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