[clang] [analyzer][clangsa] Add new option to alpha.security.cert.InvalidPtrChecker (PR #67663)
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Thu Sep 28 05:06:19 PDT 2023
Endre =?utf-8?q?Fülöp?= <endre.fulop at sigmatechnology.se>,
Endre =?utf-8?q?Fülöp?= <endre.fulop at sigmatechnology.se>,
Endre =?utf-8?q?Fülöp?= <endre.fulop at sigmatechnology.se>,
Endre =?utf-8?q?Fülöp?= <endre.fulop at sigmatechnology.se>,
Endre =?utf-8?q?Fülöp?= <endre.fulop at sigmatechnology.se>,
Endre =?utf-8?q?Fülöp?= <endre.fulop at sigmatechnology.se>
Message-ID:
In-Reply-To: <llvm/llvm-project/pull/67663/clang at github.com>
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
<details>
<summary>Changes</summary>
**This PR is a continuation of the Phabricator review https://reviews.llvm.org/D154603**
The invalidation of pointer pointers returned by subsequent calls to genenv is
suggested by the POSIX standard, but is too strict from a practical point of
view. A new checker option 'InvalidatingGetEnv' is introduced, and is set to a
more lax default value, which does not consider consecutive getenv calls
invalidating.
The handling of the main function's possible specification where an environment
pointer is also pecified as a third parameter is also considered now.
---
Full diff: https://github.com/llvm/llvm-project/pull/67663.diff
7 Files Affected:
- (modified) clang/docs/analyzer/checkers.rst (+23-2)
- (modified) clang/include/clang/StaticAnalyzer/Checkers/Checkers.td (+9)
- (modified) clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp (+89-30)
- (modified) clang/test/Analysis/analyzer-config.c (+1)
- (modified) clang/test/Analysis/cert/env34-c-cert-examples.c (+37-3)
- (modified) clang/test/Analysis/cert/env34-c.c (+1)
- (added) clang/test/Analysis/invalid-ptr-checker.c (+50)
``````````diff
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index dbd6d7787823530..1487714c72f239c 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -2399,13 +2399,34 @@ pointer. These functions include: getenv, localeconv, asctime, setlocale, strerr
char *p, *pp;
p = getenv("VAR");
- pp = getenv("VAR2");
- // subsequent call to 'getenv' invalidated previous one
+ setenv("SOMEVAR", "VALUE", /*overwrite*/1);
+ // call to 'setenv' may invalidate p
*p;
// dereferencing invalid pointer
}
+
+The ``InvalidatingGetEnv`` option is available for treating getenv calls as
+invalidating. When enabled, the checker issues a warning if getenv is called
+multiple times and their results are used without first creating a copy.
+This level of strictness might be considered overly pedantic for a standard
+getenv implementation.
+
+To enable this option, use:
+``-analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true``.
+
+By default, this option is set to *false*.
+
+When this option is enabled, warnings will be generated for scenarios like the
+following:
+
+.. code-block:: c
+
+ char* p = getenv("VAR");
+ char* pp = getenv("VAR2"); // assumes this call can invalidate `env`
+ strlen(p); // warns about accessing invalid ptr
+
alpha.security.taint
^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
index 65c1595eb6245dd..b4f65c934bf483b 100644
--- a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -997,6 +997,15 @@ let ParentPackage = ENV in {
def InvalidPtrChecker : Checker<"InvalidPtr">,
HelpText<"Finds usages of possibly invalidated pointers">,
+ CheckerOptions<[
+ CmdLineOption<Boolean,
+ "InvalidatingGetEnv",
+ "Regard getenv as an invalidating call (as per POSIX "
+ "standard), which can lead to false positives depending on "
+ "implementation.",
+ "false",
+ InAlpha>,
+ ]>,
Documentation<HasDocumentation>;
} // end "alpha.cert.env"
diff --git a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
index aae1a17bc0ae53e..ac879a208e4e962 100644
--- a/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/cert/InvalidPtrChecker.cpp
@@ -25,12 +25,20 @@
using namespace clang;
using namespace ento;
+
namespace {
+
class InvalidPtrChecker
: public Checker<check::Location, check::BeginFunction, check::PostCall> {
private:
- BugType BT{this, "Use of invalidated pointer", categories::MemoryError};
+ static const BugType *InvalidPtrBugType;
+ // For accurate emission of NoteTags, the BugType of this checker should have
+ // a unique address.
+ void InitInvalidPtrBugType() {
+ InvalidPtrBugType = new BugType(this, "Use of invalidated pointer",
+ categories::MemoryError);
+ }
void EnvpInvalidatingCall(const CallEvent &Call, CheckerContext &C) const;
@@ -38,6 +46,15 @@ class InvalidPtrChecker
CheckerContext &C) const;
// SEI CERT ENV31-C
+
+ // If set to true, consider getenv calls as invalidating operations on the
+ // environment variable buffer. This is implied in the standard, but in
+ // practice does not cause problems (in the commonly used environments).
+ bool InvalidatingGetEnv = false;
+
+ // GetEnv can be treated invalidating and non-invalidating as well.
+ const CallDescription GetEnvCall{{"getenv"}, 1};
+
const CallDescriptionMap<HandlerFn> EnvpInvalidatingFunctions = {
{{{"setenv"}, 3}, &InvalidPtrChecker::EnvpInvalidatingCall},
{{{"unsetenv"}, 1}, &InvalidPtrChecker::EnvpInvalidatingCall},
@@ -51,7 +68,6 @@ class InvalidPtrChecker
// SEI CERT ENV34-C
const CallDescriptionMap<HandlerFn> PreviousCallInvalidatingFunctions = {
- {{{"getenv"}, 1}, &InvalidPtrChecker::postPreviousReturnInvalidatingCall},
{{{"setlocale"}, 2},
&InvalidPtrChecker::postPreviousReturnInvalidatingCall},
{{{"strerror"}, 1},
@@ -62,6 +78,10 @@ class InvalidPtrChecker
&InvalidPtrChecker::postPreviousReturnInvalidatingCall},
};
+ // The private members of this checker corresponding to commandline options
+ // are set in this function.
+ friend void ento::registerInvalidPtrChecker(CheckerManager &);
+
public:
// Obtain the environment pointer from 'main()' (if present).
void checkBeginFunction(CheckerContext &C) const;
@@ -78,13 +98,18 @@ class InvalidPtrChecker
CheckerContext &C) const;
};
+const BugType *InvalidPtrChecker::InvalidPtrBugType;
+
} // namespace
// Set of memory regions that were invalidated
REGISTER_SET_WITH_PROGRAMSTATE(InvalidMemoryRegions, const MemRegion *)
// Stores the region of the environment pointer of 'main' (if present).
-REGISTER_TRAIT_WITH_PROGRAMSTATE(EnvPtrRegion, const MemRegion *)
+REGISTER_TRAIT_WITH_PROGRAMSTATE(MainEnvPtrRegion, const MemRegion *)
+
+// Stores the regions of environments returned by getenv calls.
+REGISTER_SET_WITH_PROGRAMSTATE(GetenvEnvPtrRegions, const MemRegion *)
// Stores key-value pairs, where key is function declaration and value is
// pointer to memory region returned by previous call of this function
@@ -94,23 +119,40 @@ REGISTER_MAP_WITH_PROGRAMSTATE(PreviousCallResultMap, const FunctionDecl *,
void InvalidPtrChecker::EnvpInvalidatingCall(const CallEvent &Call,
CheckerContext &C) const {
StringRef FunctionName = Call.getCalleeIdentifier()->getName();
- ProgramStateRef State = C.getState();
- const MemRegion *SymbolicEnvPtrRegion = State->get<EnvPtrRegion>();
- if (!SymbolicEnvPtrRegion)
- return;
-
- State = State->add<InvalidMemoryRegions>(SymbolicEnvPtrRegion);
- const NoteTag *Note =
- C.getNoteTag([SymbolicEnvPtrRegion, FunctionName](
- PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
- if (!BR.isInteresting(SymbolicEnvPtrRegion))
- return;
- Out << '\'' << FunctionName
- << "' call may invalidate the environment parameter of 'main'";
- });
+ auto PlaceInvalidationNote = [&C, FunctionName](ProgramStateRef State,
+ const MemRegion *Region,
+ StringRef Message,
+ ExplodedNode *Pred) {
+ State = State->add<InvalidMemoryRegions>(Region);
+
+ // Make copy of string data for the time when notes are *actually* created.
+ const NoteTag *Note =
+ C.getNoteTag([Region, FunctionName = std::string{FunctionName},
+ Message = std::string{Message}](
+ PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
+ if (!BR.isInteresting(Region) ||
+ &BR.getBugType() != InvalidPtrBugType)
+ return;
+ Out << '\'' << FunctionName << "' " << Message;
+ BR.markNotInteresting(Region);
+ });
+ return C.addTransition(State, Pred, Note);
+ };
- C.addTransition(State, Note);
+ ProgramStateRef State = C.getState();
+ ExplodedNode *CurrentChainEnd = C.getPredecessor();
+
+ if (const MemRegion *MainEnvPtr = State->get<MainEnvPtrRegion>())
+ CurrentChainEnd = PlaceInvalidationNote(
+ State, MainEnvPtr,
+ "call may invalidate the environment parameter of 'main'",
+ CurrentChainEnd);
+
+ for (const MemRegion *EnvPtr : State->get<GetenvEnvPtrRegions>())
+ CurrentChainEnd = PlaceInvalidationNote(
+ State, EnvPtr, "call may invalidate the environment returned by getenv",
+ CurrentChainEnd);
}
void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
@@ -126,7 +168,7 @@ void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
State = State->add<InvalidMemoryRegions>(PrevReg);
Note = C.getNoteTag([PrevReg, FD](PathSensitiveBugReport &BR,
llvm::raw_ostream &Out) {
- if (!BR.isInteresting(PrevReg))
+ if (!BR.isInteresting(PrevReg) || &BR.getBugType() != InvalidPtrBugType)
return;
Out << '\'';
FD->getNameForDiagnostic(Out, FD->getASTContext().getLangOpts(), true);
@@ -146,16 +188,15 @@ void InvalidPtrChecker::postPreviousReturnInvalidatingCall(
// Remember to this region.
const auto *SymRegOfRetVal = cast<SymbolicRegion>(RetVal.getAsRegion());
- const MemRegion *MR =
- const_cast<MemRegion *>(SymRegOfRetVal->getBaseRegion());
+ const MemRegion *MR = SymRegOfRetVal->getBaseRegion();
State = State->set<PreviousCallResultMap>(FD, MR);
ExplodedNode *Node = C.addTransition(State, Note);
const NoteTag *PreviousCallNote =
C.getNoteTag([MR](PathSensitiveBugReport &BR, llvm::raw_ostream &Out) {
- if (!BR.isInteresting(MR))
+ if (!BR.isInteresting(MR) || &BR.getBugType() != InvalidPtrBugType)
return;
- Out << '\'' << "'previous function call was here" << '\'';
+ Out << "'previous function call was here" << '\'';
});
C.addTransition(State, Node, PreviousCallNote);
@@ -185,6 +226,18 @@ static const MemRegion *findInvalidatedSymbolicBase(ProgramStateRef State,
// function call as an argument.
void InvalidPtrChecker::checkPostCall(const CallEvent &Call,
CheckerContext &C) const {
+
+ ProgramStateRef State = C.getState();
+
+ // Model 'getenv' calls
+ if (GetEnvCall.matches(Call)) {
+ const MemRegion *Region = Call.getReturnValue().getAsRegion();
+ if (Region) {
+ State = State->add<GetenvEnvPtrRegions>(Region);
+ C.addTransition(State);
+ }
+ }
+
// Check if function invalidates 'envp' argument of 'main'
if (const auto *Handler = EnvpInvalidatingFunctions.lookup(Call))
(this->**Handler)(Call, C);
@@ -193,14 +246,16 @@ void InvalidPtrChecker::checkPostCall(const CallEvent &Call,
if (const auto *Handler = PreviousCallInvalidatingFunctions.lookup(Call))
(this->**Handler)(Call, C);
+ // If pedantic mode is on, regard 'getenv' calls invalidating as well
+ if (InvalidatingGetEnv && GetEnvCall.matches(Call))
+ postPreviousReturnInvalidatingCall(Call, C);
+
// Check if one of the arguments of the function call is invalidated
// If call was inlined, don't report invalidated argument
if (C.wasInlined)
return;
- ProgramStateRef State = C.getState();
-
for (unsigned I = 0, NumArgs = Call.getNumArgs(); I < NumArgs; ++I) {
if (const auto *SR = dyn_cast_or_null<SymbolicRegion>(
@@ -218,8 +273,8 @@ void InvalidPtrChecker::checkPostCall(const CallEvent &Call,
C.getASTContext().getPrintingPolicy());
Out << "' in a function call";
- auto Report =
- std::make_unique<PathSensitiveBugReport>(BT, Out.str(), ErrorNode);
+ auto Report = std::make_unique<PathSensitiveBugReport>(
+ *InvalidPtrBugType, Out.str(), ErrorNode);
Report->markInteresting(InvalidatedSymbolicBase);
Report->addRange(Call.getArgSourceRange(I));
C.emitReport(std::move(Report));
@@ -243,7 +298,7 @@ void InvalidPtrChecker::checkBeginFunction(CheckerContext &C) const {
// Save the memory region pointed by the environment pointer parameter of
// 'main'.
- C.addTransition(State->set<EnvPtrRegion>(EnvpReg));
+ C.addTransition(State->set<MainEnvPtrRegion>(EnvpReg));
}
// Check if invalidated region is being dereferenced.
@@ -262,13 +317,17 @@ void InvalidPtrChecker::checkLocation(SVal Loc, bool isLoad, const Stmt *S,
return;
auto Report = std::make_unique<PathSensitiveBugReport>(
- BT, "dereferencing an invalid pointer", ErrorNode);
+ *InvalidPtrBugType, "dereferencing an invalid pointer", ErrorNode);
Report->markInteresting(InvalidatedSymbolicBase);
C.emitReport(std::move(Report));
}
void ento::registerInvalidPtrChecker(CheckerManager &Mgr) {
- Mgr.registerChecker<InvalidPtrChecker>();
+ auto *Checker = Mgr.registerChecker<InvalidPtrChecker>();
+ Checker->InvalidatingGetEnv =
+ Mgr.getAnalyzerOptions().getCheckerBooleanOption(Checker,
+ "InvalidatingGetEnv");
+ Checker->InitInvalidPtrBugType();
}
bool ento::shouldRegisterInvalidPtrChecker(const CheckerManager &) {
diff --git a/clang/test/Analysis/analyzer-config.c b/clang/test/Analysis/analyzer-config.c
index d86ca5d19219c64..22b68cd1fd4c1c0 100644
--- a/clang/test/Analysis/analyzer-config.c
+++ b/clang/test/Analysis/analyzer-config.c
@@ -11,6 +11,7 @@
// CHECK-NEXT: alpha.osx.cocoa.DirectIvarAssignment:AnnotatedFunctions = false
// CHECK-NEXT: alpha.security.MmapWriteExec:MmapProtExec = 0x04
// CHECK-NEXT: alpha.security.MmapWriteExec:MmapProtRead = 0x01
+// CHECK-NEXT: alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv = false
// CHECK-NEXT: alpha.security.taint.TaintPropagation:Config = ""
// CHECK-NEXT: alpha.unix.Errno:AllowErrnoReadOutsideConditionExpressions = true
// CHECK-NEXT: alpha.unix.StdCLibraryFunctions:DisplayLoadedSummaries = false
diff --git a/clang/test/Analysis/cert/env34-c-cert-examples.c b/clang/test/Analysis/cert/env34-c-cert-examples.c
index 19ca73f34c7ee5e..7e5b9be3cba6bb0 100644
--- a/clang/test/Analysis/cert/env34-c-cert-examples.c
+++ b/clang/test/Analysis/cert/env34-c-cert-examples.c
@@ -1,15 +1,49 @@
+// Default options.
// RUN: %clang_analyze_cc1 \
// RUN: -analyzer-checker=core,alpha.security.cert.env.InvalidPtr \
// RUN: -verify -Wno-unused %s
+//
+// Test the laxer handling of getenv function (this is the default).
+// RUN: %clang_analyze_cc1 \
+// RUN: -analyzer-checker=core,alpha.security.cert.env.InvalidPtr \
+// RUN: -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=false \
+// RUN: -verify -Wno-unused %s
+//
+// Test the stricter handling of getenv function.
+// RUN: %clang_analyze_cc1 \
+// RUN: -analyzer-checker=core,alpha.security.cert.env.InvalidPtr \
+// RUN: -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true \
+// RUN: -verify=pedantic -Wno-unused %s
#include "../Inputs/system-header-simulator.h"
char *getenv(const char *name);
+int setenv(const char *name, const char *value, int overwrite);
int strcmp(const char*, const char*);
char *strdup(const char*);
void free(void *memblock);
void *malloc(size_t size);
-void incorrect_usage(void) {
+void incorrect_usage_setenv_getenv_invalidation(void) {
+ char *tmpvar;
+ char *tempvar;
+
+ tmpvar = getenv("TMP");
+
+ if (!tmpvar)
+ return;
+
+ setenv("TEMP", "", 1); //setenv can invalidate env
+
+ if (!tmpvar)
+ return;
+
+ if (strcmp(tmpvar, "") == 0) { // body of strcmp is unknown
+ // expected-warning at -1{{use of invalidated pointer 'tmpvar' in a function call}}
+ // pedantic-warning at -2{{use of invalidated pointer 'tmpvar' in a function call}}
+ }
+}
+
+void incorrect_usage_double_getenv_invalidation(void) {
char *tmpvar;
char *tempvar;
@@ -18,13 +52,13 @@ void incorrect_usage(void) {
if (!tmpvar)
return;
- tempvar = getenv("TEMP");
+ tempvar = getenv("TEMP"); //getenv should not invalidate env in non-pedantic mode
if (!tempvar)
return;
if (strcmp(tmpvar, tempvar) == 0) { // body of strcmp is unknown
- // expected-warning at -1{{use of invalidated pointer 'tmpvar' in a function call}}
+ // pedantic-warning at -1{{use of invalidated pointer 'tmpvar' in a function call}}
}
}
diff --git a/clang/test/Analysis/cert/env34-c.c b/clang/test/Analysis/cert/env34-c.c
index dc7b0340c311ed5..94bc2cf95ccc9b0 100644
--- a/clang/test/Analysis/cert/env34-c.c
+++ b/clang/test/Analysis/cert/env34-c.c
@@ -1,5 +1,6 @@
// RUN: %clang_analyze_cc1 \
// RUN: -analyzer-checker=alpha.security.cert.env.InvalidPtr\
+// RUN: -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true \
// RUN: -analyzer-output=text -verify -Wno-unused %s
#include "../Inputs/system-header-simulator.h"
diff --git a/clang/test/Analysis/invalid-ptr-checker.c b/clang/test/Analysis/invalid-ptr-checker.c
new file mode 100644
index 000000000000000..d2250e03f3d3d2f
--- /dev/null
+++ b/clang/test/Analysis/invalid-ptr-checker.c
@@ -0,0 +1,50 @@
+// RUN: %clang_analyze_cc1 \
+// RUN: -analyzer-checker=alpha.security.cert.env.InvalidPtr \
+// RUN: -analyzer-config alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=false \
+// RUN: -analyzer-output=text -verify -Wno-unused %s
+//
+// RUN: %clang_analyze_cc1 \
+// RUN: -analyzer-checker=alpha.security.cert.env.InvalidPtr \
+// RUN: -analyzer-config \
+// RUN: alpha.security.cert.env.InvalidPtr:InvalidatingGetEnv=true \
+// RUN: -analyzer-output=text -verify=expected,pedantic -Wno-unused %s
+
+#include "Inputs/system-header-simulator.h"
+
+char *getenv(const char *name);
+int setenv(const char *name, const char *value, int overwrite);
+int strcmp(const char *, const char *);
+
+int custom_env_handler(const char **envp);
+
+void getenv_after_getenv(void) {
+ char *v1 = getenv("V1");
+ // pedantic-note at -1{{previous function call was here}}
+
+ char *v2 = getenv("V2");
+ // pedantic-note at -1{{'getenv' call may invalidate the result of the previous 'getenv'}}
+
+ strcmp(v1, v2);
+ // pedantic-warning at -1{{use of invalidated pointer 'v1' in a function call}}
+ // pedantic-note at -2{{use of invalidated pointer 'v1' in a function call}}
+}
+
+void setenv_after_getenv(void) {
+ char *v1 = getenv("VAR1");
+
+ setenv("VAR2", "...", 1);
+ // expected-note at -1{{'setenv' call may invalidate the environment returned by getenv}}
+
+ strcmp(v1, "");
+ // expected-warning at -1{{use of invalidated pointer 'v1' in a function call}}
+ // expected-note at -2{{use of invalidated pointer 'v1' in a function call}}
+}
+
+int main(int argc, const char *argv[], const char *envp[]) {
+ setenv("VAR", "...", 0);
+ // expected-note at -1 2 {{'setenv' call may invalidate the environment parameter of 'main'}}
+
+ *envp;
+ // expected-warning at -1 2 {{dereferencing an invalid pointer}}
+ // expected-note at -2 2 {{dereferencing an invalid pointer}}
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/67663
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