CheckSecuritySyntaxOnly.cpp revision b0754170b249e896298df24fa28fbd9a008a114d 
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::DragonFly;
35}
36
37namespace {
38struct DefaultBool {
39  bool val;
40  DefaultBool() : val(false) {}
41  operator bool() const { return val; }
42  DefaultBool &operator=(bool b) { val = b; return *this; }
43};
44
45struct ChecksFilter {
46  DefaultBool check_gets;
47  DefaultBool check_getpw;
48  DefaultBool check_mktemp;
49  DefaultBool check_mkstemp;
50  DefaultBool check_strcpy;
51  DefaultBool check_rand;
52  DefaultBool check_vfork;
53  DefaultBool check_FloatLoopCounter;
54  DefaultBool check_UncheckedReturn;
55};
56
57class WalkAST : public StmtVisitor<WalkAST> {
58  BugReporter &BR;
59  AnalysisDeclContext* AC;
60  enum { num_setids = 6 };
61  IdentifierInfo *II_setid[num_setids];
62
63  const bool CheckRand;
64  const ChecksFilter &filter;
65
66public:
67  WalkAST(BugReporter &br, AnalysisDeclContext* ac,
68          const ChecksFilter &f)
69  : BR(br), AC(ac), II_setid(),
70    CheckRand(isArc4RandomAvailable(BR.getContext())),
71    filter(f) {}
72
73  // Statement visitor methods.
74  void VisitCallExpr(CallExpr *CE);
75  void VisitForStmt(ForStmt *S);
76  void VisitCompoundStmt (CompoundStmt *S);
77  void VisitStmt(Stmt *S) { VisitChildren(S); }
78
79  void VisitChildren(Stmt *S);
80
81  // Helpers.
82  bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD);
83
84  typedef void (WalkAST::*FnCheck)(const CallExpr *,
85				   const FunctionDecl *);
86
87  // Checker-specific methods.
88  void checkLoopConditionForFloat(const ForStmt *FS);
89  void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD);
90  void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD);
91  void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD);
92  void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD);
93  void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD);
94  void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD);
95  void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD);
96  void checkCall_random(const CallExpr *CE, const FunctionDecl *FD);
97  void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD);
98  void checkUncheckedReturnValue(CallExpr *CE);
99};
100} // end anonymous namespace
101
102//===----------------------------------------------------------------------===//
103// AST walking.
104//===----------------------------------------------------------------------===//
105
106void WalkAST::VisitChildren(Stmt *S) {
107  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
108    if (Stmt *child = *I)
109      Visit(child);
110}
111
112void WalkAST::VisitCallExpr(CallExpr *CE) {
113  // Get the callee.
114  const FunctionDecl *FD = CE->getDirectCallee();
115
116  if (!FD)
117    return;
118
119  // Get the name of the callee. If it's a builtin, strip off the prefix.
120  IdentifierInfo *II = FD->getIdentifier();
121  if (!II)   // if no identifier, not a simple C function
122    return;
123  StringRef Name = II->getName();
124  if (Name.startswith("__builtin_"))
125    Name = Name.substr(10);
126
127  // Set the evaluation function by switching on the callee name.
128  FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name)
129    .Case("gets", &WalkAST::checkCall_gets)
130    .Case("getpw", &WalkAST::checkCall_getpw)
131    .Case("mktemp", &WalkAST::checkCall_mktemp)
132    .Case("mkstemp", &WalkAST::checkCall_mkstemp)
133    .Case("mkdtemp", &WalkAST::checkCall_mkstemp)
134    .Case("mkstemps", &WalkAST::checkCall_mkstemp)
135    .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy)
136    .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat)
137    .Case("drand48", &WalkAST::checkCall_rand)
138    .Case("erand48", &WalkAST::checkCall_rand)
139    .Case("jrand48", &WalkAST::checkCall_rand)
140    .Case("lrand48", &WalkAST::checkCall_rand)
141    .Case("mrand48", &WalkAST::checkCall_rand)
142    .Case("nrand48", &WalkAST::checkCall_rand)
143    .Case("lcong48", &WalkAST::checkCall_rand)
144    .Case("rand", &WalkAST::checkCall_rand)
145    .Case("rand_r", &WalkAST::checkCall_rand)
146    .Case("random", &WalkAST::checkCall_random)
147    .Case("vfork", &WalkAST::checkCall_vfork)
148    .Default(NULL);
149
150  // If the callee isn't defined, it is not of security concern.
151  // Check and evaluate the call.
152  if (evalFunction)
153    (this->*evalFunction)(CE, FD);
154
155  // Recurse and check children.
156  VisitChildren(CE);
157}
158
159void WalkAST::VisitCompoundStmt(CompoundStmt *S) {
160  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
161    if (Stmt *child = *I) {
162      if (CallExpr *CE = dyn_cast<CallExpr>(child))
163        checkUncheckedReturnValue(CE);
164      Visit(child);
165    }
166}
167
168void WalkAST::VisitForStmt(ForStmt *FS) {
169  checkLoopConditionForFloat(FS);
170
171  // Recurse and check children.
172  VisitChildren(FS);
173}
174
175//===----------------------------------------------------------------------===//
176// Check: floating poing variable used as loop counter.
177// Originally: <rdar://problem/6336718>
178// Implements: CERT security coding advisory FLP-30.
179//===----------------------------------------------------------------------===//
180
181static const DeclRefExpr*
182getIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) {
183  expr = expr->IgnoreParenCasts();
184
185  if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) {
186    if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() ||
187          B->getOpcode() == BO_Comma))
188      return NULL;
189
190    if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y))
191      return lhs;
192
193    if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y))
194      return rhs;
195
196    return NULL;
197  }
198
199  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) {
200    const NamedDecl *ND = DR->getDecl();
201    return ND == x || ND == y ? DR : NULL;
202  }
203
204  if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr))
205    return U->isIncrementDecrementOp()
206      ? getIncrementedVar(U->getSubExpr(), x, y) : NULL;
207
208  return NULL;
209}
210
211/// CheckLoopConditionForFloat - This check looks for 'for' statements that
212///  use a floating point variable as a loop counter.
213///  CERT: FLP30-C, FLP30-CPP.
214///
215void WalkAST::checkLoopConditionForFloat(const ForStmt *FS) {
216  if (!filter.check_FloatLoopCounter)
217    return;
218
219  // Does the loop have a condition?
220  const Expr *condition = FS->getCond();
221
222  if (!condition)
223    return;
224
225  // Does the loop have an increment?
226  const Expr *increment = FS->getInc();
227
228  if (!increment)
229    return;
230
231  // Strip away '()' and casts.
232  condition = condition->IgnoreParenCasts();
233  increment = increment->IgnoreParenCasts();
234
235  // Is the loop condition a comparison?
236  const BinaryOperator *B = dyn_cast<BinaryOperator>(condition);
237
238  if (!B)
239    return;
240
241  // Is this a comparison?
242  if (!(B->isRelationalOp() || B->isEqualityOp()))
243    return;
244
245  // Are we comparing variables?
246  const DeclRefExpr *drLHS =
247    dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts());
248  const DeclRefExpr *drRHS =
249    dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts());
250
251  // Does at least one of the variables have a floating point type?
252  drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : NULL;
253  drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : NULL;
254
255  if (!drLHS && !drRHS)
256    return;
257
258  const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : NULL;
259  const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : NULL;
260
261  if (!vdLHS && !vdRHS)
262    return;
263
264  // Does either variable appear in increment?
265  const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS);
266
267  if (!drInc)
268    return;
269
270  // Emit the error.  First figure out which DeclRefExpr in the condition
271  // referenced the compared variable.
272  const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS;
273
274  SmallVector<SourceRange, 2> ranges;
275  SmallString<256> sbuf;
276  llvm::raw_svector_ostream os(sbuf);
277
278  os << "Variable '" << drCond->getDecl()->getName()
279     << "' with floating point type '" << drCond->getType().getAsString()
280     << "' should not be used as a loop counter";
281
282  ranges.push_back(drCond->getSourceRange());
283  ranges.push_back(drInc->getSourceRange());
284
285  const char *bugType = "Floating point variable used as loop counter";
286
287  PathDiagnosticLocation FSLoc =
288    PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC);
289  BR.EmitBasicReport(AC->getDecl(),
290                     bugType, "Security", os.str(),
291                     FSLoc, ranges.data(), ranges.size());
292}
293
294//===----------------------------------------------------------------------===//
295// Check: Any use of 'gets' is insecure.
296// Originally: <rdar://problem/6335715>
297// Implements (part of): 300-BSI (buildsecurityin.us-cert.gov)
298// CWE-242: Use of Inherently Dangerous Function
299//===----------------------------------------------------------------------===//
300
301void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) {
302  if (!filter.check_gets)
303    return;
304
305  const FunctionProtoType *FPT
306    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
307  if (!FPT)
308    return;
309
310  // Verify that the function takes a single argument.
311  if (FPT->getNumArgs() != 1)
312    return;
313
314  // Is the argument a 'char*'?
315  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0));
316  if (!PT)
317    return;
318
319  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
320    return;
321
322  // Issue a warning.
323  SourceRange R = CE->getCallee()->getSourceRange();
324  PathDiagnosticLocation CELoc =
325    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
326  BR.EmitBasicReport(AC->getDecl(),
327                     "Potential buffer overflow in call to 'gets'",
328                     "Security",
329                     "Call to function 'gets' is extremely insecure as it can "
330                     "always result in a buffer overflow",
331                     CELoc, &R, 1);
332}
333
334//===----------------------------------------------------------------------===//
335// Check: Any use of 'getpwd' is insecure.
336// CWE-477: Use of Obsolete Functions
337//===----------------------------------------------------------------------===//
338
339void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) {
340  if (!filter.check_getpw)
341    return;
342
343  const FunctionProtoType *FPT
344    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
345  if (!FPT)
346    return;
347
348  // Verify that the function takes two arguments.
349  if (FPT->getNumArgs() != 2)
350    return;
351
352  // Verify the first argument type is integer.
353  if (!FPT->getArgType(0)->isIntegerType())
354    return;
355
356  // Verify the second argument type is char*.
357  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(1));
358  if (!PT)
359    return;
360
361  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
362    return;
363
364  // Issue a warning.
365  SourceRange R = CE->getCallee()->getSourceRange();
366  PathDiagnosticLocation CELoc =
367    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
368  BR.EmitBasicReport(AC->getDecl(),
369                     "Potential buffer overflow in call to 'getpw'",
370                     "Security",
371                     "The getpw() function is dangerous as it may overflow the "
372                     "provided buffer. It is obsoleted by getpwuid().",
373                     CELoc, &R, 1);
374}
375
376//===----------------------------------------------------------------------===//
377// Check: Any use of 'mktemp' is insecure.  It is obsoleted by mkstemp().
378// CWE-377: Insecure Temporary File
379//===----------------------------------------------------------------------===//
380
381void WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) {
382  if (!filter.check_mktemp) {
383    // Fall back to the security check of looking for enough 'X's in the
384    // format string, since that is a less severe warning.
385    checkCall_mkstemp(CE, FD);
386    return;
387  }
388
389  const FunctionProtoType *FPT
390    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
391  if(!FPT)
392    return;
393
394  // Verify that the function takes a single argument.
395  if (FPT->getNumArgs() != 1)
396    return;
397
398  // Verify that the argument is Pointer Type.
399  const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(0));
400  if (!PT)
401    return;
402
403  // Verify that the argument is a 'char*'.
404  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
405    return;
406
407  // Issue a waring.
408  SourceRange R = CE->getCallee()->getSourceRange();
409  PathDiagnosticLocation CELoc =
410    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
411  BR.EmitBasicReport(AC->getDecl(),
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, &R, 1);
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  SourceRange R = strArg->getSourceRange();
482  PathDiagnosticLocation CELoc =
483    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
484  SmallString<512> buf;
485  llvm::raw_svector_ostream out(buf);
486  out << "Call to '" << Name << "' should have at least 6 'X's in the"
487    " format string to be secure (" << numX << " 'X'";
488  if (numX != 1)
489    out << 's';
490  out << " seen";
491  if (suffix) {
492    out << ", " << suffix << " character";
493    if (suffix > 1)
494      out << 's';
495    out << " used as a suffix";
496  }
497  out << ')';
498  BR.EmitBasicReport(AC->getDecl(),
499                     "Insecure temporary file creation", "Security",
500                     out.str(), CELoc, &R, 1);
501}
502
503//===----------------------------------------------------------------------===//
504// Check: Any use of 'strcpy' is insecure.
505//
506// CWE-119: Improper Restriction of Operations within
507// the Bounds of a Memory Buffer
508//===----------------------------------------------------------------------===//
509void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) {
510  if (!filter.check_strcpy)
511    return;
512
513  if (!checkCall_strCommon(CE, FD))
514    return;
515
516  // Issue a warning.
517  SourceRange R = CE->getCallee()->getSourceRange();
518  PathDiagnosticLocation CELoc =
519    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
520  BR.EmitBasicReport(AC->getDecl(),
521                     "Potential insecure memory buffer bounds restriction in "
522                     "call 'strcpy'",
523                     "Security",
524                     "Call to function 'strcpy' is insecure as it does not "
525                     "provide bounding of the memory buffer. Replace "
526                     "unbounded copy functions with analogous functions that "
527                     "support length arguments such as 'strlcpy'. CWE-119.",
528                     CELoc, &R, 1);
529}
530
531//===----------------------------------------------------------------------===//
532// Check: Any use of 'strcat' is insecure.
533//
534// CWE-119: Improper Restriction of Operations within
535// the Bounds of a Memory Buffer
536//===----------------------------------------------------------------------===//
537void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) {
538  if (!filter.check_strcpy)
539    return;
540
541  if (!checkCall_strCommon(CE, FD))
542    return;
543
544  // Issue a warning.
545  SourceRange R = CE->getCallee()->getSourceRange();
546  PathDiagnosticLocation CELoc =
547    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
548  BR.EmitBasicReport(AC->getDecl(),
549                     "Potential insecure memory buffer bounds restriction in "
550                     "call 'strcat'",
551                     "Security",
552                     "Call to function 'strcat' is insecure as it does not "
553                     "provide bounding of the memory buffer. Replace "
554                     "unbounded copy functions with analogous functions that "
555                     "support length arguments such as 'strlcat'. CWE-119.",
556                     CELoc, &R, 1);
557}
558
559//===----------------------------------------------------------------------===//
560// Common check for str* functions with no bounds parameters.
561//===----------------------------------------------------------------------===//
562bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) {
563  const FunctionProtoType *FPT
564    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
565  if (!FPT)
566    return false;
567
568  // Verify the function takes two arguments, three in the _chk version.
569  int numArgs = FPT->getNumArgs();
570  if (numArgs != 2 && numArgs != 3)
571    return false;
572
573  // Verify the type for both arguments.
574  for (int i = 0; i < 2; i++) {
575    // Verify that the arguments are pointers.
576    const PointerType *PT = dyn_cast<PointerType>(FPT->getArgType(i));
577    if (!PT)
578      return false;
579
580    // Verify that the argument is a 'char*'.
581    if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
582      return false;
583  }
584
585  return true;
586}
587
588//===----------------------------------------------------------------------===//
589// Check: Linear congruent random number generators should not be used
590// Originally: <rdar://problem/63371000>
591// CWE-338: Use of cryptographically weak prng
592//===----------------------------------------------------------------------===//
593
594void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) {
595  if (!filter.check_rand || !CheckRand)
596    return;
597
598  const FunctionProtoType *FTP
599    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
600  if (!FTP)
601    return;
602
603  if (FTP->getNumArgs() == 1) {
604    // Is the argument an 'unsigned short *'?
605    // (Actually any integer type is allowed.)
606    const PointerType *PT = dyn_cast<PointerType>(FTP->getArgType(0));
607    if (!PT)
608      return;
609
610    if (! PT->getPointeeType()->isIntegerType())
611      return;
612  }
613  else if (FTP->getNumArgs() != 0)
614    return;
615
616  // Issue a warning.
617  SmallString<256> buf1;
618  llvm::raw_svector_ostream os1(buf1);
619  os1 << '\'' << *FD << "' is a poor random number generator";
620
621  SmallString<256> buf2;
622  llvm::raw_svector_ostream os2(buf2);
623  os2 << "Function '" << *FD
624      << "' is obsolete because it implements a poor random number generator."
625      << "  Use 'arc4random' instead";
626
627  SourceRange R = CE->getCallee()->getSourceRange();
628  PathDiagnosticLocation CELoc =
629    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
630  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
631                     CELoc, &R, 1);
632}
633
634//===----------------------------------------------------------------------===//
635// Check: 'random' should not be used
636// Originally: <rdar://problem/63371000>
637//===----------------------------------------------------------------------===//
638
639void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) {
640  if (!CheckRand || !filter.check_rand)
641    return;
642
643  const FunctionProtoType *FTP
644    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
645  if (!FTP)
646    return;
647
648  // Verify that the function takes no argument.
649  if (FTP->getNumArgs() != 0)
650    return;
651
652  // Issue a warning.
653  SourceRange R = CE->getCallee()->getSourceRange();
654  PathDiagnosticLocation CELoc =
655    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
656  BR.EmitBasicReport(AC->getDecl(),
657                     "'random' is not a secure random number generator",
658                     "Security",
659                     "The 'random' function produces a sequence of values that "
660                     "an adversary may be able to predict.  Use 'arc4random' "
661                     "instead", CELoc, &R, 1);
662}
663
664//===----------------------------------------------------------------------===//
665// Check: 'vfork' should not be used.
666// POS33-C: Do not use vfork().
667//===----------------------------------------------------------------------===//
668
669void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) {
670  if (!filter.check_vfork)
671    return;
672
673  // All calls to vfork() are insecure, issue a warning.
674  SourceRange R = CE->getCallee()->getSourceRange();
675  PathDiagnosticLocation CELoc =
676    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
677  BR.EmitBasicReport(AC->getDecl(),
678                     "Potential insecure implementation-specific behavior in "
679                     "call 'vfork'",
680                     "Security",
681                     "Call to function 'vfork' is insecure as it can lead to "
682                     "denial of service situations in the parent process. "
683                     "Replace calls to vfork with calls to the safer "
684                     "'posix_spawn' function",
685                     CELoc, &R, 1);
686}
687
688//===----------------------------------------------------------------------===//
689// Check: Should check whether privileges are dropped successfully.
690// Originally: <rdar://problem/6337132>
691//===----------------------------------------------------------------------===//
692
693void WalkAST::checkUncheckedReturnValue(CallExpr *CE) {
694  if (!filter.check_UncheckedReturn)
695    return;
696
697  const FunctionDecl *FD = CE->getDirectCallee();
698  if (!FD)
699    return;
700
701  if (II_setid[0] == NULL) {
702    static const char * const identifiers[num_setids] = {
703      "setuid", "setgid", "seteuid", "setegid",
704      "setreuid", "setregid"
705    };
706
707    for (size_t i = 0; i < num_setids; i++)
708      II_setid[i] = &BR.getContext().Idents.get(identifiers[i]);
709  }
710
711  const IdentifierInfo *id = FD->getIdentifier();
712  size_t identifierid;
713
714  for (identifierid = 0; identifierid < num_setids; identifierid++)
715    if (id == II_setid[identifierid])
716      break;
717
718  if (identifierid >= num_setids)
719    return;
720
721  const FunctionProtoType *FTP
722    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
723  if (!FTP)
724    return;
725
726  // Verify that the function takes one or two arguments (depending on
727  //   the function).
728  if (FTP->getNumArgs() != (identifierid < 4 ? 1 : 2))
729    return;
730
731  // The arguments must be integers.
732  for (unsigned i = 0; i < FTP->getNumArgs(); i++)
733    if (! FTP->getArgType(i)->isIntegerType())
734      return;
735
736  // Issue a warning.
737  SmallString<256> buf1;
738  llvm::raw_svector_ostream os1(buf1);
739  os1 << "Return value is not checked in call to '" << *FD << '\'';
740
741  SmallString<256> buf2;
742  llvm::raw_svector_ostream os2(buf2);
743  os2 << "The return value from the call to '" << *FD
744      << "' is not checked.  If an error occurs in '" << *FD
745      << "', the following code may execute with unexpected privileges";
746
747  SourceRange R = CE->getCallee()->getSourceRange();
748  PathDiagnosticLocation CELoc =
749    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
750  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
751                     CELoc, &R, 1);
752}
753
754//===----------------------------------------------------------------------===//
755// SecuritySyntaxChecker
756//===----------------------------------------------------------------------===//
757
758namespace {
759class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> {
760public:
761  ChecksFilter filter;
762
763  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
764                        BugReporter &BR) const {
765    WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter);
766    walker.Visit(D->getBody());
767  }
768};
769}
770
771#define REGISTER_CHECKER(name) \
772void ento::register##name(CheckerManager &mgr) {\
773  mgr.registerChecker<SecuritySyntaxChecker>()->filter.check_##name = true;\
774}
775
776REGISTER_CHECKER(gets)
777REGISTER_CHECKER(getpw)
778REGISTER_CHECKER(mkstemp)
779REGISTER_CHECKER(mktemp)
780REGISTER_CHECKER(strcpy)
781REGISTER_CHECKER(rand)
782REGISTER_CHECKER(vfork)
783REGISTER_CHECKER(FloatLoopCounter)
784REGISTER_CHECKER(UncheckedReturn)
785
786
787