Author: devnexen
Date: Tue Dec 11 10:57:07 2018
New Revision: 348884

URL: http://llvm.org/viewvc/llvm-project?rev=348884&view=rev
Log:
[analyzer][CStringChecker] evaluate explicit_bzero


- explicit_bzero has limited scope/usage only for security/crypto purposes but 
is non-optimisable version of memset/0 and bzero.
- explicit_memset has similar signature and semantics as memset but is also a 
non-optimisable version.

Reviewers: NoQ

Reviewed By: NoQ

Differential Revision: https://reviews.llvm.org/D54592


Modified:
    cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
    cfe/trunk/test/Analysis/string.c

Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp?rev=348884&r1=348883&r2=348884&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/CStringChecker.cpp Tue Dec 11 
10:57:07 2018
@@ -124,6 +124,7 @@ public:
   void evalStdCopyBackward(CheckerContext &C, const CallExpr *CE) const;
   void evalStdCopyCommon(CheckerContext &C, const CallExpr *CE) const;
   void evalMemset(CheckerContext &C, const CallExpr *CE) const;
+  void evalBzero(CheckerContext &C, const CallExpr *CE) const;
 
   // Utility methods
   std::pair<ProgramStateRef , ProgramStateRef >
@@ -158,7 +159,7 @@ public:
   static bool SummarizeRegion(raw_ostream &os, ASTContext &Ctx,
                               const MemRegion *MR);
 
-  static bool memsetAux(const Expr *DstBuffer, const Expr *CharE,
+  static bool memsetAux(const Expr *DstBuffer, SVal CharE,
                         const Expr *Size, CheckerContext &C,
                         ProgramStateRef &State);
 
@@ -1005,11 +1006,10 @@ bool CStringChecker::SummarizeRegion(raw
   }
 }
 
-bool CStringChecker::memsetAux(const Expr *DstBuffer, const Expr *CharE,
+bool CStringChecker::memsetAux(const Expr *DstBuffer, SVal CharVal,
                                const Expr *Size, CheckerContext &C,
                                ProgramStateRef &State) {
   SVal MemVal = C.getSVal(DstBuffer);
-  SVal CharVal = C.getSVal(CharE);
   SVal SizeVal = C.getSVal(Size);
   const MemRegion *MR = MemVal.getAsRegion();
   if (!MR)
@@ -2184,13 +2184,59 @@ void CStringChecker::evalMemset(CheckerC
   // According to the values of the arguments, bind the value of the second
   // argument to the destination buffer and set string length, or just
   // invalidate the destination buffer.
-  if (!memsetAux(Mem, CharE, Size, C, State))
+  if (!memsetAux(Mem, C.getSVal(CharE), Size, C, State))
     return;
 
   State = State->BindExpr(CE, LCtx, MemVal);
   C.addTransition(State);
 }
 
+void CStringChecker::evalBzero(CheckerContext &C, const CallExpr *CE) const {
+  if (CE->getNumArgs() != 2)
+    return;
+
+  CurrentFunctionDescription = "memory clearance function";
+
+  const Expr *Mem = CE->getArg(0);
+  const Expr *Size = CE->getArg(1);
+  SVal Zero = C.getSValBuilder().makeZeroVal(C.getASTContext().IntTy);
+
+  ProgramStateRef State = C.getState();
+  
+  // See if the size argument is zero.
+  SVal SizeVal = C.getSVal(Size);
+  QualType SizeTy = Size->getType();
+
+  ProgramStateRef StateZeroSize, StateNonZeroSize;
+  std::tie(StateZeroSize, StateNonZeroSize) =
+    assumeZero(C, State, SizeVal, SizeTy);
+
+  // If the size is zero, there won't be any actual memory access,
+  // In this case we just return.
+  if (StateZeroSize && !StateNonZeroSize) {
+    C.addTransition(StateZeroSize);
+    return;
+  }
+
+  // Get the value of the memory area.
+  SVal MemVal = C.getSVal(Mem);
+
+  // Ensure the memory area is not null.
+  // If it is NULL there will be a NULL pointer dereference.
+  State = checkNonNull(C, StateNonZeroSize, Mem, MemVal);
+  if (!State)
+    return;
+
+  State = CheckBufferAccess(C, State, Size, Mem);
+  if (!State)
+    return;
+
+  if (!memsetAux(Mem, Zero, Size, C, State))
+    return;
+
+  C.addTransition(State);
+}
+
 static bool isCPPStdLibraryFunction(const FunctionDecl *FD, StringRef Name) {
   IdentifierInfo *II = FD->getIdentifier();
   if (!II)
@@ -2224,7 +2270,8 @@ bool CStringChecker::evalCall(const Call
     evalFunction =  &CStringChecker::evalMemcmp;
   else if (C.isCLibraryFunction(FDecl, "memmove"))
     evalFunction =  &CStringChecker::evalMemmove;
-  else if (C.isCLibraryFunction(FDecl, "memset"))
+  else if (C.isCLibraryFunction(FDecl, "memset") || 
+    C.isCLibraryFunction(FDecl, "explicit_memset"))
     evalFunction =  &CStringChecker::evalMemset;
   else if (C.isCLibraryFunction(FDecl, "strcpy"))
     evalFunction =  &CStringChecker::evalStrcpy;
@@ -2262,6 +2309,9 @@ bool CStringChecker::evalCall(const Call
     evalFunction =  &CStringChecker::evalStdCopy;
   else if (isCPPStdLibraryFunction(FDecl, "copy_backward"))
     evalFunction =  &CStringChecker::evalStdCopyBackward;
+  else if (C.isCLibraryFunction(FDecl, "bzero") ||
+    C.isCLibraryFunction(FDecl, "explicit_bzero"))
+    evalFunction =  &CStringChecker::evalBzero;
 
   // If the callee isn't a string function, let another checker handle it.
   if (!evalFunction)

Modified: cfe/trunk/test/Analysis/string.c
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/string.c?rev=348884&r1=348883&r2=348884&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/string.c (original)
+++ cfe/trunk/test/Analysis/string.c Tue Dec 11 10:57:07 2018
@@ -1184,11 +1184,14 @@ void strsep_changes_input_string() {
 }
 
 //===----------------------------------------------------------------------===
-// memset()
+// memset() / explicit_bzero() / bzero()
 //===----------------------------------------------------------------------===
 
 void *memset(void *dest, int ch, size_t count);
 
+void bzero(void *dst, size_t count);
+void explicit_bzero(void *dest, size_t count);
+
 void *malloc(size_t size);
 void free(void *);
 
@@ -1383,6 +1386,57 @@ void memset26_upper_UCHAR_MAX() {
   clang_analyzer_eval(array[4] == 0); // expected-warning{{TRUE}}
 }
 
+void bzero1_null() {
+  char *a = NULL;
+
+  bzero(a, 10); // expected-warning{{Null pointer argument in call to memory 
clearance function}}
+}
+
+void bzero2_char_array_null() {
+  char str[] = "abcd";
+  clang_analyzer_eval(strlen(str) == 4); // expected-warning{{TRUE}}
+  bzero(str, 2);
+  clang_analyzer_eval(strlen(str) == 0); // expected-warning{{TRUE}}
+}
+
+void bzero3_char_ptr_null() {
+  char *str = "abcd";
+  clang_analyzer_eval(strlen(str) == 4); // expected-warning{{TRUE}}
+  bzero(str + 2, 2);
+  clang_analyzer_eval(strlen(str) == 0); // expected-warning{{FALSE}}
+}
+
+void explicit_bzero1_null() {
+  char *a = NULL;
+
+  explicit_bzero(a, 10); // expected-warning{{Null pointer argument in call to 
memory clearance function}}
+}
+
+void explicit_bzero2_clear_mypassword() {
+  char passwd[7] = "passwd";
+
+  explicit_bzero(passwd, sizeof(passwd)); // no-warning
+
+  clang_analyzer_eval(strlen(passwd) == 0); // expected-warning{{TRUE}}
+  clang_analyzer_eval(passwd[0] == '\0'); // expected-warning{{TRUE}}
+}
+
+void explicit_bzero3_out_ofbound() {
+  char *privkey = (char *)malloc(7);
+  const char newprivkey[10] = "mysafekey";
+
+  strcpy(privkey, "random");
+  explicit_bzero(privkey, sizeof(newprivkey));
+#ifndef SUPPRESS_OUT_OF_BOUND
+  // expected-warning@-2 {{Memory clearance function accesses out-of-bound 
array element}}
+#endif
+  clang_analyzer_eval(privkey[0] == '\0');
+#ifdef SUPPRESS_OUT_OF_BOUND
+  // expected-warning@-2 {{UNKNOWN}}
+#endif
+  free(privkey);
+}
+
 //===----------------------------------------------------------------------===
 // FIXMEs
 //===----------------------------------------------------------------------===


_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

Reply via email to