArg(1); + SVal maxlenVal = state->getSVal(maxlenExpr, LCtx); + + ProgramStateRef stateZeroSize, stateNonZeroSize; + std::tie(stateZeroSize, stateNonZeroSize) = + assumeZero(C, state, maxlenVal, maxlenExpr->getType()); + + // If the size can be zero, the result will be 0 in that case, and we don't + // have to check the string itself. + if (stateZeroSize) { + SVal zero = C.getSValBuilder().makeZeroVal(CE->getType()); + stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, zero); + C.addTransition(stateZeroSize); + } + + // If the size is GUARANTEED to be zero, we're done! + if (!stateNonZeroSize) + return; + + // Otherwise, record the assumption that the size is nonzero. + state = stateNonZeroSize; + } + + // Check that the string argument is non-null. + const Expr *Arg = CE->getArg(0); + SVal ArgVal = state->getSVal(Arg, LCtx); + + state = checkNonNull(C, state, Arg, ArgVal, 1); + + if (!state) + return; + + SVal strLength = getCStringLength(C, state, Arg, ArgVal); + + // If the argument isn't a valid C string, there's no valid state to + // transition to. + if (strLength.isUndef()) + return; + + DefinedOrUnknownSVal result = UnknownVal(); + + // If the check is for strnlen() then bind the return value to no more than + // the maxlen value. + if (IsStrnlen) { + QualType cmpTy = C.getSValBuilder().getConditionType(); + + // It's a little unfortunate to be getting this again, + // but it's not that expensive... + const Expr *maxlenExpr = CE->getArg(1); + SVal maxlenVal = state->getSVal(maxlenExpr, LCtx); + + Optional<NonLoc> strLengthNL = strLength.getAs<NonLoc>(); + Optional<NonLoc> maxlenValNL = maxlenVal.getAs<NonLoc>(); + + if (strLengthNL && maxlenValNL) { + ProgramStateRef stateStringTooLong, stateStringNotTooLong; + + // Check if the strLength is greater than the maxlen. + std::tie(stateStringTooLong, stateStringNotTooLong) = state->assume( + C.getSValBuilder() + .evalBinOpNN(state, BO_GT, *strLengthNL, *maxlenValNL, cmpTy) + .castAs<DefinedOrUnknownSVal>()); + + if (stateStringTooLong && !stateStringNotTooLong) { + // If the string is longer than maxlen, return maxlen. + result = *maxlenValNL; + } else if (stateStringNotTooLong && !stateStringTooLong) { + // If the string is shorter than maxlen, return its length. + result = *strLengthNL; + } + } + + if (result.isUnknown()) { + // If we don't have enough information for a comparison, there's + // no guarantee the full string length will actually be returned. + // All we know is the return value is the min of the string length + // and the limit. This is better than nothing. + result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx, + C.blockCount()); + NonLoc resultNL = result.castAs<NonLoc>(); + + if (strLengthNL) { + state = state->assume(C.getSValBuilder().evalBinOpNN( + state, BO_LE, resultNL, *strLengthNL, cmpTy) + .castAs<DefinedOrUnknownSVal>(), true); + } + + if (maxlenValNL) { + state = state->assume(C.getSValBuilder().evalBinOpNN( + state, BO_LE, resultNL, *maxlenValNL, cmpTy) + .castAs<DefinedOrUnknownSVal>(), true); + } + } + + } else { + // This is a plain strlen(), not strnlen(). + result = strLength.castAs<DefinedOrUnknownSVal>(); + + // If we don't know the length of the string, conjure a return + // value, so it can be used in constraints, at least. + if (result.isUnknown()) { + result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx, + C.blockCount()); + } + } + + // Bind the return value. + assert(!result.isUnknown() && "Should have conjured a value by now"); + state = state->BindExpr(CE, LCtx, result); + C.addTransition(state); +} + +void CStringChecker::evalStrcpy(CheckerContext &C, const CallExpr *CE) const { + // char *strcpy(char *restrict dst, const char *restrict src); + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ false, + /* IsBounded = */ false, + /* appendK = */ ConcatFnKind::none); +} + +void CStringChecker::evalStrncpy(CheckerContext &C, const CallExpr *CE) const { + // char *strncpy(char *restrict dst, const char *restrict src, size_t n); + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ false, + /* IsBounded = */ true, + /* appendK = */ ConcatFnKind::none); +} + +void CStringChecker::evalStpcpy(CheckerContext &C, const CallExpr *CE) const { + // char *stpcpy(char *restrict dst, const char *restrict src); + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ true, + /* IsBounded = */ false, + /* appendK = */ ConcatFnKind::none); +} + +void CStringChecker::evalStrlcpy(CheckerContext &C, const CallExpr *CE) const { + // size_t strlcpy(char *dest, const char *src, size_t size); + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ true, + /* IsBounded = */ true, + /* appendK = */ ConcatFnKind::none, + /* returnPtr = */ false); +} + +void CStringChecker::evalStrcat(CheckerContext &C, const CallExpr *CE) const { + // char *strcat(char *restrict s1, const char *restrict s2); + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ false, + /* IsBounded = */ false, + /* appendK = */ ConcatFnKind::strcat); +} + +void CStringChecker::evalStrncat(CheckerContext &C, const CallExpr *CE) const { + //char *strncat(char *restrict s1, const char *restrict s2, size_t n); + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ false, + /* IsBounded = */ true, + /* appendK = */ ConcatFnKind::strcat); +} + +void CStringChecker::evalStrlcat(CheckerContext &C, const CallExpr *CE) const { + // size_t strlcat(char *dst, const char *src, size_t size); + // It will append at most size - strlen(dst) - 1 bytes, + // NULL-terminating the result. + evalStrcpyCommon(C, CE, + /* ReturnEnd = */ false, + /* IsBounded = */ true, + /* appendK = */ ConcatFnKind::strlcat, + /* returnPtr = */ false); +} + +void CStringChecker::evalStrcpyCommon(CheckerContext &C, const CallExpr *CE, + bool ReturnEnd, bool IsBounded, + ConcatFnKind appendK, + bool returnPtr) const { + if (appendK == ConcatFnKind::none) + CurrentFunctionDescription = "string copy function"; + else + CurrentFunctionDescription = "string concatenation function"; + ProgramStateRef state = C.getState(); + const LocationContext *LCtx = C.getLocationContext(); + + // Check that the destination is non-null. + const Expr *Dst = CE->getArg(0); + SVal DstVal = state->getSVal(Dst, LCtx); + + state = checkNonNull(C, state, Dst, DstVal, 1); + if (!state) + return; + + // Check that the source is non-null. + const Expr *srcExpr = CE->getArg(1); + SVal srcVal = state->getSVal(srcExpr, LCtx); + state = checkNonNull(C, state, srcExpr, srcVal, 2); + if (!state) + return; + + // Get the string length of the source. + SVal strLength = getCStringLength(C, state, srcExpr, srcVal); + Optional<NonLoc> strLengthNL = strLength.getAs<NonLoc>(); + + // Get the string length of the destination buffer. + SVal dstStrLength = getCStringLength(C, state, Dst, DstVal); + Optional<NonLoc> dstStrLengthNL = dstStrLength.getAs<NonLoc>(); + + // If the source isn't a valid C string, give up. + if (strLength.isUndef()) + return; + + SValBuilder &svalBuilder = C.getSValBuilder(); + QualType cmpTy = svalBuilder.getConditionType(); + QualType sizeTy = svalBuilder.getContext().getSizeType(); + + // These two values allow checking two kinds of errors: + // - actual overflows caused by a source that doesn't fit in the destination + // - potential overflows caused by a bound that could exceed the destination + SVal amountCopied = UnknownVal(); + SVal maxLastElementIndex = UnknownVal(); + const char *boundWarning = nullptr; + + state = CheckOverlap(C, state, IsBounded ? CE->getArg(2) : CE->getArg(1), Dst, + srcExpr); + + if (!state) + return; + + // If the function is strncpy, strncat, etc... it is bounded. + if (IsBounded) { + // Get the max number of characters to copy. + const Expr *lenExpr = CE->getArg(2); + SVal lenVal = state->getSVal(lenExpr, LCtx); + + // Protect against misdeclared strncpy(). + lenVal = svalBuilder.evalCast(lenVal, sizeTy, lenExpr->getType()); + + Optional<NonLoc> lenValNL = lenVal.getAs<NonLoc>(); + + // If we know both values, we might be able to figure out how much + // we're copying. + if (strLengthNL && lenValNL) { + switch (appendK) { + case ConcatFnKind::none: + case ConcatFnKind::strcat: { + ProgramStateRef stateSourceTooLong, stateSourceNotTooLong; + // Check if the max number to copy is less than the length of the src. + // If the bound is equal to the source length, strncpy won't null- + // terminate the result! + std::tie(stateSourceTooLong, stateSourceNotTooLong) = state->assume( + svalBuilder + .evalBinOpNN(state, BO_GE, *strLengthNL, *lenValNL, cmpTy) + .castAs<DefinedOrUnknownSVal>()); + + if (stateSourceTooLong && !stateSourceNotTooLong) { + // Max number to copy is less than the length of the src, so the + // actual strLength copied is the max number arg. + state = stateSourceTooLong; + amountCopied = lenVal; + + } else if (!stateSourceTooLong && stateSourceNotTooLong) { + // The source buffer entirely fits in the bound. + state = stateSourceNotTooLong; + amountCopied = strLength; + } + break; + } + case ConcatFnKind::strlcat: + if (!dstStrLengthNL) + return; + + // amountCopied = min (size - dstLen - 1 , srcLen) + SVal freeSpace = svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL, + *dstStrLengthNL, sizeTy); + if (!freeSpace.getAs<NonLoc>()) + return; + freeSpace = + svalBuilder.evalBinOp(state, BO_Sub, freeSpace, + svalBuilder.makeIntVal(1, sizeTy), sizeTy); + Optional<NonLoc> freeSpaceNL = freeSpace.getAs<NonLoc>(); + + // While unlikely, it is possible that the subtraction is + // too complex to compute, let's check whether it succeeded. + if (!freeSpaceNL) + return; + SVal hasEnoughSpace = svalBuilder.evalBinOpNN( + state, BO_LE, *strLengthNL, *freeSpaceNL, cmpTy); + + ProgramStateRef TrueState, FalseState; + std::tie(TrueState, FalseState) = + state->assume(hasEnoughSpace.castAs<DefinedOrUnknownSVal>()); + + // srcStrLength <= size - dstStrLength -1 + if (TrueState && !FalseState) { + amountCopied = strLength; + } + + // srcStrLength > size - dstStrLength -1 + if (!TrueState && FalseState) { + amountCopied = freeSpace; + } + + if (TrueState && FalseState) + amountCopied = UnknownVal(); + break; + } + } + // We still want to know if the bound is known to be too large. + if (lenValNL) { + switch (appendK) { + case ConcatFnKind::strcat: + // For strncat, the check is strlen(dst) + lenVal < sizeof(dst) + + // Get the string length of the destination. If the destination is + // memory that can't have a string length, we shouldn't be copying + // into it anyway. + if (dstStrLength.isUndef()) + return; + + if (dstStrLengthNL) { + maxLastElementIndex = svalBuilder.evalBinOpNN( + state, BO_Add, *lenValNL, *dstStrLengthNL, sizeTy); + + boundWarning = "Size argument is greater than the free space in the " + "destination buffer"; + } + break; + case ConcatFnKind::none: + case ConcatFnKind::strlcat: + // For strncpy and strlcat, this is just checking + // that lenVal <= sizeof(dst). + // (Yes, strncpy and strncat differ in how they treat termination. + // strncat ALWAYS terminates, but strncpy doesn't.) + + // We need a special case for when the copy size is zero, in which + // case strncpy will do no work at all. Our bounds check uses n-1 + // as the last element accessed, so n == 0 is problematic. + ProgramStateRef StateZeroSize, StateNonZeroSize; + std::tie(StateZeroSize, StateNonZeroSize) = + assumeZero(C, state, *lenValNL, sizeTy); + + // If the size is known to be zero, we're done. + if (StateZeroSize && !StateNonZeroSize) { + if (returnPtr) { + StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, DstVal); + } else { + if (appendK == ConcatFnKind::none) { + // strlcpy returns strlen(src) + StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, strLength); + } else { + // strlcat returns strlen(src) + strlen(dst) + SVal retSize = svalBuilder.evalBinOp( + state, BO_Add, strLength, dstStrLength, sizeTy); + StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, retSize); + } + } + C.addTransition(StateZeroSize); + return; + } + + // Otherwise, go ahead and figure out the last element we'll touch. + // We don't record the non-zero assumption here because we can't + // be sure. We won't warn on a possible zero. + NonLoc one = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>(); + maxLastElementIndex = + svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL, one, sizeTy); + boundWarning = "Size argument is greater than the length of the " + "destination buffer"; + break; + } + } + } else { + // The function isn't bounded. The amount copied should match the length + // of the source buffer. + amountCopied = strLength; + } + + assert(state); + + // This represents the number of characters copied into the destination + // buffer. (It may not actually be the strlen if the destination buffer + // is not terminated.) + SVal finalStrLength = UnknownVal(); + SVal strlRetVal = UnknownVal(); + + if (appendK == ConcatFnKind::none && !returnPtr) { + // strlcpy returns the sizeof(src) + strlRetVal = strLength; + } + + // If this is an appending function (strcat, strncat...) then set the + // string length to strlen(src) + strlen(dst) since the buffer will + // ultimately contain both. + if (appendK != ConcatFnKind::none) { + // Get the string length of the destination. If the destination is memory + // that can't have a string length, we shouldn't be copying into it anyway. + if (dstStrLength.isUndef()) + return; + + if (appendK == ConcatFnKind::strlcat && dstStrLengthNL && strLengthNL) { + strlRetVal = svalBuilder.evalBinOpNN(state, BO_Add, *strLengthNL, + *dstStrLengthNL, sizeTy); + } + + Optional<NonLoc> amountCopiedNL = amountCopied.getAs<NonLoc>(); + + // If we know both string lengths, we might know the final string length. + if (amountCopiedNL && dstStrLengthNL) { + // Make sure the two lengths together don't overflow a size_t. + state = checkAdditionOverflow(C, state, *amountCopiedNL, *dstStrLengthNL); + if (!state) + return; + + finalStrLength = svalBuilder.evalBinOpNN(state, BO_Add, *amountCopiedNL, + *dstStrLengthNL, sizeTy); + } + + // If we couldn't get a single value for the final string length, + // we can at least bound it by the individual lengths. + if (finalStrLength.isUnknown()) { + // Try to get a "hypothetical" string length symbol, which we can later + // set as a real value if that turns out to be the case. + finalStrLength = getCStringLength(C, state, CE, DstVal, true); + assert(!finalStrLength.isUndef()); + + if (Optional<NonLoc> finalStrLengthNL = finalStrLength.getAs<NonLoc>()) { + if (amountCopiedNL && appendK == ConcatFnKind::none) { + // we overwrite dst string with the src + // finalStrLength >= srcStrLength + SVal sourceInResult = svalBuilder.evalBinOpNN( + state, BO_GE, *finalStrLengthNL, *amountCopiedNL, cmpTy); + state = state->assume(sourceInResult.castAs<DefinedOrUnknownSVal>(), + true); + if (!state) + return; + } + + if (dstStrLengthNL && appendK != ConcatFnKind::none) { + // we extend the dst string with the src + // finalStrLength >= dstStrLength + SVal destInResult = svalBuilder.evalBinOpNN(state, BO_GE, + *finalStrLengthNL, + *dstStrLengthNL, + cmpTy); + state = + state->assume(destInResult.castAs<DefinedOrUnknownSVal>(), true); + if (!state) + return; + } + } + } + + } else { + // Otherwise, this is a copy-over function (strcpy, strncpy, ...), and + // the final string length will match the input string length. + finalStrLength = amountCopied; + } + + SVal Result; + + if (returnPtr) { + // The final result of the function will either be a pointer past the last + // copied element, or a pointer to the start of the destination buffer. + Result = (ReturnEnd ? UnknownVal() : DstVal); + } else { + if (appendK == ConcatFnKind::strlcat || appendK == ConcatFnKind::none) + //strlcpy, strlcat + Result = strlRetVal; + else + Result = finalStrLength; + } + + assert(state); + + // If the destination is a MemRegion, try to check for a buffer overflow and + // record the new string length. + if (Optional<loc::MemRegionVal> dstRegVal = + DstVal.getAs<loc::MemRegionVal>()) { + QualType ptrTy = Dst->getType(); + + // If we have an exact value on a bounded copy, use that to check for + // overflows, rather than our estimate about how much is actually copied. + if (boundWarning) { + if (Optional<NonLoc> maxLastNL = maxLastElementIndex.getAs<NonLoc>()) { + SVal maxLastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal, + *maxLastNL, ptrTy); + state = CheckLocation(C, state, CE->getArg(2), maxLastElement, + boundWarning); + if (!state) + return; + } + } + + // Then, if the final length is known... + if (Optional<NonLoc> knownStrLength = finalStrLength.getAs<NonLoc>()) { + SVal lastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal, + *knownStrLength, ptrTy); + + // ...and we haven't checked the bound, we'll check the actual copy. + if (!boundWarning) { + const char * const warningMsg = + "String copy function overflows destination buffer"; + state = CheckLocation(C, state, Dst, lastElement, warningMsg); + if (!state) + return; + } + + // If this is a stpcpy-style copy, the last element is the return value. + if (returnPtr && ReturnEnd) + Result = lastElement; + } + + // Invalidate the destination (regular invalidation without pointer-escaping + // the address of the top-level region). This must happen before we set the + // C string length because invalidation will clear the length. + // FIXME: Even if we can't perfectly model the copy, we should see if we + // can use LazyCompoundVals to copy the source values into the destination. + // This would probably remove any existing bindings past the end of the + // string, but that's still an improvement over blank invalidation. + state = InvalidateBuffer(C, state, Dst, *dstRegVal, + /*IsSourceBuffer*/false, nullptr); + + // Invalidate the source (const-invalidation without const-pointer-escaping + // the address of the top-level region). + state = InvalidateBuffer(C, state, srcExpr, srcVal, /*IsSourceBuffer*/true, + nullptr); + + // Set the C string length of the destination, if we know it. + if (IsBounded && (appendK == ConcatFnKind::none)) { + // strncpy is annoying in that it doesn't guarantee to null-terminate + // the result string. If the original string didn't fit entirely inside + // the bound (including the null-terminator), we don't know how long the + // result is. + if (amountCopied != strLength) + finalStrLength = UnknownVal(); + } + state = setCStringLength(state, dstRegVal->getRegion(), finalStrLength); + } + + assert(state); + + if (returnPtr) { + // If this is a stpcpy-style copy, but we were unable to check for a buffer + // overflow, we still need a result. Conjure a return value. + if (ReturnEnd && Result.isUnknown()) { + Result = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount()); + } + } + // Set the return value. + state = state->BindExpr(CE, LCtx, Result); + C.addTransition(state); +} + +void CStringChecker::evalStrcmp(CheckerContext &C, const CallExpr *CE) const { + //int strcmp(const char *s1, const char *s2); + evalStrcmpCommon(C, CE, /* IsBounded = */ false, /* IgnoreCase = */ false); +} + +void CStringChecker::evalStrncmp(CheckerContext &C, const CallExpr *CE) const { + //int strncmp(const char *s1, const char *s2, size_t n); + evalStrcmpCommon(C, CE, /* IsBounded = */ true, /* IgnoreCase = */ false); +} + +void CStringChecker::evalStrcasecmp(CheckerContext &C, + const CallExpr *CE) const { + //int strcasecmp(const char *s1, const char *s2); + evalStrcmpCommon(C, CE, /* IsBounded = */ false, /* IgnoreCase = */ true); +} + +void CStringChecker::evalStrncasecmp(CheckerContext &C, + const CallExpr *CE) const { + //int strncasecmp(const char *s1, const char *s2, size_t n); + evalStrcmpCommon(C, CE, /* IsBounded = */ true, /* IgnoreCase = */ true); +} + +void CStringChecker::evalStrcmpCommon(CheckerContext &C, const CallExpr *CE, + bool IsBounded, bool IgnoreCase) const { + CurrentFunctionDescription = "string comparison function"; + ProgramStateRef state = C.getState(); + const LocationContext *LCtx = C.getLocationContext(); + + // Check that the first string is non-null + const Expr *s1 = CE->getArg(0); + SVal s1Val = state->getSVal(s1, LCtx); + state = checkNonNull(C, state, s1, s1Val, 1); + if (!state) + return; + + // Check that the second string is non-null. + const Expr *s2 = CE->getArg(1); + SVal s2Val = state->getSVal(s2, LCtx); + state = checkNonNull(C, state, s2, s2Val, 2); + if (!state) + return; + + // Get the string length of the first string or give up. + SVal s1Length = getCStringLength(C, state, s1, s1Val); + if (s1Length.isUndef()) + return; + + // Get the string length of the second string or give up. + SVal s2Length = getCStringLength(C, state, s2, s2Val); + if (s2Length.isUndef()) + return; + + // If we know the two buffers are the same, we know the result is 0. + // First, get the two buffers' addresses. Another checker will have already + // made sure they're not undefined. + DefinedOrUnknownSVal LV = s1Val.castAs<DefinedOrUnknownSVal>(); + DefinedOrUnknownSVal RV = s2Val.castAs<DefinedOrUnknownSVal>(); + + // See if they are the same. + SValBuilder &svalBuilder = C.getSValBuilder(); + DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV); + ProgramStateRef StSameBuf, StNotSameBuf; + std::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf); + + // If the two arguments might be the same buffer, we know the result is 0, + // and we only need to check one size. + if (StSameBuf) { + StSameBuf = StSameBuf->BindExpr(CE, LCtx, + svalBuilder.makeZeroVal(CE->getType())); + C.addTransition(StSameBuf); + + // If the two arguments are GUARANTEED to be the same, we're done! + if (!StNotSameBuf) + return; + } + + assert(StNotSameBuf); + state = StNotSameBuf; + + // At this point we can go about comparing the two buffers. + // For now, we only do this if they're both known string literals. + + // Attempt to extract string literals from both expressions. + const StringLiteral *s1StrLiteral = getCStringLiteral(C, state, s1, s1Val); + const StringLiteral *s2StrLiteral = getCStringLiteral(C, state, s2, s2Val); + bool canComputeResult = false; + SVal resultVal = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx, + C.blockCount()); + + if (s1StrLiteral && s2StrLiteral) { + StringRef s1StrRef = s1StrLiteral->getString(); + StringRef s2StrRef = s2StrLiteral->getString(); + + if (IsBounded) { + // Get the max number of characters to compare. + const Expr *lenExpr = CE->getArg(2); + SVal lenVal = state->getSVal(lenExpr, LCtx); + + // If the length is known, we can get the right substrings. + if (const llvm::APSInt *len = svalBuilder.getKnownValue(state, lenVal)) { + // Create substrings of each to compare the prefix. + s1StrRef = s1StrRef.substr(0, (size_t)len->getZExtValue()); + s2StrRef = s2StrRef.substr(0, (size_t)len->getZExtValue()); + canComputeResult = true; + } + } else { + // This is a normal, unbounded strcmp. + canComputeResult = true; + } + + if (canComputeResult) { + // Real strcmp stops at null characters. + size_t s1Term = s1StrRef.find('\0'); + if (s1Term != StringRef::npos) + s1StrRef = s1StrRef.substr(0, s1Term); + + size_t s2Term = s2StrRef.find('\0'); + if (s2Term != StringRef::npos) + s2StrRef = s2StrRef.substr(0, s2Term); + + // Use StringRef's comparison methods to compute the actual result. + int compareRes = IgnoreCase ? s1StrRef.compare_lower(s2StrRef) + : s1StrRef.compare(s2StrRef); + + // The strcmp function returns an integer greater than, equal to, or less + // than zero, [c11, p7.24.4.2]. + if (compareRes == 0) { + resultVal = svalBuilder.makeIntVal(compareRes, CE->getType()); + } + else { + DefinedSVal zeroVal = svalBuilder.makeIntVal(0, CE->getType()); + // Constrain strcmp's result range based on the result of StringRef's + // comparison methods. + BinaryOperatorKind op = (compareRes == 1) ? BO_GT : BO_LT; + SVal compareWithZero = + svalBuilder.evalBinOp(state, op, resultVal, zeroVal, + svalBuilder.getConditionType()); + DefinedSVal compareWithZeroVal = compareWithZero.castAs<DefinedSVal>(); + state = state->assume(compareWithZeroVal, true); + } + } + } + + state = state->BindExpr(CE, LCtx, resultVal); + + // Record this as a possible path. + C.addTransition(state); +} + +void CStringChecker::evalStrsep(CheckerContext &C, const CallExpr *CE) const { + //char *strsep(char **stringp, const char *delim); + // Sanity: does the search string parameter match the return type? + const Expr *SearchStrPtr = CE->getArg(0); + QualType CharPtrTy = SearchStrPtr->getType()->getPointeeType(); + if (CharPtrTy.isNull() || + CE->getType().getUnqualifiedType() != CharPtrTy.getUnqualifiedType()) + return; + + CurrentFunctionDescription = "strsep()"; + ProgramStateRef State = C.getState(); + const LocationContext *LCtx = C.getLocationContext(); + + // Check that the search string pointer is non-null (though it may point to + // a null string). + SVal SearchStrVal = State->getSVal(SearchStrPtr, LCtx); + State = checkNonNull(C, State, SearchStrPtr, SearchStrVal, 1); + if (!State) + return; + + // Check that the delimiter string is non-null. + const Expr *DelimStr = CE->getArg(1); + SVal DelimStrVal = State->getSVal(DelimStr, LCtx); + State = checkNonNull(C, State, DelimStr, DelimStrVal, 2); + if (!State) + return; + + SValBuilder &SVB = C.getSValBuilder(); + SVal Result; + if (Optional<Loc> SearchStrLoc = SearchStrVal.getAs<Loc>()) { + // Get the current value of the search string pointer, as a char*. + Result = State->getSVal(*SearchStrLoc, CharPtrTy); + + // Invalidate the search string, representing the change of one delimiter + // character to NUL. + State = InvalidateBuffer(C, State, SearchStrPtr, Result, + /*IsSourceBuffer*/false, nullptr); + + // Overwrite the search string pointer. The new value is either an address + // further along in the same string, or NULL if there are no more tokens. + State = State->bindLoc(*SearchStrLoc, + SVB.conjureSymbolVal(getTag(), + CE, + LCtx, + CharPtrTy, + C.blockCount()), + LCtx); + } else { + assert(SearchStrVal.isUnknown()); + // Conjure a symbolic value. It's the best we can do. + Result = SVB.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount()); + } + + // Set the return value, and finish. + State = State->BindExpr(CE, LCtx, Result); + C.addTransition(State); +} + +// These should probably be moved into a C++ standard library checker. +void CStringChecker::evalStdCopy(CheckerContext &C, const CallExpr *CE) const { + evalStdCopyCommon(C, CE); +} + +void CStringChecker::evalStdCopyBackward(CheckerContext &C, + const CallExpr *CE) const { + evalStdCopyCommon(C, CE); +} + +void CStringChecker::evalStdCopyCommon(CheckerContext &C, + const CallExpr *CE) const { + if (!CE->getArg(2)->getType()->isPointerType()) + return; + + ProgramStateRef State = C.getState(); + + const LocationContext *LCtx = C.getLocationContext(); + + // template <class _InputIterator, class _OutputIterator> + // _OutputIterator + // copy(_InputIterator __first, _InputIterator __last, + // _OutputIterator __result) + + // Invalidate the destination buffer + const Expr *Dst = CE->getArg(2); + SVal DstVal = State->getSVal(Dst, LCtx); + State = InvalidateBuffer(C, State, Dst, DstVal, /*IsSource=*/false, + /*Size=*/nullptr); + + SValBuilder &SVB = C.getSValBuilder(); + + SVal ResultVal = SVB.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount()); + State = State->BindExpr(CE, LCtx, ResultVal); + + C.addTransition(State); +} + +void CStringChecker::evalMemset(CheckerContext &C, const CallExpr *CE) const { + CurrentFunctionDescription = "memory set function"; + + const Expr *Mem = CE->getArg(0); + const Expr *CharE = CE->getArg(1); + const Expr *Size = CE->getArg(2); + ProgramStateRef State = C.getState(); + + // See if the size argument is zero. + const LocationContext *LCtx = C.getLocationContext(); + SVal SizeVal = State->getSVal(Size, LCtx); + QualType SizeTy = Size->getType(); + + ProgramStateRef StateZeroSize, StateNonZeroSize; + std::tie(StateZeroSize, StateNonZeroSize) = + assumeZero(C, State, SizeVal, SizeTy); + + // Get the value of the memory area. + SVal MemVal = State->getSVal(Mem, LCtx); + + // If the size is zero, there won't be any actual memory access, so + // just bind the return value to the Mem buffer and return. + if (StateZeroSize && !StateNonZeroSize) { + StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, MemVal); + C.addTransition(StateZeroSize); + return; + } + + // Ensure the memory area is not null. + // If it is NULL there will be a NULL pointer dereference. + State = checkNonNull(C, StateNonZeroSize, Mem, MemVal, 1); + if (!State) + return; + + State = CheckBufferAccess(C, State, Size, Mem); + if (!State) + return; + + // According to the values of the arguments, bind the value of the second + // argument to the destination buffer and set string length, or just + // invalidate the destination buffer. + if (!memsetAux(Mem, C.getSVal(CharE), Size, C, State)) + return; + + State = State->BindExpr(CE, LCtx, MemVal); + C.addTransition(State); +} + +void CStringChecker::evalBzero(CheckerContext &C, const CallExpr *CE) const { + CurrentFunctionDescription = "memory clearance function"; + + const Expr *Mem = CE->getArg(0); + const Expr *Size = CE->getArg(1); + SVal Zero = C.getSValBuilder().makeZeroVal(C.getASTContext().IntTy); + + ProgramStateRef State = C.getState(); + + // See if the size argument is zero. + SVal SizeVal = C.getSVal(Size); + QualType SizeTy = Size->getType(); + + ProgramStateRef StateZeroSize, StateNonZeroSize; + std::tie(StateZeroSize, StateNonZeroSize) = + assumeZero(C, State, SizeVal, SizeTy); + + // If the size is zero, there won't be any actual memory access, + // In this case we just return. + if (StateZeroSize && !StateNonZeroSize) { + C.addTransition(StateZeroSize); + return; + } + + // Get the value of the memory area. + SVal MemVal = C.getSVal(Mem); + + // Ensure the memory area is not null. + // If it is NULL there will be a NULL pointer dereference. + State = checkNonNull(C, StateNonZeroSize, Mem, MemVal, 1); + if (!State) + return; + + State = CheckBufferAccess(C, State, Size, Mem); + if (!State) + return; + + if (!memsetAux(Mem, Zero, Size, C, State)) + return; + + C.addTransition(State); +} + +//===----------------------------------------------------------------------===// +// The driver method, and other Checker callbacks. +//===----------------------------------------------------------------------===// + +CStringChecker::FnCheck CStringChecker::identifyCall(const CallEvent &Call, + CheckerContext &C) const { + const auto *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr()); + if (!CE) + return nullptr; + + const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl()); + if (!FD) + return nullptr; + + if (Call.isCalled(StdCopy)) { + return &CStringChecker::evalStdCopy; + } else if (Call.isCalled(StdCopyBackward)) { + return &CStringChecker::evalStdCopyBackward; + } + + // Pro-actively check that argument types are safe to do arithmetic upon. + // We do not want to crash if someone accidentally passes a structure + // into, say, a C++ overload of any of these functions. We could not check + // that for std::copy because they may have arguments of other types. + for (auto I : CE->arguments()) { + QualType T = I->getType(); + if (!T->isIntegralOrEnumerationType() && !T->isPointerType()) + return nullptr; + } + + const FnCheck *Callback = Callbacks.lookup(Call); + if (Callback) + return *Callback; + + return nullptr; +} + +bool CStringChecker::evalCall(const CallEvent &Call, CheckerContext &C) const { + FnCheck Callback = identifyCall(Call, C); + + // If the callee isn't a string function, let another checker handle it. + if (!Callback) + return false; + + // Check and evaluate the call. + const auto *CE = cast<CallExpr>(Call.getOriginExpr()); + (this->*Callback)(C, CE); + + // If the evaluate call resulted in no change, chain to the next eval call + // handler. + // Note, the custom CString evaluation calls assume that basic safety + // properties are held. However, if the user chooses to turn off some of these + // checks, we ignore the issues and leave the call evaluation to a generic + // handler. + return C.isDifferent(); +} + +void CStringChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const { + // Record string length for char a[] = "abc"; + ProgramStateRef state = C.getState(); + + for (const auto *I : DS->decls()) { + const VarDecl *D = dyn_cast<VarDecl>(I); + if (!D) + continue; + + // FIXME: Handle array fields of structs. + if (!D->getType()->isArrayType()) + continue; + + const Expr *Init = D->getInit(); + if (!Init) + continue; + if (!isa<StringLiteral>(Init)) + continue; + + Loc VarLoc = state->getLValue(D, C.getLocationContext()); + const MemRegion *MR = VarLoc.getAsRegion(); + if (!MR) + continue; + + SVal StrVal = C.getSVal(Init); + assert(StrVal.isValid() && "Initializer string is unknown or undefined"); + DefinedOrUnknownSVal strLength = + getCStringLength(C, state, Init, StrVal).castAs<DefinedOrUnknownSVal>(); + + state = state->set<CStringLength>(MR, strLength); + } + + C.addTransition(state); +} + +ProgramStateRef +CStringChecker::checkRegionChanges(ProgramStateRef state, + const InvalidatedSymbols *, + ArrayRef<const MemRegion *> ExplicitRegions, + ArrayRef<const MemRegion *> Regions, + const LocationContext *LCtx, + const CallEvent *Call) const { + CStringLengthTy Entries = state->get<CStringLength>(); + if (Entries.isEmpty()) + return state; + + llvm::SmallPtrSet<const MemRegion *, 8> Invalidated; + llvm::SmallPtrSet<const MemRegion *, 32> SuperRegions; + + // First build sets for the changed regions and their super-regions. + for (ArrayRef<const MemRegion *>::iterator + I = Regions.begin(), E = Regions.end(); I != E; ++I) { + const MemRegion *MR = *I; + Invalidated.insert(MR); + + SuperRegions.insert(MR); + while (const SubRegion *SR = dyn_cast<SubRegion>(MR)) { + MR = SR->getSuperRegion(); + SuperRegions.insert(MR); + } + } + + CStringLengthTy::Factory &F = state->get_context<CStringLength>(); + + // Then loop over the entries in the current state. + for (CStringLengthTy::iterator I = Entries.begin(), + E = Entries.end(); I != E; ++I) { + const MemRegion *MR = I.getKey(); + + // Is this entry for a super-region of a changed region? + if (SuperRegions.count(MR)) { + Entries = F.remove(Entries, MR); + continue; + } + + // Is this entry for a sub-region of a changed region? + const MemRegion *Super = MR; + while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) { + Super = SR->getSuperRegion(); + if (Invalidated.count(Super)) { + Entries = F.remove(Entries, MR); + break; + } + } + } + + return state->set<CStringLength>(Entries); +} + +void CStringChecker::checkLiveSymbols(ProgramStateRef state, + SymbolReaper &SR) const { + // Mark all symbols in our string length map as valid. + CStringLengthTy Entries = state->get<CStringLength>(); + + for (CStringLengthTy::iterator I = Entries.begin(), E = Entries.end(); + I != E; ++I) { + SVal Len = I.getData(); + + for (SymExpr::symbol_iterator si = Len.symbol_begin(), + se = Len.symbol_end(); si != se; ++si) + SR.markInUse(*si); + } +} + +void CStringChecker::checkDeadSymbols(SymbolReaper &SR, + CheckerContext &C) const { + ProgramStateRef state = C.getState(); + CStringLengthTy Entries = state->get<CStringLength>(); + if (Entries.isEmpty()) + return; + + CStringLengthTy::Factory &F = state->get_context<CStringLength>(); + for (CStringLengthTy::iterator I = Entries.begin(), E = Entries.end(); + I != E; ++I) { + SVal Len = I.getData(); + if (SymbolRef Sym = Len.getAsSymbol()) { + if (SR.isDead(Sym)) + Entries = F.remove(Entries, I.getKey()); + } + } + + state = state->set<CStringLength>(Entries); + C.addTransition(state); +} + +void ento::registerCStringModeling(CheckerManager &Mgr) { + Mgr.registerChecker<CStringChecker>(); +} + +bool ento::shouldRegisterCStringModeling(const LangOptions &LO) { + return true; +} + +#define REGISTER_CHECKER(name) \ + void ento::register##name(CheckerManager &mgr) { \ + CStringChecker *checker = mgr.getChecker<CStringChecker>(); \ + checker->Filter.Check##name = true; \ + checker->Filter.CheckName##name = mgr.getCurrentCheckerName(); \ + } \ + \ + bool ento::shouldRegister##name(const LangOptions &LO) { return true; } + +REGISTER_CHECKER(CStringNullArg) +REGISTER_CHECKER(CStringOutOfBounds) +REGISTER_CHECKER(CStringBufferOverlap) +REGISTER_CHECKER(CStringNotNullTerm) |