head 1.1; branch 1.1.1; access; symbols netbsd-11-0-RC4:1.1.1.6 netbsd-11-0-RC3:1.1.1.6 netbsd-11-0-RC2:1.1.1.6 netbsd-11-0-RC1:1.1.1.6 perseant-exfatfs-base-20250801:1.1.1.6 netbsd-11:1.1.1.6.0.10 netbsd-11-base:1.1.1.6 netbsd-10-1-RELEASE:1.1.1.6 perseant-exfatfs-base-20240630:1.1.1.6 perseant-exfatfs:1.1.1.6.0.8 perseant-exfatfs-base:1.1.1.6 netbsd-8-3-RELEASE:1.1.1.3 netbsd-9-4-RELEASE:1.1.1.5 netbsd-10-0-RELEASE:1.1.1.6 netbsd-10-0-RC6:1.1.1.6 netbsd-10-0-RC5:1.1.1.6 netbsd-10-0-RC4:1.1.1.6 netbsd-10-0-RC3:1.1.1.6 netbsd-10-0-RC2:1.1.1.6 netbsd-10-0-RC1:1.1.1.6 netbsd-10:1.1.1.6.0.6 netbsd-10-base:1.1.1.6 netbsd-9-3-RELEASE:1.1.1.5 cjep_sun2x:1.1.1.6.0.4 cjep_sun2x-base:1.1.1.6 cjep_staticlib_x-base1:1.1.1.6 netbsd-9-2-RELEASE:1.1.1.5 cjep_staticlib_x:1.1.1.6.0.2 cjep_staticlib_x-base:1.1.1.6 netbsd-9-1-RELEASE:1.1.1.5 phil-wifi-20200421:1.1.1.6 phil-wifi-20200411:1.1.1.6 phil-wifi-20200406:1.1.1.6 netbsd-8-2-RELEASE:1.1.1.3 netbsd-9-0-RELEASE:1.1.1.5 netbsd-9-0-RC2:1.1.1.5 netbsd-9-0-RC1:1.1.1.5 netbsd-9:1.1.1.5.0.2 netbsd-9-base:1.1.1.5 phil-wifi-20190609:1.1.1.5 netbsd-8-1-RELEASE:1.1.1.3 netbsd-8-1-RC1:1.1.1.3 pgoyette-compat-merge-20190127:1.1.1.4.2.1 pgoyette-compat-20190127:1.1.1.5 pgoyette-compat-20190118:1.1.1.5 pgoyette-compat-1226:1.1.1.5 pgoyette-compat-1126:1.1.1.5 pgoyette-compat-1020:1.1.1.5 pgoyette-compat-0930:1.1.1.5 pgoyette-compat-0906:1.1.1.5 netbsd-7-2-RELEASE:1.1.1.2 pgoyette-compat-0728:1.1.1.5 clang-337282:1.1.1.5 netbsd-8-0-RELEASE:1.1.1.3 phil-wifi:1.1.1.4.0.4 phil-wifi-base:1.1.1.4 pgoyette-compat-0625:1.1.1.4 netbsd-8-0-RC2:1.1.1.3 pgoyette-compat-0521:1.1.1.4 pgoyette-compat-0502:1.1.1.4 pgoyette-compat-0422:1.1.1.4 netbsd-8-0-RC1:1.1.1.3 pgoyette-compat-0415:1.1.1.4 pgoyette-compat-0407:1.1.1.4 pgoyette-compat-0330:1.1.1.4 pgoyette-compat-0322:1.1.1.4 pgoyette-compat-0315:1.1.1.4 netbsd-7-1-2-RELEASE:1.1.1.2 pgoyette-compat:1.1.1.4.0.2 pgoyette-compat-base:1.1.1.4 netbsd-7-1-1-RELEASE:1.1.1.2 clang-319952:1.1.1.4 matt-nb8-mediatek:1.1.1.3.0.12 matt-nb8-mediatek-base:1.1.1.3 clang-309604:1.1.1.4 perseant-stdc-iso10646:1.1.1.3.0.10 perseant-stdc-iso10646-base:1.1.1.3 netbsd-8:1.1.1.3.0.8 netbsd-8-base:1.1.1.3 prg-localcount2-base3:1.1.1.3 prg-localcount2-base2:1.1.1.3 prg-localcount2-base1:1.1.1.3 prg-localcount2:1.1.1.3.0.6 prg-localcount2-base:1.1.1.3 pgoyette-localcount-20170426:1.1.1.3 bouyer-socketcan-base1:1.1.1.3 pgoyette-localcount-20170320:1.1.1.3 netbsd-7-1:1.1.1.2.0.14 netbsd-7-1-RELEASE:1.1.1.2 netbsd-7-1-RC2:1.1.1.2 clang-294123:1.1.1.3 netbsd-7-nhusb-base-20170116:1.1.1.2 bouyer-socketcan:1.1.1.3.0.4 bouyer-socketcan-base:1.1.1.3 clang-291444:1.1.1.3 pgoyette-localcount-20170107:1.1.1.3 netbsd-7-1-RC1:1.1.1.2 pgoyette-localcount-20161104:1.1.1.3 netbsd-7-0-2-RELEASE:1.1.1.2 localcount-20160914:1.1.1.3 netbsd-7-nhusb:1.1.1.2.0.12 netbsd-7-nhusb-base:1.1.1.2 clang-280599:1.1.1.3 pgoyette-localcount-20160806:1.1.1.3 pgoyette-localcount-20160726:1.1.1.3 pgoyette-localcount:1.1.1.3.0.2 pgoyette-localcount-base:1.1.1.3 netbsd-7-0-1-RELEASE:1.1.1.2 clang-261930:1.1.1.3 netbsd-7-0:1.1.1.2.0.10 netbsd-7-0-RELEASE:1.1.1.2 netbsd-7-0-RC3:1.1.1.2 netbsd-7-0-RC2:1.1.1.2 netbsd-7-0-RC1:1.1.1.2 clang-237755:1.1.1.2 clang-232565:1.1.1.2 clang-227398:1.1.1.2 tls-maxphys-base:1.1.1.2 tls-maxphys:1.1.1.2.0.8 netbsd-7:1.1.1.2.0.6 netbsd-7-base:1.1.1.2 clang-215315:1.1.1.2 clang-209886:1.1.1.2 yamt-pagecache:1.1.1.2.0.4 yamt-pagecache-base9:1.1.1.2 tls-earlyentropy:1.1.1.2.0.2 tls-earlyentropy-base:1.1.1.2 riastradh-xf86-video-intel-2-7-1-pre-2-21-15:1.1.1.2 riastradh-drm2-base3:1.1.1.2 clang-202566:1.1.1.2 clang-201163:1.1.1.1 clang-199312:1.1.1.1 clang-198450:1.1.1.1 clang-196603:1.1.1.1 clang-195771:1.1.1.1 LLVM:1.1.1; locks; strict; comment @// @; 1.1 date 2013.11.28.14.14.52; author joerg; state Exp; branches 1.1.1.1; next ; commitid ow8OybrawrB1f3fx; 1.1.1.1 date 2013.11.28.14.14.52; author joerg; state Exp; branches; next 1.1.1.2; commitid ow8OybrawrB1f3fx; 1.1.1.2 date 2014.03.04.19.55.00; author joerg; state Exp; branches 1.1.1.2.4.1 1.1.1.2.8.1; next 1.1.1.3; commitid 29z1hJonZISIXprx; 1.1.1.3 date 2016.02.27.22.12.06; author joerg; state Exp; branches; next 1.1.1.4; commitid tIimz3oDlh1NpBWy; 1.1.1.4 date 2017.08.01.19.35.16; author joerg; state Exp; branches 1.1.1.4.2.1 1.1.1.4.4.1; next 1.1.1.5; commitid pMuDy65V0VicSx1A; 1.1.1.5 date 2018.07.17.18.31.07; author joerg; state Exp; branches; next 1.1.1.6; commitid wDzL46ALjrCZgwKA; 1.1.1.6 date 2019.11.13.22.19.28; author joerg; state dead; branches; next ; commitid QD8YATxuNG34YJKB; 1.1.1.2.4.1 date 2014.03.04.19.55.00; author yamt; state dead; branches; next 1.1.1.2.4.2; commitid WSrDtL5nYAUyiyBx; 1.1.1.2.4.2 date 2014.05.22.16.18.30; author yamt; state Exp; branches; next ; commitid WSrDtL5nYAUyiyBx; 1.1.1.2.8.1 date 2014.03.04.19.55.00; author tls; state dead; branches; next 1.1.1.2.8.2; commitid jTnpym9Qu0o4R1Nx; 1.1.1.2.8.2 date 2014.08.19.23.47.31; author tls; state Exp; branches; next ; commitid jTnpym9Qu0o4R1Nx; 1.1.1.4.2.1 date 2018.07.28.04.33.23; author pgoyette; state Exp; branches; next ; commitid 1UP1xAIUxv1ZgRLA; 1.1.1.4.4.1 date 2019.06.10.21.45.28; author christos; state Exp; branches; next 1.1.1.4.4.2; commitid jtc8rnCzWiEEHGqB; 1.1.1.4.4.2 date 2020.04.13.07.46.38; author martin; state dead; branches; next ; commitid X01YhRUPVUDaec4C; desc @@ 1.1 log @Initial revision @ text @//== CStringSyntaxChecker.cpp - CoreFoundation containers API *- C++ -*-==// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // An AST checker that looks for common pitfalls when using C string APIs. // - Identifies erroneous patterns in the last argument to strncat - the number // of bytes to copy. // //===----------------------------------------------------------------------===// #include "ClangSACheckers.h" #include "clang/AST/Expr.h" #include "clang/AST/OperationKinds.h" #include "clang/AST/StmtVisitor.h" #include "clang/Analysis/AnalysisContext.h" #include "clang/Basic/TargetInfo.h" #include "clang/Basic/TypeTraits.h" #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" #include "clang/StaticAnalyzer/Core/Checker.h" #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" #include "llvm/ADT/SmallString.h" #include "llvm/Support/raw_ostream.h" using namespace clang; using namespace ento; namespace { class WalkAST: public StmtVisitor { BugReporter &BR; AnalysisDeclContext* AC; /// Check if two expressions refer to the same declaration. inline bool sameDecl(const Expr *A1, const Expr *A2) { if (const DeclRefExpr *D1 = dyn_cast(A1->IgnoreParenCasts())) if (const DeclRefExpr *D2 = dyn_cast(A2->IgnoreParenCasts())) return D1->getDecl() == D2->getDecl(); return false; } /// Check if the expression E is a sizeof(WithArg). inline bool isSizeof(const Expr *E, const Expr *WithArg) { if (const UnaryExprOrTypeTraitExpr *UE = dyn_cast(E)) if (UE->getKind() == UETT_SizeOf) return sameDecl(UE->getArgumentExpr(), WithArg); return false; } /// Check if the expression E is a strlen(WithArg). inline bool isStrlen(const Expr *E, const Expr *WithArg) { if (const CallExpr *CE = dyn_cast(E)) { const FunctionDecl *FD = CE->getDirectCallee(); if (!FD) return false; return (CheckerContext::isCLibraryFunction(FD, "strlen") && sameDecl(CE->getArg(0), WithArg)); } return false; } /// Check if the expression is an integer literal with value 1. inline bool isOne(const Expr *E) { if (const IntegerLiteral *IL = dyn_cast(E)) return (IL->getValue().isIntN(1)); return false; } inline StringRef getPrintableName(const Expr *E) { if (const DeclRefExpr *D = dyn_cast(E->IgnoreParenCasts())) return D->getDecl()->getName(); return StringRef(); } /// Identify erroneous patterns in the last argument to strncat - the number /// of bytes to copy. bool containsBadStrncatPattern(const CallExpr *CE); public: WalkAST(BugReporter &br, AnalysisDeclContext* ac) : BR(br), AC(ac) { } // Statement visitor methods. void VisitChildren(Stmt *S); void VisitStmt(Stmt *S) { VisitChildren(S); } void VisitCallExpr(CallExpr *CE); }; } // end anonymous namespace // The correct size argument should look like following: // strncat(dst, src, sizeof(dst) - strlen(dest) - 1); // We look for the following anti-patterns: // - strncat(dst, src, sizeof(dst) - strlen(dst)); // - strncat(dst, src, sizeof(dst) - 1); // - strncat(dst, src, sizeof(dst)); bool WalkAST::containsBadStrncatPattern(const CallExpr *CE) { if (CE->getNumArgs() != 3) return false; const Expr *DstArg = CE->getArg(0); const Expr *SrcArg = CE->getArg(1); const Expr *LenArg = CE->getArg(2); // Identify wrong size expressions, which are commonly used instead. if (const BinaryOperator *BE = dyn_cast(LenArg->IgnoreParenCasts())) { // - sizeof(dst) - strlen(dst) if (BE->getOpcode() == BO_Sub) { const Expr *L = BE->getLHS(); const Expr *R = BE->getRHS(); if (isSizeof(L, DstArg) && isStrlen(R, DstArg)) return true; // - sizeof(dst) - 1 if (isSizeof(L, DstArg) && isOne(R->IgnoreParenCasts())) return true; } } // - sizeof(dst) if (isSizeof(LenArg, DstArg)) return true; // - sizeof(src) if (isSizeof(LenArg, SrcArg)) return true; return false; } void WalkAST::VisitCallExpr(CallExpr *CE) { const FunctionDecl *FD = CE->getDirectCallee(); if (!FD) return; if (CheckerContext::isCLibraryFunction(FD, "strncat")) { if (containsBadStrncatPattern(CE)) { const Expr *DstArg = CE->getArg(0); const Expr *LenArg = CE->getArg(2); PathDiagnosticLocation Loc = PathDiagnosticLocation::createBegin(LenArg, BR.getSourceManager(), AC); StringRef DstName = getPrintableName(DstArg); SmallString<256> S; llvm::raw_svector_ostream os(S); os << "Potential buffer overflow. "; if (!DstName.empty()) { os << "Replace with 'sizeof(" << DstName << ") " "- strlen(" << DstName <<") - 1'"; os << " or u"; } else os << "U"; os << "se a safer 'strlcat' API"; BR.EmitBasicReport(FD, "Anti-pattern in the argument", "C String API", os.str(), Loc, LenArg->getSourceRange()); } } // Recurse and check children. VisitChildren(CE); } void WalkAST::VisitChildren(Stmt *S) { for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I != E; ++I) if (Stmt *child = *I) Visit(child); } namespace { class CStringSyntaxChecker: public Checker { public: void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr, BugReporter &BR) const { WalkAST walker(BR, Mgr.getAnalysisDeclContext(D)); walker.Visit(D->getBody()); } }; } void ento::registerCStringSyntaxChecker(CheckerManager &mgr) { mgr.registerChecker(); } @ 1.1.1.1 log @Import Clang 3.4rc1 r195771. @ text @@ 1.1.1.2 log @Import Clang 3.5svn r202566. @ text @a33 1 const CheckerBase *Checker; d84 3 a86 2 WalkAST(const CheckerBase *checker, BugReporter &br, AnalysisDeclContext *ac) : Checker(checker), BR(br), AC(ac) {} d160 2 a161 3 BR.EmitBasicReport(FD, Checker, "Anti-pattern in the argument", "C String API", os.str(), Loc, LenArg->getSourceRange()); d182 1 a182 1 WalkAST walker(this, BR, Mgr.getAnalysisDeclContext(D)); @ 1.1.1.3 log @Import Clang 3.8.0rc3 r261930. @ text @d171 4 a174 3 for (Stmt *Child : S->children()) if (Child) Visit(Child); @ 1.1.1.4 log @Import clang r309604 from branches/release_50 @ text @d39 3 a41 3 bool sameDecl(const Expr *A1, const Expr *A2) { if (const auto *D1 = dyn_cast(A1->IgnoreParenCasts())) if (const auto *D2 = dyn_cast(A2->IgnoreParenCasts())) d47 4 a50 3 bool isSizeof(const Expr *E, const Expr *WithArg) { if (const auto *UE = dyn_cast(E)) if (UE->getKind() == UETT_SizeOf && !UE->isArgumentType()) d56 2 a57 2 bool isStrlen(const Expr *E, const Expr *WithArg) { if (const auto *CE = dyn_cast(E)) { d68 2 a69 2 bool isOne(const Expr *E) { if (const auto *IL = dyn_cast(E)) d74 2 a75 2 StringRef getPrintableName(const Expr *E) { if (const auto *D = dyn_cast(E->IgnoreParenCasts())) d85 2 a86 2 WalkAST(const CheckerBase *Checker, BugReporter &BR, AnalysisDeclContext *AC) : Checker(Checker), BR(BR), AC(AC) {} d111 2 a112 1 if (const auto *BE = dyn_cast(LenArg->IgnoreParenCasts())) { @ 1.1.1.4.4.1 log @Sync with HEAD @ text @d19 1 a19 1 #include "clang/Analysis/AnalysisDeclContext.h" @ 1.1.1.4.4.2 log @Mostly merge changes from HEAD upto 20200411 @ text @@ 1.1.1.4.2.1 log @Sync with HEAD @ text @d19 1 a19 1 #include "clang/Analysis/AnalysisDeclContext.h" @ 1.1.1.5 log @Import clang r337282 from trunk @ text @d19 1 a19 1 #include "clang/Analysis/AnalysisDeclContext.h" @ 1.1.1.6 log @Mark old LLVM instance as dead. @ text @@ 1.1.1.2.8.1 log @file CStringSyntaxChecker.cpp was added on branch tls-maxphys on 2014-08-19 23:47:31 +0000 @ text @d1 192 @ 1.1.1.2.8.2 log @Rebase to HEAD as of a few days ago. @ text @a0 192 //== CStringSyntaxChecker.cpp - CoreFoundation containers API *- C++ -*-==// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // An AST checker that looks for common pitfalls when using C string APIs. // - Identifies erroneous patterns in the last argument to strncat - the number // of bytes to copy. // //===----------------------------------------------------------------------===// #include "ClangSACheckers.h" #include "clang/AST/Expr.h" #include "clang/AST/OperationKinds.h" #include "clang/AST/StmtVisitor.h" #include "clang/Analysis/AnalysisContext.h" #include "clang/Basic/TargetInfo.h" #include "clang/Basic/TypeTraits.h" #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" #include "clang/StaticAnalyzer/Core/Checker.h" #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" #include "llvm/ADT/SmallString.h" #include "llvm/Support/raw_ostream.h" using namespace clang; using namespace ento; namespace { class WalkAST: public StmtVisitor { const CheckerBase *Checker; BugReporter &BR; AnalysisDeclContext* AC; /// Check if two expressions refer to the same declaration. inline bool sameDecl(const Expr *A1, const Expr *A2) { if (const DeclRefExpr *D1 = dyn_cast(A1->IgnoreParenCasts())) if (const DeclRefExpr *D2 = dyn_cast(A2->IgnoreParenCasts())) return D1->getDecl() == D2->getDecl(); return false; } /// Check if the expression E is a sizeof(WithArg). inline bool isSizeof(const Expr *E, const Expr *WithArg) { if (const UnaryExprOrTypeTraitExpr *UE = dyn_cast(E)) if (UE->getKind() == UETT_SizeOf) return sameDecl(UE->getArgumentExpr(), WithArg); return false; } /// Check if the expression E is a strlen(WithArg). inline bool isStrlen(const Expr *E, const Expr *WithArg) { if (const CallExpr *CE = dyn_cast(E)) { const FunctionDecl *FD = CE->getDirectCallee(); if (!FD) return false; return (CheckerContext::isCLibraryFunction(FD, "strlen") && sameDecl(CE->getArg(0), WithArg)); } return false; } /// Check if the expression is an integer literal with value 1. inline bool isOne(const Expr *E) { if (const IntegerLiteral *IL = dyn_cast(E)) return (IL->getValue().isIntN(1)); return false; } inline StringRef getPrintableName(const Expr *E) { if (const DeclRefExpr *D = dyn_cast(E->IgnoreParenCasts())) return D->getDecl()->getName(); return StringRef(); } /// Identify erroneous patterns in the last argument to strncat - the number /// of bytes to copy. bool containsBadStrncatPattern(const CallExpr *CE); public: WalkAST(const CheckerBase *checker, BugReporter &br, AnalysisDeclContext *ac) : Checker(checker), BR(br), AC(ac) {} // Statement visitor methods. void VisitChildren(Stmt *S); void VisitStmt(Stmt *S) { VisitChildren(S); } void VisitCallExpr(CallExpr *CE); }; } // end anonymous namespace // The correct size argument should look like following: // strncat(dst, src, sizeof(dst) - strlen(dest) - 1); // We look for the following anti-patterns: // - strncat(dst, src, sizeof(dst) - strlen(dst)); // - strncat(dst, src, sizeof(dst) - 1); // - strncat(dst, src, sizeof(dst)); bool WalkAST::containsBadStrncatPattern(const CallExpr *CE) { if (CE->getNumArgs() != 3) return false; const Expr *DstArg = CE->getArg(0); const Expr *SrcArg = CE->getArg(1); const Expr *LenArg = CE->getArg(2); // Identify wrong size expressions, which are commonly used instead. if (const BinaryOperator *BE = dyn_cast(LenArg->IgnoreParenCasts())) { // - sizeof(dst) - strlen(dst) if (BE->getOpcode() == BO_Sub) { const Expr *L = BE->getLHS(); const Expr *R = BE->getRHS(); if (isSizeof(L, DstArg) && isStrlen(R, DstArg)) return true; // - sizeof(dst) - 1 if (isSizeof(L, DstArg) && isOne(R->IgnoreParenCasts())) return true; } } // - sizeof(dst) if (isSizeof(LenArg, DstArg)) return true; // - sizeof(src) if (isSizeof(LenArg, SrcArg)) return true; return false; } void WalkAST::VisitCallExpr(CallExpr *CE) { const FunctionDecl *FD = CE->getDirectCallee(); if (!FD) return; if (CheckerContext::isCLibraryFunction(FD, "strncat")) { if (containsBadStrncatPattern(CE)) { const Expr *DstArg = CE->getArg(0); const Expr *LenArg = CE->getArg(2); PathDiagnosticLocation Loc = PathDiagnosticLocation::createBegin(LenArg, BR.getSourceManager(), AC); StringRef DstName = getPrintableName(DstArg); SmallString<256> S; llvm::raw_svector_ostream os(S); os << "Potential buffer overflow. "; if (!DstName.empty()) { os << "Replace with 'sizeof(" << DstName << ") " "- strlen(" << DstName <<") - 1'"; os << " or u"; } else os << "U"; os << "se a safer 'strlcat' API"; BR.EmitBasicReport(FD, Checker, "Anti-pattern in the argument", "C String API", os.str(), Loc, LenArg->getSourceRange()); } } // Recurse and check children. VisitChildren(CE); } void WalkAST::VisitChildren(Stmt *S) { for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I != E; ++I) if (Stmt *child = *I) Visit(child); } namespace { class CStringSyntaxChecker: public Checker { public: void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr, BugReporter &BR) const { WalkAST walker(this, BR, Mgr.getAnalysisDeclContext(D)); walker.Visit(D->getBody()); } }; } void ento::registerCStringSyntaxChecker(CheckerManager &mgr) { mgr.registerChecker(); } @ 1.1.1.2.4.1 log @file CStringSyntaxChecker.cpp was added on branch yamt-pagecache on 2014-05-22 16:18:30 +0000 @ text @d1 192 @ 1.1.1.2.4.2 log @sync with head. for a reference, the tree before this commit was tagged as yamt-pagecache-tag8. this commit was splitted into small chunks to avoid a limitation of cvs. ("Protocol error: too many arguments") @ text @a0 192 //== CStringSyntaxChecker.cpp - CoreFoundation containers API *- C++ -*-==// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // An AST checker that looks for common pitfalls when using C string APIs. // - Identifies erroneous patterns in the last argument to strncat - the number // of bytes to copy. // //===----------------------------------------------------------------------===// #include "ClangSACheckers.h" #include "clang/AST/Expr.h" #include "clang/AST/OperationKinds.h" #include "clang/AST/StmtVisitor.h" #include "clang/Analysis/AnalysisContext.h" #include "clang/Basic/TargetInfo.h" #include "clang/Basic/TypeTraits.h" #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" #include "clang/StaticAnalyzer/Core/Checker.h" #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" #include "llvm/ADT/SmallString.h" #include "llvm/Support/raw_ostream.h" using namespace clang; using namespace ento; namespace { class WalkAST: public StmtVisitor { const CheckerBase *Checker; BugReporter &BR; AnalysisDeclContext* AC; /// Check if two expressions refer to the same declaration. inline bool sameDecl(const Expr *A1, const Expr *A2) { if (const DeclRefExpr *D1 = dyn_cast(A1->IgnoreParenCasts())) if (const DeclRefExpr *D2 = dyn_cast(A2->IgnoreParenCasts())) return D1->getDecl() == D2->getDecl(); return false; } /// Check if the expression E is a sizeof(WithArg). inline bool isSizeof(const Expr *E, const Expr *WithArg) { if (const UnaryExprOrTypeTraitExpr *UE = dyn_cast(E)) if (UE->getKind() == UETT_SizeOf) return sameDecl(UE->getArgumentExpr(), WithArg); return false; } /// Check if the expression E is a strlen(WithArg). inline bool isStrlen(const Expr *E, const Expr *WithArg) { if (const CallExpr *CE = dyn_cast(E)) { const FunctionDecl *FD = CE->getDirectCallee(); if (!FD) return false; return (CheckerContext::isCLibraryFunction(FD, "strlen") && sameDecl(CE->getArg(0), WithArg)); } return false; } /// Check if the expression is an integer literal with value 1. inline bool isOne(const Expr *E) { if (const IntegerLiteral *IL = dyn_cast(E)) return (IL->getValue().isIntN(1)); return false; } inline StringRef getPrintableName(const Expr *E) { if (const DeclRefExpr *D = dyn_cast(E->IgnoreParenCasts())) return D->getDecl()->getName(); return StringRef(); } /// Identify erroneous patterns in the last argument to strncat - the number /// of bytes to copy. bool containsBadStrncatPattern(const CallExpr *CE); public: WalkAST(const CheckerBase *checker, BugReporter &br, AnalysisDeclContext *ac) : Checker(checker), BR(br), AC(ac) {} // Statement visitor methods. void VisitChildren(Stmt *S); void VisitStmt(Stmt *S) { VisitChildren(S); } void VisitCallExpr(CallExpr *CE); }; } // end anonymous namespace // The correct size argument should look like following: // strncat(dst, src, sizeof(dst) - strlen(dest) - 1); // We look for the following anti-patterns: // - strncat(dst, src, sizeof(dst) - strlen(dst)); // - strncat(dst, src, sizeof(dst) - 1); // - strncat(dst, src, sizeof(dst)); bool WalkAST::containsBadStrncatPattern(const CallExpr *CE) { if (CE->getNumArgs() != 3) return false; const Expr *DstArg = CE->getArg(0); const Expr *SrcArg = CE->getArg(1); const Expr *LenArg = CE->getArg(2); // Identify wrong size expressions, which are commonly used instead. if (const BinaryOperator *BE = dyn_cast(LenArg->IgnoreParenCasts())) { // - sizeof(dst) - strlen(dst) if (BE->getOpcode() == BO_Sub) { const Expr *L = BE->getLHS(); const Expr *R = BE->getRHS(); if (isSizeof(L, DstArg) && isStrlen(R, DstArg)) return true; // - sizeof(dst) - 1 if (isSizeof(L, DstArg) && isOne(R->IgnoreParenCasts())) return true; } } // - sizeof(dst) if (isSizeof(LenArg, DstArg)) return true; // - sizeof(src) if (isSizeof(LenArg, SrcArg)) return true; return false; } void WalkAST::VisitCallExpr(CallExpr *CE) { const FunctionDecl *FD = CE->getDirectCallee(); if (!FD) return; if (CheckerContext::isCLibraryFunction(FD, "strncat")) { if (containsBadStrncatPattern(CE)) { const Expr *DstArg = CE->getArg(0); const Expr *LenArg = CE->getArg(2); PathDiagnosticLocation Loc = PathDiagnosticLocation::createBegin(LenArg, BR.getSourceManager(), AC); StringRef DstName = getPrintableName(DstArg); SmallString<256> S; llvm::raw_svector_ostream os(S); os << "Potential buffer overflow. "; if (!DstName.empty()) { os << "Replace with 'sizeof(" << DstName << ") " "- strlen(" << DstName <<") - 1'"; os << " or u"; } else os << "U"; os << "se a safer 'strlcat' API"; BR.EmitBasicReport(FD, Checker, "Anti-pattern in the argument", "C String API", os.str(), Loc, LenArg->getSourceRange()); } } // Recurse and check children. VisitChildren(CE); } void WalkAST::VisitChildren(Stmt *S) { for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I != E; ++I) if (Stmt *child = *I) Visit(child); } namespace { class CStringSyntaxChecker: public Checker { public: void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr, BugReporter &BR) const { WalkAST walker(this, BR, Mgr.getAnalysisDeclContext(D)); walker.Visit(D->getBody()); } }; } void ento::registerCStringSyntaxChecker(CheckerManager &mgr) { mgr.registerChecker(); } @