CheckSecuritySyntaxOnly.cpp revision 42f74f21ece01dc8573d5377859d327fbb23b26c 
1//==- CheckSecuritySyntaxOnly.cpp - Basic security checks --------*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file defines a set of flow-insensitive security checks.
11//
12//===----------------------------------------------------------------------===//
13
14#include "ClangSACheckers.h"
15#include "clang/Analysis/AnalysisContext.h"
16#include "clang/AST/StmtVisitor.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/StaticAnalyzer/Core/Checker.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
21#include "llvm/ADT/SmallString.h"
22#include "llvm/ADT/StringSwitch.h"
23#include "llvm/Support/raw_ostream.h"
24
25using namespace clang;
26using namespace ento;
27
28static bool isArc4RandomAvailable(const ASTContext &Ctx) {
29  const llvm::Triple &T = Ctx.getTargetInfo().getTriple();
30  return T.getVendor() == llvm::Triple::Apple ||
31         T.getOS() == llvm::Triple::FreeBSD ||
32         T.getOS() == llvm::Triple::NetBSD ||
33         T.getOS() == llvm::Triple::OpenBSD ||
34         T.getOS() == llvm::Triple::Bitrig ||
35         T.getOS() == llvm::Triple::DragonFly;
36}
37
38namespace {
39struct DefaultBool {
40  bool val;
41  DefaultBool() : val(false) {}
42  operator bool() const { return val; }
43  DefaultBool &operator=(bool b) { val = b; return *this; }
44};
45
46struct ChecksFilter {
47  DefaultBool check_gets;
48  DefaultBool check_getpw;
49  DefaultBool check_mktemp;
50  DefaultBool check_mkstemp;
51  DefaultBool check_strcpy;
52  DefaultBool check_rand;
53  DefaultBool check_vfork;
54  DefaultBool check_FloatLoopCounter;
55  DefaultBool check_UncheckedReturn;
56};
57
58class WalkAST : public StmtVisitor<WalkAST> {
59  BugReporter &BR;
60  AnalysisDeclContext* AC;
61  enum { num_setids = 6 };
62  IdentifierInfo *II_setid[num_setids];
63
64  const bool CheckRand;
65  const ChecksFilter &filter;
66
67public:
68  WalkAST(BugReporter &br, AnalysisDeclContext* ac,
69          const ChecksFilter &f)
70  : BR(br), AC(ac), II_setid(),
71    CheckRand(isArc4RandomAvailable(BR.getContext())),
72    filter(f) {}
73
74  // Statement visitor methods.
75  void VisitCallExpr(CallExpr *CE);
76  void VisitForStmt(ForStmt *S);
77  void VisitCompoundStmt (CompoundStmt *S);
78  void VisitStmt(Stmt *S) { VisitChildren(S); }
79
80  void VisitChildren(Stmt *S);
81
82  // Helpers.
83  bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD);
84
85  typedef void (WalkAST::*FnCheck)(const CallExpr *,
86				   const FunctionDecl *);
87
88  // Checker-specific methods.
89  void checkLoopConditionForFloat(const ForStmt *FS);
90  void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD);
91  void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD);
92  void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD);
93  void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD);
94  void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD);
95  void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD);
96  void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD);
97  void checkCall_random(const CallExpr *CE, const FunctionDecl *FD);
98  void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD);
99  void checkUncheckedReturnValue(CallExpr *CE);
100};
101} // end anonymous namespace
102
103//===----------------------------------------------------------------------===//
104// AST walking.
105//===----------------------------------------------------------------------===//
106
107void WalkAST::VisitChildren(Stmt *S) {
108  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
109    if (Stmt *child = *I)
110      Visit(child);
111}
112
113void WalkAST::VisitCallExpr(CallExpr *CE) {
114  // Get the callee.
115  const FunctionDecl *FD = CE->getDirectCallee();
116
117  if (!FD)
118    return;
119
120  // Get the name of the callee. If it's a builtin, strip off the prefix.
121  IdentifierInfo *II = FD->getIdentifier();
122  if (!II)   // if no identifier, not a simple C function
123    return;
124  StringRef Name = II->getName();
125  if (Name.startswith("__builtin_"))
126    Name = Name.substr(10);
127
128  // Set the evaluation function by switching on the callee name.
129  FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name)
130    .Case("gets", &WalkAST::checkCall_gets)
131    .Case("getpw", &WalkAST::checkCall_getpw)
132    .Case("mktemp", &WalkAST::checkCall_mktemp)
133    .Case("mkstemp", &WalkAST::checkCall_mkstemp)
134    .Case("mkdtemp", &WalkAST::checkCall_mkstemp)
135    .Case("mkstemps", &WalkAST::checkCall_mkstemp)
136    .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy)
137    .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat)
138    .Case("drand48", &WalkAST::checkCall_rand)
139    .Case("erand48", &WalkAST::checkCall_rand)
140    .Case("jrand48", &WalkAST::checkCall_rand)
141    .Case("lrand48", &WalkAST::checkCall_rand)
142    .Case("mrand48", &WalkAST::checkCall_rand)
143    .Case("nrand48", &WalkAST::checkCall_rand)
144    .Case("lcong48", &WalkAST::checkCall_rand)
145    .Case("rand", &WalkAST::checkCall_rand)
146    .Case("rand_r", &WalkAST::checkCall_rand)
147    .Case("random", &WalkAST::checkCall_random)
148    .Case("vfork", &WalkAST::checkCall_vfork)
149    .Default(NULL);
150
151  // If the callee isn't defined, it is not of security concern.
152  // Check and evaluate the call.
153  if (evalFunction)
154    (this->*evalFunction)(CE, FD);
155
156  // Recurse and check children.
157  VisitChildren(CE);
158}
159
160void WalkAST::VisitCompoundStmt(CompoundStmt *S) {
161  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
162    if (Stmt *child = *I) {
163      if (CallExpr *CE = dyn_cast<CallExpr>(child))
164        checkUncheckedReturnValue(CE);
165      Visit(child);
166    }
167}
168
169void WalkAST::VisitForStmt(ForStmt *FS) {
170  checkLoopConditionForFloat(FS);
171
172  // Recurse and check children.
173  VisitChildren(FS);
174}
175
176//===----------------------------------------------------------------------===//
177// Check: floating poing variable used as loop counter.
178// Originally: <rdar://problem/6336718>
179// Implements: CERT security coding advisory FLP-30.
180//===----------------------------------------------------------------------===//
181
182static const DeclRefExpr*
183getIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) {
184  expr = expr->IgnoreParenCasts();
185
186  if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) {
187    if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() ||
188          B->getOpcode() == BO_Comma))
189      return NULL;
190
191    if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y))
192      return lhs;
193
194    if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y))
195      return rhs;
196
197    return NULL;
198  }
199
200  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) {
201    const NamedDecl *ND = DR->getDecl();
202    return ND == x || ND == y ? DR : NULL;
203  }
204
205  if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr))
206    return U->isIncrementDecrementOp()
207      ? getIncrementedVar(U->getSubExpr(), x, y) : NULL;
208
209  return NULL;
210}
211
212/// CheckLoopConditionForFloat - This check looks for 'for' statements that
213///  use a floating point variable as a loop counter.
214///  CERT: FLP30-C, FLP30-CPP.
215///
216void WalkAST::checkLoopConditionForFloat(const ForStmt *FS) {
217  if (!filter.check_FloatLoopCounter)
218    return;
219
220  // Does the loop have a condition?
221  const Expr *condition = FS->getCond();
222
223  if (!condition)
224    return;
225
226  // Does the loop have an increment?
227  const Expr *increment = FS->getInc();
228
229  if (!increment)
230    return;
231
232  // Strip away '()' and casts.
233  condition = condition->IgnoreParenCasts();
234  increment = increment->IgnoreParenCasts();
235
236  // Is the loop condition a comparison?
237  const BinaryOperator *B = dyn_cast<BinaryOperator>(condition);
238
239  if (!B)
240    return;
241
242  // Is this a comparison?
243  if (!(B->isRelationalOp() || B->isEqualityOp()))
244    return;
245
246  // Are we comparing variables?
247  const DeclRefExpr *drLHS =
248    dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts());
249  const DeclRefExpr *drRHS =
250    dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts());
251
252  // Does at least one of the variables have a floating point type?
253  drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : NULL;
254  drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : NULL;
255
256  if (!drLHS && !drRHS)
257    return;
258
259  const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : NULL;
260  const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : NULL;
261
262  if (!vdLHS && !vdRHS)
263    return;
264
265  // Does either variable appear in increment?
266  const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS);
267
268  if (!drInc)
269    return;
270
271  // Emit the error.  First figure out which DeclRefExpr in the condition
272  // referenced the compared variable.
273  const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS;
274
275  SmallVector<SourceRange, 2> ranges;
276  SmallString<256> sbuf;
277  llvm::raw_svector_ostream os(sbuf);
278
279  os << "Variable '" << drCond->getDecl()->getName()
280     << "' with floating point type '" << drCond->getType().getAsString()
281     << "' should not be used as a loop counter";
282
283  ranges.push_back(drCond->getSourceRange());
284  ranges.push_back(drInc->getSourceRange());
285
286  const char *bugType = "Floating point variable used as loop counter";
287
288  PathDiagnosticLocation FSLoc =
289    PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC);
290  BR.EmitBasicReport(AC->getDecl(),
291                     bugType, "Security", os.str(),
292                     FSLoc, ranges.data(), ranges.size());
293}
294
295//===----------------------------------------------------------------------===//
296// Check: Any use of 'gets' is insecure.
297// Originally: <rdar://problem/6335715>
298// Implements (part of): 300-BSI (buildsecurityin.us-cert.gov)
299// CWE-242: Use of Inherently Dangerous Function
300//===----------------------------------------------------------------------===//
301
302void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) {
303  if (!filter.check_gets)
304    return;
305
306  const FunctionProtoType *FPT
307    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
308  if (!FPT)
309    return;
310
311  // Verify that the function takes a single argument.
312  if (FPT->getNumArgs() != 1)
313    return;
314
315  // Is the argument a 'char*'?
316  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0));
317  if (!PT)
318    return;
319
320  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
321    return;
322
323  // Issue a warning.
324  SourceRange R = CE->getCallee()->getSourceRange();
325  PathDiagnosticLocation CELoc =
326    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
327  BR.EmitBasicReport(AC->getDecl(),
328                     "Potential buffer overflow in call to 'gets'",
329                     "Security",
330                     "Call to function 'gets' is extremely insecure as it can "
331                     "always result in a buffer overflow",
332                     CELoc, &R, 1);
333}
334
335//===----------------------------------------------------------------------===//
336// Check: Any use of 'getpwd' is insecure.
337// CWE-477: Use of Obsolete Functions
338//===----------------------------------------------------------------------===//
339
340void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) {
341  if (!filter.check_getpw)
342    return;
343
344  const FunctionProtoType *FPT
345    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
346  if (!FPT)
347    return;
348
349  // Verify that the function takes two arguments.
350  if (FPT->getNumArgs() != 2)
351    return;
352
353  // Verify the first argument type is integer.
354  if (!FPT->getArgType(0)->isIntegerType())
355    return;
356
357  // Verify the second argument type is char*.
358  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(1));
359  if (!PT)
360    return;
361
362  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
363    return;
364
365  // Issue a warning.
366  SourceRange R = CE->getCallee()->getSourceRange();
367  PathDiagnosticLocation CELoc =
368    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
369  BR.EmitBasicReport(AC->getDecl(),
370                     "Potential buffer overflow in call to 'getpw'",
371                     "Security",
372                     "The getpw() function is dangerous as it may overflow the "
373                     "provided buffer. It is obsoleted by getpwuid().",
374                     CELoc, &R, 1);
375}
376
377//===----------------------------------------------------------------------===//
378// Check: Any use of 'mktemp' is insecure.  It is obsoleted by mkstemp().
379// CWE-377: Insecure Temporary File
380//===----------------------------------------------------------------------===//
381
382void WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) {
383  if (!filter.check_mktemp) {
384    // Fall back to the security check of looking for enough 'X's in the
385    // format string, since that is a less severe warning.
386    checkCall_mkstemp(CE, FD);
387    return;
388  }
389
390  const FunctionProtoType *FPT
391    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
392  if(!FPT)
393    return;
394
395  // Verify that the function takes a single argument.
396  if (FPT->getNumArgs() != 1)
397    return;
398
399  // Verify that the argument is Pointer Type.
400  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0));
401  if (!PT)
402    return;
403
404  // Verify that the argument is a 'char*'.
405  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
406    return;
407
408  // Issue a waring.
409  SourceRange R = CE->getCallee()->getSourceRange();
410  PathDiagnosticLocation CELoc =
411    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
412  BR.EmitBasicReport(AC->getDecl(),
413                     "Potential insecure temporary file in call 'mktemp'",
414                     "Security",
415                     "Call to function 'mktemp' is insecure as it always "
416                     "creates or uses insecure temporary file.  Use 'mkstemp' "
417                     "instead",
418                     CELoc, &R, 1);
419}
420
421
422//===----------------------------------------------------------------------===//
423// Check: Use of 'mkstemp', 'mktemp', 'mkdtemp' should contain at least 6 X's.
424//===----------------------------------------------------------------------===//
425
426void WalkAST::checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD) {
427  if (!filter.check_mkstemp)
428    return;
429
430  StringRef Name = FD->getIdentifier()->getName();
431  std::pair<signed, signed> ArgSuffix =
432    llvm::StringSwitch<std::pair<signed, signed> >(Name)
433      .Case("mktemp", std::make_pair(0,-1))
434      .Case("mkstemp", std::make_pair(0,-1))
435      .Case("mkdtemp", std::make_pair(0,-1))
436      .Case("mkstemps", std::make_pair(0,1))
437      .Default(std::make_pair(-1, -1));
438
439  assert(ArgSuffix.first >= 0 && "Unsupported function");
440
441  // Check if the number of arguments is consistent with out expectations.
442  unsigned numArgs = CE->getNumArgs();
443  if ((signed) numArgs <= ArgSuffix.first)
444    return;
445
446  const StringLiteral *strArg =
447    dyn_cast<StringLiteral>(CE->getArg((unsigned)ArgSuffix.first)
448                              ->IgnoreParenImpCasts());
449
450  // Currently we only handle string literals.  It is possible to do better,
451  // either by looking at references to const variables, or by doing real
452  // flow analysis.
453  if (!strArg || strArg->getCharByteWidth() != 1)
454    return;
455
456  // Count the number of X's, taking into account a possible cutoff suffix.
457  StringRef str = strArg->getString();
458  unsigned numX = 0;
459  unsigned n = str.size();
460
461  // Take into account the suffix.
462  unsigned suffix = 0;
463  if (ArgSuffix.second >= 0) {
464    const Expr *suffixEx = CE->getArg((unsigned)ArgSuffix.second);
465    llvm::APSInt Result;
466    if (!suffixEx->EvaluateAsInt(Result, BR.getContext()))
467      return;
468    // FIXME: Issue a warning.
469    if (Result.isNegative())
470      return;
471    suffix = (unsigned) Result.getZExtValue();
472    n = (n > suffix) ? n - suffix : 0;
473  }
474
475  for (unsigned i = 0; i < n; ++i)
476    if (str[i] == 'X') ++numX;
477
478  if (numX >= 6)
479    return;
480
481  // Issue a warning.
482  SourceRange R = strArg->getSourceRange();
483  PathDiagnosticLocation CELoc =
484    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
485  SmallString<512> buf;
486  llvm::raw_svector_ostream out(buf);
487  out << "Call to '" << Name << "' should have at least 6 'X's in the"
488    " format string to be secure (" << numX << " 'X'";
489  if (numX != 1)
490    out << 's';
491  out << " seen";
492  if (suffix) {
493    out << ", " << suffix << " character";
494    if (suffix > 1)
495      out << 's';
496    out << " used as a suffix";
497  }
498  out << ')';
499  BR.EmitBasicReport(AC->getDecl(),
500                     "Insecure temporary file creation", "Security",
501                     out.str(), CELoc, &R, 1);
502}
503
504//===----------------------------------------------------------------------===//
505// Check: Any use of 'strcpy' is insecure.
506//
507// CWE-119: Improper Restriction of Operations within
508// the Bounds of a Memory Buffer
509//===----------------------------------------------------------------------===//
510void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) {
511  if (!filter.check_strcpy)
512    return;
513
514  if (!checkCall_strCommon(CE, FD))
515    return;
516
517  // Issue a warning.
518  SourceRange R = CE->getCallee()->getSourceRange();
519  PathDiagnosticLocation CELoc =
520    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
521  BR.EmitBasicReport(AC->getDecl(),
522                     "Potential insecure memory buffer bounds restriction in "
523                     "call 'strcpy'",
524                     "Security",
525                     "Call to function 'strcpy' is insecure as it does not "
526                     "provide bounding of the memory buffer. Replace "
527                     "unbounded copy functions with analogous functions that "
528                     "support length arguments such as 'strlcpy'. CWE-119.",
529                     CELoc, &R, 1);
530}
531
532//===----------------------------------------------------------------------===//
533// Check: Any use of 'strcat' is insecure.
534//
535// CWE-119: Improper Restriction of Operations within
536// the Bounds of a Memory Buffer
537//===----------------------------------------------------------------------===//
538void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) {
539  if (!filter.check_strcpy)
540    return;
541
542  if (!checkCall_strCommon(CE, FD))
543    return;
544
545  // Issue a warning.
546  SourceRange R = CE->getCallee()->getSourceRange();
547  PathDiagnosticLocation CELoc =
548    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
549  BR.EmitBasicReport(AC->getDecl(),
550                     "Potential insecure memory buffer bounds restriction in "
551                     "call 'strcat'",
552                     "Security",
553                     "Call to function 'strcat' is insecure as it does not "
554                     "provide bounding of the memory buffer. Replace "
555                     "unbounded copy functions with analogous functions that "
556                     "support length arguments such as 'strlcat'. CWE-119.",
557                     CELoc, &R, 1);
558}
559
560//===----------------------------------------------------------------------===//
561// Common check for str* functions with no bounds parameters.
562//===----------------------------------------------------------------------===//
563bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) {
564  const FunctionProtoType *FPT
565    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
566  if (!FPT)
567    return false;
568
569  // Verify the function takes two arguments, three in the _chk version.
570  int numArgs = FPT->getNumArgs();
571  if (numArgs != 2 && numArgs != 3)
572    return false;
573
574  // Verify the type for both arguments.
575  for (int i = 0; i < 2; i++) {
576    // Verify that the arguments are pointers.
577    const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(i));
578    if (!PT)
579      return false;
580
581    // Verify that the argument is a 'char*'.
582    if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
583      return false;
584  }
585
586  return true;
587}
588
589//===----------------------------------------------------------------------===//
590// Check: Linear congruent random number generators should not be used
591// Originally: <rdar://problem/63371000>
592// CWE-338: Use of cryptographically weak prng
593//===----------------------------------------------------------------------===//
594
595void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) {
596  if (!filter.check_rand || !CheckRand)
597    return;
598
599  const FunctionProtoType *FTP
600    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
601  if (!FTP)
602    return;
603
604  if (FTP->getNumArgs() == 1) {
605    // Is the argument an 'unsigned short *'?
606    // (Actually any integer type is allowed.)
607    const PointerType *PT = dyn_cast<PointerType>(FTP->getArgType(0));
608    if (!PT)
609      return;
610
611    if (! PT->getPointeeType()->isIntegerType())
612      return;
613  }
614  else if (FTP->getNumArgs() != 0)
615    return;
616
617  // Issue a warning.
618  SmallString<256> buf1;
619  llvm::raw_svector_ostream os1(buf1);
620  os1 << '\'' << *FD << "' is a poor random number generator";
621
622  SmallString<256> buf2;
623  llvm::raw_svector_ostream os2(buf2);
624  os2 << "Function '" << *FD
625      << "' is obsolete because it implements a poor random number generator."
626      << "  Use 'arc4random' instead";
627
628  SourceRange R = CE->getCallee()->getSourceRange();
629  PathDiagnosticLocation CELoc =
630    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
631  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
632                     CELoc, &R, 1);
633}
634
635//===----------------------------------------------------------------------===//
636// Check: 'random' should not be used
637// Originally: <rdar://problem/63371000>
638//===----------------------------------------------------------------------===//
639
640void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) {
641  if (!CheckRand || !filter.check_rand)
642    return;
643
644  const FunctionProtoType *FTP
645    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
646  if (!FTP)
647    return;
648
649  // Verify that the function takes no argument.
650  if (FTP->getNumArgs() != 0)
651    return;
652
653  // Issue a warning.
654  SourceRange R = CE->getCallee()->getSourceRange();
655  PathDiagnosticLocation CELoc =
656    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
657  BR.EmitBasicReport(AC->getDecl(),
658                     "'random' is not a secure random number generator",
659                     "Security",
660                     "The 'random' function produces a sequence of values that "
661                     "an adversary may be able to predict.  Use 'arc4random' "
662                     "instead", CELoc, &R, 1);
663}
664
665//===----------------------------------------------------------------------===//
666// Check: 'vfork' should not be used.
667// POS33-C: Do not use vfork().
668//===----------------------------------------------------------------------===//
669
670void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) {
671  if (!filter.check_vfork)
672    return;
673
674  // All calls to vfork() are insecure, issue a warning.
675  SourceRange R = CE->getCallee()->getSourceRange();
676  PathDiagnosticLocation CELoc =
677    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
678  BR.EmitBasicReport(AC->getDecl(),
679                     "Potential insecure implementation-specific behavior in "
680                     "call 'vfork'",
681                     "Security",
682                     "Call to function 'vfork' is insecure as it can lead to "
683                     "denial of service situations in the parent process. "
684                     "Replace calls to vfork with calls to the safer "
685                     "'posix_spawn' function",
686                     CELoc, &R, 1);
687}
688
689//===----------------------------------------------------------------------===//
690// Check: Should check whether privileges are dropped successfully.
691// Originally: <rdar://problem/6337132>
692//===----------------------------------------------------------------------===//
693
694void WalkAST::checkUncheckedReturnValue(CallExpr *CE) {
695  if (!filter.check_UncheckedReturn)
696    return;
697
698  const FunctionDecl *FD = CE->getDirectCallee();
699  if (!FD)
700    return;
701
702  if (II_setid[0] == NULL) {
703    static const char * const identifiers[num_setids] = {
704      "setuid", "setgid", "seteuid", "setegid",
705      "setreuid", "setregid"
706    };
707
708    for (size_t i = 0; i < num_setids; i++)
709      II_setid[i] = &BR.getContext().Idents.get(identifiers[i]);
710  }
711
712  const IdentifierInfo *id = FD->getIdentifier();
713  size_t identifierid;
714
715  for (identifierid = 0; identifierid < num_setids; identifierid++)
716    if (id == II_setid[identifierid])
717      break;
718
719  if (identifierid >= num_setids)
720    return;
721
722  const FunctionProtoType *FTP
723    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
724  if (!FTP)
725    return;
726
727  // Verify that the function takes one or two arguments (depending on
728  //   the function).
729  if (FTP->getNumArgs() != (identifierid < 4 ? 1 : 2))
730    return;
731
732  // The arguments must be integers.
733  for (unsigned i = 0; i < FTP->getNumArgs(); i++)
734    if (! FTP->getArgType(i)->isIntegerType())
735      return;
736
737  // Issue a warning.
738  SmallString<256> buf1;
739  llvm::raw_svector_ostream os1(buf1);
740  os1 << "Return value is not checked in call to '" << *FD << '\'';
741
742  SmallString<256> buf2;
743  llvm::raw_svector_ostream os2(buf2);
744  os2 << "The return value from the call to '" << *FD
745      << "' is not checked.  If an error occurs in '" << *FD
746      << "', the following code may execute with unexpected privileges";
747
748  SourceRange R = CE->getCallee()->getSourceRange();
749  PathDiagnosticLocation CELoc =
750    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
751  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
752                     CELoc, &R, 1);
753}
754
755//===----------------------------------------------------------------------===//
756// SecuritySyntaxChecker
757//===----------------------------------------------------------------------===//
758
759namespace {
760class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> {
761public:
762  ChecksFilter filter;
763
764  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
765                        BugReporter &BR) const {
766    WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter);
767    walker.Visit(D->getBody());
768  }
769};
770}
771
772#define REGISTER_CHECKER(name) \
773void ento::register##name(CheckerManager &mgr) {\
774  mgr.registerChecker<SecuritySyntaxChecker>()->filter.check_##name = true;\
775}
776
777REGISTER_CHECKER(gets)
778REGISTER_CHECKER(getpw)
779REGISTER_CHECKER(mkstemp)
780REGISTER_CHECKER(mktemp)
781REGISTER_CHECKER(strcpy)
782REGISTER_CHECKER(rand)
783REGISTER_CHECKER(vfork)
784REGISTER_CHECKER(FloatLoopCounter)
785REGISTER_CHECKER(UncheckedReturn)
786
787
788