CheckSecuritySyntaxOnly.cpp revision dbcc7561f6964404c590f42454a249af5324fa44 
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::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 ChecksFilter {
40  DefaultBool check_gets;
41  DefaultBool check_getpw;
42  DefaultBool check_mktemp;
43  DefaultBool check_mkstemp;
44  DefaultBool check_strcpy;
45  DefaultBool check_rand;
46  DefaultBool check_vfork;
47  DefaultBool check_FloatLoopCounter;
48  DefaultBool check_UncheckedReturn;
49};
50
51class WalkAST : public StmtVisitor<WalkAST> {
52  BugReporter &BR;
53  AnalysisDeclContext* AC;
54  enum { num_setids = 6 };
55  IdentifierInfo *II_setid[num_setids];
56
57  const bool CheckRand;
58  const ChecksFilter &filter;
59
60public:
61  WalkAST(BugReporter &br, AnalysisDeclContext* ac,
62          const ChecksFilter &f)
63  : BR(br), AC(ac), II_setid(),
64    CheckRand(isArc4RandomAvailable(BR.getContext())),
65    filter(f) {}
66
67  // Statement visitor methods.
68  void VisitCallExpr(CallExpr *CE);
69  void VisitForStmt(ForStmt *S);
70  void VisitCompoundStmt (CompoundStmt *S);
71  void VisitStmt(Stmt *S) { VisitChildren(S); }
72
73  void VisitChildren(Stmt *S);
74
75  // Helpers.
76  bool checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD);
77
78  typedef void (WalkAST::*FnCheck)(const CallExpr *,
79				   const FunctionDecl *);
80
81  // Checker-specific methods.
82  void checkLoopConditionForFloat(const ForStmt *FS);
83  void checkCall_gets(const CallExpr *CE, const FunctionDecl *FD);
84  void checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD);
85  void checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD);
86  void checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD);
87  void checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD);
88  void checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD);
89  void checkCall_rand(const CallExpr *CE, const FunctionDecl *FD);
90  void checkCall_random(const CallExpr *CE, const FunctionDecl *FD);
91  void checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD);
92  void checkUncheckedReturnValue(CallExpr *CE);
93};
94} // end anonymous namespace
95
96//===----------------------------------------------------------------------===//
97// AST walking.
98//===----------------------------------------------------------------------===//
99
100void WalkAST::VisitChildren(Stmt *S) {
101  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
102    if (Stmt *child = *I)
103      Visit(child);
104}
105
106void WalkAST::VisitCallExpr(CallExpr *CE) {
107  // Get the callee.
108  const FunctionDecl *FD = CE->getDirectCallee();
109
110  if (!FD)
111    return;
112
113  // Get the name of the callee. If it's a builtin, strip off the prefix.
114  IdentifierInfo *II = FD->getIdentifier();
115  if (!II)   // if no identifier, not a simple C function
116    return;
117  StringRef Name = II->getName();
118  if (Name.startswith("__builtin_"))
119    Name = Name.substr(10);
120
121  // Set the evaluation function by switching on the callee name.
122  FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name)
123    .Case("gets", &WalkAST::checkCall_gets)
124    .Case("getpw", &WalkAST::checkCall_getpw)
125    .Case("mktemp", &WalkAST::checkCall_mktemp)
126    .Case("mkstemp", &WalkAST::checkCall_mkstemp)
127    .Case("mkdtemp", &WalkAST::checkCall_mkstemp)
128    .Case("mkstemps", &WalkAST::checkCall_mkstemp)
129    .Cases("strcpy", "__strcpy_chk", &WalkAST::checkCall_strcpy)
130    .Cases("strcat", "__strcat_chk", &WalkAST::checkCall_strcat)
131    .Case("drand48", &WalkAST::checkCall_rand)
132    .Case("erand48", &WalkAST::checkCall_rand)
133    .Case("jrand48", &WalkAST::checkCall_rand)
134    .Case("lrand48", &WalkAST::checkCall_rand)
135    .Case("mrand48", &WalkAST::checkCall_rand)
136    .Case("nrand48", &WalkAST::checkCall_rand)
137    .Case("lcong48", &WalkAST::checkCall_rand)
138    .Case("rand", &WalkAST::checkCall_rand)
139    .Case("rand_r", &WalkAST::checkCall_rand)
140    .Case("random", &WalkAST::checkCall_random)
141    .Case("vfork", &WalkAST::checkCall_vfork)
142    .Default(NULL);
143
144  // If the callee isn't defined, it is not of security concern.
145  // Check and evaluate the call.
146  if (evalFunction)
147    (this->*evalFunction)(CE, FD);
148
149  // Recurse and check children.
150  VisitChildren(CE);
151}
152
153void WalkAST::VisitCompoundStmt(CompoundStmt *S) {
154  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
155    if (Stmt *child = *I) {
156      if (CallExpr *CE = dyn_cast<CallExpr>(child))
157        checkUncheckedReturnValue(CE);
158      Visit(child);
159    }
160}
161
162void WalkAST::VisitForStmt(ForStmt *FS) {
163  checkLoopConditionForFloat(FS);
164
165  // Recurse and check children.
166  VisitChildren(FS);
167}
168
169//===----------------------------------------------------------------------===//
170// Check: floating poing variable used as loop counter.
171// Originally: <rdar://problem/6336718>
172// Implements: CERT security coding advisory FLP-30.
173//===----------------------------------------------------------------------===//
174
175static const DeclRefExpr*
176getIncrementedVar(const Expr *expr, const VarDecl *x, const VarDecl *y) {
177  expr = expr->IgnoreParenCasts();
178
179  if (const BinaryOperator *B = dyn_cast<BinaryOperator>(expr)) {
180    if (!(B->isAssignmentOp() || B->isCompoundAssignmentOp() ||
181          B->getOpcode() == BO_Comma))
182      return NULL;
183
184    if (const DeclRefExpr *lhs = getIncrementedVar(B->getLHS(), x, y))
185      return lhs;
186
187    if (const DeclRefExpr *rhs = getIncrementedVar(B->getRHS(), x, y))
188      return rhs;
189
190    return NULL;
191  }
192
193  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(expr)) {
194    const NamedDecl *ND = DR->getDecl();
195    return ND == x || ND == y ? DR : NULL;
196  }
197
198  if (const UnaryOperator *U = dyn_cast<UnaryOperator>(expr))
199    return U->isIncrementDecrementOp()
200      ? getIncrementedVar(U->getSubExpr(), x, y) : NULL;
201
202  return NULL;
203}
204
205/// CheckLoopConditionForFloat - This check looks for 'for' statements that
206///  use a floating point variable as a loop counter.
207///  CERT: FLP30-C, FLP30-CPP.
208///
209void WalkAST::checkLoopConditionForFloat(const ForStmt *FS) {
210  if (!filter.check_FloatLoopCounter)
211    return;
212
213  // Does the loop have a condition?
214  const Expr *condition = FS->getCond();
215
216  if (!condition)
217    return;
218
219  // Does the loop have an increment?
220  const Expr *increment = FS->getInc();
221
222  if (!increment)
223    return;
224
225  // Strip away '()' and casts.
226  condition = condition->IgnoreParenCasts();
227  increment = increment->IgnoreParenCasts();
228
229  // Is the loop condition a comparison?
230  const BinaryOperator *B = dyn_cast<BinaryOperator>(condition);
231
232  if (!B)
233    return;
234
235  // Is this a comparison?
236  if (!(B->isRelationalOp() || B->isEqualityOp()))
237    return;
238
239  // Are we comparing variables?
240  const DeclRefExpr *drLHS =
241    dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenLValueCasts());
242  const DeclRefExpr *drRHS =
243    dyn_cast<DeclRefExpr>(B->getRHS()->IgnoreParenLValueCasts());
244
245  // Does at least one of the variables have a floating point type?
246  drLHS = drLHS && drLHS->getType()->isRealFloatingType() ? drLHS : NULL;
247  drRHS = drRHS && drRHS->getType()->isRealFloatingType() ? drRHS : NULL;
248
249  if (!drLHS && !drRHS)
250    return;
251
252  const VarDecl *vdLHS = drLHS ? dyn_cast<VarDecl>(drLHS->getDecl()) : NULL;
253  const VarDecl *vdRHS = drRHS ? dyn_cast<VarDecl>(drRHS->getDecl()) : NULL;
254
255  if (!vdLHS && !vdRHS)
256    return;
257
258  // Does either variable appear in increment?
259  const DeclRefExpr *drInc = getIncrementedVar(increment, vdLHS, vdRHS);
260
261  if (!drInc)
262    return;
263
264  // Emit the error.  First figure out which DeclRefExpr in the condition
265  // referenced the compared variable.
266  assert(drInc->getDecl());
267  const DeclRefExpr *drCond = vdLHS == drInc->getDecl() ? drLHS : drRHS;
268
269  SmallVector<SourceRange, 2> ranges;
270  SmallString<256> sbuf;
271  llvm::raw_svector_ostream os(sbuf);
272
273  os << "Variable '" << drCond->getDecl()->getName()
274     << "' with floating point type '" << drCond->getType().getAsString()
275     << "' should not be used as a loop counter";
276
277  ranges.push_back(drCond->getSourceRange());
278  ranges.push_back(drInc->getSourceRange());
279
280  const char *bugType = "Floating point variable used as loop counter";
281
282  PathDiagnosticLocation FSLoc =
283    PathDiagnosticLocation::createBegin(FS, BR.getSourceManager(), AC);
284  BR.EmitBasicReport(AC->getDecl(),
285                     bugType, "Security", os.str(),
286                     FSLoc, ranges.data(), ranges.size());
287}
288
289//===----------------------------------------------------------------------===//
290// Check: Any use of 'gets' is insecure.
291// Originally: <rdar://problem/6335715>
292// Implements (part of): 300-BSI (buildsecurityin.us-cert.gov)
293// CWE-242: Use of Inherently Dangerous Function
294//===----------------------------------------------------------------------===//
295
296void WalkAST::checkCall_gets(const CallExpr *CE, const FunctionDecl *FD) {
297  if (!filter.check_gets)
298    return;
299
300  const FunctionProtoType *FPT
301    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
302  if (!FPT)
303    return;
304
305  // Verify that the function takes a single argument.
306  if (FPT->getNumArgs() != 1)
307    return;
308
309  // Is the argument a 'char*'?
310  const PointerType *PT = FPT->getArgType(0)->getAs<PointerType>();
311  if (!PT)
312    return;
313
314  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
315    return;
316
317  // Issue a warning.
318  SourceRange R = CE->getCallee()->getSourceRange();
319  PathDiagnosticLocation CELoc =
320    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
321  BR.EmitBasicReport(AC->getDecl(),
322                     "Potential buffer overflow in call to 'gets'",
323                     "Security",
324                     "Call to function 'gets' is extremely insecure as it can "
325                     "always result in a buffer overflow",
326                     CELoc, &R, 1);
327}
328
329//===----------------------------------------------------------------------===//
330// Check: Any use of 'getpwd' is insecure.
331// CWE-477: Use of Obsolete Functions
332//===----------------------------------------------------------------------===//
333
334void WalkAST::checkCall_getpw(const CallExpr *CE, const FunctionDecl *FD) {
335  if (!filter.check_getpw)
336    return;
337
338  const FunctionProtoType *FPT
339    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
340  if (!FPT)
341    return;
342
343  // Verify that the function takes two arguments.
344  if (FPT->getNumArgs() != 2)
345    return;
346
347  // Verify the first argument type is integer.
348  if (!FPT->getArgType(0)->isIntegralOrUnscopedEnumerationType())
349    return;
350
351  // Verify the second argument type is char*.
352  const PointerType *PT = FPT->getArgType(1)->getAs<PointerType>();
353  if (!PT)
354    return;
355
356  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
357    return;
358
359  // Issue a warning.
360  SourceRange R = CE->getCallee()->getSourceRange();
361  PathDiagnosticLocation CELoc =
362    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
363  BR.EmitBasicReport(AC->getDecl(),
364                     "Potential buffer overflow in call to 'getpw'",
365                     "Security",
366                     "The getpw() function is dangerous as it may overflow the "
367                     "provided buffer. It is obsoleted by getpwuid().",
368                     CELoc, &R, 1);
369}
370
371//===----------------------------------------------------------------------===//
372// Check: Any use of 'mktemp' is insecure.  It is obsoleted by mkstemp().
373// CWE-377: Insecure Temporary File
374//===----------------------------------------------------------------------===//
375
376void WalkAST::checkCall_mktemp(const CallExpr *CE, const FunctionDecl *FD) {
377  if (!filter.check_mktemp) {
378    // Fall back to the security check of looking for enough 'X's in the
379    // format string, since that is a less severe warning.
380    checkCall_mkstemp(CE, FD);
381    return;
382  }
383
384  const FunctionProtoType *FPT
385    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
386  if(!FPT)
387    return;
388
389  // Verify that the function takes a single argument.
390  if (FPT->getNumArgs() != 1)
391    return;
392
393  // Verify that the argument is Pointer Type.
394  const PointerType *PT = FPT->getArgType(0)->getAs<PointerType>();
395  if (!PT)
396    return;
397
398  // Verify that the argument is a 'char*'.
399  if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
400    return;
401
402  // Issue a waring.
403  SourceRange R = CE->getCallee()->getSourceRange();
404  PathDiagnosticLocation CELoc =
405    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
406  BR.EmitBasicReport(AC->getDecl(),
407                     "Potential insecure temporary file in call 'mktemp'",
408                     "Security",
409                     "Call to function 'mktemp' is insecure as it always "
410                     "creates or uses insecure temporary file.  Use 'mkstemp' "
411                     "instead",
412                     CELoc, &R, 1);
413}
414
415
416//===----------------------------------------------------------------------===//
417// Check: Use of 'mkstemp', 'mktemp', 'mkdtemp' should contain at least 6 X's.
418//===----------------------------------------------------------------------===//
419
420void WalkAST::checkCall_mkstemp(const CallExpr *CE, const FunctionDecl *FD) {
421  if (!filter.check_mkstemp)
422    return;
423
424  StringRef Name = FD->getIdentifier()->getName();
425  std::pair<signed, signed> ArgSuffix =
426    llvm::StringSwitch<std::pair<signed, signed> >(Name)
427      .Case("mktemp", std::make_pair(0,-1))
428      .Case("mkstemp", std::make_pair(0,-1))
429      .Case("mkdtemp", std::make_pair(0,-1))
430      .Case("mkstemps", std::make_pair(0,1))
431      .Default(std::make_pair(-1, -1));
432
433  assert(ArgSuffix.first >= 0 && "Unsupported function");
434
435  // Check if the number of arguments is consistent with out expectations.
436  unsigned numArgs = CE->getNumArgs();
437  if ((signed) numArgs <= ArgSuffix.first)
438    return;
439
440  const StringLiteral *strArg =
441    dyn_cast<StringLiteral>(CE->getArg((unsigned)ArgSuffix.first)
442                              ->IgnoreParenImpCasts());
443
444  // Currently we only handle string literals.  It is possible to do better,
445  // either by looking at references to const variables, or by doing real
446  // flow analysis.
447  if (!strArg || strArg->getCharByteWidth() != 1)
448    return;
449
450  // Count the number of X's, taking into account a possible cutoff suffix.
451  StringRef str = strArg->getString();
452  unsigned numX = 0;
453  unsigned n = str.size();
454
455  // Take into account the suffix.
456  unsigned suffix = 0;
457  if (ArgSuffix.second >= 0) {
458    const Expr *suffixEx = CE->getArg((unsigned)ArgSuffix.second);
459    llvm::APSInt Result;
460    if (!suffixEx->EvaluateAsInt(Result, BR.getContext()))
461      return;
462    // FIXME: Issue a warning.
463    if (Result.isNegative())
464      return;
465    suffix = (unsigned) Result.getZExtValue();
466    n = (n > suffix) ? n - suffix : 0;
467  }
468
469  for (unsigned i = 0; i < n; ++i)
470    if (str[i] == 'X') ++numX;
471
472  if (numX >= 6)
473    return;
474
475  // Issue a warning.
476  SourceRange R = strArg->getSourceRange();
477  PathDiagnosticLocation CELoc =
478    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
479  SmallString<512> buf;
480  llvm::raw_svector_ostream out(buf);
481  out << "Call to '" << Name << "' should have at least 6 'X's in the"
482    " format string to be secure (" << numX << " 'X'";
483  if (numX != 1)
484    out << 's';
485  out << " seen";
486  if (suffix) {
487    out << ", " << suffix << " character";
488    if (suffix > 1)
489      out << 's';
490    out << " used as a suffix";
491  }
492  out << ')';
493  BR.EmitBasicReport(AC->getDecl(),
494                     "Insecure temporary file creation", "Security",
495                     out.str(), CELoc, &R, 1);
496}
497
498//===----------------------------------------------------------------------===//
499// Check: Any use of 'strcpy' is insecure.
500//
501// CWE-119: Improper Restriction of Operations within
502// the Bounds of a Memory Buffer
503//===----------------------------------------------------------------------===//
504void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) {
505  if (!filter.check_strcpy)
506    return;
507
508  if (!checkCall_strCommon(CE, FD))
509    return;
510
511  // Issue a warning.
512  SourceRange R = CE->getCallee()->getSourceRange();
513  PathDiagnosticLocation CELoc =
514    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
515  BR.EmitBasicReport(AC->getDecl(),
516                     "Potential insecure memory buffer bounds restriction in "
517                     "call 'strcpy'",
518                     "Security",
519                     "Call to function 'strcpy' is insecure as it does not "
520                     "provide bounding of the memory buffer. Replace "
521                     "unbounded copy functions with analogous functions that "
522                     "support length arguments such as 'strlcpy'. CWE-119.",
523                     CELoc, &R, 1);
524}
525
526//===----------------------------------------------------------------------===//
527// Check: Any use of 'strcat' is insecure.
528//
529// CWE-119: Improper Restriction of Operations within
530// the Bounds of a Memory Buffer
531//===----------------------------------------------------------------------===//
532void WalkAST::checkCall_strcat(const CallExpr *CE, const FunctionDecl *FD) {
533  if (!filter.check_strcpy)
534    return;
535
536  if (!checkCall_strCommon(CE, FD))
537    return;
538
539  // Issue a warning.
540  SourceRange R = CE->getCallee()->getSourceRange();
541  PathDiagnosticLocation CELoc =
542    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
543  BR.EmitBasicReport(AC->getDecl(),
544                     "Potential insecure memory buffer bounds restriction in "
545                     "call 'strcat'",
546                     "Security",
547                     "Call to function 'strcat' is insecure as it does not "
548                     "provide bounding of the memory buffer. Replace "
549                     "unbounded copy functions with analogous functions that "
550                     "support length arguments such as 'strlcat'. CWE-119.",
551                     CELoc, &R, 1);
552}
553
554//===----------------------------------------------------------------------===//
555// Common check for str* functions with no bounds parameters.
556//===----------------------------------------------------------------------===//
557bool WalkAST::checkCall_strCommon(const CallExpr *CE, const FunctionDecl *FD) {
558  const FunctionProtoType *FPT
559    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
560  if (!FPT)
561    return false;
562
563  // Verify the function takes two arguments, three in the _chk version.
564  int numArgs = FPT->getNumArgs();
565  if (numArgs != 2 && numArgs != 3)
566    return false;
567
568  // Verify the type for both arguments.
569  for (int i = 0; i < 2; i++) {
570    // Verify that the arguments are pointers.
571    const PointerType *PT = FPT->getArgType(i)->getAs<PointerType>();
572    if (!PT)
573      return false;
574
575    // Verify that the argument is a 'char*'.
576    if (PT->getPointeeType().getUnqualifiedType() != BR.getContext().CharTy)
577      return false;
578  }
579
580  return true;
581}
582
583//===----------------------------------------------------------------------===//
584// Check: Linear congruent random number generators should not be used
585// Originally: <rdar://problem/63371000>
586// CWE-338: Use of cryptographically weak prng
587//===----------------------------------------------------------------------===//
588
589void WalkAST::checkCall_rand(const CallExpr *CE, const FunctionDecl *FD) {
590  if (!filter.check_rand || !CheckRand)
591    return;
592
593  const FunctionProtoType *FTP
594    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
595  if (!FTP)
596    return;
597
598  if (FTP->getNumArgs() == 1) {
599    // Is the argument an 'unsigned short *'?
600    // (Actually any integer type is allowed.)
601    const PointerType *PT = FTP->getArgType(0)->getAs<PointerType>();
602    if (!PT)
603      return;
604
605    if (! PT->getPointeeType()->isIntegralOrUnscopedEnumerationType())
606      return;
607  }
608  else if (FTP->getNumArgs() != 0)
609    return;
610
611  // Issue a warning.
612  SmallString<256> buf1;
613  llvm::raw_svector_ostream os1(buf1);
614  os1 << '\'' << *FD << "' is a poor random number generator";
615
616  SmallString<256> buf2;
617  llvm::raw_svector_ostream os2(buf2);
618  os2 << "Function '" << *FD
619      << "' is obsolete because it implements a poor random number generator."
620      << "  Use 'arc4random' instead";
621
622  SourceRange R = CE->getCallee()->getSourceRange();
623  PathDiagnosticLocation CELoc =
624    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
625  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
626                     CELoc, &R, 1);
627}
628
629//===----------------------------------------------------------------------===//
630// Check: 'random' should not be used
631// Originally: <rdar://problem/63371000>
632//===----------------------------------------------------------------------===//
633
634void WalkAST::checkCall_random(const CallExpr *CE, const FunctionDecl *FD) {
635  if (!CheckRand || !filter.check_rand)
636    return;
637
638  const FunctionProtoType *FTP
639    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
640  if (!FTP)
641    return;
642
643  // Verify that the function takes no argument.
644  if (FTP->getNumArgs() != 0)
645    return;
646
647  // Issue a warning.
648  SourceRange R = CE->getCallee()->getSourceRange();
649  PathDiagnosticLocation CELoc =
650    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
651  BR.EmitBasicReport(AC->getDecl(),
652                     "'random' is not a secure random number generator",
653                     "Security",
654                     "The 'random' function produces a sequence of values that "
655                     "an adversary may be able to predict.  Use 'arc4random' "
656                     "instead", CELoc, &R, 1);
657}
658
659//===----------------------------------------------------------------------===//
660// Check: 'vfork' should not be used.
661// POS33-C: Do not use vfork().
662//===----------------------------------------------------------------------===//
663
664void WalkAST::checkCall_vfork(const CallExpr *CE, const FunctionDecl *FD) {
665  if (!filter.check_vfork)
666    return;
667
668  // All calls to vfork() are insecure, issue a warning.
669  SourceRange R = CE->getCallee()->getSourceRange();
670  PathDiagnosticLocation CELoc =
671    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
672  BR.EmitBasicReport(AC->getDecl(),
673                     "Potential insecure implementation-specific behavior in "
674                     "call 'vfork'",
675                     "Security",
676                     "Call to function 'vfork' is insecure as it can lead to "
677                     "denial of service situations in the parent process. "
678                     "Replace calls to vfork with calls to the safer "
679                     "'posix_spawn' function",
680                     CELoc, &R, 1);
681}
682
683//===----------------------------------------------------------------------===//
684// Check: Should check whether privileges are dropped successfully.
685// Originally: <rdar://problem/6337132>
686//===----------------------------------------------------------------------===//
687
688void WalkAST::checkUncheckedReturnValue(CallExpr *CE) {
689  if (!filter.check_UncheckedReturn)
690    return;
691
692  const FunctionDecl *FD = CE->getDirectCallee();
693  if (!FD)
694    return;
695
696  if (II_setid[0] == NULL) {
697    static const char * const identifiers[num_setids] = {
698      "setuid", "setgid", "seteuid", "setegid",
699      "setreuid", "setregid"
700    };
701
702    for (size_t i = 0; i < num_setids; i++)
703      II_setid[i] = &BR.getContext().Idents.get(identifiers[i]);
704  }
705
706  const IdentifierInfo *id = FD->getIdentifier();
707  size_t identifierid;
708
709  for (identifierid = 0; identifierid < num_setids; identifierid++)
710    if (id == II_setid[identifierid])
711      break;
712
713  if (identifierid >= num_setids)
714    return;
715
716  const FunctionProtoType *FTP
717    = dyn_cast<FunctionProtoType>(FD->getType().IgnoreParens());
718  if (!FTP)
719    return;
720
721  // Verify that the function takes one or two arguments (depending on
722  //   the function).
723  if (FTP->getNumArgs() != (identifierid < 4 ? 1 : 2))
724    return;
725
726  // The arguments must be integers.
727  for (unsigned i = 0; i < FTP->getNumArgs(); i++)
728    if (! FTP->getArgType(i)->isIntegralOrUnscopedEnumerationType())
729      return;
730
731  // Issue a warning.
732  SmallString<256> buf1;
733  llvm::raw_svector_ostream os1(buf1);
734  os1 << "Return value is not checked in call to '" << *FD << '\'';
735
736  SmallString<256> buf2;
737  llvm::raw_svector_ostream os2(buf2);
738  os2 << "The return value from the call to '" << *FD
739      << "' is not checked.  If an error occurs in '" << *FD
740      << "', the following code may execute with unexpected privileges";
741
742  SourceRange R = CE->getCallee()->getSourceRange();
743  PathDiagnosticLocation CELoc =
744    PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
745  BR.EmitBasicReport(AC->getDecl(), os1.str(), "Security", os2.str(),
746                     CELoc, &R, 1);
747}
748
749//===----------------------------------------------------------------------===//
750// SecuritySyntaxChecker
751//===----------------------------------------------------------------------===//
752
753namespace {
754class SecuritySyntaxChecker : public Checker<check::ASTCodeBody> {
755public:
756  ChecksFilter filter;
757
758  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
759                        BugReporter &BR) const {
760    WalkAST walker(BR, mgr.getAnalysisDeclContext(D), filter);
761    walker.Visit(D->getBody());
762  }
763};
764}
765
766#define REGISTER_CHECKER(name) \
767void ento::register##name(CheckerManager &mgr) {\
768  mgr.registerChecker<SecuritySyntaxChecker>()->filter.check_##name = true;\
769}
770
771REGISTER_CHECKER(gets)
772REGISTER_CHECKER(getpw)
773REGISTER_CHECKER(mkstemp)
774REGISTER_CHECKER(mktemp)
775REGISTER_CHECKER(strcpy)
776REGISTER_CHECKER(rand)
777REGISTER_CHECKER(vfork)
778REGISTER_CHECKER(FloatLoopCounter)
779REGISTER_CHECKER(UncheckedReturn)
780
781
782