r322410 - [analyzer] Don't flag strcpy of string literals into sufficiently large buffers.

[Artem Dergachev via cfe-commits]

Author: dergachev
Date: Fri Jan 12 14:12:11 2018
New Revision: 322410

URL: http://llvm.org/viewvc/llvm-project?rev=322410&view=rev
Log:
[analyzer] Don't flag strcpy of string literals into sufficiently large buffers.

In the security package, we have a simple syntactic check that warns about
strcpy() being insecure, due to potential buffer overflows.

Suppress that check's warning in the trivial situation when the source is an
immediate null-terminated string literal and the target is an immediate
sufficiently large buffer.

Patch by András Leitereg!

Differential Revision: https://reviews.llvm.org/D41384

Modified:
    cfe/trunk/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
    cfe/trunk/test/Analysis/security-syntax-checks.m

Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp?rev=322410&r1=322409&r2=322410&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp Fri Jan 12 14:12:11 2018
@@ -510,6 +510,17 @@ void WalkAST::checkCall_strcpy(const Cal
   if (!checkCall_strCommon(CE, FD))
     return;
 
+  const auto *Target = CE->getArg(0)->IgnoreImpCasts(),
+             *Source = CE->getArg(1)->IgnoreImpCasts();
+  if (const auto *DeclRef = dyn_cast<DeclRefExpr>(Target))
+    if (const auto *Array = dyn_cast<ConstantArrayType>(DeclRef->getType())) {
+      uint64_t ArraySize = BR.getContext().getTypeSize(Array) / 8;
+      if (const auto *String = dyn_cast<StringLiteral>(Source)) {
+        if (ArraySize >= String->getLength() + 1)
+          return;
+      }
+    }
+
   // Issue a warning.
   PathDiagnosticLocation CELoc =
     PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);

Modified: cfe/trunk/test/Analysis/security-syntax-checks.m
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/security-syntax-checks.m?rev=322410&r1=322409&r2=322410&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/security-syntax-checks.m (original)
+++ cfe/trunk/test/Analysis/security-syntax-checks.m Fri Jan 12 14:12:11 2018
@@ -146,6 +146,16 @@ void test_strcpy() {
   strcpy(x, y); //expected-warning{{Call to function 'strcpy' is insecure as it does not provide bounding of the memory buffer. Replace unbounded copy functions with analogous functions that support length arguments such as 'strlcpy'. CWE-119}}
 }
 
+void test_strcpy_2() {
+  char x[4];
+  strcpy(x, "abcd"); //expected-warning{{Call to function 'strcpy' is insecure as it does not provide bounding of the memory buffer. Replace unbounded copy functions with analogous functions that support length arguments such as 'strlcpy'. CWE-119}}
+}
+
+void test_strcpy_safe() {
+  char x[5];
+  strcpy(x, "abcd");
+}
+
 //===----------------------------------------------------------------------===
 // strcat()
 //===----------------------------------------------------------------------===