From: Artem Dergachev <artem.dergachev@gmail.com>
Date: Fri, 12 Jan 2018 22:12:11 +0000 (+0000)
Subject: [analyzer] Don't flag strcpy of string literals into sufficiently large buffers.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bdecb5f0d423364d024597699ffd3838cea08035;p=clang

[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


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@322410 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp b/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
index 6dbacad7f2..62831be26e 100644
--- a/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
+++ b/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
@@ -510,6 +510,17 @@ void WalkAST::checkCall_strcpy(const CallExpr *CE, const FunctionDecl *FD) {
   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);
diff --git a/test/Analysis/security-syntax-checks.m b/test/Analysis/security-syntax-checks.m
index 04a4c7d866..8560ba29e7 100644
--- a/test/Analysis/security-syntax-checks.m
+++ b/test/Analysis/security-syntax-checks.m
@@ -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()
 //===----------------------------------------------------------------------===