[clang] 289725f - [analyzer] New optin.taint.TaintedAlloc checker for catching unbounded memory allocation calls (#92420)
via cfe-commits
cfe-commits at lists.llvm.org
Wed Jun 5 07:33:34 PDT 2024
Author: Daniel Krupp
Date: 2024-06-05T16:33:31+02:00
New Revision: 289725f11c579348ec49c8c606de4291314db0d9
URL: https://github.com/llvm/llvm-project/commit/289725f11c579348ec49c8c606de4291314db0d9
DIFF: https://github.com/llvm/llvm-project/commit/289725f11c579348ec49c8c606de4291314db0d9.diff
LOG: [analyzer] New optin.taint.TaintedAlloc checker for catching unbounded memory allocation calls (#92420)
A new optional checker (optin.taint.TaintedAlloc) will warn if a memory
allocation function (malloc, calloc, realloc, alloca, operator new[]) is
called with a tainted (attacker controlled) size parameter.
A large, maliciously set size value can trigger memory exhaustion. To
get this warning, the alpha.security.taint.TaintPropagation checker also
needs to be switched on.
The warning will only be emitted, if the analyzer cannot prove that the
size is below reasonable bounds (<SIZE_MAX/4).
Added:
Modified:
clang/docs/analyzer/checkers.rst
clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
clang/test/Analysis/malloc.c
clang/test/Analysis/malloc.cpp
clang/test/Analysis/taint-diagnostic-visitor.c
Removed:
################################################################################
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index 1ae6e9c000420..f53dd545df5a9 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -599,7 +599,7 @@ Warns when a nullable pointer is returned from a function that has _Nonnull retu
optin
^^^^^
-Checkers for portability, performance or coding style specific rules.
+Checkers for portability, performance, optional security and coding style specific rules.
.. _optin-core-EnumCastOutOfRange:
@@ -938,6 +938,53 @@ optin.portability.UnixAPI
"""""""""""""""""""""""""
Finds implementation-defined behavior in UNIX/Posix functions.
+.. _optin-taint-TaintedAlloc:
+
+optin.taint.TaintedAlloc (C, C++)
+"""""""""""""""""""""""""""""""""
+
+This checker warns for cases when the ``size`` parameter of the ``malloc`` ,
+``calloc``, ``realloc``, ``alloca`` or the size parameter of the
+array new C++ operator is tainted (potentially attacker controlled).
+If an attacker can inject a large value as the size parameter, memory exhaustion
+denial of service attack can be carried out.
+
+The ``alpha.security.taint.TaintPropagation`` checker also needs to be enabled for
+this checker to give warnings.
+
+The analyzer emits warning only if it cannot prove that the size parameter is
+within reasonable bounds (``<= SIZE_MAX/4``). This functionality partially
+covers the SEI Cert coding standard rule `INT04-C
+<https://wiki.sei.cmu.edu/confluence/display/c/INT04-C.+Enforce+limits+on+integer+values+originating+from+tainted+sources>`_.
+
+You can silence this warning either by bound checking the ``size`` parameter, or
+by explicitly marking the ``size`` parameter as sanitized. See the
+:ref:`alpha-security-taint-TaintPropagation` checker for more details.
+
+.. code-block:: c
+
+ void vulnerable(void) {
+ size_t size = 0;
+ scanf("%zu", &size);
+ int *p = malloc(size); // warn: malloc is called with a tainted (potentially attacker controlled) value
+ free(p);
+ }
+
+ void not_vulnerable(void) {
+ size_t size = 0;
+ scanf("%zu", &size);
+ if (1024 < size)
+ return;
+ int *p = malloc(size); // No warning expected as the the user input is bound
+ free(p);
+ }
+
+ void vulnerable_cpp(void) {
+ size_t size = 0;
+ scanf("%zu", &size);
+ int *ptr = new int[size];// warn: Memory allocation function is called with a tainted (potentially attacker controlled) value
+ delete[] ptr;
+ }
.. _security-checkers:
diff --git a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
index 636eeb45f9980..a7f62ef7f2d07 100644
--- a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -36,6 +36,7 @@ def CoreAlpha : Package<"core">, ParentPackage<Alpha>;
// Note: OptIn is *not* intended for checkers that are too noisy to be on by
// default. Such checkers belong in the alpha package.
def OptIn : Package<"optin">;
+
def CoreOptIn : Package<"core">, ParentPackage<OptIn>;
// In the Portability package reside checkers for finding code that relies on
@@ -43,6 +44,9 @@ def CoreOptIn : Package<"core">, ParentPackage<OptIn>;
// development, but unwanted for developers who target only a single platform.
def PortabilityOptIn : Package<"portability">, ParentPackage<OptIn>;
+// Optional checkers related to taint security analysis.
+def TaintOptIn : Package<"taint">, ParentPackage<OptIn>;
+
def Nullability : Package<"nullability">,
PackageOptions<[
CmdLineOption<Boolean,
@@ -1718,6 +1722,23 @@ def UnixAPIPortabilityChecker : Checker<"UnixAPI">,
} // end optin.portability
+
+//===----------------------------------------------------------------------===//
+// Taint checkers.
+//===----------------------------------------------------------------------===//
+
+let ParentPackage = TaintOptIn in {
+
+def TaintedAllocChecker: Checker<"TaintedAlloc">,
+ HelpText<"Check for memory allocations, where the size parameter "
+ "might be a tainted (attacker controlled) value.">,
+ Dependencies<[DynamicMemoryModeling]>,
+ //FIXME: GenericTaintChecker should be a dependency, but only after it
+ //is transformed into a modeling checker
+ Documentation<HasDocumentation>;
+
+} // end "optin.taint"
+
//===----------------------------------------------------------------------===//
// NonDeterminism checkers.
//===----------------------------------------------------------------------===//
diff --git a/clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
index 34af7fb131f5a..467cf8889b6d3 100644
--- a/clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
@@ -60,6 +60,7 @@
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/Lexer.h"
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/StaticAnalyzer/Checkers/Taint.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
@@ -322,6 +323,7 @@ class MallocChecker
CK_NewDeleteLeaksChecker,
CK_MismatchedDeallocatorChecker,
CK_InnerPointerChecker,
+ CK_TaintedAllocChecker,
CK_NumCheckKinds
};
@@ -365,6 +367,7 @@ class MallocChecker
mutable std::unique_ptr<BugType> BT_MismatchedDealloc;
mutable std::unique_ptr<BugType> BT_OffsetFree[CK_NumCheckKinds];
mutable std::unique_ptr<BugType> BT_UseZerroAllocated[CK_NumCheckKinds];
+ mutable std::unique_ptr<BugType> BT_TaintedAlloc;
#define CHECK_FN(NAME) \
void NAME(const CallEvent &Call, CheckerContext &C) const;
@@ -462,6 +465,13 @@ class MallocChecker
};
bool isMemCall(const CallEvent &Call) const;
+ void reportTaintBug(StringRef Msg, ProgramStateRef State, CheckerContext &C,
+ llvm::ArrayRef<SymbolRef> TaintedSyms,
+ AllocationFamily Family) const;
+
+ void checkTaintedness(CheckerContext &C, const CallEvent &Call,
+ const SVal SizeSVal, ProgramStateRef State,
+ AllocationFamily Family) const;
// TODO: Remove mutable by moving the initializtaion to the registry function.
mutable std::optional<uint64_t> KernelZeroFlagVal;
@@ -521,9 +531,9 @@ class MallocChecker
/// malloc leaves it undefined.
/// \param [in] State The \c ProgramState right before allocation.
/// \returns The ProgramState right after allocation.
- [[nodiscard]] static ProgramStateRef
+ [[nodiscard]] ProgramStateRef
MallocMemAux(CheckerContext &C, const CallEvent &Call, const Expr *SizeEx,
- SVal Init, ProgramStateRef State, AllocationFamily Family);
+ SVal Init, ProgramStateRef State, AllocationFamily Family) const;
/// Models memory allocation.
///
@@ -534,9 +544,10 @@ class MallocChecker
/// malloc leaves it undefined.
/// \param [in] State The \c ProgramState right before allocation.
/// \returns The ProgramState right after allocation.
- [[nodiscard]] static ProgramStateRef
- MallocMemAux(CheckerContext &C, const CallEvent &Call, SVal Size, SVal Init,
- ProgramStateRef State, AllocationFamily Family);
+ [[nodiscard]] ProgramStateRef MallocMemAux(CheckerContext &C,
+ const CallEvent &Call, SVal Size,
+ SVal Init, ProgramStateRef State,
+ AllocationFamily Family) const;
// Check if this malloc() for special flags. At present that means M_ZERO or
// __GFP_ZERO (in which case, treat it like calloc).
@@ -649,8 +660,9 @@ class MallocChecker
/// \param [in] Call The expression that reallocated memory
/// \param [in] State The \c ProgramState right before reallocation.
/// \returns The ProgramState right after allocation.
- [[nodiscard]] static ProgramStateRef
- CallocMem(CheckerContext &C, const CallEvent &Call, ProgramStateRef State);
+ [[nodiscard]] ProgramStateRef CallocMem(CheckerContext &C,
+ const CallEvent &Call,
+ ProgramStateRef State) const;
/// See if deallocation happens in a suspicious context. If so, escape the
/// pointers that otherwise would have been deallocated and return true.
@@ -1695,6 +1707,11 @@ MallocChecker::processNewAllocation(const CXXAllocatorCall &Call,
// MallocUpdateRefState() instead of MallocMemAux() which breaks the
// existing binding.
SVal Target = Call.getObjectUnderConstruction();
+ if (Call.getOriginExpr()->isArray()) {
+ if (auto SizeEx = NE->getArraySize())
+ checkTaintedness(C, Call, C.getSVal(*SizeEx), State, AF_CXXNewArray);
+ }
+
State = MallocUpdateRefState(C, NE, State, Family, Target);
State = ProcessZeroAllocCheck(Call, 0, State, Target);
return State;
@@ -1779,7 +1796,7 @@ ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
const CallEvent &Call,
const Expr *SizeEx, SVal Init,
ProgramStateRef State,
- AllocationFamily Family) {
+ AllocationFamily Family) const {
if (!State)
return nullptr;
@@ -1787,10 +1804,66 @@ ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
return MallocMemAux(C, Call, C.getSVal(SizeEx), Init, State, Family);
}
+void MallocChecker::reportTaintBug(StringRef Msg, ProgramStateRef State,
+ CheckerContext &C,
+ llvm::ArrayRef<SymbolRef> TaintedSyms,
+ AllocationFamily Family) const {
+ if (ExplodedNode *N = C.generateNonFatalErrorNode(State, this)) {
+ if (!BT_TaintedAlloc)
+ BT_TaintedAlloc.reset(new BugType(CheckNames[CK_TaintedAllocChecker],
+ "Tainted Memory Allocation",
+ categories::TaintedData));
+ auto R = std::make_unique<PathSensitiveBugReport>(*BT_TaintedAlloc, Msg, N);
+ for (auto TaintedSym : TaintedSyms) {
+ R->markInteresting(TaintedSym);
+ }
+ C.emitReport(std::move(R));
+ }
+}
+
+void MallocChecker::checkTaintedness(CheckerContext &C, const CallEvent &Call,
+ const SVal SizeSVal, ProgramStateRef State,
+ AllocationFamily Family) const {
+ if (!ChecksEnabled[CK_TaintedAllocChecker])
+ return;
+ std::vector<SymbolRef> TaintedSyms =
+ taint::getTaintedSymbols(State, SizeSVal);
+ if (TaintedSyms.empty())
+ return;
+
+ SValBuilder &SVB = C.getSValBuilder();
+ QualType SizeTy = SVB.getContext().getSizeType();
+ QualType CmpTy = SVB.getConditionType();
+ // In case the symbol is tainted, we give a warning if the
+ // size is larger than SIZE_MAX/4
+ BasicValueFactory &BVF = SVB.getBasicValueFactory();
+ const llvm::APSInt MaxValInt = BVF.getMaxValue(SizeTy);
+ NonLoc MaxLength =
+ SVB.makeIntVal(MaxValInt / APSIntType(MaxValInt).getValue(4));
+ std::optional<NonLoc> SizeNL = SizeSVal.getAs<NonLoc>();
+ auto Cmp = SVB.evalBinOpNN(State, BO_GE, *SizeNL, MaxLength, CmpTy)
+ .getAs<DefinedOrUnknownSVal>();
+ if (!Cmp)
+ return;
+ auto [StateTooLarge, StateNotTooLarge] = State->assume(*Cmp);
+ if (!StateTooLarge && StateNotTooLarge) {
+ // We can prove that size is not too large so there is no issue.
+ return;
+ }
+
+ std::string Callee = "Memory allocation function";
+ if (Call.getCalleeIdentifier())
+ Callee = Call.getCalleeIdentifier()->getName().str();
+ reportTaintBug(
+ Callee + " is called with a tainted (potentially attacker controlled) "
+ "value. Make sure the value is bound checked.",
+ State, C, TaintedSyms, Family);
+}
+
ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
const CallEvent &Call, SVal Size,
SVal Init, ProgramStateRef State,
- AllocationFamily Family) {
+ AllocationFamily Family) const {
if (!State)
return nullptr;
@@ -1819,9 +1892,7 @@ ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
if (Size.isUndef())
Size = UnknownVal();
- // TODO: If Size is tainted and we cannot prove that it is within
- // reasonable bounds, emit a warning that an attacker may
- // provoke a memory exhaustion error.
+ checkTaintedness(C, Call, Size, State, AF_Malloc);
// Set the region's extent.
State = setDynamicExtent(State, RetVal.getAsRegion(),
@@ -2761,7 +2832,7 @@ MallocChecker::ReallocMemAux(CheckerContext &C, const CallEvent &Call,
ProgramStateRef MallocChecker::CallocMem(CheckerContext &C,
const CallEvent &Call,
- ProgramStateRef State) {
+ ProgramStateRef State) const {
if (!State)
return nullptr;
@@ -3734,3 +3805,4 @@ REGISTER_CHECKER(MallocChecker)
REGISTER_CHECKER(NewDeleteChecker)
REGISTER_CHECKER(NewDeleteLeaksChecker)
REGISTER_CHECKER(MismatchedDeallocatorChecker)
+REGISTER_CHECKER(TaintedAllocChecker)
diff --git a/clang/test/Analysis/malloc.c b/clang/test/Analysis/malloc.c
index e5cb45ba73352..8ee29aeb324f7 100644
--- a/clang/test/Analysis/malloc.c
+++ b/clang/test/Analysis/malloc.c
@@ -3,7 +3,9 @@
// RUN: -analyzer-checker=alpha.deadcode.UnreachableCode \
// RUN: -analyzer-checker=alpha.core.CastSize \
// RUN: -analyzer-checker=unix \
-// RUN: -analyzer-checker=debug.ExprInspection
+// RUN: -analyzer-checker=debug.ExprInspection \
+// RUN: -analyzer-checker=alpha.security.taint.TaintPropagation \
+// RUN: -analyzer-checker=optin.taint.TaintedAlloc
#include "Inputs/system-header-simulator.h"
@@ -48,6 +50,45 @@ void myfoo(int *p);
void myfooint(int p);
char *fooRetPtr(void);
+void t1(void) {
+ size_t size = 0;
+ scanf("%zu", &size);
+ int *p = malloc(size); // expected-warning{{malloc is called with a tainted (potentially attacker controlled) value}}
+ free(p);
+}
+
+void t2(void) {
+ size_t size = 0;
+ scanf("%zu", &size);
+ int *p = calloc(size,2); // expected-warning{{calloc is called with a tainted (potentially attacker controlled) value}}
+ free(p);
+}
+
+void t3(void) {
+ size_t size = 0;
+ scanf("%zu", &size);
+ if (1024 < size)
+ return;
+ int *p = malloc(size); // No warning expected as the the user input is bound
+ free(p);
+}
+
+void t4(void) {
+ size_t size = 0;
+ int *p = malloc(sizeof(int));
+ scanf("%zu", &size);
+ p = (int*) realloc((void*) p, size); // expected-warning{{realloc is called with a tainted (potentially attacker controlled) value}}
+ free(p);
+}
+
+void t5(void) {
+ size_t size = 0;
+ int *p = alloca(sizeof(int));
+ scanf("%zu", &size);
+ p = (int*) alloca(size); // expected-warning{{alloca is called with a tainted (potentially attacker controlled) value}}
+}
+
+
void f1(void) {
int *p = malloc(12);
return; // expected-warning{{Potential leak of memory pointed to by 'p'}}
diff --git a/clang/test/Analysis/malloc.cpp b/clang/test/Analysis/malloc.cpp
index 300b344ab25d6..7af1b59e04a5a 100644
--- a/clang/test/Analysis/malloc.cpp
+++ b/clang/test/Analysis/malloc.cpp
@@ -3,7 +3,9 @@
// RUN: -analyzer-checker=alpha.deadcode.UnreachableCode \
// RUN: -analyzer-checker=alpha.core.CastSize \
// RUN: -analyzer-checker=unix.Malloc \
-// RUN: -analyzer-checker=cplusplus.NewDelete
+// RUN: -analyzer-checker=cplusplus.NewDelete \
+// RUN: -analyzer-checker=alpha.security.taint.TaintPropagation \
+// RUN: -analyzer-checker=optin.taint.TaintedAlloc
// RUN: %clang_analyze_cc1 -w -verify %s \
// RUN: -triple i386-unknown-linux-gnu \
@@ -11,14 +13,18 @@
// RUN: -analyzer-checker=alpha.deadcode.UnreachableCode \
// RUN: -analyzer-checker=alpha.core.CastSize \
// RUN: -analyzer-checker=unix.Malloc \
-// RUN: -analyzer-checker=cplusplus.NewDelete
+// RUN: -analyzer-checker=cplusplus.NewDelete \
+// RUN: -analyzer-checker=alpha.security.taint.TaintPropagation \
+// RUN: -analyzer-checker=optin.taint.TaintedAlloc
// RUN: %clang_analyze_cc1 -w -verify %s -DTEST_INLINABLE_ALLOCATORS \
// RUN: -analyzer-checker=core \
// RUN: -analyzer-checker=alpha.deadcode.UnreachableCode \
// RUN: -analyzer-checker=alpha.core.CastSize \
// RUN: -analyzer-checker=unix.Malloc \
-// RUN: -analyzer-checker=cplusplus.NewDelete
+// RUN: -analyzer-checker=cplusplus.NewDelete \
+// RUN: -analyzer-checker=alpha.security.taint.TaintPropagation \
+// RUN: -analyzer-checker=optin.taint.TaintedAlloc
// RUN: %clang_analyze_cc1 -w -verify %s -DTEST_INLINABLE_ALLOCATORS \
// RUN: -triple i386-unknown-linux-gnu \
@@ -26,7 +32,9 @@
// RUN: -analyzer-checker=alpha.deadcode.UnreachableCode \
// RUN: -analyzer-checker=alpha.core.CastSize \
// RUN: -analyzer-checker=unix.Malloc \
-// RUN: -analyzer-checker=cplusplus.NewDelete
+// RUN: -analyzer-checker=cplusplus.NewDelete \
+// RUN: -analyzer-checker=alpha.security.taint.TaintPropagation \
+// RUN: -analyzer-checker=optin.taint.TaintedAlloc
#include "Inputs/system-header-simulator-cxx.h"
@@ -36,6 +44,14 @@ void free(void *);
void *realloc(void *ptr, size_t size);
void *calloc(size_t nmemb, size_t size);
char *strdup(const char *s);
+int scanf( const char* format, ... );
+
+void taintAlloc() {
+ size_t size = 0;
+ scanf("%zu", &size);
+ int *ptr = new int[size];// expected-warning{{Memory allocation function is called with a tainted (potentially attacker controlled) value}}
+ delete[] ptr;
+}
void checkThatMallocCheckerIsRunning() {
malloc(4);
diff --git a/clang/test/Analysis/taint-diagnostic-visitor.c b/clang/test/Analysis/taint-diagnostic-visitor.c
index b8b3710a7013e..f51423646e8ae 100644
--- a/clang/test/Analysis/taint-diagnostic-visitor.c
+++ b/clang/test/Analysis/taint-diagnostic-visitor.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -analyze -analyzer-checker=alpha.security.taint,core,alpha.security.ArrayBoundV2 -analyzer-output=text -verify %s
+// RUN: %clang_cc1 -analyze -analyzer-checker=alpha.security.taint,core,alpha.security.ArrayBoundV2,optin.taint.TaintedAlloc -analyzer-output=text -verify %s
// This file is for testing enhanced diagnostics produced by the GenericTaintChecker
@@ -115,3 +115,12 @@ void multipleTaintedArgs(void) {
system(buf); // expected-warning {{Untrusted data is passed to a system call}}
// expected-note at -1{{Untrusted data is passed to a system call}}
}
+
+void testTaintedMalloc(){
+ size_t size = 0;
+ scanf("%zu", &size); // expected-note {{Taint originated here}}
+ // expected-note at -1 {{Taint propagated to the 2nd argument}}
+ int *p = malloc(size);// expected-warning{{malloc is called with a tainted (potentially attacker controlled) value}}
+ // expected-note at -1{{malloc is called with a tainted (potentially attacker controlled) value}}
+ free(p);
+}
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