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