CheckSecuritySyntaxOnly.cpp revision d0f3d7148ca761fda2243528b2b62f916770f546 
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  assert(drInc->getDecl());
274  const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS;
275
276  SmallVector<SourceRange, 2> ranges;
277  SmallString<256> sbuf;
278  llvm::raw_svector_ostream os(sbuf);
279
280  os << "Variable '" << drCond->getDecl()->getName()
281     << "' with floating point type '" << drCond->getType().getAsString()
282     << "' should not be used as a loop counter";
283
284  ranges.push_back(drCond->getSourceRange());
285  ranges.push_back(drInc->getSourceRange());
286
287  const char *bugType = "Floating point variable used as loop counter";
288
289  PathDiagnosticLocation FSLoc =
290    PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC);
291  BR.EmitBasicReport(AC->getDecl(),
292                     bugType, "Security", os.str(),
293                     FSLoc, ranges.data(), ranges.size());
294}
295
296//===----------------------------------------------------------------------===//
297// Check: Any use of 'gets' is insecure.
298// Originally: <rdar://problem/6335715>
299// Implements (part of): 300-BSI (buildsecurityin.us-cert.gov)
300// CWE-242: Use of Inherently Dangerous Function
301//===----------------------------------------------------------------------===//
302
303void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) {
304  if (!filter.check_gets)
305    return;
306
307  const FunctionProtoType *FPT
308    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
309  if (!FPT)
310    return;
311
312  // Verify that the function takes a single argument.
313  if (FPT->getNumArgs() != 1)
314    return;
315
316  // Is the argument a 'char*'?
317  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0));
318  if (!PT)
319    return;
320
321  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
322    return;
323
324  // Issue a warning.
325  SourceRange R = CE->getCallee()->getSourceRange();
326  PathDiagnosticLocation CELoc =
327    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
328  BR.EmitBasicReport(AC->getDecl(),
329                     "Potential buffer overflow in call to 'gets'",
330                     "Security",
331                     "Call to function 'gets' is extremely insecure as it can "
332                     "always result in a buffer overflow",
333                     CELoc, &R, 1);
334}
335
336//===----------------------------------------------------------------------===//
337// Check: Any use of 'getpwd' is insecure.
338// CWE-477: Use of Obsolete Functions
339//===----------------------------------------------------------------------===//
340
341void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) {
342  if (!filter.check_getpw)
343    return;
344
345  const FunctionProtoType *FPT
346    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
347  if (!FPT)
348    return;
349
350  // Verify that the function takes two arguments.
351  if (FPT->getNumArgs() != 2)
352    return;
353
354  // Verify the first argument type is integer.
355  if (!FPT->getArgType(0)->isIntegerType())
356    return;
357
358  // Verify the second argument type is char*.
359  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(1));
360  if (!PT)
361    return;
362
363  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
364    return;
365
366  // Issue a warning.
367  SourceRange R = CE->getCallee()->getSourceRange();
368  PathDiagnosticLocation CELoc =
369    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
370  BR.EmitBasicReport(AC->getDecl(),
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, &R, 1);
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
392    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
393  if(!FPT)
394    return;
395
396  // Verify that the function takes a single argument.
397  if (FPT->getNumArgs() != 1)
398    return;
399
400  // Verify that the argument is Pointer Type.
401  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0));
402  if (!PT)
403    return;
404
405  // Verify that the argument is a 'char*'.
406  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
407    return;
408
409  // Issue a waring.
410  SourceRange R = CE->getCallee()->getSourceRange();
411  PathDiagnosticLocation CELoc =
412    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
413  BR.EmitBasicReport(AC->getDecl(),
414                     "Potential insecure temporary file in call 'mktemp'",
415                     "Security",
416                     "Call to function 'mktemp' is insecure as it always "
417                     "creates or uses insecure temporary file.  Use 'mkstemp' "
418                     "instead",
419                     CELoc, &R, 1);
420}
421
422
423//===----------------------------------------------------------------------===//
424// Check: Use of 'mkstemp', 'mktemp', 'mkdtemp' should contain at least 6 X's.
425//===----------------------------------------------------------------------===//
426
427void WalkAST::checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD) {
428  if (!filter.check_mkstemp)
429    return;
430
431  StringRef Name = FD->getIdentifier()->getName();
432  std::pair<signed, signed> ArgSuffix =
433    llvm::StringSwitch<std::pair<signed, signed> >(Name)
434      .Case("mktemp", std::make_pair(0,-1))
435      .Case("mkstemp", std::make_pair(0,-1))
436      .Case("mkdtemp", std::make_pair(0,-1))
437      .Case("mkstemps", std::make_pair(0,1))
438      .Default(std::make_pair(-1, -1));
439
440  assert(ArgSuffix.first >= 0 && "Unsupported function");
441
442  // Check if the number of arguments is consistent with out expectations.
443  unsigned numArgs = CE->getNumArgs();
444  if ((signed) numArgs <= ArgSuffix.first)
445    return;
446
447  const StringLiteral *strArg =
448    dyn_cast<StringLiteral>(CE->getArg((unsigned)ArgSuffix.first)
449                              ->IgnoreParenImpCasts());
450
451  // Currently we only handle string literals.  It is possible to do better,
452  // either by looking at references to const variables, or by doing real
453  // flow analysis.
454  if (!strArg || strArg->getCharByteWidth() != 1)
455    return;
456
457  // Count the number of X's, taking into account a possible cutoff suffix.
458  StringRef str = strArg->getString();
459  unsigned numX = 0;
460  unsigned n = str.size();
461
462  // Take into account the suffix.
463  unsigned suffix = 0;
464  if (ArgSuffix.second >= 0) {
465    const Expr *suffixEx = CE->getArg((unsigned)ArgSuffix.second);
466    llvm::APSInt Result;
467    if (!suffixEx->EvaluateAsInt(Result, BR.getContext()))
468      return;
469    // FIXME: Issue a warning.
470    if (Result.isNegative())
471      return;
472    suffix = (unsigned) Result.getZExtValue();
473    n = (n > suffix) ? n - suffix : 0;
474  }
475
476  for (unsigned i = 0; i < n; ++i)
477    if (str[i] == 'X') ++numX;
478
479  if (numX >= 6)
480    return;
481
482  // Issue a warning.
483  SourceRange R = strArg->getSourceRange();
484  PathDiagnosticLocation CELoc =
485    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
486  SmallString<512> buf;
487  llvm::raw_svector_ostream out(buf);
488  out << "Call to '" << Name << "' should have at least 6 'X's in the"
489    " format string to be secure (" << numX << " 'X'";
490  if (numX != 1)
491    out << 's';
492  out << " seen";
493  if (suffix) {
494    out << ", " << suffix << " character";
495    if (suffix > 1)
496      out << 's';
497    out << " used as a suffix";
498  }
499  out << ')';
500  BR.EmitBasicReport(AC->getDecl(),
501                     "Insecure temporary file creation", "Security",
502                     out.str(), CELoc, &R, 1);
503}
504
505//===----------------------------------------------------------------------===//
506// Check: Any use of 'strcpy' is insecure.
507//
508// CWE-119: Improper Restriction of Operations within
509// the Bounds of a Memory Buffer
510//===----------------------------------------------------------------------===//
511void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) {
512  if (!filter.check_strcpy)
513    return;
514
515  if (!checkCall_strCommon(CE, FD))
516    return;
517
518  // Issue a warning.
519  SourceRange R = CE->getCallee()->getSourceRange();
520  PathDiagnosticLocation CELoc =
521    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
522  BR.EmitBasicReport(AC->getDecl(),
523                     "Potential insecure memory buffer bounds restriction in "
524                     "call 'strcpy'",
525                     "Security",
526                     "Call to function 'strcpy' is insecure as it does not "
527                     "provide bounding of the memory buffer. Replace "
528                     "unbounded copy functions with analogous functions that "
529                     "support length arguments such as 'strlcpy'. CWE-119.",
530                     CELoc, &R, 1);
531}
532
533//===----------------------------------------------------------------------===//
534// Check: Any use of 'strcat' is insecure.
535//
536// CWE-119: Improper Restriction of Operations within
537// the Bounds of a Memory Buffer
538//===----------------------------------------------------------------------===//
539void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) {
540  if (!filter.check_strcpy)
541    return;
542
543  if (!checkCall_strCommon(CE, FD))
544    return;
545
546  // Issue a warning.
547  SourceRange R = CE->getCallee()->getSourceRange();
548  PathDiagnosticLocation CELoc =
549    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
550  BR.EmitBasicReport(AC->getDecl(),
551                     "Potential insecure memory buffer bounds restriction in "
552                     "call 'strcat'",
553                     "Security",
554                     "Call to function 'strcat' is insecure as it does not "
555                     "provide bounding of the memory buffer. Replace "
556                     "unbounded copy functions with analogous functions that "
557                     "support length arguments such as 'strlcat'. CWE-119.",
558                     CELoc, &R, 1);
559}
560
561//===----------------------------------------------------------------------===//
562// Common check for str* functions with no bounds parameters.
563//===----------------------------------------------------------------------===//
564bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) {
565  const FunctionProtoType *FPT
566    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
567  if (!FPT)
568    return false;
569
570  // Verify the function takes two arguments, three in the _chk version.
571  int numArgs = FPT->getNumArgs();
572  if (numArgs != 2 && numArgs != 3)
573    return false;
574
575  // Verify the type for both arguments.
576  for (int i = 0; i < 2; i++) {
577    // Verify that the arguments are pointers.
578    const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(i));
579    if (!PT)
580      return false;
581
582    // Verify that the argument is a 'char*'.
583    if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
584      return false;
585  }
586
587  return true;
588}
589
590//===----------------------------------------------------------------------===//
591// Check: Linear congruent random number generators should not be used
592// Originally: <rdar://problem/63371000>
593// CWE-338: Use of cryptographically weak prng
594//===----------------------------------------------------------------------===//
595
596void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) {
597  if (!filter.check_rand || !CheckRand)
598    return;
599
600  const FunctionProtoType *FTP
601    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
602  if (!FTP)
603    return;
604
605  if (FTP->getNumArgs() == 1) {
606    // Is the argument an 'unsigned short *'?
607    // (Actually any integer type is allowed.)
608    const PointerType *PT = dyn_cast<PointerType>(FTP->getArgType(0));
609    if (!PT)
610      return;
611
612    if (! PT->getPointeeType()->isIntegerType())
613      return;
614  }
615  else if (FTP->getNumArgs() != 0)
616    return;
617
618  // Issue a warning.
619  SmallString<256> buf1;
620  llvm::raw_svector_ostream os1(buf1);
621  os1 << '\'' << *FD << "' is a poor random number generator";
622
623  SmallString<256> buf2;
624  llvm::raw_svector_ostream os2(buf2);
625  os2 << "Function '" << *FD
626      << "' is obsolete because it implements a poor random number generator."
627      << "  Use 'arc4random' instead";
628
629  SourceRange R = CE->getCallee()->getSourceRange();
630  PathDiagnosticLocation CELoc =
631    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
632  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
633                     CELoc, &R, 1);
634}
635
636//===----------------------------------------------------------------------===//
637// Check: 'random' should not be used
638// Originally: <rdar://problem/63371000>
639//===----------------------------------------------------------------------===//
640
641void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) {
642  if (!CheckRand || !filter.check_rand)
643    return;
644
645  const FunctionProtoType *FTP
646    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
647  if (!FTP)
648    return;
649
650  // Verify that the function takes no argument.
651  if (FTP->getNumArgs() != 0)
652    return;
653
654  // Issue a warning.
655  SourceRange R = CE->getCallee()->getSourceRange();
656  PathDiagnosticLocation CELoc =
657    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
658  BR.EmitBasicReport(AC->getDecl(),
659                     "'random' is not a secure random number generator",
660                     "Security",
661                     "The 'random' function produces a sequence of values that "
662                     "an adversary may be able to predict.  Use 'arc4random' "
663                     "instead", CELoc, &R, 1);
664}
665
666//===----------------------------------------------------------------------===//
667// Check: 'vfork' should not be used.
668// POS33-C: Do not use vfork().
669//===----------------------------------------------------------------------===//
670
671void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) {
672  if (!filter.check_vfork)
673    return;
674
675  // All calls to vfork() are insecure, issue a warning.
676  SourceRange R = CE->getCallee()->getSourceRange();
677  PathDiagnosticLocation CELoc =
678    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
679  BR.EmitBasicReport(AC->getDecl(),
680                     "Potential insecure implementation-specific behavior in "
681                     "call 'vfork'",
682                     "Security",
683                     "Call to function 'vfork' is insecure as it can lead to "
684                     "denial of service situations in the parent process. "
685                     "Replace calls to vfork with calls to the safer "
686                     "'posix_spawn' function",
687                     CELoc, &R, 1);
688}
689
690//===----------------------------------------------------------------------===//
691// Check: Should check whether privileges are dropped successfully.
692// Originally: <rdar://problem/6337132>
693//===----------------------------------------------------------------------===//
694
695void WalkAST::checkUncheckedReturnValue(CallExpr *CE) {
696  if (!filter.check_UncheckedReturn)
697    return;
698
699  const FunctionDecl *FD = CE->getDirectCallee();
700  if (!FD)
701    return;
702
703  if (II_setid[0] == NULL) {
704    static const char * const identifiers[num_setids] = {
705      "setuid", "setgid", "seteuid", "setegid",
706      "setreuid", "setregid"
707    };
708
709    for (size_t i = 0; i < num_setids; i++)
710      II_setid[i] = &BR.getContext().Idents.get(identifiers[i]);
711  }
712
713  const IdentifierInfo *id = FD->getIdentifier();
714  size_t identifierid;
715
716  for (identifierid = 0; identifierid < num_setids; identifierid++)
717    if (id == II_setid[identifierid])
718      break;
719
720  if (identifierid >= num_setids)
721    return;
722
723  const FunctionProtoType *FTP
724    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
725  if (!FTP)
726    return;
727
728  // Verify that the function takes one or two arguments (depending on
729  //   the function).
730  if (FTP->getNumArgs() != (identifierid < 4 ? 1 : 2))
731    return;
732
733  // The arguments must be integers.
734  for (unsigned i = 0; i < FTP->getNumArgs(); i++)
735    if (! FTP->getArgType(i)->isIntegerType())
736      return;
737
738  // Issue a warning.
739  SmallString<256> buf1;
740  llvm::raw_svector_ostream os1(buf1);
741  os1 << "Return value is not checked in call to '" << *FD << '\'';
742
743  SmallString<256> buf2;
744  llvm::raw_svector_ostream os2(buf2);
745  os2 << "The return value from the call to '" << *FD
746      << "' is not checked.  If an error occurs in '" << *FD
747      << "', the following code may execute with unexpected privileges";
748
749  SourceRange R = CE->getCallee()->getSourceRange();
750  PathDiagnosticLocation CELoc =
751    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
752  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
753                     CELoc, &R, 1);
754}
755
756//===----------------------------------------------------------------------===//
757// SecuritySyntaxChecker
758//===----------------------------------------------------------------------===//
759
760namespace {
761class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> {
762public:
763  ChecksFilter filter;
764
765  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
766                        BugReporter &BR) const {
767    WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter);
768    walker.Visit(D->getBody());
769  }
770};
771}
772
773#define REGISTER_CHECKER(name) \
774void ento::register##name(CheckerManager &mgr) {\
775  mgr.registerChecker<SecuritySyntaxChecker>()->filter.check_##name = true;\
776}
777
778REGISTER_CHECKER(gets)
779REGISTER_CHECKER(getpw)
780REGISTER_CHECKER(mkstemp)
781REGISTER_CHECKER(mktemp)
782REGISTER_CHECKER(strcpy)
783REGISTER_CHECKER(rand)
784REGISTER_CHECKER(vfork)
785REGISTER_CHECKER(FloatLoopCounter)
786REGISTER_CHECKER(UncheckedReturn)
787
788
789