devnexen updated this revision to Diff 133564.
Repository:
rC Clang
https://reviews.llvm.org/D42645
Files:
include/clang/StaticAnalyzer/Checkers/Checkers.td
lib/StaticAnalyzer/Checkers/CMakeLists.txt
lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
test/Analysis/mmap-writeexec.c
Index: test/Analysis/mmap-writeexec.c
===================================================================
--- test/Analysis/mmap-writeexec.c
+++ test/Analysis/mmap-writeexec.c
@@ -0,0 +1,36 @@
+// RUN: %clang_analyze_cc1 -triple i686-unknown-linux -analyzer-checker=security.MmapWriteExec -analyzer-config security.MmapWriteExec:MmapProtExec=1 -analyzer-config security.MmapWriteExec:MmapProtRead=4 -DUSE_ALTERNATIVE_PROT_EXEC_DEFINITION -verify %s
+// RUN: %clang_analyze_cc1 -triple x86_64-unknown-apple-darwin10 -analyzer-checker=security.MmapWriteExec -verify %s
+
+#define PROT_WRITE 0x02
+#ifndef USE_ALTERNATIVE_PROT_EXEC_DEFINITION
+#define PROT_EXEC 0x04
+#define PROT_READ 0x01
+#else
+#define PROT_EXEC 0x01
+#define PROT_READ 0x04
+#endif
+#define MAP_PRIVATE 0x0002
+#define MAP_ANON 0x1000
+#define MAP_FIXED 0x0010
+#define NULL ((void *)0)
+
+typedef __typeof(sizeof(int)) size_t;
+void *mmap(void *, size_t, int, int, int, long);
+
+void f1()
+{
+ void *a = mmap(NULL, 16, PROT_READ | PROT_EXEC, MAP_PRIVATE | MAP_ANON, -1, 0); // no-warning
+ void *b = mmap(a, 16, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED | MAP_ANON, -1, 0); // no-warning
+ void *c = mmap(NULL, 32, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANON, -1, 0); // expected-warning{{Both PROT_WRITE and PROT_EXEC flags are set. This can lead to exploitable memory regions, which could be overwritten with malicious code}}
+ (void)a;
+ (void)b;
+ (void)c;
+}
+
+void f2()
+{
+ void *(*callm)(void *, size_t, int, int, int, long);
+ callm = mmap;
+ int prot = PROT_WRITE | PROT_EXEC;
+ (void)callm(NULL, 1024, prot, MAP_PRIVATE | MAP_ANON, -1, 0); // expected-warning{{Both PROT_WRITE and PROT_EXEC flags are set. This can lead to exploitable memory regions, which could be overwritten with malicious code}}
+}
Index: lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
+++ lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
@@ -0,0 +1,87 @@
+// MmapWriteExecChecker.cpp - Check for the prot argument -----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This checker tests the 3rd argument of mmap's calls to check if
+// it is writable and executable in the same time. It's somehow
+// an optional checker since for example in JIT libraries it is pretty common.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.h"
+
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+
+using namespace clang;
+using namespace ento;
+using llvm::APSInt;
+
+namespace {
+class MmapWriteExecChecker : public Checker<check::PreCall> {
+ CallDescription MmapFn;
+ static int ProtWrite;
+ static int ProtExec;
+ static int ProtRead;
+ mutable std::unique_ptr<BugType> BT;
+public:
+ MmapWriteExecChecker() : MmapFn("mmap", 6) {}
+ void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
+ int ProtExecOv;
+ int ProtReadOv;
+};
+}
+
+int MmapWriteExecChecker::ProtWrite = 0x02;
+int MmapWriteExecChecker::ProtExec = 0x04;
+int MmapWriteExecChecker::ProtRead = 0x01;
+
+void MmapWriteExecChecker::checkPreCall(const CallEvent &Call,
+ CheckerContext &C) const {
+ if (Call.isCalled(MmapFn)) {
+ SVal ProtVal = Call.getArgSVal(2);
+ Optional<nonloc::ConcreteInt> ProtLoc = ProtVal.getAs<nonloc::ConcreteInt>();
+ int64_t Prot = ProtLoc->getValue().getSExtValue();
+ if (ProtExecOv != ProtExec)
+ ProtExec = ProtExecOv;
+ if (ProtReadOv != ProtRead)
+ ProtRead = ProtReadOv;
+
+ // Wrong settings
+ if (ProtRead == ProtExec)
+ return;
+
+ if ((Prot & (ProtWrite | ProtExec)) == (ProtWrite | ProtExec)) {
+ if (!BT)
+ BT.reset(new BugType(this, "W^X check fails, Write Exec prot flags set", "Security"));
+
+ ExplodedNode *N = C.generateNonFatalErrorNode();
+ if (!N)
+ return;
+
+ auto Report = llvm::make_unique<BugReport>(
+ *BT, "Both PROT_WRITE and PROT_EXEC flags are set. This can "
+ "lead to exploitable memory regions, which could be overwritten "
+ "with malicious code", N);
+ Report->addRange(Call.getArgSourceRange(2));
+ C.emitReport(std::move(Report));
+ }
+ }
+}
+
+void ento::registerMmapWriteExecChecker(CheckerManager &mgr) {
+ MmapWriteExecChecker *Mwec =
+ mgr.registerChecker<MmapWriteExecChecker>();
+ Mwec->ProtExecOv =
+ mgr.getAnalyzerOptions().getOptionAsInteger("MmapProtExec", 0x04, Mwec);
+ Mwec->ProtReadOv =
+ mgr.getAnalyzerOptions().getOptionAsInteger("MmapProtRead", 0x01, Mwec);
+}
Index: lib/StaticAnalyzer/Checkers/CMakeLists.txt
===================================================================
--- lib/StaticAnalyzer/Checkers/CMakeLists.txt
+++ lib/StaticAnalyzer/Checkers/CMakeLists.txt
@@ -49,6 +49,7 @@
MallocChecker.cpp
MallocOverflowSecurityChecker.cpp
MallocSizeofChecker.cpp
+ MmapWriteExecChecker.cpp
MisusedMovedObjectChecker.cpp
MPI-Checker/MPIBugReporter.cpp
MPI-Checker/MPIChecker.cpp
Index: include/clang/StaticAnalyzer/Checkers/Checkers.td
===================================================================
--- include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -394,6 +394,10 @@
def FloatLoopCounter : Checker<"FloatLoopCounter">,
HelpText<"Warn on using a floating point value as a loop counter (CERT: FLP30-C, FLP30-CPP)">,
DescFile<"CheckSecuritySyntaxOnly.cpp">;
+
+ def MmapWriteExecChecker : Checker<"MmapWriteExec">,
+ HelpText<"Warn on mmap() calls that are both writable and executable">,
+ DescFile<"MmapWriteExecChecker.cpp">;
}
let ParentPackage = SecurityAlpha in {
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