[clang-tidy] Add a new Android check "android-cloexec-socket"

Summary: socket() is better to include SOCK_CLOEXEC in its type argument to avoid the file descriptor leakage.

Reviewers: chh, Eugene.Zelenko, alexfh, hokein, aaron.ballman

Reviewed By: chh, alexfh

Subscribers: srhines, mgorny, JDevlieghere, xazax.hun, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D34913

llvm-svn: 307818

clang-tools-extra/clang-tidy/android/AndroidTidyModule.cpp

@@ -13,6 +13,7 @@
 #include "CloexecCreatCheck.h"
 #include "CloexecFopenCheck.h"
 #include "CloexecOpenCheck.h"
+#include "CloexecSocketCheck.h"
 
 using namespace clang::ast_matchers;
 
@@ -27,6 +28,7 @@ class AndroidModule : public ClangTidyModule {
     CheckFactories.registerCheck<CloexecCreatCheck>("android-cloexec-creat");
     CheckFactories.registerCheck<CloexecFopenCheck>("android-cloexec-fopen");
     CheckFactories.registerCheck<CloexecOpenCheck>("android-cloexec-open");
+    CheckFactories.registerCheck<CloexecSocketCheck>("android-cloexec-socket");
   }
 };
 

clang-tools-extra/clang-tidy/android/CMakeLists.txt

@@ -5,6 +5,7 @@ add_clang_library(clangTidyAndroidModule
   CloexecCreatCheck.cpp
   CloexecFopenCheck.cpp
   CloexecOpenCheck.cpp
+  CloexecSocketCheck.cpp
 
   LINK_LIBS
   clangAST

clang-tools-extra/clang-tidy/android/CloexecOpenCheck.cpp

@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "CloexecOpenCheck.h"
+#include "../utils/ASTUtils.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
@@ -18,35 +19,8 @@ namespace clang {
 namespace tidy {
 namespace android {
 
-namespace {
 static constexpr const char *O_CLOEXEC = "O_CLOEXEC";
 
-bool hasCloseOnExecFlag(const Expr *Flags, const SourceManager &SM,
-                        const LangOptions &LangOpts) {
-  // If the Flag is an integer constant, check it.
-  if (isa<IntegerLiteral>(Flags)) {
-    if (!SM.isMacroBodyExpansion(Flags->getLocStart()) &&
-        !SM.isMacroArgExpansion(Flags->getLocStart()))
-      return false;
-
-    // Get the Marco name.
-    auto MacroName = Lexer::getSourceText(
-        CharSourceRange::getTokenRange(Flags->getSourceRange()), SM, LangOpts);
-
-    return MacroName == O_CLOEXEC;
-  }
-  // If it's a binary OR operation.
-  if (const auto *BO = dyn_cast<BinaryOperator>(Flags))
-    if (BO->getOpcode() == clang::BinaryOperatorKind::BO_Or)
-      return hasCloseOnExecFlag(BO->getLHS()->IgnoreParenCasts(), SM,
-                                LangOpts) ||
-             hasCloseOnExecFlag(BO->getRHS()->IgnoreParenCasts(), SM, LangOpts);
-
-  // Otherwise, assume it has the flag.
-  return true;
-}
-} // namespace
-
 void CloexecOpenCheck::registerMatchers(MatchFinder *Finder) {
   auto CharPointerType = hasType(pointerType(pointee(isAnyCharacter())));
 
@@ -82,8 +56,8 @@ void CloexecOpenCheck::check(const MatchFinder::MatchResult &Result) {
 
   // Check the required flag.
   SourceManager &SM = *Result.SourceManager;
-  if (hasCloseOnExecFlag(FlagArg->IgnoreParenCasts(), SM,
-                         Result.Context->getLangOpts()))
+  if (utils::exprHasBitFlagWithSpelling(FlagArg->IgnoreParenCasts(), SM,
+                     Result.Context->getLangOpts(), O_CLOEXEC))
     return;
 
   SourceLocation EndLoc =

clang-tools-extra/clang-tidy/android/CloexecSocketCheck.cpp

@@ -0,0 +1,57 @@
+//===--- CloexecSocketCheck.cpp - clang-tidy-------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CloexecSocketCheck.h"
+#include "../utils/ASTUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+static constexpr const char *SOCK_CLOEXEC = "SOCK_CLOEXEC";
+
+void CloexecSocketCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(isExternC(), returns(isInteger()),
+                                   hasName("socket"),
+                                   hasParameter(0, hasType(isInteger())),
+                                   hasParameter(1, hasType(isInteger())),
+                                   hasParameter(2, hasType(isInteger())))
+                          .bind("funcDecl")))
+          .bind("socketFn"),
+      this);
+}
+
+void CloexecSocketCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *MatchedCall = Result.Nodes.getNodeAs<CallExpr>("socketFn");
+  const auto *FD = Result.Nodes.getNodeAs<FunctionDecl>("funcDecl");
+  const Expr *FlagArg = MatchedCall->getArg(1);
+  SourceManager &SM = *Result.SourceManager;
+
+  if (utils::exprHasBitFlagWithSpelling(FlagArg->IgnoreParenCasts(), SM,
+                     Result.Context->getLangOpts(), SOCK_CLOEXEC))
+    return;
+
+  SourceLocation EndLoc =
+      Lexer::getLocForEndOfToken(SM.getFileLoc(FlagArg->getLocEnd()), 0, SM,
+                                 Result.Context->getLangOpts());
+
+  diag(EndLoc, "%0 should use %1 where possible")
+      << FD << SOCK_CLOEXEC
+      << FixItHint::CreateInsertion(EndLoc,
+                                    (Twine(" | ") + SOCK_CLOEXEC).str());
+}
+
+} // namespace android
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/android/CloexecSocketCheck.h

@@ -0,0 +1,35 @@
+//===--- CloexecSocketCheck.h - clang-tidy-----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_SOCKET_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_SOCKET_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+/// Finds code that uses socket() without using the SOCK_CLOEXEC flag.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-socket.html
+class CloexecSocketCheck : public ClangTidyCheck {
+public:
+  CloexecSocketCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace android
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_SOCKET_H

clang-tools-extra/clang-tidy/utils/ASTUtils.cpp

@@ -11,6 +11,7 @@
 
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Lex/Lexer.h"
 
 namespace clang {
 namespace tidy {
@@ -39,6 +40,33 @@ bool IsBinaryOrTernary(const Expr *E) {
   return false;
 }
 
+bool exprHasBitFlagWithSpelling(const Expr *Flags, const SourceManager &SM,
+                                const LangOptions &LangOpts,
+                                StringRef FlagName) {
+  // If the Flag is an integer constant, check it.
+  if (isa<IntegerLiteral>(Flags)) {
+    if (!SM.isMacroBodyExpansion(Flags->getLocStart()) &&
+        !SM.isMacroArgExpansion(Flags->getLocStart()))
+      return false;
+
+    // Get the marco name.
+    auto MacroName = Lexer::getSourceText(
+        CharSourceRange::getTokenRange(Flags->getSourceRange()), SM, LangOpts);
+
+    return MacroName == FlagName;
+  }
+  // If it's a binary OR operation.
+  if (const auto *BO = dyn_cast<BinaryOperator>(Flags))
+    if (BO->getOpcode() == clang::BinaryOperatorKind::BO_Or)
+      return exprHasBitFlagWithSpelling(BO->getLHS()->IgnoreParenCasts(), SM,
+                                        LangOpts, FlagName) ||
+             exprHasBitFlagWithSpelling(BO->getRHS()->IgnoreParenCasts(), SM,
+                                        LangOpts, FlagName);
+
+  // Otherwise, assume it has the flag.
+  return true;
+}
+
 } // namespace utils
 } // namespace tidy
 } // namespace clang

clang-tools-extra/clang-tidy/utils/ASTUtils.h

@@ -20,6 +20,13 @@ const FunctionDecl *getSurroundingFunction(ASTContext &Context,
                                            const Stmt &Statement);
 // Determine whether Expr is a Binary or Ternary expression.
 bool IsBinaryOrTernary(const Expr *E);
+
+/// Checks whether a macro flag is present in the given argument. Only considers
+/// cases of single match or match in a binary OR expression. For example,
+/// <needed-flag> or <flag> | <needed-flag> | ...
+bool exprHasBitFlagWithSpelling(const Expr *Flags, const SourceManager &SM,
+                                const LangOptions &LangOpts,
+                                StringRef FlagName);
 } // namespace utils
 } // namespace tidy
 } // namespace clang

clang-tools-extra/docs/ReleaseNotes.rst

@@ -73,6 +73,12 @@ Improvements to clang-tidy
 
   Checks if the required mode ``e`` exists in the mode argument of ``fopen()``.
 
+- New `android-cloexec-socket
+  <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-socket.html>`_ check
+
+  Checks if the required file flag ``SOCK_CLOEXEC`` is present in the argument of
+  ``socket()``.
+
 - New `cert-dcl21-cpp
   <http://clang.llvm.org/extra/clang-tidy/checks/cert-dcl21-cpp.html>`_ check
 

clang-tools-extra/docs/clang-tidy/checks/android-cloexec-socket.rst

@@ -0,0 +1,18 @@
+.. title:: clang-tidy - android-cloexec-socket
+
+android-cloexec-socket
+======================
+
+``socket()`` should include ``SOCK_CLOEXEC`` in its type argument to avoid the
+file descriptor leakage. Without this flag, an opened sensitive file would
+remain open across a fork+exec to a lower-privileged SELinux domain.
+
+Examples:
+
+.. code-block:: c++
+
+  socket(domain, type, SOCK_STREAM);
+
+  // becomes
+
+  socket(domain, type, SOCK_STREAM | SOCK_CLOEXEC);

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -7,6 +7,7 @@ Clang-Tidy Checks
    android-cloexec-creat
    android-cloexec-fopen
    android-cloexec-open
+   android-cloexec-socket
    boost-use-to-string
    cert-dcl03-c (redirects to misc-static-assert) <cert-dcl03-c>
    cert-dcl21-cpp

clang-tools-extra/test/clang-tidy/android-cloexec-socket.cpp

@@ -0,0 +1,75 @@
+// RUN: %check_clang_tidy %s android-cloexec-socket %t
+
+#define SOCK_STREAM 1
+#define SOCK_DGRAM 2
+#define __O_CLOEXEC 3
+#define SOCK_CLOEXEC __O_CLOEXEC
+#define TEMP_FAILURE_RETRY(exp) \
+  ({                            \
+    int _rc;                    \
+    do {                        \
+      _rc = (exp);              \
+    } while (_rc == -1);        \
+  })
+
+extern "C" int socket(int domain, int type, int protocol);
+
+void a() {
+  socket(0, SOCK_STREAM, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: 'socket' should use SOCK_CLOEXEC where possible [android-cloexec-socket]
+  // CHECK-FIXES: socket(0, SOCK_STREAM | SOCK_CLOEXEC, 0)
+  TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM, 0));
+  // CHECK-MESSAGES: :[[@LINE-1]]:43: warning: 'socket'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_CLOEXEC, 0))
+  socket(0, SOCK_STREAM | SOCK_DGRAM, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:37: warning: 'socket'
+  // CHECK-FIXES: socket(0, SOCK_STREAM | SOCK_DGRAM | SOCK_CLOEXEC, 0)
+  TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_DGRAM, 0));
+  // CHECK-MESSAGES: :[[@LINE-1]]:56: warning: 'socket'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_DGRAM | SOCK_CLOEXEC, 0))
+}
+
+void f() {
+  socket(0, 3, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: 'socket'
+  // CHECK-FIXES: socket(0, 3 | SOCK_CLOEXEC, 0)
+  TEMP_FAILURE_RETRY(socket(0, 3, 0));
+  // CHECK-MESSAGES: :[[@LINE-1]]:33: warning: 'socket'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(socket(0, 3 | SOCK_CLOEXEC, 0))
+
+  int flag = 3;
+  socket(0, flag, 0);
+  TEMP_FAILURE_RETRY(socket(0, flag, 0));
+}
+
+namespace i {
+int socket(int domain, int type, int protocol);
+
+void d() {
+  socket(0, SOCK_STREAM, 0);
+  TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM, 0));
+  socket(0, SOCK_STREAM | SOCK_DGRAM, 0);
+  TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_DGRAM, 0));
+}
+
+} // namespace i
+
+void e() {
+  socket(0, SOCK_CLOEXEC, 0);
+  TEMP_FAILURE_RETRY(socket(0, SOCK_CLOEXEC, 0));
+  socket(0, SOCK_STREAM | SOCK_CLOEXEC, 0);
+  TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_CLOEXEC, 0));
+  socket(0, SOCK_STREAM | SOCK_CLOEXEC | SOCK_DGRAM, 0);
+  TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_CLOEXEC | SOCK_DGRAM, 0));
+}
+
+class G {
+public:
+  int socket(int domain, int type, int protocol);
+  void d() {
+    socket(0, SOCK_STREAM, 0);
+    TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM, 0));
+    socket(0, SOCK_STREAM | SOCK_DGRAM, 0);
+    TEMP_FAILURE_RETRY(socket(0, SOCK_STREAM | SOCK_DGRAM, 0));
+  }
+};