1 //== GenericTaintChecker.cpp ----------------------------------- -*- C++ -*--=//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This checker defines the attack surface for generic taint propagation.
10 //
11 // The taint information produced by it might be useful to other checkers. For
12 // example, checkers should report errors which involve tainted data more
13 // aggressively, even if the involved symbols are under constrained.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "Yaml.h"
18 #include "clang/AST/Attr.h"
19 #include "clang/Basic/Builtins.h"
20 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
21 #include "clang/StaticAnalyzer/Checkers/Taint.h"
22 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
23 #include "clang/StaticAnalyzer/Core/Checker.h"
24 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
25 #include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
26 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
27 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
28 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
29 #include "llvm/ADT/StringExtras.h"
30 #include "llvm/ADT/StringRef.h"
31 #include "llvm/Support/YAMLTraits.h"
32
33 #include <limits>
34 #include <memory>
35 #include <optional>
36 #include <utility>
37 #include <vector>
38
39 #define DEBUG_TYPE "taint-checker"
40
41 using namespace clang;
42 using namespace ento;
43 using namespace taint;
44
45 using llvm::ImmutableSet;
46
47 namespace {
48
49 class GenericTaintChecker;
50
51 /// Check for CWE-134: Uncontrolled Format String.
52 constexpr llvm::StringLiteral MsgUncontrolledFormatString =
53 "Untrusted data is used as a format string "
54 "(CWE-134: Uncontrolled Format String)";
55
56 /// Check for:
57 /// CERT/STR02-C. "Sanitize data passed to complex subsystems"
58 /// CWE-78, "Failure to Sanitize Data into an OS Command"
59 constexpr llvm::StringLiteral MsgSanitizeSystemArgs =
60 "Untrusted data is passed to a system call "
61 "(CERT/STR02-C. Sanitize data passed to complex subsystems)";
62
63 /// Check if tainted data is used as a custom sink's parameter.
64 constexpr llvm::StringLiteral MsgCustomSink =
65 "Untrusted data is passed to a user-defined sink";
66
67 using ArgIdxTy = int;
68 using ArgVecTy = llvm::SmallVector<ArgIdxTy, 2>;
69
70 /// Denotes the return value.
71 constexpr ArgIdxTy ReturnValueIndex{-1};
72
fromArgumentCount(unsigned Count)73 static ArgIdxTy fromArgumentCount(unsigned Count) {
74 assert(Count <=
75 static_cast<std::size_t>(std::numeric_limits<ArgIdxTy>::max()) &&
76 "ArgIdxTy is not large enough to represent the number of arguments.");
77 return Count;
78 }
79
80 /// Check if the region the expression evaluates to is the standard input,
81 /// and thus, is tainted.
82 /// FIXME: Move this to Taint.cpp.
isStdin(SVal Val,const ASTContext & ACtx)83 bool isStdin(SVal Val, const ASTContext &ACtx) {
84 // FIXME: What if Val is NonParamVarRegion?
85
86 // The region should be symbolic, we do not know it's value.
87 const auto *SymReg = dyn_cast_or_null<SymbolicRegion>(Val.getAsRegion());
88 if (!SymReg)
89 return false;
90
91 // Get it's symbol and find the declaration region it's pointing to.
92 const auto *DeclReg =
93 dyn_cast_or_null<DeclRegion>(SymReg->getSymbol()->getOriginRegion());
94 if (!DeclReg)
95 return false;
96
97 // This region corresponds to a declaration, find out if it's a global/extern
98 // variable named stdin with the proper type.
99 if (const auto *D = dyn_cast_or_null<VarDecl>(DeclReg->getDecl())) {
100 D = D->getCanonicalDecl();
101 if (D->getName() == "stdin" && D->hasExternalStorage() && D->isExternC()) {
102 const QualType FILETy = ACtx.getFILEType().getCanonicalType();
103 const QualType Ty = D->getType().getCanonicalType();
104
105 if (Ty->isPointerType())
106 return Ty->getPointeeType() == FILETy;
107 }
108 }
109 return false;
110 }
111
getPointeeOf(ProgramStateRef State,Loc LValue)112 SVal getPointeeOf(ProgramStateRef State, Loc LValue) {
113 const QualType ArgTy = LValue.getType(State->getStateManager().getContext());
114 if (!ArgTy->isPointerType() || !ArgTy->getPointeeType()->isVoidType())
115 return State->getSVal(LValue);
116
117 // Do not dereference void pointers. Treat them as byte pointers instead.
118 // FIXME: we might want to consider more than just the first byte.
119 return State->getSVal(LValue, State->getStateManager().getContext().CharTy);
120 }
121
122 /// Given a pointer/reference argument, return the value it refers to.
getPointeeOf(ProgramStateRef State,SVal Arg)123 std::optional<SVal> getPointeeOf(ProgramStateRef State, SVal Arg) {
124 if (auto LValue = Arg.getAs<Loc>())
125 return getPointeeOf(State, *LValue);
126 return std::nullopt;
127 }
128
129 /// Given a pointer, return the SVal of its pointee or if it is tainted,
130 /// otherwise return the pointer's SVal if tainted.
131 /// Also considers stdin as a taint source.
getTaintedPointeeOrPointer(ProgramStateRef State,SVal Arg)132 std::optional<SVal> getTaintedPointeeOrPointer(ProgramStateRef State,
133 SVal Arg) {
134 if (auto Pointee = getPointeeOf(State, Arg))
135 if (isTainted(State, *Pointee)) // FIXME: isTainted(...) ? Pointee : None;
136 return Pointee;
137
138 if (isTainted(State, Arg))
139 return Arg;
140 return std::nullopt;
141 }
142
isTaintedOrPointsToTainted(ProgramStateRef State,SVal ExprSVal)143 bool isTaintedOrPointsToTainted(ProgramStateRef State, SVal ExprSVal) {
144 return getTaintedPointeeOrPointer(State, ExprSVal).has_value();
145 }
146
147 /// Helps in printing taint diagnostics.
148 /// Marks the incoming parameters of a function interesting (to be printed)
149 /// when the return value, or the outgoing parameters are tainted.
taintOriginTrackerTag(CheckerContext & C,std::vector<SymbolRef> TaintedSymbols,std::vector<ArgIdxTy> TaintedArgs,const LocationContext * CallLocation)150 const NoteTag *taintOriginTrackerTag(CheckerContext &C,
151 std::vector<SymbolRef> TaintedSymbols,
152 std::vector<ArgIdxTy> TaintedArgs,
153 const LocationContext *CallLocation) {
154 return C.getNoteTag([TaintedSymbols = std::move(TaintedSymbols),
155 TaintedArgs = std::move(TaintedArgs), CallLocation](
156 PathSensitiveBugReport &BR) -> std::string {
157 SmallString<256> Msg;
158 // We give diagnostics only for taint related reports
159 if (!BR.isInteresting(CallLocation) ||
160 BR.getBugType().getCategory() != categories::TaintedData) {
161 return "";
162 }
163 if (TaintedSymbols.empty())
164 return "Taint originated here";
165
166 for (auto Sym : TaintedSymbols) {
167 BR.markInteresting(Sym);
168 }
169 LLVM_DEBUG(for (auto Arg
170 : TaintedArgs) {
171 llvm::dbgs() << "Taint Propagated from argument " << Arg + 1 << "\n";
172 });
173 return "";
174 });
175 }
176
177 /// Helps in printing taint diagnostics.
178 /// Marks the function interesting (to be printed)
179 /// when the return value, or the outgoing parameters are tainted.
taintPropagationExplainerTag(CheckerContext & C,std::vector<SymbolRef> TaintedSymbols,std::vector<ArgIdxTy> TaintedArgs,const LocationContext * CallLocation)180 const NoteTag *taintPropagationExplainerTag(
181 CheckerContext &C, std::vector<SymbolRef> TaintedSymbols,
182 std::vector<ArgIdxTy> TaintedArgs, const LocationContext *CallLocation) {
183 assert(TaintedSymbols.size() == TaintedArgs.size());
184 return C.getNoteTag([TaintedSymbols = std::move(TaintedSymbols),
185 TaintedArgs = std::move(TaintedArgs), CallLocation](
186 PathSensitiveBugReport &BR) -> std::string {
187 SmallString<256> Msg;
188 llvm::raw_svector_ostream Out(Msg);
189 // We give diagnostics only for taint related reports
190 if (TaintedSymbols.empty() ||
191 BR.getBugType().getCategory() != categories::TaintedData) {
192 return "";
193 }
194 int nofTaintedArgs = 0;
195 for (auto [Idx, Sym] : llvm::enumerate(TaintedSymbols)) {
196 if (BR.isInteresting(Sym)) {
197 BR.markInteresting(CallLocation);
198 if (TaintedArgs[Idx] != ReturnValueIndex) {
199 LLVM_DEBUG(llvm::dbgs() << "Taint Propagated to argument "
200 << TaintedArgs[Idx] + 1 << "\n");
201 if (nofTaintedArgs == 0)
202 Out << "Taint propagated to the ";
203 else
204 Out << ", ";
205 Out << TaintedArgs[Idx] + 1
206 << llvm::getOrdinalSuffix(TaintedArgs[Idx] + 1) << " argument";
207 nofTaintedArgs++;
208 } else {
209 LLVM_DEBUG(llvm::dbgs() << "Taint Propagated to return value.\n");
210 Out << "Taint propagated to the return value";
211 }
212 }
213 }
214 return std::string(Out.str());
215 });
216 }
217
218 /// ArgSet is used to describe arguments relevant for taint detection or
219 /// taint application. A discrete set of argument indexes and a variadic
220 /// argument list signified by a starting index are supported.
221 class ArgSet {
222 public:
223 ArgSet() = default;
ArgSet(ArgVecTy && DiscreteArgs,std::optional<ArgIdxTy> VariadicIndex=std::nullopt)224 ArgSet(ArgVecTy &&DiscreteArgs,
225 std::optional<ArgIdxTy> VariadicIndex = std::nullopt)
226 : DiscreteArgs(std::move(DiscreteArgs)),
227 VariadicIndex(std::move(VariadicIndex)) {}
228
contains(ArgIdxTy ArgIdx) const229 bool contains(ArgIdxTy ArgIdx) const {
230 if (llvm::is_contained(DiscreteArgs, ArgIdx))
231 return true;
232
233 return VariadicIndex && ArgIdx >= *VariadicIndex;
234 }
235
isEmpty() const236 bool isEmpty() const { return DiscreteArgs.empty() && !VariadicIndex; }
237
238 private:
239 ArgVecTy DiscreteArgs;
240 std::optional<ArgIdxTy> VariadicIndex;
241 };
242
243 /// A struct used to specify taint propagation rules for a function.
244 ///
245 /// If any of the possible taint source arguments is tainted, all of the
246 /// destination arguments should also be tainted. If ReturnValueIndex is added
247 /// to the dst list, the return value will be tainted.
248 class GenericTaintRule {
249 /// Arguments which are taints sinks and should be checked, and a report
250 /// should be emitted if taint reaches these.
251 ArgSet SinkArgs;
252 /// Arguments which should be sanitized on function return.
253 ArgSet FilterArgs;
254 /// Arguments which can participate in taint propagation. If any of the
255 /// arguments in PropSrcArgs is tainted, all arguments in PropDstArgs should
256 /// be tainted.
257 ArgSet PropSrcArgs;
258 ArgSet PropDstArgs;
259
260 /// A message that explains why the call is sensitive to taint.
261 std::optional<StringRef> SinkMsg;
262
263 GenericTaintRule() = default;
264
GenericTaintRule(ArgSet && Sink,ArgSet && Filter,ArgSet && Src,ArgSet && Dst,std::optional<StringRef> SinkMsg=std::nullopt)265 GenericTaintRule(ArgSet &&Sink, ArgSet &&Filter, ArgSet &&Src, ArgSet &&Dst,
266 std::optional<StringRef> SinkMsg = std::nullopt)
267 : SinkArgs(std::move(Sink)), FilterArgs(std::move(Filter)),
268 PropSrcArgs(std::move(Src)), PropDstArgs(std::move(Dst)),
269 SinkMsg(SinkMsg) {}
270
271 public:
272 /// Make a rule that reports a warning if taint reaches any of \p FilterArgs
273 /// arguments.
Sink(ArgSet && SinkArgs,std::optional<StringRef> Msg=std::nullopt)274 static GenericTaintRule Sink(ArgSet &&SinkArgs,
275 std::optional<StringRef> Msg = std::nullopt) {
276 return {std::move(SinkArgs), {}, {}, {}, Msg};
277 }
278
279 /// Make a rule that sanitizes all FilterArgs arguments.
Filter(ArgSet && FilterArgs)280 static GenericTaintRule Filter(ArgSet &&FilterArgs) {
281 return {{}, std::move(FilterArgs), {}, {}};
282 }
283
284 /// Make a rule that unconditionally taints all Args.
285 /// If Func is provided, it must also return true for taint to propagate.
Source(ArgSet && SourceArgs)286 static GenericTaintRule Source(ArgSet &&SourceArgs) {
287 return {{}, {}, {}, std::move(SourceArgs)};
288 }
289
290 /// Make a rule that taints all PropDstArgs if any of PropSrcArgs is tainted.
Prop(ArgSet && SrcArgs,ArgSet && DstArgs)291 static GenericTaintRule Prop(ArgSet &&SrcArgs, ArgSet &&DstArgs) {
292 return {{}, {}, std::move(SrcArgs), std::move(DstArgs)};
293 }
294
295 /// Process a function which could either be a taint source, a taint sink, a
296 /// taint filter or a taint propagator.
297 void process(const GenericTaintChecker &Checker, const CallEvent &Call,
298 CheckerContext &C) const;
299
300 /// Handles the resolution of indexes of type ArgIdxTy to Expr*-s.
GetArgExpr(ArgIdxTy ArgIdx,const CallEvent & Call)301 static const Expr *GetArgExpr(ArgIdxTy ArgIdx, const CallEvent &Call) {
302 return ArgIdx == ReturnValueIndex ? Call.getOriginExpr()
303 : Call.getArgExpr(ArgIdx);
304 };
305
306 /// Functions for custom taintedness propagation.
307 static bool UntrustedEnv(CheckerContext &C);
308 };
309
310 using RuleLookupTy = CallDescriptionMap<GenericTaintRule>;
311
312 /// Used to parse the configuration file.
313 struct TaintConfiguration {
314 using NameScopeArgs = std::tuple<std::string, std::string, ArgVecTy>;
315 enum class VariadicType { None, Src, Dst };
316
317 struct Common {
318 std::string Name;
319 std::string Scope;
320 };
321
322 struct Sink : Common {
323 ArgVecTy SinkArgs;
324 };
325
326 struct Filter : Common {
327 ArgVecTy FilterArgs;
328 };
329
330 struct Propagation : Common {
331 ArgVecTy SrcArgs;
332 ArgVecTy DstArgs;
333 VariadicType VarType;
334 ArgIdxTy VarIndex;
335 };
336
337 std::vector<Propagation> Propagations;
338 std::vector<Filter> Filters;
339 std::vector<Sink> Sinks;
340
341 TaintConfiguration() = default;
342 TaintConfiguration(const TaintConfiguration &) = default;
343 TaintConfiguration(TaintConfiguration &&) = default;
344 TaintConfiguration &operator=(const TaintConfiguration &) = default;
345 TaintConfiguration &operator=(TaintConfiguration &&) = default;
346 };
347
348 struct GenericTaintRuleParser {
GenericTaintRuleParser__anoncee4e0c00111::GenericTaintRuleParser349 GenericTaintRuleParser(CheckerManager &Mgr) : Mgr(Mgr) {}
350 /// Container type used to gather call identification objects grouped into
351 /// pairs with their corresponding taint rules. It is temporary as it is used
352 /// to finally initialize RuleLookupTy, which is considered to be immutable.
353 using RulesContTy = std::vector<std::pair<CallDescription, GenericTaintRule>>;
354 RulesContTy parseConfiguration(const std::string &Option,
355 TaintConfiguration &&Config) const;
356
357 private:
358 using NamePartsTy = llvm::SmallVector<StringRef, 2>;
359
360 /// Validate part of the configuration, which contains a list of argument
361 /// indexes.
362 void validateArgVector(const std::string &Option, const ArgVecTy &Args) const;
363
364 template <typename Config> static NamePartsTy parseNameParts(const Config &C);
365
366 // Takes the config and creates a CallDescription for it and associates a Rule
367 // with that.
368 template <typename Config>
369 static void consumeRulesFromConfig(const Config &C, GenericTaintRule &&Rule,
370 RulesContTy &Rules);
371
372 void parseConfig(const std::string &Option, TaintConfiguration::Sink &&P,
373 RulesContTy &Rules) const;
374 void parseConfig(const std::string &Option, TaintConfiguration::Filter &&P,
375 RulesContTy &Rules) const;
376 void parseConfig(const std::string &Option,
377 TaintConfiguration::Propagation &&P,
378 RulesContTy &Rules) const;
379
380 CheckerManager &Mgr;
381 };
382
383 class GenericTaintChecker : public Checker<check::PreCall, check::PostCall> {
384 public:
385 void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
386 void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
387
388 void printState(raw_ostream &Out, ProgramStateRef State, const char *NL,
389 const char *Sep) const override;
390
391 /// Generate a report if the expression is tainted or points to tainted data.
392 bool generateReportIfTainted(const Expr *E, StringRef Msg,
393 CheckerContext &C) const;
394
395 bool isTaintReporterCheckerEnabled = false;
396 std::optional<BugType> BT;
397
398 private:
399 bool checkUncontrolledFormatString(const CallEvent &Call,
400 CheckerContext &C) const;
401
402 void taintUnsafeSocketProtocol(const CallEvent &Call,
403 CheckerContext &C) const;
404
405 /// The taint rules are initalized with the help of a CheckerContext to
406 /// access user-provided configuration.
407 void initTaintRules(CheckerContext &C) const;
408
409 // TODO: The two separate `CallDescriptionMap`s were introduced when
410 // `CallDescription` was unable to restrict matches to the global namespace
411 // only. This limitation no longer exists, so the following two maps should
412 // be unified.
413 mutable std::optional<RuleLookupTy> StaticTaintRules;
414 mutable std::optional<RuleLookupTy> DynamicTaintRules;
415 };
416 } // end of anonymous namespace
417
418 /// YAML serialization mapping.
419 LLVM_YAML_IS_SEQUENCE_VECTOR(TaintConfiguration::Sink)
420 LLVM_YAML_IS_SEQUENCE_VECTOR(TaintConfiguration::Filter)
421 LLVM_YAML_IS_SEQUENCE_VECTOR(TaintConfiguration::Propagation)
422
423 namespace llvm {
424 namespace yaml {
425 template <> struct MappingTraits<TaintConfiguration> {
mappingllvm::yaml::MappingTraits426 static void mapping(IO &IO, TaintConfiguration &Config) {
427 IO.mapOptional("Propagations", Config.Propagations);
428 IO.mapOptional("Filters", Config.Filters);
429 IO.mapOptional("Sinks", Config.Sinks);
430 }
431 };
432
433 template <> struct MappingTraits<TaintConfiguration::Sink> {
mappingllvm::yaml::MappingTraits434 static void mapping(IO &IO, TaintConfiguration::Sink &Sink) {
435 IO.mapRequired("Name", Sink.Name);
436 IO.mapOptional("Scope", Sink.Scope);
437 IO.mapRequired("Args", Sink.SinkArgs);
438 }
439 };
440
441 template <> struct MappingTraits<TaintConfiguration::Filter> {
mappingllvm::yaml::MappingTraits442 static void mapping(IO &IO, TaintConfiguration::Filter &Filter) {
443 IO.mapRequired("Name", Filter.Name);
444 IO.mapOptional("Scope", Filter.Scope);
445 IO.mapRequired("Args", Filter.FilterArgs);
446 }
447 };
448
449 template <> struct MappingTraits<TaintConfiguration::Propagation> {
mappingllvm::yaml::MappingTraits450 static void mapping(IO &IO, TaintConfiguration::Propagation &Propagation) {
451 IO.mapRequired("Name", Propagation.Name);
452 IO.mapOptional("Scope", Propagation.Scope);
453 IO.mapOptional("SrcArgs", Propagation.SrcArgs);
454 IO.mapOptional("DstArgs", Propagation.DstArgs);
455 IO.mapOptional("VariadicType", Propagation.VarType);
456 IO.mapOptional("VariadicIndex", Propagation.VarIndex);
457 }
458 };
459
460 template <> struct ScalarEnumerationTraits<TaintConfiguration::VariadicType> {
enumerationllvm::yaml::ScalarEnumerationTraits461 static void enumeration(IO &IO, TaintConfiguration::VariadicType &Value) {
462 IO.enumCase(Value, "None", TaintConfiguration::VariadicType::None);
463 IO.enumCase(Value, "Src", TaintConfiguration::VariadicType::Src);
464 IO.enumCase(Value, "Dst", TaintConfiguration::VariadicType::Dst);
465 }
466 };
467 } // namespace yaml
468 } // namespace llvm
469
470 /// A set which is used to pass information from call pre-visit instruction
471 /// to the call post-visit. The values are signed integers, which are either
472 /// ReturnValueIndex, or indexes of the pointer/reference argument, which
473 /// points to data, which should be tainted on return.
REGISTER_MAP_WITH_PROGRAMSTATE(TaintArgsOnPostVisit,const LocationContext *,ImmutableSet<ArgIdxTy>)474 REGISTER_MAP_WITH_PROGRAMSTATE(TaintArgsOnPostVisit, const LocationContext *,
475 ImmutableSet<ArgIdxTy>)
476 REGISTER_SET_FACTORY_WITH_PROGRAMSTATE(ArgIdxFactory, ArgIdxTy)
477
478 void GenericTaintRuleParser::validateArgVector(const std::string &Option,
479 const ArgVecTy &Args) const {
480 for (ArgIdxTy Arg : Args) {
481 if (Arg < ReturnValueIndex) {
482 Mgr.reportInvalidCheckerOptionValue(
483 Mgr.getChecker<GenericTaintChecker>(), Option,
484 "an argument number for propagation rules greater or equal to -1");
485 }
486 }
487 }
488
489 template <typename Config>
490 GenericTaintRuleParser::NamePartsTy
parseNameParts(const Config & C)491 GenericTaintRuleParser::parseNameParts(const Config &C) {
492 NamePartsTy NameParts;
493 if (!C.Scope.empty()) {
494 // If the Scope argument contains multiple "::" parts, those are considered
495 // namespace identifiers.
496 StringRef{C.Scope}.split(NameParts, "::", /*MaxSplit*/ -1,
497 /*KeepEmpty*/ false);
498 }
499 NameParts.emplace_back(C.Name);
500 return NameParts;
501 }
502
503 template <typename Config>
consumeRulesFromConfig(const Config & C,GenericTaintRule && Rule,RulesContTy & Rules)504 void GenericTaintRuleParser::consumeRulesFromConfig(const Config &C,
505 GenericTaintRule &&Rule,
506 RulesContTy &Rules) {
507 NamePartsTy NameParts = parseNameParts(C);
508 Rules.emplace_back(CallDescription(CDM::Unspecified, NameParts),
509 std::move(Rule));
510 }
511
parseConfig(const std::string & Option,TaintConfiguration::Sink && S,RulesContTy & Rules) const512 void GenericTaintRuleParser::parseConfig(const std::string &Option,
513 TaintConfiguration::Sink &&S,
514 RulesContTy &Rules) const {
515 validateArgVector(Option, S.SinkArgs);
516 consumeRulesFromConfig(S, GenericTaintRule::Sink(std::move(S.SinkArgs)),
517 Rules);
518 }
519
parseConfig(const std::string & Option,TaintConfiguration::Filter && S,RulesContTy & Rules) const520 void GenericTaintRuleParser::parseConfig(const std::string &Option,
521 TaintConfiguration::Filter &&S,
522 RulesContTy &Rules) const {
523 validateArgVector(Option, S.FilterArgs);
524 consumeRulesFromConfig(S, GenericTaintRule::Filter(std::move(S.FilterArgs)),
525 Rules);
526 }
527
parseConfig(const std::string & Option,TaintConfiguration::Propagation && P,RulesContTy & Rules) const528 void GenericTaintRuleParser::parseConfig(const std::string &Option,
529 TaintConfiguration::Propagation &&P,
530 RulesContTy &Rules) const {
531 validateArgVector(Option, P.SrcArgs);
532 validateArgVector(Option, P.DstArgs);
533 bool IsSrcVariadic = P.VarType == TaintConfiguration::VariadicType::Src;
534 bool IsDstVariadic = P.VarType == TaintConfiguration::VariadicType::Dst;
535 std::optional<ArgIdxTy> JustVarIndex = P.VarIndex;
536
537 ArgSet SrcDesc(std::move(P.SrcArgs),
538 IsSrcVariadic ? JustVarIndex : std::nullopt);
539 ArgSet DstDesc(std::move(P.DstArgs),
540 IsDstVariadic ? JustVarIndex : std::nullopt);
541
542 consumeRulesFromConfig(
543 P, GenericTaintRule::Prop(std::move(SrcDesc), std::move(DstDesc)), Rules);
544 }
545
546 GenericTaintRuleParser::RulesContTy
parseConfiguration(const std::string & Option,TaintConfiguration && Config) const547 GenericTaintRuleParser::parseConfiguration(const std::string &Option,
548 TaintConfiguration &&Config) const {
549
550 RulesContTy Rules;
551
552 for (auto &F : Config.Filters)
553 parseConfig(Option, std::move(F), Rules);
554
555 for (auto &S : Config.Sinks)
556 parseConfig(Option, std::move(S), Rules);
557
558 for (auto &P : Config.Propagations)
559 parseConfig(Option, std::move(P), Rules);
560
561 return Rules;
562 }
563
initTaintRules(CheckerContext & C) const564 void GenericTaintChecker::initTaintRules(CheckerContext &C) const {
565 // Check for exact name match for functions without builtin substitutes.
566 // Use qualified name, because these are C functions without namespace.
567
568 if (StaticTaintRules || DynamicTaintRules)
569 return;
570
571 using RulesConstructionTy =
572 std::vector<std::pair<CallDescription, GenericTaintRule>>;
573 using TR = GenericTaintRule;
574
575 RulesConstructionTy GlobalCRules{
576 // Sources
577 {{CDM::CLibrary, {"fdopen"}}, TR::Source({{ReturnValueIndex}})},
578 {{CDM::CLibrary, {"fopen"}}, TR::Source({{ReturnValueIndex}})},
579 {{CDM::CLibrary, {"freopen"}}, TR::Source({{ReturnValueIndex}})},
580 {{CDM::CLibrary, {"getch"}}, TR::Source({{ReturnValueIndex}})},
581 {{CDM::CLibrary, {"getchar"}}, TR::Source({{ReturnValueIndex}})},
582 {{CDM::CLibrary, {"getchar_unlocked"}}, TR::Source({{ReturnValueIndex}})},
583 {{CDM::CLibrary, {"gets"}}, TR::Source({{0, ReturnValueIndex}})},
584 {{CDM::CLibrary, {"gets_s"}}, TR::Source({{0, ReturnValueIndex}})},
585 {{CDM::CLibrary, {"scanf"}}, TR::Source({{}, 1})},
586 {{CDM::CLibrary, {"scanf_s"}}, TR::Source({{}, 1})},
587 {{CDM::CLibrary, {"wgetch"}}, TR::Source({{ReturnValueIndex}})},
588 // Sometimes the line between taint sources and propagators is blurry.
589 // _IO_getc is choosen to be a source, but could also be a propagator.
590 // This way it is simpler, as modeling it as a propagator would require
591 // to model the possible sources of _IO_FILE * values, which the _IO_getc
592 // function takes as parameters.
593 {{CDM::CLibrary, {"_IO_getc"}}, TR::Source({{ReturnValueIndex}})},
594 {{CDM::CLibrary, {"getcwd"}}, TR::Source({{0, ReturnValueIndex}})},
595 {{CDM::CLibrary, {"getwd"}}, TR::Source({{0, ReturnValueIndex}})},
596 {{CDM::CLibrary, {"readlink"}}, TR::Source({{1, ReturnValueIndex}})},
597 {{CDM::CLibrary, {"readlinkat"}}, TR::Source({{2, ReturnValueIndex}})},
598 {{CDM::CLibrary, {"get_current_dir_name"}},
599 TR::Source({{ReturnValueIndex}})},
600 {{CDM::CLibrary, {"gethostname"}}, TR::Source({{0}})},
601 {{CDM::CLibrary, {"getnameinfo"}}, TR::Source({{2, 4}})},
602 {{CDM::CLibrary, {"getseuserbyname"}}, TR::Source({{1, 2}})},
603 {{CDM::CLibrary, {"getgroups"}}, TR::Source({{1, ReturnValueIndex}})},
604 {{CDM::CLibrary, {"getlogin"}}, TR::Source({{ReturnValueIndex}})},
605 {{CDM::CLibrary, {"getlogin_r"}}, TR::Source({{0}})},
606
607 // Props
608 {{CDM::CLibrary, {"accept"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
609 {{CDM::CLibrary, {"atoi"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
610 {{CDM::CLibrary, {"atol"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
611 {{CDM::CLibrary, {"atoll"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
612 {{CDM::CLibrary, {"fgetc"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
613 {{CDM::CLibrary, {"fgetln"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
614 {{CDM::CLibraryMaybeHardened, {"fgets"}},
615 TR::Prop({{2}}, {{0, ReturnValueIndex}})},
616 {{CDM::CLibraryMaybeHardened, {"fgetws"}},
617 TR::Prop({{2}}, {{0, ReturnValueIndex}})},
618 {{CDM::CLibrary, {"fscanf"}}, TR::Prop({{0}}, {{}, 2})},
619 {{CDM::CLibrary, {"fscanf_s"}}, TR::Prop({{0}}, {{}, 2})},
620 {{CDM::CLibrary, {"sscanf"}}, TR::Prop({{0}}, {{}, 2})},
621 {{CDM::CLibrary, {"sscanf_s"}}, TR::Prop({{0}}, {{}, 2})},
622
623 {{CDM::CLibrary, {"getc"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
624 {{CDM::CLibrary, {"getc_unlocked"}},
625 TR::Prop({{0}}, {{ReturnValueIndex}})},
626 {{CDM::CLibrary, {"getdelim"}}, TR::Prop({{3}}, {{0}})},
627 // TODO: this intends to match the C function `getline()`, but the call
628 // description also matches the C++ function `std::getline()`; it should
629 // be ruled out by some additional logic.
630 {{CDM::CLibrary, {"getline"}}, TR::Prop({{2}}, {{0}})},
631 {{CDM::CLibrary, {"getw"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
632 {{CDM::CLibraryMaybeHardened, {"pread"}},
633 TR::Prop({{0, 1, 2, 3}}, {{1, ReturnValueIndex}})},
634 {{CDM::CLibraryMaybeHardened, {"read"}},
635 TR::Prop({{0, 2}}, {{1, ReturnValueIndex}})},
636 {{CDM::CLibraryMaybeHardened, {"fread"}},
637 TR::Prop({{3}}, {{0, ReturnValueIndex}})},
638 {{CDM::CLibraryMaybeHardened, {"recv"}},
639 TR::Prop({{0}}, {{1, ReturnValueIndex}})},
640 {{CDM::CLibraryMaybeHardened, {"recvfrom"}},
641 TR::Prop({{0}}, {{1, ReturnValueIndex}})},
642
643 {{CDM::CLibrary, {"ttyname"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
644 {{CDM::CLibrary, {"ttyname_r"}},
645 TR::Prop({{0}}, {{1, ReturnValueIndex}})},
646
647 {{CDM::CLibrary, {"basename"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
648 {{CDM::CLibrary, {"dirname"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
649 {{CDM::CLibrary, {"fnmatch"}}, TR::Prop({{1}}, {{ReturnValueIndex}})},
650
651 {{CDM::CLibrary, {"mbtowc"}}, TR::Prop({{1}}, {{0, ReturnValueIndex}})},
652 {{CDM::CLibrary, {"wctomb"}}, TR::Prop({{1}}, {{0, ReturnValueIndex}})},
653 {{CDM::CLibrary, {"wcwidth"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
654
655 {{CDM::CLibrary, {"memcmp"}},
656 TR::Prop({{0, 1, 2}}, {{ReturnValueIndex}})},
657 {{CDM::CLibraryMaybeHardened, {"memcpy"}},
658 TR::Prop({{1, 2}}, {{0, ReturnValueIndex}})},
659 {{CDM::CLibraryMaybeHardened, {"memmove"}},
660 TR::Prop({{1, 2}}, {{0, ReturnValueIndex}})},
661 {{CDM::CLibraryMaybeHardened, {"bcopy"}}, TR::Prop({{0, 2}}, {{1}})},
662
663 // Note: "memmem" and its variants search for a byte sequence ("needle")
664 // in a larger area ("haystack"). Currently we only propagate taint from
665 // the haystack to the result, but in theory tampering with the needle
666 // could also produce incorrect results.
667 {{CDM::CLibrary, {"memmem"}}, TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
668 {{CDM::CLibrary, {"strstr"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
669 {{CDM::CLibrary, {"strcasestr"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
670
671 // Analogously, the following functions search for a byte within a buffer
672 // and we only propagate taint from the buffer to the result.
673 {{CDM::CLibraryMaybeHardened, {"memchr"}},
674 TR::Prop({{0}}, {{ReturnValueIndex}})},
675 {{CDM::CLibraryMaybeHardened, {"memrchr"}},
676 TR::Prop({{0}}, {{ReturnValueIndex}})},
677 {{CDM::CLibrary, {"rawmemchr"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
678 {{CDM::CLibraryMaybeHardened, {"strchr"}},
679 TR::Prop({{0}}, {{ReturnValueIndex}})},
680 {{CDM::CLibraryMaybeHardened, {"strrchr"}},
681 TR::Prop({{0}}, {{ReturnValueIndex}})},
682 {{CDM::CLibraryMaybeHardened, {"strchrnul"}},
683 TR::Prop({{0}}, {{ReturnValueIndex}})},
684 {{CDM::CLibrary, {"index"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
685 {{CDM::CLibrary, {"rindex"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
686
687 // FIXME: In case of arrays, only the first element of the array gets
688 // tainted.
689 {{CDM::CLibrary, {"qsort"}}, TR::Prop({{0}}, {{0}})},
690 {{CDM::CLibrary, {"qsort_r"}}, TR::Prop({{0}}, {{0}})},
691
692 {{CDM::CLibrary, {"strcmp"}}, TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
693 {{CDM::CLibrary, {"strcasecmp"}},
694 TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
695 {{CDM::CLibrary, {"strncmp"}},
696 TR::Prop({{0, 1, 2}}, {{ReturnValueIndex}})},
697 {{CDM::CLibrary, {"strncasecmp"}},
698 TR::Prop({{0, 1, 2}}, {{ReturnValueIndex}})},
699 {{CDM::CLibrary, {"strspn"}}, TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
700 {{CDM::CLibrary, {"strcspn"}}, TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
701 {{CDM::CLibrary, {"strpbrk"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
702
703 {{CDM::CLibrary, {"strndup"}}, TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
704 {{CDM::CLibrary, {"strndupa"}}, TR::Prop({{0, 1}}, {{ReturnValueIndex}})},
705 {{CDM::CLibrary, {"strdup"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
706 {{CDM::CLibrary, {"strdupa"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
707 {{CDM::CLibrary, {"wcsdup"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
708
709 // strlen, wcslen, strnlen and alike intentionally don't propagate taint.
710 // See the details here: https://github.com/llvm/llvm-project/pull/66086
711
712 {{CDM::CLibrary, {"strtol"}}, TR::Prop({{0}}, {{1, ReturnValueIndex}})},
713 {{CDM::CLibrary, {"strtoll"}}, TR::Prop({{0}}, {{1, ReturnValueIndex}})},
714 {{CDM::CLibrary, {"strtoul"}}, TR::Prop({{0}}, {{1, ReturnValueIndex}})},
715 {{CDM::CLibrary, {"strtoull"}}, TR::Prop({{0}}, {{1, ReturnValueIndex}})},
716
717 {{CDM::CLibrary, {"tolower"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
718 {{CDM::CLibrary, {"toupper"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
719
720 {{CDM::CLibrary, {"isalnum"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
721 {{CDM::CLibrary, {"isalpha"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
722 {{CDM::CLibrary, {"isascii"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
723 {{CDM::CLibrary, {"isblank"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
724 {{CDM::CLibrary, {"iscntrl"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
725 {{CDM::CLibrary, {"isdigit"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
726 {{CDM::CLibrary, {"isgraph"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
727 {{CDM::CLibrary, {"islower"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
728 {{CDM::CLibrary, {"isprint"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
729 {{CDM::CLibrary, {"ispunct"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
730 {{CDM::CLibrary, {"isspace"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
731 {{CDM::CLibrary, {"isupper"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
732 {{CDM::CLibrary, {"isxdigit"}}, TR::Prop({{0}}, {{ReturnValueIndex}})},
733
734 {{CDM::CLibraryMaybeHardened, {"strcpy"}},
735 TR::Prop({{1}}, {{0, ReturnValueIndex}})},
736 {{CDM::CLibraryMaybeHardened, {"stpcpy"}},
737 TR::Prop({{1}}, {{0, ReturnValueIndex}})},
738 {{CDM::CLibraryMaybeHardened, {"strcat"}},
739 TR::Prop({{0, 1}}, {{0, ReturnValueIndex}})},
740 {{CDM::CLibraryMaybeHardened, {"wcsncat"}},
741 TR::Prop({{0, 1}}, {{0, ReturnValueIndex}})},
742 {{CDM::CLibraryMaybeHardened, {"strncpy"}},
743 TR::Prop({{1, 2}}, {{0, ReturnValueIndex}})},
744 {{CDM::CLibraryMaybeHardened, {"strncat"}},
745 TR::Prop({{0, 1, 2}}, {{0, ReturnValueIndex}})},
746 {{CDM::CLibraryMaybeHardened, {"strlcpy"}}, TR::Prop({{1, 2}}, {{0}})},
747 {{CDM::CLibraryMaybeHardened, {"strlcat"}}, TR::Prop({{0, 1, 2}}, {{0}})},
748
749 // Usually the matching mode `CDM::CLibraryMaybeHardened` is sufficient
750 // for unified handling of a function `FOO()` and its hardened variant
751 // `__FOO_chk()`, but in the "sprintf" family the extra parameters of the
752 // hardened variants are inserted into the middle of the parameter list,
753 // so that would not work in their case.
754 // int snprintf(char * str, size_t maxlen, const char * format, ...);
755 {{CDM::CLibrary, {"snprintf"}},
756 TR::Prop({{1, 2}, 3}, {{0, ReturnValueIndex}})},
757 // int sprintf(char * str, const char * format, ...);
758 {{CDM::CLibrary, {"sprintf"}},
759 TR::Prop({{1}, 2}, {{0, ReturnValueIndex}})},
760 // int __snprintf_chk(char * str, size_t maxlen, int flag, size_t strlen,
761 // const char * format, ...);
762 {{CDM::CLibrary, {"__snprintf_chk"}},
763 TR::Prop({{1, 4}, 5}, {{0, ReturnValueIndex}})},
764 // int __sprintf_chk(char * str, int flag, size_t strlen, const char *
765 // format, ...);
766 {{CDM::CLibrary, {"__sprintf_chk"}},
767 TR::Prop({{3}, 4}, {{0, ReturnValueIndex}})},
768
769 // Sinks
770 {{CDM::CLibrary, {"system"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
771 {{CDM::CLibrary, {"popen"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
772 {{CDM::CLibrary, {"execl"}}, TR::Sink({{}, {0}}, MsgSanitizeSystemArgs)},
773 {{CDM::CLibrary, {"execle"}}, TR::Sink({{}, {0}}, MsgSanitizeSystemArgs)},
774 {{CDM::CLibrary, {"execlp"}}, TR::Sink({{}, {0}}, MsgSanitizeSystemArgs)},
775 {{CDM::CLibrary, {"execv"}}, TR::Sink({{0, 1}}, MsgSanitizeSystemArgs)},
776 {{CDM::CLibrary, {"execve"}},
777 TR::Sink({{0, 1, 2}}, MsgSanitizeSystemArgs)},
778 {{CDM::CLibrary, {"fexecve"}},
779 TR::Sink({{0, 1, 2}}, MsgSanitizeSystemArgs)},
780 {{CDM::CLibrary, {"execvp"}}, TR::Sink({{0, 1}}, MsgSanitizeSystemArgs)},
781 {{CDM::CLibrary, {"execvpe"}},
782 TR::Sink({{0, 1, 2}}, MsgSanitizeSystemArgs)},
783 {{CDM::CLibrary, {"dlopen"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
784
785 // malloc, calloc, alloca, realloc, memccpy
786 // are intentionally not marked as taint sinks because unconditional
787 // reporting for these functions generates many false positives.
788 // These taint sinks should be implemented in other checkers with more
789 // sophisticated sanitation heuristics.
790
791 {{CDM::CLibrary, {"setproctitle"}},
792 TR::Sink({{0}, 1}, MsgUncontrolledFormatString)},
793 {{CDM::CLibrary, {"setproctitle_fast"}},
794 TR::Sink({{0}, 1}, MsgUncontrolledFormatString)}};
795
796 if (TR::UntrustedEnv(C)) {
797 // void setproctitle_init(int argc, char *argv[], char *envp[])
798 // TODO: replace `MsgCustomSink` with a message that fits this situation.
799 GlobalCRules.push_back({{CDM::CLibrary, {"setproctitle_init"}},
800 TR::Sink({{1, 2}}, MsgCustomSink)});
801
802 // `getenv` returns taint only in untrusted environments.
803 GlobalCRules.push_back(
804 {{CDM::CLibrary, {"getenv"}}, TR::Source({{ReturnValueIndex}})});
805 }
806
807 StaticTaintRules.emplace(std::make_move_iterator(GlobalCRules.begin()),
808 std::make_move_iterator(GlobalCRules.end()));
809
810 // User-provided taint configuration.
811 CheckerManager *Mgr = C.getAnalysisManager().getCheckerManager();
812 assert(Mgr);
813 GenericTaintRuleParser ConfigParser{*Mgr};
814 std::string Option{"Config"};
815 StringRef ConfigFile =
816 Mgr->getAnalyzerOptions().getCheckerStringOption(this, Option);
817 std::optional<TaintConfiguration> Config =
818 getConfiguration<TaintConfiguration>(*Mgr, this, Option, ConfigFile);
819 if (!Config) {
820 // We don't have external taint config, no parsing required.
821 DynamicTaintRules = RuleLookupTy{};
822 return;
823 }
824
825 GenericTaintRuleParser::RulesContTy Rules{
826 ConfigParser.parseConfiguration(Option, std::move(*Config))};
827
828 DynamicTaintRules.emplace(std::make_move_iterator(Rules.begin()),
829 std::make_move_iterator(Rules.end()));
830 }
831
checkPreCall(const CallEvent & Call,CheckerContext & C) const832 void GenericTaintChecker::checkPreCall(const CallEvent &Call,
833 CheckerContext &C) const {
834 initTaintRules(C);
835
836 // FIXME: this should be much simpler.
837 if (const auto *Rule =
838 Call.isGlobalCFunction() ? StaticTaintRules->lookup(Call) : nullptr)
839 Rule->process(*this, Call, C);
840 else if (const auto *Rule = DynamicTaintRules->lookup(Call))
841 Rule->process(*this, Call, C);
842
843 // FIXME: These edge cases are to be eliminated from here eventually.
844 //
845 // Additional check that is not supported by CallDescription.
846 // TODO: Make CallDescription be able to match attributes such as printf-like
847 // arguments.
848 checkUncontrolledFormatString(Call, C);
849
850 // TODO: Modeling sockets should be done in a specific checker.
851 // Socket is a source, which taints the return value.
852 taintUnsafeSocketProtocol(Call, C);
853 }
854
checkPostCall(const CallEvent & Call,CheckerContext & C) const855 void GenericTaintChecker::checkPostCall(const CallEvent &Call,
856 CheckerContext &C) const {
857 // Set the marked values as tainted. The return value only accessible from
858 // checkPostStmt.
859 ProgramStateRef State = C.getState();
860 const StackFrameContext *CurrentFrame = C.getStackFrame();
861
862 // Depending on what was tainted at pre-visit, we determined a set of
863 // arguments which should be tainted after the function returns. These are
864 // stored in the state as TaintArgsOnPostVisit set.
865 TaintArgsOnPostVisitTy TaintArgsMap = State->get<TaintArgsOnPostVisit>();
866
867 const ImmutableSet<ArgIdxTy> *TaintArgs = TaintArgsMap.lookup(CurrentFrame);
868 if (!TaintArgs)
869 return;
870 assert(!TaintArgs->isEmpty());
871
872 LLVM_DEBUG(for (ArgIdxTy I
873 : *TaintArgs) {
874 llvm::dbgs() << "PostCall<";
875 Call.dump(llvm::dbgs());
876 llvm::dbgs() << "> actually wants to taint arg index: " << I << '\n';
877 });
878
879 const NoteTag *InjectionTag = nullptr;
880 std::vector<SymbolRef> TaintedSymbols;
881 std::vector<ArgIdxTy> TaintedIndexes;
882 for (ArgIdxTy ArgNum : *TaintArgs) {
883 // Special handling for the tainted return value.
884 if (ArgNum == ReturnValueIndex) {
885 State = addTaint(State, Call.getReturnValue());
886 std::vector<SymbolRef> TaintedSyms =
887 getTaintedSymbols(State, Call.getReturnValue());
888 if (!TaintedSyms.empty()) {
889 TaintedSymbols.push_back(TaintedSyms[0]);
890 TaintedIndexes.push_back(ArgNum);
891 }
892 continue;
893 }
894 // The arguments are pointer arguments. The data they are pointing at is
895 // tainted after the call.
896 if (auto V = getPointeeOf(State, Call.getArgSVal(ArgNum))) {
897 State = addTaint(State, *V);
898 std::vector<SymbolRef> TaintedSyms = getTaintedSymbols(State, *V);
899 if (!TaintedSyms.empty()) {
900 TaintedSymbols.push_back(TaintedSyms[0]);
901 TaintedIndexes.push_back(ArgNum);
902 }
903 }
904 }
905 // Create a NoteTag callback, which prints to the user where the taintedness
906 // was propagated to.
907 InjectionTag = taintPropagationExplainerTag(C, TaintedSymbols, TaintedIndexes,
908 Call.getCalleeStackFrame(0));
909 // Clear up the taint info from the state.
910 State = State->remove<TaintArgsOnPostVisit>(CurrentFrame);
911 C.addTransition(State, InjectionTag);
912 }
913
printState(raw_ostream & Out,ProgramStateRef State,const char * NL,const char * Sep) const914 void GenericTaintChecker::printState(raw_ostream &Out, ProgramStateRef State,
915 const char *NL, const char *Sep) const {
916 printTaint(State, Out, NL, Sep);
917 }
918
process(const GenericTaintChecker & Checker,const CallEvent & Call,CheckerContext & C) const919 void GenericTaintRule::process(const GenericTaintChecker &Checker,
920 const CallEvent &Call, CheckerContext &C) const {
921 ProgramStateRef State = C.getState();
922 const ArgIdxTy CallNumArgs = fromArgumentCount(Call.getNumArgs());
923
924 /// Iterate every call argument, and get their corresponding Expr and SVal.
925 const auto ForEachCallArg = [&C, &Call, CallNumArgs](auto &&Fun) {
926 for (ArgIdxTy I = ReturnValueIndex; I < CallNumArgs; ++I) {
927 const Expr *E = GetArgExpr(I, Call);
928 Fun(I, E, C.getSVal(E));
929 }
930 };
931
932 /// Check for taint sinks.
933 ForEachCallArg([this, &Checker, &C, &State](ArgIdxTy I, const Expr *E, SVal) {
934 // Add taintedness to stdin parameters
935 if (isStdin(C.getSVal(E), C.getASTContext())) {
936 State = addTaint(State, C.getSVal(E));
937 }
938 if (SinkArgs.contains(I) && isTaintedOrPointsToTainted(State, C.getSVal(E)))
939 Checker.generateReportIfTainted(E, SinkMsg.value_or(MsgCustomSink), C);
940 });
941
942 /// Check for taint filters.
943 ForEachCallArg([this, &State](ArgIdxTy I, const Expr *E, SVal S) {
944 if (FilterArgs.contains(I)) {
945 State = removeTaint(State, S);
946 if (auto P = getPointeeOf(State, S))
947 State = removeTaint(State, *P);
948 }
949 });
950
951 /// Check for taint propagation sources.
952 /// A rule will make the destination variables tainted if PropSrcArgs
953 /// is empty (taints the destination
954 /// arguments unconditionally), or if any of its signified
955 /// args are tainted in context of the current CallEvent.
956 bool IsMatching = PropSrcArgs.isEmpty();
957 std::vector<SymbolRef> TaintedSymbols;
958 std::vector<ArgIdxTy> TaintedIndexes;
959 ForEachCallArg([this, &C, &IsMatching, &State, &TaintedSymbols,
960 &TaintedIndexes](ArgIdxTy I, const Expr *E, SVal) {
961 std::optional<SVal> TaintedSVal =
962 getTaintedPointeeOrPointer(State, C.getSVal(E));
963 IsMatching =
964 IsMatching || (PropSrcArgs.contains(I) && TaintedSVal.has_value());
965
966 // We track back tainted arguments except for stdin
967 if (TaintedSVal && !isStdin(*TaintedSVal, C.getASTContext())) {
968 std::vector<SymbolRef> TaintedArgSyms =
969 getTaintedSymbols(State, *TaintedSVal);
970 if (!TaintedArgSyms.empty()) {
971 llvm::append_range(TaintedSymbols, TaintedArgSyms);
972 TaintedIndexes.push_back(I);
973 }
974 }
975 });
976
977 // Early return for propagation rules which dont match.
978 // Matching propagations, Sinks and Filters will pass this point.
979 if (!IsMatching)
980 return;
981
982 const auto WouldEscape = [](SVal V, QualType Ty) -> bool {
983 if (!isa<Loc>(V))
984 return false;
985
986 const bool IsNonConstRef = Ty->isReferenceType() && !Ty.isConstQualified();
987 const bool IsNonConstPtr =
988 Ty->isPointerType() && !Ty->getPointeeType().isConstQualified();
989
990 return IsNonConstRef || IsNonConstPtr;
991 };
992
993 /// Propagate taint where it is necessary.
994 auto &F = State->getStateManager().get_context<ArgIdxFactory>();
995 ImmutableSet<ArgIdxTy> Result = F.getEmptySet();
996 ForEachCallArg(
997 [&](ArgIdxTy I, const Expr *E, SVal V) {
998 if (PropDstArgs.contains(I)) {
999 LLVM_DEBUG(llvm::dbgs() << "PreCall<"; Call.dump(llvm::dbgs());
1000 llvm::dbgs()
1001 << "> prepares tainting arg index: " << I << '\n';);
1002 Result = F.add(Result, I);
1003 }
1004
1005 // Taint property gets lost if the variable is passed as a
1006 // non-const pointer or reference to a function which is
1007 // not inlined. For matching rules we want to preserve the taintedness.
1008 // TODO: We should traverse all reachable memory regions via the
1009 // escaping parameter. Instead of doing that we simply mark only the
1010 // referred memory region as tainted.
1011 if (WouldEscape(V, E->getType()) && getTaintedPointeeOrPointer(State, V)) {
1012 LLVM_DEBUG(if (!Result.contains(I)) {
1013 llvm::dbgs() << "PreCall<";
1014 Call.dump(llvm::dbgs());
1015 llvm::dbgs() << "> prepares tainting arg index: " << I << '\n';
1016 });
1017 Result = F.add(Result, I);
1018 }
1019 });
1020
1021 if (!Result.isEmpty())
1022 State = State->set<TaintArgsOnPostVisit>(C.getStackFrame(), Result);
1023 const NoteTag *InjectionTag = taintOriginTrackerTag(
1024 C, std::move(TaintedSymbols), std::move(TaintedIndexes),
1025 Call.getCalleeStackFrame(0));
1026 C.addTransition(State, InjectionTag);
1027 }
1028
UntrustedEnv(CheckerContext & C)1029 bool GenericTaintRule::UntrustedEnv(CheckerContext &C) {
1030 return !C.getAnalysisManager()
1031 .getAnalyzerOptions()
1032 .ShouldAssumeControlledEnvironment;
1033 }
1034
generateReportIfTainted(const Expr * E,StringRef Msg,CheckerContext & C) const1035 bool GenericTaintChecker::generateReportIfTainted(const Expr *E, StringRef Msg,
1036 CheckerContext &C) const {
1037 assert(E);
1038 if (!isTaintReporterCheckerEnabled)
1039 return false;
1040 std::optional<SVal> TaintedSVal =
1041 getTaintedPointeeOrPointer(C.getState(), C.getSVal(E));
1042
1043 if (!TaintedSVal)
1044 return false;
1045
1046 // Generate diagnostic.
1047 assert(BT);
1048 static CheckerProgramPointTag Tag(BT->getCheckerName(), Msg);
1049 if (ExplodedNode *N = C.generateNonFatalErrorNode(C.getState(), &Tag)) {
1050 auto report = std::make_unique<PathSensitiveBugReport>(*BT, Msg, N);
1051 report->addRange(E->getSourceRange());
1052 for (auto TaintedSym : getTaintedSymbols(C.getState(), *TaintedSVal)) {
1053 report->markInteresting(TaintedSym);
1054 }
1055 C.emitReport(std::move(report));
1056 return true;
1057 }
1058 return false;
1059 }
1060
1061 /// TODO: remove checking for printf format attributes and socket whitelisting
1062 /// from GenericTaintChecker, and that means the following functions:
1063 /// getPrintfFormatArgumentNum,
1064 /// GenericTaintChecker::checkUncontrolledFormatString,
1065 /// GenericTaintChecker::taintUnsafeSocketProtocol
1066
getPrintfFormatArgumentNum(const CallEvent & Call,const CheckerContext & C,ArgIdxTy & ArgNum)1067 static bool getPrintfFormatArgumentNum(const CallEvent &Call,
1068 const CheckerContext &C,
1069 ArgIdxTy &ArgNum) {
1070 // Find if the function contains a format string argument.
1071 // Handles: fprintf, printf, sprintf, snprintf, vfprintf, vprintf, vsprintf,
1072 // vsnprintf, syslog, custom annotated functions.
1073 const Decl *CallDecl = Call.getDecl();
1074 if (!CallDecl)
1075 return false;
1076 const FunctionDecl *FDecl = CallDecl->getAsFunction();
1077 if (!FDecl)
1078 return false;
1079
1080 const ArgIdxTy CallNumArgs = fromArgumentCount(Call.getNumArgs());
1081
1082 for (const auto *Format : FDecl->specific_attrs<FormatAttr>()) {
1083 ArgNum = Format->getFormatIdx() - 1;
1084 if ((Format->getType()->getName() == "printf") && CallNumArgs > ArgNum)
1085 return true;
1086 }
1087
1088 return false;
1089 }
1090
checkUncontrolledFormatString(const CallEvent & Call,CheckerContext & C) const1091 bool GenericTaintChecker::checkUncontrolledFormatString(
1092 const CallEvent &Call, CheckerContext &C) const {
1093 // Check if the function contains a format string argument.
1094 ArgIdxTy ArgNum = 0;
1095 if (!getPrintfFormatArgumentNum(Call, C, ArgNum))
1096 return false;
1097
1098 // If either the format string content or the pointer itself are tainted,
1099 // warn.
1100 return generateReportIfTainted(Call.getArgExpr(ArgNum),
1101 MsgUncontrolledFormatString, C);
1102 }
1103
taintUnsafeSocketProtocol(const CallEvent & Call,CheckerContext & C) const1104 void GenericTaintChecker::taintUnsafeSocketProtocol(const CallEvent &Call,
1105 CheckerContext &C) const {
1106 if (Call.getNumArgs() < 1)
1107 return;
1108 const IdentifierInfo *ID = Call.getCalleeIdentifier();
1109 if (!ID)
1110 return;
1111 if (ID->getName() != "socket")
1112 return;
1113
1114 SourceLocation DomLoc = Call.getArgExpr(0)->getExprLoc();
1115 StringRef DomName = C.getMacroNameOrSpelling(DomLoc);
1116 // Allow internal communication protocols.
1117 bool SafeProtocol = DomName == "AF_SYSTEM" || DomName == "AF_LOCAL" ||
1118 DomName == "AF_UNIX" || DomName == "AF_RESERVED_36";
1119 if (SafeProtocol)
1120 return;
1121
1122 ProgramStateRef State = C.getState();
1123 auto &F = State->getStateManager().get_context<ArgIdxFactory>();
1124 ImmutableSet<ArgIdxTy> Result = F.add(F.getEmptySet(), ReturnValueIndex);
1125 State = State->set<TaintArgsOnPostVisit>(C.getStackFrame(), Result);
1126 C.addTransition(State);
1127 }
1128
1129 /// Checker registration
registerTaintPropagationChecker(CheckerManager & Mgr)1130 void ento::registerTaintPropagationChecker(CheckerManager &Mgr) {
1131 Mgr.registerChecker<GenericTaintChecker>();
1132 }
1133
shouldRegisterTaintPropagationChecker(const CheckerManager & mgr)1134 bool ento::shouldRegisterTaintPropagationChecker(const CheckerManager &mgr) {
1135 return true;
1136 }
1137
registerGenericTaintChecker(CheckerManager & Mgr)1138 void ento::registerGenericTaintChecker(CheckerManager &Mgr) {
1139 GenericTaintChecker *checker = Mgr.getChecker<GenericTaintChecker>();
1140 checker->isTaintReporterCheckerEnabled = true;
1141 checker->BT.emplace(Mgr.getCurrentCheckerName(), "Use of Untrusted Data",
1142 categories::TaintedData);
1143 }
1144
shouldRegisterGenericTaintChecker(const CheckerManager & mgr)1145 bool ento::shouldRegisterGenericTaintChecker(const CheckerManager &mgr) {
1146 return true;
1147 }
1148